Engineering Report Number: ER-591 

Prepared By: Alan N. Bunner 

Subject: Optical Coating in Space 

P u bl icat ion Review : 

A. Bunner, Program Manager 

J. - &sso, Deputy Director, Advanced Systems I 

5i??&dki 

R. Labinger, Director, Advan d Systems 

w 

Distribution; 

A. Bunner 

R. Labinger 

J. Russo 

B. Tirri 

A. Vaughan 

Abstract : 

Date: October 27, 1983 

This report constitutes a technological appraisal of the steps required 

to approach the goal of in-situ optical coating, cleaning and re-coating 

the optical elements of a remote telescope in space. Emphasis is placed 

on the high ultraviolet throughput that a telescope using bare aluminum 

mirrors would offer. A preliminary design is suggested for an Orbital 

Coating Laboratory to answer basic technical questions. 

ii 
PERKIN-ELMER ER-591 

PREFACE 

The work described in this report was performed by the Space Science Civision of the 

Perkin-Elmer Corporation. The work was sponsored by the National Aeronautics and 

Space Administration (NASA) under a program called "Innovative Uses of the Space 

Station". 

A few words of guidance: In this report, all references are collected together in 

Section 8 and numbered. The first 133 of these are arranged alphabetically. The 

remaining references are arranged in no particular order, except roughly as they are 

cited in the text. Citations throughout the text refer to these references by numbers in 

parentheses, such as (18, 19). 

A separate appendix provides a bibliography covering the particular subject of the use 

of mirrors in space for ultraviolet wavelengths and the effects of degradation of 

reflectivity of such mirrors. This bibliography (Appendix E) duplicates many of the 

references in Section 8 and is included as a potentially useful reference tool which can 

be separated from this report. 

In this report we will be found guilty of using the unconventional acronym FUV for the 

far ultraviolet spectral region (b900 a - 1800 81, as this is a useful shorthand for the 

spectral range where pure aluminum offers a significant advantage in mirror 

refelctivity. Other acronyms are listed in Appendix A. 

The optical constants (n and k) at far ultraviolet wavelengths for some of the optical 

materials considered in this study are tabulated as a function of wavelength for 

reference in Appendix C. 

Finally, an index (Appendix F) is offered to assist the reader in finding some discussion 

of a few particular subjects. 

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PERKIN-ELMER 

Section 

1 

1.1 

1.2 

1.3 

2 

2.1 

2.2 

2.3 

3 

3.1 

3.2 

3.3 

3.4 

3.4.1 

3.4.2 

3.4.3 

3.4.4 

3.4.5 

3.4.6 

3.4.7 

3.4.8 

3.4.9 

3.4.10 

3.4.1 1 

3.5 

4 

4.1 

4.2 

4.3 

4.4 

4.5 

4.6 

5 

5.1 

5.2 

5.3 

5.4 

. _.. 

ER-591 

TABLE OF CONTENTS 

- Title Page 

PREFACE .......................................... iii 

INTRODUCTION..................................... 1 

Motivation and Goals .............................. 2 

Requirements for Coating in Space .................. 9 

Questions Addressed in this Study ................... 10 

HISTORY ........................................... 14 

Laboratory Experiments ........................... 23 

Salyut 4 Solar Telescope ........................... 32 

Space Shuttle Coating Degradation Experiments.. ..... 38 

THE DESIGN OF AN ORBITAL COATING LABORATORY . Research Questions to be Answered ................. Orbit............................................ 

The Molecular Shield Concept ...................... Laboratory Design ................................ Requirements and Constraints ................... Layout ....................................... Coating Materials .............................. Evaporators ................................... Stray Light Control ............................ Reflectometer ................................. Plasma Discharge Cleaning ...................... Atmospheric Oxygen Cleaning ................... Liquid Cleaning ................................ Power Supplies ................................ Pointing System ............................... Astronaut Involvement ............................. 

41 

41 

42 

48 

54 * 54 

55 

63 

66 

67 

70 

70 

73 

74 

74 

75 

75 

EXPERIMENTS WITH AN 'ORBITAL COATING 

LABORATORY..................................... 78 

Rate of Aluminum Oxidation ....................... 78 

Shuttle/Space Station Ram Flow Effects ............. 80 

Rate of Photopolymerization ....................... 81 

Re-aluminizing Demonstration ...................... 82 

Atom Beam Cleaning Demonstration ................. 87 

Conclusions and Recommendations .................. 91 

A SPACE STATION COATING FACILITY ............... 94 

Space Station Integration .......................... 94 

Transit Container ................................. 97 

Chemical Storage and Reclamation Unit ............. 98 

Protective Masking Requirements ................... 99 

iv 
... .... ............ 

PERKIN-ELMER ER-591 

Section 

5.5 

5.6 

5.7 

5.8 

5.9 

5.10 

5.1 1 

5.12 

5.13 

6 

6.1 

6.2 

6.3 

6.4 

TABLE OF CONTENTS (Continued) 

. 

Title 

Film Stripping Unit ................................ Chemical Cleaning Unit ............................ Mirror Assembly Coating Station .................... Plasma Cleaning System ........................... 

Film Thickness Measuring System ................... Reflectance Measuring System ...................... Operation of a Space Station Coating Facility ......... Summary ........................................ 

Coating System ................................... 

IN-SITU COATING OF LARGE SPACE TELESCOPE 

MIRRORS ......................................... System Description ................................ Evaporator Description ............................ Uniformity and Thickness Considerations ............. Summary ........................................ 

7 CONCLUSIONS AND RECOMMENDATIONS ............. 8 REFERENCES ....................................... 

APPENDIX A DICTIONARY OF ACRONYMS ........................ 

APPENDIX B FORTRAN OPTICAL COATING REFLECTIVITY 

PROGRAM ........................................ 

APPENDIX C TABLES OF OPTICAL CONSTANTS .................... 

APPENDIX D FORTRAN MOLECULAR FLUX PROGRAM ............. 

APPENDIX E BIBLIOGRAPHY ON THE CONTAMINATION AND 

DEGRADATION OF MIRRORS AND OPTICAL 

ELEMENTS IN A SPACE ENVIRONMENT .............. APPENDIX F INDEX ............................................. 

V 

Page 

100 

101 

101 

102 

102 

103 

103 

104 

105 

107 

107 

109 

109 

112 

114 

116 

130 

132 

144 

153 

157 

171 

............ .......... .... ...... .. 
PERKIN-ELMER 

LIST OF ILLUSTRATIONS 

Figure 

1 

2 

3 

4 

5 

6 

7 

8 

9 

10 

11 

12 

- Title 

Wavelengths of Important Spectral Lines in the Far 

Reflectivity at Normal Incidence of Pure Aluminum 

Ultraviolet. From Reference 7 ....................... 

and of Aluminum with the Usual 250 a MgF2 

Protective Coating .................................. Far Ultraviolet Reflectivities at Normal Incidence of 

Aluminum, Aluminum + MgF2 as used in Space Telescope, 

Aluminum + LiF as used in OAO-Copernicus, Chemically 

Vapor Deposited Silicon Carbide, and Osmium .......... Far Ultraviolet Reflectivities at Normal Incidence of 

Tungsten, Osmium, Rhenium, Rhodium, Ruthenium, 

Three Stages of Development towards Applying Optical 

A Concept for an Orbital Mirror Recoating Facility 

Iridium, Platinum and Gold ........................... 

Coatingsin Space ................................... 

(OMRF), from a Perkin-Elmer/Lockheed 1967 Design 

Study ............................................. UVSO Telescope Concept with a Ring of Six Aluminizers 

for the Primary Mirror and 3 Aluminizers for the 

Secondary Mirror (129) .............................. 

= 900 . 1200 a (129) ....... 

Concept for the UVSO Spectrograph with Aluminizers 

for the Gratings, Low Dispersion Plane Mirror and 

Collimator Mirror Used for 

Layout Showing Dimension of UVSO Spectrograph and 

Alternate Positions for Aluminizers (1 29) .............. Microdensitometer Tracings of a Glass Plate Used as a 

Substrate for the Experimental REVAP Mirror Coating.. . The Initial Reflectance Decrease of Freshly Deposited 

Aluminum Films in Vacuum in the Vacuum Ultraviolet 

as a Function of Time ............................... 

Reflectance of Evaporated Aluminum, as a Function 

of Time and WavelengtH ............................. 

The Effect of Aging in Vacuum and in Air on the 

.- 

ER-591 

Page 

3 

5 

6 

7 

12 

16 

18 

19 

20 

22 

24 

25 

vi 
PERKIN-EL ER-591 

Figure 

13 

14 

15 

16 

17 

18 

19 

20 

21 

22 

23 

LIST OF ILLUSTRATIONS (Continued) 

- Title Page 

The Calculated Effect of Oxide Films of Various Thickness 

on the Reflectance of Aluminum at 584, 736, 1026 and 

1216 Angstroms. Adapted from Hass and Hunter 

(59, 62, 63). ........................................ 26 

of Freshly Deposited Aluminum Films Before Exposure 

to Air at A= 1216 a (92) ............................. Effect of Butadiene Contamination and Plasma Exposure 

on Reflectance of 1/2x MgF2 Over Aluminum Coated 

Mirror............................................. 29 

Effect of Butadiene Contamination and Plasma Cleaning 

on Reflectance of 1/2h MgF2 Over Aluminum-Coated 

Mirror, for Wavelengths from 90-280 nm ............... 

Coated Cer-Vit Mirror Exposed to Atomic Oxygen.. ..... 

Effect of the Speed of Evaporation on the Reflectance 

28 

30 

31 

Reflectance Recovery of an Irradiated MgFz/AlumOrbiting Solar Telescope on the Space Station Salyut-4 

Layout of Orbiting Solar Telescope on Salyut-4, Showing 

(154) .............................................. 33 

Evaporators (21, 154) ................................ 34 

Location of Main Mirror, Pointing Mirror, and Aluminum 

OST Telescope Optics. (a) Main Mirror Module Showing 

Protective Cover and Two Aluminum Evaporators. (b) 

Pointing Mirror Module Showing Protective Cover and 

Two Aluminum Evaporators .......................... Calculated Normal Incidence Reflectivity of Aluminum, 

With and Without 5 A Oxide Layer, Using Optical 

Constants of Appendix C and ltOPTCOAT1t Program of 

Appendix B ........................................ Sticking Coefficient of Oxygen on Aluminum as a 

Constituent Number Density and Temperature as a 

Function of Total Oxygen Weight Gain ................. 

Function of Altitude for a Terrestrial Atmospheric 

Model with an Exospheric Temperature of 1000°K ....... 

37 

44 

45 

47 

vii 
PERKIN-ELMER 

.- 

ER-591 

LIST OF ILLUSTRATIONS (Continued) 

Figure 

24 

25 

26 

27 

28 

29 

30 

31 

32 

33 

34 

Title 

Atomic Oxygen Concentration and Atmospheric Density 

- 

as a Function of Altitude and Solar Activity, from 

Reference 135. STS-3 and -4 show the altitudes for 

two early Shuttle flights ............................. Rise in Atomic Oxygen Concentration from 1975 to 1982 

Schematic Representative of the Molecular Shield 

at an 800 km Altitude, from Reference 135.. ........... 

Geometry in the Drifting Gas, Illustrating Typical 

Molecular Trajectories .............................. Pressure Reduction Factor Resulting from a Molecular 

Shield of Various Solid Angles Placed Ahead of a Test 

Point Moving at 7.55 km/sec, for Different Exospheric 

Temperatures, T ..................................... Sketch of Concept for an Orbiting Optical Coating 

Laboratory, with 2-axis Gimbals for Orienting. The 

heavy arrow indicates the direction of atmospheric 

flow .............................................. Cross-Section through Interior of Orbiting Coating 

Reflectivity Measurement Scheme Using Reflected 

Top View of Orbital Coating Laboratory, Showing Internal 

Isometric Sketch of Interior of Orbiting Coating 

Laboratory, Showing Principal Components ............. 

Sunlight from Both of Two Mirrors .................... 

Baffle Arrangement ................................. 

Laboratory, Showing One of the Solid Walls Separating 

Interior Compartments, in which is Mounted One of the 

Rotateable Test Mirrors ............................. 

Collimator. (a) Compound Parabolic Concentrator, 

(b) Large Solid Angle Cone with Angle-Defining Baffles, 

(c) Straight "Gun Barrel" with Internal Baffles .......... 

Reflectivity. Parallel Sunlight from the Flat Mirrors 

Enters the Enclosure. The Concave Grating is Rocked 

about an Axis Perpendicular to the Page to Scan 

Wavelength ......................................... 

Three Concepts for the Design of an Evaporator 

Schematic Diagram of Monochromator for Measuring 

. Page 

49 

50 

52 

53 

58 

60 

61 

64 

65 

68 

71 

viii 
PERKIN-ELMER ER-591 

Figure 

35 

36 

37 

38 

39 

40 

41 

42 

43 

44 

45 

46 

47 

48 

49 

LIST OF ILLUSTRATIONS (Continued) 

- Title 

Top View of the Monochromator Package Showing the 

Constraint on Pointing of Orbital Laboratory Due to 

Desired Three Degrees of Motion ..................... 

Flux of Atmospheric Atomic Oxygen. The Optical Axis 

of the Laboratory can Point into the Figure of Revolution 

Generated by a 550 - wide Cone. ...................... Variations of the Sensitivity of the LPSP Solar-Pointed 

Instrument on OSO-8 Versus Time After Launch in 

Days(16) .......................................... Deterioration of the Sensitivity of the University of 

Colorado Solar-Pointed Telescope on OSO-8 with Time . . The Effect of Reflectivity at 

Various Common Oils Found in Manufacturing 

= 1236 A of Thin Films of 

Areas (168) ........................................ 

Dipco 868 Oil (168). ................................. 

Bundle Reaching the Monochromator ................... 

Thin-Film Equilibrium Thickness versus Temperature for 

The Effect of Increasing Scatter on the Size of the Light 

Concept for a High Vacuum Orbital Laboratory, with 

Molecular Shield, Located on Long Boom Extending 

from Free-Flyer Platform (from Reference 166) ........ 

Subsystems for a Semi-permanent Space Station Coating 

Facility ........................................... Artist's Concept for a Future Space Station Including 

Materials Processing Facilities such as an Optical 

Baseline Optical System for a Large Space Telescope 

Tungsten Stranded Wire Helical Coil Source ............. Primary Mirror Evaporator Configuration ............... One Possible Configuration for Locating Secondary 

Mirror Evaporators .................................. Distributions &f Major Constitutents of Neutral 

Atmosphere at Extremes of Solar Activity ............. 

Task Structure Block Diagram Showing All the Principal 

Coating Facility .................................... 

Requiring In-situ Coating ............................ 

Page 

72 

76 

83 

84 

85 

86 

90 

93 

95 

96 

108 

110 

111 

113 

156 

ix 
PERMIN-€LMER 

Table 

1 

2 

3 

4 

5 

6 

7 

8 

9 

ER-59 1 

LIST OF TABLES 

- Tilte 

Salyut 4 OST Telescope Optics . . . . . . . . . . . . . . . . . . . . . . . Estimated Variability of the Sun . . . . . . . . . . . . . . . . . . . . . . . Reflectivity of Aluminum Over a A1203 + A1 Multilayer 

Sandwich .......................................... Normal Incidence Reflectivity of Pure Aluminum . . . . . . . . . Computation of Reflectivity of 280 a Aluminum Over 

Iridium ............................................ Optical Constants of Aluminum in Far Ultraviolet . . . . . . . . Optical Constants of Aluminum Oxide (Al203) in Far 

Ultraviolet......................................... 

Optical Constants of Iridium in Far Ultraviolet.. . . . . . . . . . Optical Constants of Lithium Fluoride (LiF) in Far 

Ultraviolet......................................... 

Page 

35 

57 

88 

140 

142 

145 

147 

149 

151 

X 
PERKIN-ELMER 

._. . 

ER-591 

SECTION 1 

INTRODUCTION 

This report documents the results of a six month study into the advantages, feasibility 

and possible techniques of applying optical coatings in space. 

This study was conducted as a part of NASA's "Innovative Use of the Space Station" 

Program. The intent of this NASA program was to solicit novel ideas from a wide 

community of parties interested in the uses of space, as a part of a larger investigation 

into the potential requirements for and attributes of a permanently manned space 

station, as it might be used for science, applications, technology development, 

commercial utilization and national security. NASA's goal is to solicit the best possible 

advice before committing to a specific functional architecture for the space station 

(134). 

Although a baseline design for the space station does not yet exist, the attributed of the 

system design are likely to include (134): 

o 

o 

o 

o 

A permanent manned presence in space 

Both manned and unmanned elements 

Low-Earth orbit for the first manned element 

Delivery to space from the Space Shuttle 

o An operational phase of the space station which might begin as early as 1990 

Corollary attributed specifically related to science, applications, and technology 

utilization may also include (1 34): 

o Permanent facilities for conducting research 

o The potential for continuous manned interaction with research facilities 

which are in close proximity to the manned elements 

I 
... .. . . .. . . . . . . . . . , . ._ . .~ - . . ... . . . .. . 

PERKIN-ELMER ER-591 

o The potential for repetitive (if not continuous) manned interaction with 

unmanned research facilities in earth orbit at any altitude or inclination. 

The present study is motivated by scientific goals-the desire to produce efficient space 

telescopes for astronomy, particularly for ultraviolet wavelengths--but the connection 

to the space station is that we will discuss an unmanned research facility in earth orbit 

that is operated by men in space. Later phases of a program to develop optical coating 

in space may involve manned interaction with a space station facility that would 

constitute a production facility rather than a research laboratory. 

The author would like to acknowledge the help, ideas and advice of Bruce Tirri, Alan 

Wissinger and Arthur Vaughan, all of Perkin-Elmer, Jim Heaney and John Osantowski of 

Goddard Space Flight Center, George Hass, formerly of Night Vision Laboratoriest 

Professor Bob Wilson of University College London, Michael Sanford, Peter Barker and 

William Burton of Rutherford Appleton Laboratory and A. V. Bruns of the Crimean 

Astrophysical Observatory. These and many other individuals contributed their 

thoughts generously to this study. 

1.1 MOTIVATION AND GOALS 

One of the most important and scientifically rewarding portions of the electromagnetic 

spectrum in astrophysics is the far ultraviolet--800 A to 1200 8. Molecular hydrogen, a 

major constituent of the interstellar gas, and deuterium, a crucial probe of cosmological questions, can be studied in detail only at these wavelengths. Furthermore, hot 

plasma in the interstellar medium, in the atmospheres of hot stars and in other objects 

ranging from planets to quasars, with temperatures between 200,OOOK and 2,00,00OK, is 

studied best with observations in this wavelength range (Figure 1). The interstellar OVI 

absorption lines discovered by OAO-Copernicus at 1032 and 1038 A represented an 

important new phase of the gas in our galaxy (7, 135). 

Except for the one mission, OAO-Copernicus, which fluorished from 1972 to 1980, and a 

few solar physics instruments, no space astronomy project has included this important 

spectral region. OAO-2, the European TD-I, the International Ultraviolet Explorer, the 

Spacelab ultraviolet telescopes scheduled to fly on OSS-3, and the Space Telescope all 

were not designed to include this spectral range. The reason is straightforward. There 

2 
PERKIN-ELMER 

1 

1 - 

SPEC1 ES 

HI 

01 

H2 

He I 

He IT 

CIfI 

CZ 

NY 

OY 

OX 

Ne PIT: 

Ne 

Mg = 

Mq = 

Mq x 

Si XI1 

Fe IX 

Fa X 

Fe XTI 

Fe x3L 

Fe XZI 

Fe XPITI 

Fe XlX 

Fe XXI 

FexxIp 

LOG N 

12.00 

7.2 

6. - 11.7 

I I .oo 

I I .oo 

8.57 

8.57 

8.06 

8.83 

8.83 

7.45 

7.45 

7.54 

7.54 

7.54 

7.55 

7.40 

- LOG T 

4 .O 

4 .O 

I .9 

4.3 

4.3 

4.9 

5. I 

5.3 

5.5 

5.5 

5.8 

5.9 

6.1 

6. I 

6.2 

6.5 

c 6.0 

6.2 

6.4 

6.6 

6.8 

7. I 

7.2 

7.2 

7.5 

- 

IMPORTANT STRONG LINES 

Figure 1. Wavelengths of Important Spectral Lines 

in the Far Ultraviolet. Fram Reference 7. 

3 
PERKIN-ELMER ER-591 

is only one telescope mirror material that has a high reflectivity in the spectral range 

from 800 a to 2000 a at near-normal incidence, and hence high telescope throughput, 

and that is pure aluminum. However, aluminum is very reactive and in a terrestrial 

environment it quickly forms an oxide layer of AI203 with a serious loss of reflectivity 

at all wavelengths shorter than 2000 A. Therefore, aluminized mirrors are usually 

overcoated with MgF2 or LiF to protect the aluminum from oxidation. This allows 

retaining high reflectivity from 1200 A to 2000 A, but at the cost of introducing a 

strong absorption edge at I150 A (MgF2) or 1000 A (LiF). 

The gain in reflectivity that is possible with a pure aluminum mirror coating over other 

coatings commonly used or suggested for the far ultraviolet is shown in Figures 2-4. 

If a pure aluminum mirror (or grating) coating could be achieved in a space telescope, 

one gain would then. be a significant increase in spectral range, including the 

scientifically very important 800-1200 A regime. Therefore, one motivation for 

developing the techniques for applying optical coatings in space, in an environment 

where aluminum will not quickly oxidize, is to open this new spectral region to study in 

astronomy with high throughput instrumentation, permitting spectroscopy with high 

spectral resolution and the study of faint objects. Several recent proposals or plans for 

future space astronomy programs are based on the desire to observe in this spectral 

range: the Far Ultraviolet Spectroscopic Explorer (FUSE) (7, 1351, the international 

mission "Columbus" based on the FUSE concept (1471, the United Kingdom proposal for 

an Ultraviolet Space Observatory (UVSO) (1 29, 1351, the Hopkins Ultraviolet Telescope 

(HUT) scheduled for flight on the Shuttle's OSS-3 mission (136), the fvMagellanll mission 

studied by the European Space Agency (1371, the Grazing Incidence Solar Telescope 

(GRIST) also studied by ESA (1381, the Solar XUV Facility studied by NASA-GSFC in 

1976 (139), among others. 

A second motivation for developing the capability for coating optics in space comes 

from the desire to recover from a condition of degraded reflectivity that might be 

caused by mirror contamination. Throughout the ultraviolet region from 900 A to 

3000 A, the reflectivity of mirror surfaces can be easily spoiled by outgassed organic 

vapors, photopolymerization or even oxidation. Examples of these effects are described 

further in Section 2.1. As telescopes become larger in size and are designed for longer 

4 
PERKIN-ELMER 

a 

a 

H 

5 
.- . . _. _- 

PERKIN-ELMER 

0 

0 

ro 

8 

v 

6 

. .. 
PERKIN-ELMER 

W 

u 

z 

0 

W 

A 

(r 

w 

tz 

W 

0 

W 

P 

s 

a 

a 

50 - 

40 - 

30 - 

20 - 

500 1000 1500 2000 

- WAVELENGTH &I cLvc7i3 

Pt 

30 - 

: 'r 

AU 20 c 

f 

- 

-2, ..- Ay' %- IO- I' LL. 

tt,,, 11,,, 11 1,) 

OJ 500 1000 1500 2000 

WAVELENGTH 6) a9 

Figure 4. Far Ultraviolet Reflectivities at Normal Incidence of 

Tungsten, Osmium, Rhenium, Rhodium, Ruthenium, Iridium, 

Platinum and Gold (63, 71, 135). 

7 
PERKIN-ELMER ER-591 

lifetimes, aging effects may degrade the optical surfaces sufficiently that re-coating is 

desireable. If telescope optics can be re-coated in space, the costly and timeconsuming process of returning the telescope to earth, refurbishment, and re-boosting 

the telescope to orbit is avoided. For telescopes in geosynchronous orbit, from which 

we do not yet have the capability to retrieve satellites, or deep space, the motivation 

for in-space refurbishment is particularly strong. 

Even in the absence of aging or degradation effects in space, there is a motivation to 

avoid coating the mirrors for a sophisticated space telescope years before they will be 

used. In a major space telescope program, the long pre-launch environment poses risks 

to the mirror surface quality which could be avoided by applying the final coating after 

the telescope is in space. 

Solar telescopes have a particular risk of degradation of reflectivity because of the 

posssibility of solar ultraviolet-induced photopolymerization of organic "tars" on mirror 

surf aces which are exposed simultaneously to intense ionizing radiation and organic 

gases (satellite outgassing). See References 16, 17, 61, 65, 66, 69, 72, 75, 110 130. 

A cleaning and re-coating capability might be particularly useful on a deep-space 

telescope such as might be included on Solar Probe (142, 143) or Star Probe (140, 141), 

coming within ~0.1 AU of the Sun. 

These are the circumstances motivating the development of techniques for optical 

coating in space. The eventual goals of such a development program are: 

1. The construction of future space telescopes whose optical elements have the 

full reflectivity from 700 A to 3000 a of the highest curve in Figure 2. 

The construction of future space telescopes with a built-in capability for 

refurbishing their throughput through renewed optical coatings. 

2. 

The purpose of the present study is to plan a path towards the above goals, identifying 

the problems, the questions to be answered and the techniques that might be used. 

There may in fact be other applications for applying optical coatings or thermal 

coatings in a space environment besides the above applications to ultraviolet 

8 
PERKIN-ELMER ER-59 1 

astronomy. There may be other coating materials useful in other wavelength regions 

which, like aluminum, react too readily in a normal earth environment. 

1.2 REQUIREMENTS FOR COATING IN SPACE 

To achieve the goals discussed in the previous paragraphs, a space-based coating system 

would have to satisfy the following requirements: 

1. 

2. 

3. 

4. 

5. 

- 6. 

7. 

8. 

9. 

10. 

11. 

The optical surfaces must be cleanable to the extend required for successful 

re-coating. 

The design should allow for repeated re-deposition of a new optical coating, 

up to, say, 10 occasions. 

The coatings must adhere to the substrate or to the previous layer and be 

resistant to the normal thermal changes of the substrate. 

The surfaces must be reasonably smooth to ensure low-scatter performance. 

The applied coatings must fully cover the desired optical surface to a 

reasonably uniform thickness. 

The applied coatings must not extend beyond the target mirrors to reach 

critical surfaces in a telescope assembly where the evaporated material 

would spoil the absorbing properties of an optical baffle or the insulating 

properties of a high voltage insulator, for example. 

It must be possible to monitor the thickness and/or reflectivity of the 

deposited coatings. 

The coating system should not require excessive power. 

The coating system should be capable of operating without manned intervention, at least without manned access to the heart of a delicate telescope 

assembly . The following materials are considered potentially useful: aluminum, 

iridium and lithium fluoride (See Section 3.4.3). The coating system should 

be capable of depositing these materials. 

The coating process must be reliable. 

9 
PERKIN-ELMER ER-591 

Concerning Point No. 5 above, the simultaneous achievement of high reflectivity over a 

large surface area and state-of-the-art (~3%) thickness uniformity in an optical coating 

may be very difficult in a space environment, especially in an in-situ telescope 

situation. In a diffraction-limited ultraviolet telescope such as the Space Telescope, 

the requirement on coating thickness uniformity is strict because gradients in the 

coating thickness could actually disturb the mirror figure. In this study, our concern is 

more with large far-ultraviolet throughput than with diffraction-limited performance. 

Concerning Point No. 10 above, we will consider in this report the particular cases of 

aluminum over iridium and lithium fluoride over aluminum. 

We are not considering in this report multi-layer coatings such as are used to achieve 

particular sharply-tuned interference effects or filters. 

The above list of requirements would apply either to a space-based optical coating 

facility, that is, a general-purpose coating chamber to which mirrors or gratings could 

be brought to receive a new coating, or to a coating arrangement built into a nextgeneration space telescope for in-situ optical coating. 

1.3 QUESTIONS ADDRESSED IN THIS STUDY 

This study constitutes a technological appraisal of the steps required to approach the 

goal of in-situ optical coating, cleaning and re-coating the optical elements of a remote 

telescope in space. What prevents us from designing such a telescope today? 

For one thing, a space telescope designed to be coated in space represents a costly 

investment with a high level of risk, until the techniques have been successfully 

demonstrated. Moreover, there are a number of technical questions that need to be 

answered before one could completely plan for such a space observatory. The 

significant open questions include the following: 

1. How high in altitude does a telescope with bare aluminum mirror surfaces 

need to be, to avoid rapid oxidation from residual atmospheric oxygen? 

What are the effects of the orbital velocity through the residual atmosphere 

on the lifetime of an aluminum surface being used as a far ultraviolet 

reflector? 

2. 

10 
PERKIN-ELMER ER-591 

3. Can a coating source be designed that satisfies requirements no. 2 (reusable), 5 (uniform), and 6 (no spill-over) of Page 9? 

4. What are the effects of repeated coating, oxidation, re-coating, on VUV 

mirror reflectivity, roughness and scatter? 

Are there alternate ways to achieve long-life high ultraviolet reflectivity 

surfaces, or to extend the lifetime of a bare aluminum surface in Earth 

orbit? 

5. 

6. How much does the inevitable environment of spacecraft outgassing limit 

the lifetime of a bare aluminum ultraviolet mirror surface? 

Some of the above questions may be answerable by means of carefully designed ground 

laboratory experiments. Some of the others (for example, items 1, 2 and 6 above) may 

best be answered in space orbital laboratory experiments. Certainly the need to 

successfully demonstrate in-orbit coating techniques requires an orbital coating 

laboratory. 

. 

Besides the ground-based laboratory experiments, we may envision three categories or 

stages of space-based experimentation leading to our final goal of in-situ coating of 

optics in space observatories (see Figure 5): 

Stage 1: Orbital Coating Laboratory Experiments. Controlled experiments 

and demonstration tests designed to answer the above questions. 

Stage 2: Space Station Coating Facility. A semi-permanent "coating 

chamber" built into a manned space station (for example) that 

serves to utilize the vacuum of space and the earth orbital 

environment to coat or re-coat telescope mirrors without the costs 

of transportation to and from Earth, and without the dust, humidity 

and handling problems of the Earth environment. This facility 

would be flexible enough to handle mirrors and mirror segments of 

all sizes and a variety of coating materials. Removal of mirrors 

and mirror segments from a telescope assembly and re-installation 

into a telescope assembly might be required. 
PERKIN-EL 

c3 

z 

0 

0 

i= 

a 

W 

e 

VI 

2 

2 

12 
ER-591 

Stage 3: In-situ Coating in Space Observatories. Built-in apparatus for 

coating and re-coating gratings and/or mirror elements in space 

telescopes. This category of coating operation would be controlled 

in real time by remote control and would not require removal or 

handling of the optical components. 

This report will examine these three categories of optical coating operations in a space 

environment. Some hardware design ideas that might be appropriate will be suggested. 

The most immediate need in a program of development of these concepts are the 

laboratory experiments and demonstration tests that serve to answer the basic 

questions posed on Page 10. Therefore a major topic of this study will be the 

conceptual design of an orbital coating laboratory versatile enough to perform a variety 

of useful experiments and demonstrations, with a description of some of the important 

experiments to be carried out with such a laboratory. 

13 
PERKIN-ELMER 

SECTION 2 

HISTORY 

ER-591 

Ultraviolet astronomers have considered the merits of optical coating with pure 

aluminum in the vacuum of space for many years (144). The high vacuum ultraviolet 

reflectance of aluminum and the rapid rate of oxidation in air were both certainly 

recognized prior to 1956 (145). There was little active development of the idea for 

several reasons: (1) Optical coating is a power-hungry procedure. Early space 

astronomy missions could not contemplate using 500-5000 watts for thermal evaporation. (2) Even the earliest suggestions to coat mirrors in space included the caveat that 

the presence of high altitude oxygen would restrict the use of bare aluminum to high 

Earth orbits. 

The earliest published discussion of mirror aluminizing in space of which I am aware is 

the Perkin-Elmer final report (reference 1) of a feasibility study for the "Princeton 

Advanced Satellite" (which later became OAO-Copernicus). This 1965-66 report 

identified most of the advantages and disadvantages of coating optics in space which 

are still the main considerations today. A concluding paragraph from this discussion is 

reproduced here (1): 

"The possibility of coating optics in space in order to achieve a pure aluminum 

film having a much higher reflectivity in the 900 8, to 1200 8, region than 

overcoated films is extremely attractive. For a near earth orbit (125 miles to 

500 miles) the pressure varies from to lom9 mm Hg which is similar to 

pressures achieved with present coating facilities. Oxygen contamination in near 

earth orbits is, therefore, likely to be as serious a problem as it is in earthbound 

faciities and no advantage is apparent in this case. For a 20,000 mile 

synchronous orbit the pressure is below 10-12 mm Hg and some advantage may 

be obtained with a space coating facility provided that outgassing from the 

satellite did not nullify the effect of a higher orbital altitude. A space coating 

facility would require a minimum of 5 KW of power for approximately 10 seconds 

14 
PERMIN-EL ER-591 

to evaporate the aluminum and a motorized mask assembly to achieve a uniform 

distribution. In order to prevent a reflective coating being applied to the 

telescope tube, this structure would probably have to be separated from the 

primary during the coating process. In conclusion, optical coating in space is 

unlikely to be attractive until manned missions to synchronous altitude and 

beyond are contemplated. The advantages to be gained with a spaceborne 

coating facility, even under the most advantageous conditions, such as with a 

contaminated or abrased mirror surface, are not readily apparent. They will 

depend in part of advances in the state-of-the-art with earthbound coating 

facilities and in part on feasibility experiments aimed at cleaning and coating 

optical surfaces by future high altitude manned missions." 

A later (1967) design study (Reference 2) by Perkin-Elmer for a segmented 2-meter 

telescope, proposed to fly as a part of the Apollo Extension System program, arrived at 

a design for an Orbital Mirror Recoating Facility (OMRF), to be attached to the Saturn 

SIV-B orbital workshop, wherein mirror segments could be cleaned and re-coated by 

remote control, with all mirror processing controlled and monitored by astronauts in the 

workshop. Coating experiments were suggested for this 'facility. See Figure 6. The 

workshop later became 5kylabt1, but without the 2-meter telescope or the OMRF. 

Later studies (Reference 3) developed these coating concepts for a 2-meter astronomical telescope design that would later become the Large Space Telescope. 

A key paper by Hass and Hunter (59) concluded that only at altitudes greater than 1500 

km could a mirror coating lifetime of a year or more be achieved. These authors also 

pointed out that the lifetime would strongly depend on the angle made by the telescope 

tube with the flight vector of an orbiting space vehicle, both because of the increased 

pressure on the leading side and became of the higher "sticking probability" of atoms at 

higher kinetic energy. 

An important series of measurements was carried out by James B. Heaney in 1967-68 

aboard the geosynchronous satellite ATS-3 (65). The specular reflectance versus 

wavelength of various coatings and mirror surfaces including MgF2, aluminum, A1203 

and SiO.2 were monitored for radiation-induced degradation over a two year period. The 

effects of solar ultraviolet radiation and charged particle radiation were separated by 

15 
PERKIN-ELMER 

Figure 6. A Concept for an Orbital Mirror Recoating 

Facility (OMRF), from a Perkin-Elmer/Lockheed 

1967 design study (2). 

16 
PERKIN-ELMER ER-591 

the use of transmitting quartz shields (which passed the ultraviolet radiation for 

h> 1600 A but stopped the particles). This experiment showed substantial losses in uv 

reflectivity for all samples after ~1% years, especially for those samples that were 

exposed to the h41600 solar radiation and charged particle radiation. The unshielded 

vapor-deposited aluminum (uncoated but naturally oxidized) suffered up to 90% loss of 

reflectance in the 3000 A to 4000 a band. The observed degradation may have been due 

to a uv-induced contamination (photopolymerization) in the case of the shielded 

samples, and an erosion of the coatings (charged particle induced sputtering?) in the 

case of the unshielded samples. 

In 1981, Heaney and Herzig (151) proposed a study of both plasma gun cleaning and recoating of optical components in a space environment. This proposal was motivated 

partly by the wish to investigate a potential long-run cost savings for the Space 

Telescope program, but Heaney and Herzig also pointed out that procedures developed 

for in-orbit cleaning might also find application in extending the lifetime of solar cell 

arrays and thermal control surfaces. 

Recently, the concept of applying aluminum mirror coatings in space received new 

attention in a proposal (135, 129) for an Ultraviolet Space Observatory (UVSO) from 

Professor Robert Wilson of University College London and colleagues in Great Britain. 

This proposal sketched a design for a one-meter Ritchey-Chretien telescope for 

A= 900 8, to 1200 a astronomy, to be flown as a free-flyer in geosynchronous orbit. The 

authors suggested that the primary and secondary mirrors could be aluminized before 

launch and either be allowed to naturally oxidize or be overcoated with a temporary 

protective MgFZ coating (146) and then re-aluminized in orbit by means of barrelshaped aluminum evaporator guns for each of the two mirrors. See Figures 7, 8 and 9. 

A laboratory program to experiment with evaporator gun design, baffling, and re-usable 

aluminum evaporators is being carried out at Rutherford Appleton Laboratory to answer 

some basic design questions (146, 148). 

Moreover, Wilson and his colleagues have suggested (129, 146) that the optics and 

gratings in a ultraviolet spectrograph for such a telescope would be even more 

amenable to aluminizing in orbit, as the reflectivity of the gratings is just as 

17 
PERKIN-ELMER 

,/ 

, 

I’ 

.. 

W 

i 
PERKIN-ELMER 

Q !I ', I .I i

19 
PERKIN-ELMER 

FES 

I 

In 

BAF 

I HUTTER 

%E 

a REDUNDANT DETECTORS I-' INCLUDING EHT UNIT. ALUMINISER X 

LOCATION 

Figure 9. Layout Showing Dimension of WSO 

Spectrograph and Alternate Positions 

for Aluminizers (129). 

20 
PERKIN-ELMER 

important to system throughpu as the 

ER-591 

Aescope optics and their smaller size makes the 

coating job easier. This possibility is also being considered for the Tolumbusff FarUltraviolet Spectrographic Explorer mission, formerly known as "FUSE" (7, 135, 146, 

147). 

An alternative concept for achieving unoxidized aluminum mirror surfaces for high FUV 

reflectivity is being studied by William M. Burton and colleagues at the Rutherford 

Appleton Laboratory in Great Britain. In this concept (23, 24, 1481, a mirror is first 

coated with pure aluminum is an ultra-high vacuum evaporator in a ground-based 

coating chamber and then immediately overcoated with a thin protective layer of zinc 

or cadmium (or other suitable volatile material) to prevent oxidation of the aluminum 

during the time interval prior to achieving earth orbit. Once in space, the volatile 

protective film would be removed by controlled heating (or possibly by ion bombardment or plasma etching or some other technique) to expose the original clean pure 

aluminum mirror surface. The re-evaporated protective coating would be condensed on 

a collector surface placed over the mirror for this purpose. Burton calls this concept of 

a Removable Volatile Aluminum Protection coating which is 9-evaporated" in a high 

vacuum space environment a "REVAP" coating (23, 24). Figure 10 (23, 24) illustrates a 

laboratory demonstration of this technique. A glass surface was coated with two 

partially overlapping regions of aluminum and zinc with an estimated thickness of 

~500 A. After an initial microdensitometer scan (solid line) the coating was heated in a 

vacuum to 2OOOC - 300OC to ffrevaporatefthe zinc. The final microdensitometer scan 

(dotted line) shows that the zinc coating appears to have totally disappeared. 

This concept is, of course, a promising approach to achieving unoxidized aluminum 

mirror surfaces in space. A program of laboratory experiments at Rutherford Appleton 

Laboratory is in progress to further develop this technique (23, 24, 148). Some of the 

questions that will have to be answered are: (1) Can a protective "REVAP" material be 

found that will not diffuse into the aluminum in the several months between deposition 

and re-evaporation? (2) Will the last few angstroms of the protective coating evaporate 

along with the bulk material or may surface bonding effects make removal of these last 

atomic layers more difficult? (3) Will the final reflectivity in the far ultraviolet be 

close to the theoretical value for pure aluminum? (4) Can a completely smooth, low 

scatter, aluminum surface be achieved? (5) Does the mirror heating cause any 

21 
PERKIN-ELMER 

5.0- 

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i 

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9.5- 

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1 .OF 

j 

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I 

f 

oeiore 

REVAF 

; after 

* REVAP 

-1 1 I 

15 

or"'. .. . . * .- ...*..* * 

.cI 0 5 iJ 

nm 

Figure 10. Microdensitometer tracings of a glass plate used as a substrate 

for the experimental REVAP mirror coating. 

the composite coating is shown above the optical density scan 

curves. The lower curve (dotted) shows the scan made after 

revaporation of the zinc coating (23, 24). 

The structure of 

22 
PERKIN-ELMER ER-591 

unwanted effects to either the mirror or the desired final coatings? (6) Can the 

"REVAP" coating be completely collected and removed from the telescope environment 

without condensing on inappropriate surfaces? 

In connection with this last question, it is worth noting that low vapor pressure metal 

coatings such as cadmium was formerly used in space hardware (on electrical 

connectors, for example) and was notorious for its tendency to evaporate in flight and 

redeposit elsewhere, such as on high-voltage feedthroughs (149). 

2.1 LABORATORY EXPERIMENTS 

A number of important experiments have taken place in ground-based laboratories over 

the past 20 years to shed some light on the lifetime of bare aluminum coatings and 

contamination effects that can degrade the far ultraviolet reflectivity of mirrors. 

Madden et a1 (91, 92) showed that at the shortest wavelengths they studied (1025 A) a 

loss of reflectivity of pure aluminum due to oxidation can be seen within 30 seconds of 

time in a vacuum of N 1 x torr. Figures 11 and 12 show the short-term 

(p W 1 x 10-6 torr) and the longer term (p"- 3 x 10-7 torr) rate of loss in ultraviolet 

reflectivity (40, 91, 92). The implication from these data is that at h= 1025 A and at 

1 x 10-6 torr, the expected time to suffer a drop of reflectivity from 86% to 20% is 

about one hour (62, 63). During the initial 30 seconds or so of this period, an oxide layer 

forms on pure aluminum at a rate on the order of one monolayer (4 A) per second at 

p 1 x lom6 torr (91, 150). This rate of penetration then slows down, the total oxide 

layer thickness asympototically approaching -40 b, (57, 59, 63) with a time constant on 

the order of one hour (77, 81, 92). Presumably the mechanism for the oxidation of the 

first 2 monolayers is different from subsequent oxidation. In the case of the first 

monolayers, every oxygen atom which strikes the surface reacts with a probability near 

1. As the oxide thickness approaches 30 or 40 A, however, the penetration of the 

oxygen must proceed by a diffusion reaction, a place-exchange process between the 

chemisorbed oxygen and the underlying aluminum atoms (39, 81, 83, 92). 

Figure 13 shows the calculated reflectivity at normal incidence for AI + A1203 as a 

function of oxide thickness at 4 different far ultraviolet wavelengths (57, 59, 62, 63, 

92). From this figure, we can see that whereas -3 a of A1203 can be tolerated on the 

23 
PERKIN-ELMER 

0 50 100 150 

SECONDS AFTER DEPOSITION 

MINUTES AITER DEWSrrlON 

MINUTES AFTER DEPOSITION 

Figure 11. The Initial Reflectance Decrease of Freshly Deposited Aluminum 

Films in Vacuum in the Ultraviolet as a Function of Time, (a) 

the First 250 Seconds, at a Pressure % 1 x Torr, (b) the 

First 16 Minutes, at a Pressure % 4 x Torr, at an 

Incidence Angle of 60' for A = 584& (c) Over 40 Minutes 

Time, at a Pressure of 3-5 x Torr (92). 

24 
PERKIN-ELMER 

W o z

l- o 

W 

u. -I 

a 

kq I- z 

W 0 

w P 

a 

1001 I 

I I I I I I 1 

1000 1200 1400 1600 1800 -2OOO 2200 2400 

WAVELENGTH (At 

REFLECTANCE OF EVAPORATED ALUMINUM FILMS BEFORE 

a AFTER I HOUR, I DAY 6 I MONTH EXPOSURE TO AIR 

IN THE WAVELENTH REGION FROM IO001 TO 2400i. 

Figure 12. The Effect of Aging in Vacuum and in Air on the Reflectance 

of Evaporated Aluminum, as a Function of Time and Wavelength. 

(a) These films were exposed to air after 8 minutes (92). 

(b) Reflectance of evaporated aluminum films before, and after 

1 hour, 1 day and 1 month exposure to one atmosphere of air (77). 

25 
PERKIN-ELMER 

- 

THICKNESS OF AL;z03 (ANGSTROMS) --j 

Figure 13. The calculated effect of oxide films of various thicknesses 

on the reflectance of aluminum at 584, 736, 1026 and 1216 

Angstroms. Adapted from Hass and Hunter (59, 62, 63). The 

terminal (maximum) AX203 thickness for naturally oxidized 

aluminum is about 40 Angstroms (62, 92, 150). 

26 
PERKIN-ELMER ER-591 

surface of an aluminum mirror for far ultraviolet use, a thickness of &5 A of A1203 

causes a ~15% drop in reflectivity at A= 736 A. We may therefore take 5 a as the 

maximum tolerable oxide thickness on bare aluminum and as the point at which recoating with fresh aluminum would become desireable. 

It has also been shown in the laboratory (62, 91, 92) that a high rate of aluminum 

deposition yields a higher ultraviolet reflectivity than a slow rate (Figure 14). 

According to Madden et a1 (921, for a given partial pressure of oxygen, the higher the 

aluminum deposition rate, the less oxygen will be trapped into the film to produce the 

strongly absorbing aluminum oxide. Moreover, a higher deposition rate results in a 

tighter, more compact film structure which is more resistant to later oxidation. 

In addition to aluminum oxide, other strongly uv-absorbing contaminant films have been 

studied, in both laboratory and space flight environments, which may be more or less 

independent of the material of the substrate. Hass and Hunter (61) and others (50, 669 

76, 49, 98, 115, 128) have shown in laboratory demonstrations that uv-absorbing films of 

organic high vapor pressure residue can build up on mirror surfaces when both organic 

gases and ionizing radiation (either ultraviolet radiation or charged particles) are 

present at the mirror surface. The mechanism is thought to be radiation-induced crosslinking or photopolymerization of organic molecules striking the mirror surface (49, 56, 

61). 

t 

Laboratory efforts at removal of such chemically-altered deposited films have shown 

that heating the substrate to encourage evaporation, and even liquid solvent cleaning, 

are generally ineffective at removing polymerized contaminant films (49, 66, 98). The 

film may be removed by polishing the surface with a mild abrasive such as calcium 

carbonate (49, 661, but this brute-force technique is not very practical for a space 

telescope. Two techniques for restoring the ultraviolet reflectivity of polymercontaminated mirrors have been proven in the laboratory: (1) plasma etching and (2) 

exposure to atomic oxygen. Plasma etching or atom bombardment cleaning (51, 150, 

152, 153) sputters away a surface film by mechanically milling away the undesired layer 

atom by atom, using either ions or neutral atoms (eg. argon) of typically 2 keV kinetic 

energy. Atomic oxygen (Figures 15-17) adds the chemical effect of oxidation, which 

converts a contaminant polymer film into volatile compounds which then evaporate (49, 

27 
PERKIN-ELMER 

a 

Figure 14. Effect of the speed of evaporation on the reflectance 

of freshly degosited aluminum films before exposure to 

air at A 1216A. The times indicated on the curves 

represent the duration of the evaporations. All films 

were 700-900& thick (92). 

28 
PERKIN-ELMER 

t; 

t; 

8 

w 

a 

Q 

c (Yc) 

c 

29 
PERKIN-ELMER 
PERKIN-ELMER 

- 1 I I I I I--- 

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I 

I 

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0, 

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3 

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8 

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c 
PERKIN-ELMER ER-591 

50). These are the same techniques used in coating chambers and in semiconductor 

production facilities to prepare a substrate for the deposition of a thin film. The 

contaminant removal rate is much higher when an oxidation reaction is involved. 

Furthermore, atomic oxygen cleaning has the chemically selective property of removing 

hydrocarbons without removing more stable compounds such as MgF2 (49). Figure 17 

shows the recovery of the ultraviolet reflectance of a proton-induced polymer 

contaminated mirror exposed to un-accelerated atomic oxygen at 0.45 torr (49). The 

ion gun technique has the property of spatial selectivity; that is, the ion beam can be 

steered to remove material in one area while avoiding another area. 

2.2 SALYUT 4 SOLAR TELESCOPE 

Optical coating in orbit has actually been accomplished once, in 1975 on the Orbiting 

Solar Telescope (OST) on board the Soviet manned space station Salyut 4 (19, 20, 21, 

154). The solar astronomers who designed this ultraviolet telescope (A.V. Bruns, A.B. 

Severny and others) realized that the ultraviolet reflectivity of the two principal 

mirrors could be severely degraded by the combination of ionizing (solar ultraviolet) 

radiation and organic contaminants (2 1). They therefore arranged to have aluminum 

evaporators mounted in front of both a 28 cm flat pointing mirror and a 25 cm parabolic 

main mirror which could be activated in flight to refresh the coatings. Salyut 4 was 

launched into a 337-350 km altitude, 51.60 inclination orbit on December 26, 1974 

(Figure 18). The parabolic main mirror (Figure 19) was re-aluminized with about 800 

of thermally-evaporated aluminum once during January-February 1975 and the flat 

pointing mirror was re-aluminized once during June-July 1975 (19, 154). This demonstration had a mixed success. As an engineering demonstration, the coating experiment 

worked well. However, there was no improvement of ultraviolet reflectivity observed, 

presumably because of a rapid oxidation of the aluminum by oxygen atoms present in 

the telescope area. 

The coatings on the OST optical elements are summarized in Table 1. The parabolic 

main mirror was launched with a Ge+ZnS optical coating (57) so as to have low 

reflectance in the visible spectrum and thus reduce the visible and near ultraviolet 

stray light entering the OST ultraviolet spectrograph. The in-orbit aluminizing of the 

main mirror had the interesting secondary effect of evaporating the contaminant film 

32 
Figure 18. Orbiting Solar Telescope on the 

Space Station Salyut-4 (154). 

33 
PERKIN-ELMER 

G SULAR TELESCOPE (OST) 

Figure 19. Layout of Orbiting Solar Telescope on 

Salyut-4, Showing Location of Main Mirror, 

Pointing Mirror, and Aluminum Evaporators 

(21, 154). 

34 
PERMIN-ELMER 

TABLE 1 

Mirror 

Pointing Mirror 

(off-axis parabola) 

I 

Spectrograph 

Gratings 

Salyut 4 OST Telescope Optics 

ER-591 

I Coatings. I Substrate 

Sytal At launch: 

(Zerodur) A1 (1000 8) + LiF (160 A) + MgF2 (15 A) 

Added in fli ht: 

A1 (+-SO0 5 

Sytal At launch: 

(Zerodur) Al (1000 8) + Ge (M600 8) + ZnS (~450 fi) 

Added in fli ht: 

A1 (~800 K 

At launch: 

A1 + Ge + ZnS 

35 
PERKIN-ELMER ER-591 

from a badly contaminated reflective slit jaw, due to the increased heat dumped on the 

slit jaw by the newly-aluminized Ge+ZnS mirror. 

Some other design details of the Salyut 4 solar telescope are worth noting. The 

aluminum evaporators were designed to be reusable, although in flight each mirror was 

coated only once (154). The flight mirrors were mounted into the instrument only at 

the last possible opportunity after all ground testing was complete. (Qualification 

mirrors were used for prior testing.) The back and side surfaces of the flight sytal 

(zerodur) mirrors were polished and aluminized to provide a higher normal operating 

temperature and thus minimize the amount of condensation of contaminants on the 

mirror faces. To further protect the mirrors from condensation, especially during the 

period immediately after insertion of the telescope into orbit, which was considered to 

be the most risky period for potential contamination of the optics, both the main mirror 

and the pointing mirror were equipped with clean metal protective covers, which were 

opened when observations were begun (21). Both the protective cover and the two 

symmetrically placed aluminum evaporators can be seen in Figure 20. Finally, to 

protect the hydroscopic LiF-coated pointing mirror from possible degradation due to 

humidity, this mirror was given a very thin (15 8) coating of MgF2 over the LiF. 

Moreover, the instrument was kept in a dry atmosphere during pre-launch testing, and a 

cannister of 3 kgm of silica gel was used for backup protection during particularly risky 

periods such as transportation. 

The conclusions that may be drawn from the Salyut 4 OST experience are (1) clean 

protective covers for contamination-sensitive optics are effective at minimizing 

condensation, as seen by comparison of the unprotected reflective slit jaw to the 

protected main mirror and pointing mirror on OST, (2) 350 kilometers is an insufficient 

altitude for pure aluminum mirror coatings, and (3) a large, complex manned space 

station such as Salyut 4 is certain to create its own atmosphere of outgassed vapors. It 

is not clear whether spacecraft outgassing or residual Earth atmosphere was the 

primary limitation to the aluminizing experiments on Salyut 4. A.V. Bruns suggests that 

spacecraft outgassing may have been the real limitation to the lifetime of the bare 

aluminum (Reference 21, Section 111). In any case, it is clear that telescopes using bare 

aluminum mirrors require an extremely low outgassing environment and a geometry 

36 
PERKIN-ELMER 

Figure 20. OST Telescope Optics. 

(a) Main Mirror Module Showing Protective 

Cover and Two Aluminum Evaporators. 

(b) Pointing Mirror Module Showing Protective 

Cover and Two Aluminum Evaporators (21). 

37 
PERKIN-ELMER ER-591 

that permits rapid venting of outgas products and that avoids intercepting residual 

atmosphere. 

To the best of our knowledge, the in-orbit aluminizing procedure has not been repeated 

by the Russian astronomers. 

For comparison, two normal-incidence solar instruments for FUV and EUV wavelengths 

flew on the large manned Skylab mission at an altitude of 435 km in 1973-74. These 

instruments were the Extreme Ultraviolet Spectroheliometer, S-055, for wavelengths 

from 300 to 1340 a (11, 157, 159, 160) and the NRL EUV and Ultraviolet Spectroheliographs, S-082A and S-O82B, for wavelengths from 175 to 615 a and 970 A to 3940 14 

(76, 155, 156, 158, 159). The mirrors and gratings in these instruments used iridium 

(S-OSS), gold (S-082A) and MgF2 (S-082B) optical coatings. Although these instruments 

did not have to contend with bare aluminum coatings, they did face the risk of 

photopolymerization on the optical surfaces from the combined effects of outgassing 

and solar ultraviolet. No significant in-flight degradation of throughput was observed in 

any of these instruments (155, 157), presumably because of a vigorous and thorough 

program of contamination prevention in both the selection of materials and handling of 

the instruments (11, 76). 

2.3 SPACE SHUTTLE COATING DEGRADATION EXPERIMENTS 

The first few flights of the U. S. Space Shuttle have been at altitudes of 200-315 

kilometers. At these low altitudes the density of residual atmospheric atomic oxygen is 

high. (The number density of atomic oxygen at 200 km is ~4 x 109 atoms cm-3; the 

total atmospheric density is NIOio cm-3 or ~2.8 x10-7 torr.) Many observations of the 

degradation of various coatings on the Shuttle have now been recorded. This 

degradation appears to be due in part of the high atomic oxygen density, high light 

velocity into the atmospheric gas, and in some cases the simultaneous exposure to solar 

ultraviolet radiation. Some of the observations on Flights STS-1 through STS-4 and 

proposed mechanisms are listed below (5, 87, 161, 162, 164). 

o Polymer films such as kapton, paint binders, torlon thermal blanket buttons, 

were oxidized and/or removed by sputtering. Kapton (polyamide) erosion 

was as much as 0.1 mil (2.514 in 6-day mission. 

38 
PERMIN-EL ER-591 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

Loss of material from mylar sample on STS-4 was 0.07 mil(l.8d. 

Loss of material from teflon sample on STS-4 was 0.003 mil (0.OSp). 

Carbon coatings and aquadag suffered complete loss (2000 A), presumably 

oxidized to CO and evaporated. 

Osmium coatings suffered complete loss (1 20-2000 81, presumably oxidized 

to osmium tetroxide (0~04) and evaporated. 

Silver coating suffered complete oxidation to Ag20. Coating changed color 

but did not evaporate. 

The above reactions were accelerated by both exposure to the vehicle ram 

direction (flight vector) - and to direct solar exposure, as evidenced by 

observed shadowing effects. 

No degradation of MgF2, iridium, gold, platinum or aluminum surfaces have 

yet (October 1983) been observed on Shuttle flights, presumably due to the 

chemical stability of these materials. 

Metallic coatings of aluminum, gold or platinum served to completely 

protect surfaces of kapton, mylar, kevlar from oxidation, even for metal 

film thicknesses of only 250 A. 

When material erosion measurements are normalized into a measure of 

reactivity, namely (material loss (in cm))/(fIuence = atoms impinging on 

surface per cm2), this reactivity is more or less a constant for a given 

material, for example: the reactivity of kapton is 1 to 2 x 10-24 cm3 per 

oxygen atom. 

A baffled pressure gauge on the STS-3 flight showed pressure increases up 

to a factor of 200 over the expected normal ambient atmospheric pressure, 

due to ram effects of the vehicle's 7.55 km/sec motion into the atmospheric 

gas ( 162). 

The temperature-controlled quartz crystal microbalances (TQCM's) on the 

Contamination Monitor Package on STS-3 showed accretion rates as high as 

29 angstroms per hour (at -3OOC) of molecular contaminants during portions 

39 
PERKIN-ELMER ER-591 

of this 241 kilometer altitude mission, and evaporation rates as high as 37 

angstroms per hour (at +600C) during llbakeout't periods (163, 164). 

Observations of the diffuse glow surrounding the Orbiter surfaces which 

faced into the direction of motion of the vehicle are consistent with an 

interaction of atmospheric 0 with the vehicle surface or with adsorbed OH 

in the vehicle surfaces. At a 240 km altitude, the flux of oxygen atoms 

striking the exposed surface areas of the Orbiter is 1.4 x 1015 atoms (cm2 

sec)-l (6, 12, 94, 95, 112, 116, 121, 131, 132). 

o 

The lessons learned from these Space Shuttle experiments conducted to date include: 

(1) Reactive optical coatings (such as osmium and presumably aluminum) will oxidize 

very quickly in a Space Shuttle environment at altitudes 6 315 km, (2) the rate of 

reaction is greatly enhanced by exposure of the surface to the vehicle flight direction, 

(3) the Shuttle is a major source of outgassing itself, so that even surfaces sheltered 

from the vehicle ram direction still suffer oxidation. 

40 
PERKIN-ELMER ER-591 

SECTION 3 

THE DESIGN OF AN ORBITAL COATING LABORATORY 

The real purpose of an Orbital Coating Laboratory is to assess the viability of coating, 

cleaning and re-coating reflective elements for use in the far ultraviolet in a space 

vacuum environment. In this section we will derive a conceptual design for an orbiting 

laboratory that is capable of both coating experiments and feasibility demonstrations. 

We will list the research questions that could be addressed with a versatile coating 

laboratory, the requirements on the vehicle carrying such a laboratory, and describe a 

possible experimental layout. 

3.1 RESEARCH QUESTIONS TO BE ANSWERED 

The principal research question to be studied in an orbiting optical coating laboratory is 

the lifetime of the far ultraviolet reflectivity, determined by oxidation, of pure 

aluminum optical coatings deposited in the vacuum of space. We need to understand 

the way in which this lifetime may be maximized by careful selection of the range of 

telescope pointing direction with respect to the orbital flight direction and by other 

geometrical shielding techniques. The goal of these lifetime measurements is to 

provide sufficient data to allow extrapolation to a real orbiting telescope configuration, 

so as to allow estimation of lifetime for a real FUV telescope in a particular orbit. A 

related research question of interest for future solar-pointed telescopes is to investigate the dependence of t h e r a t e of oxidation of aluminum on incident solar radiation. 

Another research problem to be studied is the reflecting properties of an aluminum 

coating that has been deposited on top of a thin oxide layer or even a built-up sandwich 

of many AI + A1203 layers, all produced in a space vacuum environment. The ability of 

such a mirror or grating to continue to provide high reflectivity and low scatter at all 

wavelengths needs to be tested. 

Secondary research goals for an orbiting optical coating laboratory are concerned with 

the build-up and removal of contaminating films which again can spoil the far 
PERMIN-ELMER ER-591 

ultraviolet reflectivity of optical surrxes. Whereas a fresh aluminum coating is known 

to adhere well to an A1203 film, most evaporated coatings do not adhere well to an 

organic polymer film and therefore an organic contaminant layer must be removed 

before re-coating. One possible cleaning technique that cannot easily be simulated in a 

ground laboratory test is exposure of the contaminated surface to the flow of atomic 

oxygen in the residual Earth atmosphere, which has high oxidizing power at an orbital 

velocity of 7.6 km/sec (4.8 electron volts of kinetic energy). Atomic oxygen cleaning 

by either a built-in atom bombardment source or by the orbital ambient oxygen flow 

can be expected to literally burn off an organic contaminant layer but also of course 

oxidize an aluminum surface. The experiment that needs to be conducted is to learn 

whether aluminizing which follows such a cleaning process can yield a high-reflectivity 

low-scatter mirror for ultraviolet observations. 

Finally, experiments on the rate of degradation of reflectivity due to photolyticallyreacted outgas contaminants are possible in the same orbital laboratory, since the 

natural "oil-free high vacuum system" of space provides a controlled enviornment for 

measuring the rate of degradation versus ultraviolet flux, substrate temperature and 

ambient gas density. Such experiments are of key interest to future solar telescopes 

such as for the telescope optics and the heat rejection mirrors for NASA's Solar Optical 

Telescope (56, 165, 167, 168). 

Other uses for a space-based "vacuum research facility" have been described in a very 

interesting 1979 JPL study on "Instrumentation Concepts and Requirements for a Space 

Vacuum Research Facility" (1 66). 

3.2 ORBIT 

How high an orbit is required to perform useful in-space coating experiments, and how 

high an orbit will probably be required to provide 6 months of useful life for an actual 

bare aluminum telescope? We will consider the second question first. 

From the material reviewed in Section 2.1, we concluded that an A1203 thickness of 

~5 A was the maximum. tolerable oxide thickness if significant loss of far ultraviolet 

reflectivity is to be avoided. We have used a general purpose computer program 

("OPTCOAT", Appendix B) to calculate the normal incidence reflectivity of thin layers 

42 
PERKIN-ELMER ER-591 

of A1203 over aluminum for the full wavelength range from A= 500 ft. to 1800 8, as a 

function of oxide thickness. For these calculations, we used optical constants for 

aluminum from the Deutsche Physikalische Gesellschaft "Physics Data" compilation 

(169) and optical constants for A1203 from the Hamburg Electron Synchrotron (DESY) 

group (170). These calculations (Figure 21) show that a 5 A A1203 thickness (about 5 

monolayers) leads to a ~30% loss in "figure of merit" for a bare aluminum mirror. (The 

figure of merit here is defined as a weighted average of the normal incidence 

reflectivity from h = 500 to 1800 8, with extra weight on the astrophysically 

significant 900 A to 1216 A region.) 

There are many sources of data on what oxygen exposure is required for an A1203 

build-up of the above amount (39, 46, 57, 59, 62, 63, 77, 81, 83, 92). Estimates of this 

exposure based on these data range from 15 to 3000 Langmuirs" of oxygen exposure. 

At the low end of this scale, the data of Madden, Canfield and Hass (92) indicate that a 

20% drop in reflectivity at is reached with an air exposure of only 100 

seconds at p S 8 x torr, suggesting a useful lifetime of only ~16 Langmuirs. At a 

high end of the scale, the data of Krueger and Pollack (83) show N 2 A of oxide on 

exposure to 5x torr of dry 02 for 100 minutes, ie. 3000 Langmuirs. The data of 

Kirk and Huber (81) which suggests an oxide thickness of 2 A after 16 minutes of 

2 x torr (200 Langmuirs) may be representative of data close to the geometric 

mean between these two extreme estimates. 

= 1025 

It is clear from all data sources that the first ~2 monolayers of oxide are produced very 

quickly with a high oxygen sticking efficiency while deeper penetration of the oxide 

layer occurs with a much reduced oxygen sticking efficiency (39, 83, 81, 92). See 

Figure 22. 

Taking 200 Langmuirs as a rough estimate of the maximum allowable oxygen exposure, 

a 6 month lifetime corresponds to 1.27 x 1O-l1 torr of oxygen, which occurs at an 

altitude of ~760 km. Since there is at least an order of magnitude possible error in this 

* One Langmuir=10-6 torr-seconds, that is, one second at 10-6 mm Hg, or 10 seconds 

at mm Hg, for example. 

43 
PERKIN-ELMER 

0 

-m 

0 

44 
Sticking Coefficient vs. Weight Goin of O2 

P’ 5xld’Torr “Dry 02* 23.C 

.. .., -0 .. *. e. ** * ’ *. 

0. 

0 1030i Thick SOOhin 0 

1030i Thick SOOhin e. 

.* 

Figure 22. Sticking Coefficient of Oxygen or Aluminum as a 

function of total oxygen weight gain. A monolayer 

of oxygen atoms on each available site corresponds 

to ‘L 7 .Ox10-8 gm/cm2. From Krueger and Pollack (83). 

45 
PERKIN-ELMER ER-591 

exposure estimate, the minimum allowable altitude could be as high as 900 km (166, 

171, 172). Although this estimate is somewhat more optimistic than the estimate of 

1500 km for required perigee altitude given by Hass and Hunter (591, the estimate of 

-900 km still poses a dilemma for the concept of flying bare aluminum optics in Earth 

orbit. Altitudes no higher than 900 km (486 nautical miles) can be tolerated in order to 

avoid interference with the trapped radiation belts and the South Atlantic Anomaly (7). 

The detectors typically used in far ultraviolet astronomy are sensitive to charged 

particles and the fraction of the Earth's surface that is free from high energy particles 

shrinks as the altitude increases (7, 173). So to avoid a high level of particle 

background, an ultraviolet space telescope must either be placed below 900 km or in a 

circular or somewhat eccentric geosynchronous orbit. The geosynchronous orbit is 

almost certain to provide a sufficient lifetime against oxidation, provided the instrument and spacecraft are designed to release extremely low levels of outgassed oxygen 

or water vapor. 

The one exception to the minimum altitude requirement imposed by oxidation considerations is the molecular shield situation, discussed in the next section. 

The above orbital altitude requirements for a long-lived ultraviolet telescope using bare 

aluminum optics do not apply to the Orbital Coating Laboratory. The in-space optical 

coating experiments that we envision can best be done at a much lower altitude where 

the time constants of oxidation reactions can be more easily measured. The important 

constraint is only that the measurements can be extendable to allow predicting 

lifetimes for higher orbits. In order that a lifetime of, say, 90 minutes (one orbit) or 

more can be achieved with an oxygen concentration equal to the ambient density, an 

oxygen partial pressure of 43.7 x torr is necessary, and an altitude 3 360 km is 

required (166, 171, 172). See Figures 23 and 49." This is in the range of current Space 

Shuttle altitudes such as the Long Duration Exposure Facility (LDEF) mission 

(463 kilometers). The preferred orbit for an Orbiting Coating Laboratory would be 

* For an ideal gas, p (torr) = 1.03 x 10-19. n (atoms/cm3). T (OK). 

46 
PERKIN-ELMER 

E 

0 

r-4 

c - 

W 

P 

3 

c 

3 

4 

800 WO loo0 io2 io4 io6 io8 loio 

-3 TEMPERATURE, K 

NUMBER DENSITY, cm 

Figure 23. Constituent Number Density and Temperature as a 

Function of Altitude for a Terrestrial Atmospheric 

Model with an Exospheric Temperature of 1000°K (166). 

47 
PERMIN-EL ER-591 

elliptical, spanning altitudes "etween ~400 km an^ -9 m, because with this range of 

altitudes sampled, the ambient atmospheric density is a variable that can be put to use 

in experiments, as was done with Atmospheric Explorer satellites (121, 132). 

In fact, atmospheric density and the atomic oxygen concentration are a strong function 

of solar activity (Figure 24) and of time in the solar cycle (Figure 25). An orbital 

aluminizing laboratory and an aluminum-coated space telescope must be designed for 

the worst case concentration (135, 172). 

In Section 3.4 of this report, we suggest that the Sun be used as a relatively constant 

ultraviolet source for the purpose of measuring reflectivity and also for contamination 

experiments involving photopolymerization. Therefore there is an optimum orbital 

configuration for an Optical Coating Laboratory: the Sun should be near an orbital 

pole, so that the line of sight into the laboratory's optical measurement chamber is 

roughly perpendicular to the flight vector for reflectivity measurements, and never 

need be closer than 900 to the flight vector at other times. This suggests that the 

orbital plane should be as close as possible to perpendicular to the ecliptic plane, 

(inclination 3560). 

3.3 THE MOLECULAR SHIELD CONCEPT 

A concept which has real potential merit is the idea of using a molecular shield in low 

Earth orbit to block the flow of atmospheric gas due to a spacecraft's orbital velocity, 

thereby achieving a large reduction in pressure over the natural ambient pressure at 

that altitude. This concept has been recently studied by workers at NASA's Jet 

Propulsion Laboratory and Langley Research Center (161, 171, 174, 175, 176, 177). 

The concept is simple: Since the orbital velocity of a low Earth orbit satellite 

(-7.6 km/sec) is much higher than the Maxwellian speed of the atmospheric atoms 

(typically ~1.2 km/sec), there is virtually no probability for an atmospheric atom to 

enter an instrument compartment from the hemisphere on the llwakell side, opposite the 

flight direction. This fact has led researchers to consider the design of experiments in 

a 5pace Vacuum Research Facility" (166) to use this unique opportunity of an ultrahigh vacuum together with a collimated 5eV atomic beam (the atmospheric flow). 

Experiments that have been suggested for such a facility include surface physics 

48 
PERKIN-ELMER 

ATOM1G.OXYGEN CONCENTRATION AND 

ATMOSPHERIC DENSITY AS A 

FUNCTION OF ALTITUDE 

21' I I 1 I 

\. \0 ATWAIC OXYGEN 

1% X ATMOSPHERIC DENSIT 

~JNIMUM 

SOLAR 

- ACTIVITY 

\ 

T'RoS-N' NOAA 6, 1 ,-NIMBUS ' 

400 600 800 loo0 1200 

ALTITUDE (kilometers) 

Atomic Oxygen Concentration and Atmospheric 

Density as a Function of Altitude and Solar 

Activity, from Reference 135. STS-3 and -4 

show the altitudes for two early Shuttle flights. 

49 
PERKIN-ELMER 

C 

- 

m 

N 

a, 

Li 

rl 

Fr 

2Y 

50 
PERMIN-ELMER ER-591 

studies, electron spectroscopy for chemical analysis (ESC A), molecular beam experiments, gas dynamics and thin film research. The shield material need be no more 

substantial than aluminum foil. Since the mean free path at altitudes of 200 km or 

more is 0.4 km or greater, all atoms or molecules may be considered to follow straight 

line trajectories. 

Figure 26 (1 66) illustrates schematically the molecular shield concept. 

We have written a general purpose computer program (Appendix D) for calculating the 

pressure or the residual density at a test point that is surrounded by an arbitrary 

geometry of shielding in a Maxwellian gas drifting at an arbitrary velocity. Calculations with this program show that even for the worst case atmospheric model 

(exospheric temperature = 2100oK), a factor of 108 reduction in pressure is theoretically achieved by a shield which covers only 2.6 steradians in front of the test point. 

See Figure 27. 

Of course this full pressure reduction will never be achieved in practice because of gas 

released by the payload itself (207). However, with proper care in the selection of 

materials and the timing of gas-venting activities and providing a geometry for rapid 

venting of released gases, it seems likely that a factor of 200 reduction in atomic 

oxygen flux can be achieved with a shield that blocks no more than 50% of the sky from 

view. This would be an acceptable compromise for a far ultraviolet telescope. A bare 

aluminum telescope could then survive for 36 months at an altitude of 600 kilometers, 

close to the planned altitude of Space Telescope. 

What will be the ultimate pressure achievable in a satellite-due solely to outgassing? 

Clean satellites have measured gas densities as low as 2 x lo4 atoms/cm3 (-2 x 

torr). This may be close to the limit attainable with a space telescope. Fortunately the 

lifetime of bare aluminum coatings at this density is >3 years. 

We propose that the molecular shield concept be applied in the Orbital Coating 

Laboratory. In this case the shield need consist of little besides a solid surface facing 

the flight direction and a small shield to shadow any apertures opening to the ambient 

vacuum. 

51 
PERKIN-ELMER 

--/ HEMISPHERICAL SHELL 

MOLECULAR COLLISION / 

Figure 26. Schematic representation of the molecular shield 

geometry in the drifting gas, illustrating typical 

molecular trajectories: (la) and (lb) are freestream molecules where the flux of (la)-type molecules is much greater than the flux of (1b)-type 

molecules; (2) are desorbed molecules from the shield; 

(3) are desorbed molecules from the experiment; and 

(4) are molecules scattered from the Orbiter (from 

Reference 166). 

52 
PERKIN-ELMER b 4 I t I I 5 I 

Figure 27. Pressure Reduction Factor Resulting from a Molecular 

Shield of Various Solid Angles Placed Ahead of a Test 

Point Moving at 7.55 km/sec, for Different Exospheric 

Temperatures, T. 

53 
PERKIN-ELMER ER-591 

3.4 LABORATORY DESIGN 

In the following paragraphs, we will consider some aspects of the conceptual design of 

an orbiting optical coating laboratory. These concepts are obviously very preliminary; a 

more thorough study would undoubtedly find improvements. The dual goals here are to 

conduct a realistic demonstration of the techniques of in-space optical coating with 

pure aluminum, and to carry out experiments that will answer many of the research 

questions discussed in Section 3.1. 

3.4.1 Requirements and Constraints 

In Section 1.2, we listed the general requirements for optical coating in a remote space 

environment. Here we will list some of the requirements and constraints for the 

particular case of a versatile experimental laboratory on a Space Station or platform or 

independent f ree-f lyer . 

I. Low outgassing hardware: The payload must be designed for the lowest 

possible level of in-orbit outgassing. The Space Shuttle may be an 

incompatible vehicle for these experiments unless the laboratory is carried 

at the end of a long boom (166). A more appropriate platform for this 

laboratory will probably be a clean, unmanned space platform (178, 179, 180, 

181, 200) or an automonous 5PARTAN" mission (182). 

2. Heaters: The laboratory should be equipped with heaters to drive off 

adsorbed gases from any adsorption-prone materials. The mirrors should be 

provided with heaters to allow variation of substrate temperature over the 

range 0 to +80OC. 

3. Pointing: The laboratory% entrance aperture will need to be pointed 

towards the Sun (to within - +1/4 degree) and held for several minutes for 

some experiments. A two-axis steering system and a solar aspect sensor 

will be needed. 

4. Coating Runs: Up to 16 independent coating runs must be accommodated. 

The amount of material deposited on each mirror must be somewhat 

controllable. 

54 
PERMIN-EL ER-591 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

Reflectometer-Monochromator: The Laboratory must have provision for 

measuring broad band (AX40 to 100 %) reflectivity over the range from 

X Z 700 A to 2200 8. 

Sensitivity: Reflectivities will be measured ranging from 92% to N 0.1%. 

The reflectometer must be capable of sensing changes in reflectivity of 3% 

(minimum) and a factor of 100 (maximum). 

Pressure Measurements: The Laboratory should be equipped with a device 

to monitor pressures in the optical measurement compartment in the range 

10-10 to 10-5 torr. 

Venting and Outgassing: The laboratory must be sufficiently well vented to 

the ambient vacuum that a high pumping speed is achieved following a 

coating or a cleaning operation. 

Coating Monitor: A quartz crystal microbalance is needed to monitor the 

amount of evaporant deposited on each mirror at each coating operation. 

Atom Beam Cleaning: 

cleaning contaminant films from each mirror prior to re-coating. 

Scatter: Repeated re-coating of a test mirror with intervening oxidation 

may lead to a roughness build-up of the mirror surface (183). Although the 

measurement of mirror scatter is not a primary goal here, the facility 

should have some power to characterize a serious change in mirror scatter. 

Mission Duration: 

most of the experiments suggested in section 4 within a period of -28 days. 

The laboratory must be equipped with a means of 

The laboratory should be capable of performing all or 

3.4.2 Layout 

Three particularly significant design details need to be decided at the start: (1) 

whether to work with numerous small mirror test samples or a few large Yelescopelike" mirrors, (2) the choice of technique for applying an optical coating (thermal 

evaporation, electron-beam evaporation, sputtering, plasma ion deposition), and (3) the 

choice of FUV light source for the measurement of reflectivity. 

55 
PERKIN-ELMER ER-591 

An in-flight optical coating feasibility demonstration has also recently been proposed by 

Dr. William M. Burton of Rutherford Appleton Laboratory (1 48) and called "Aluminum 

Coating Experimentt1 (ACE). Burton's concept called for a number ,(reight) of small 

(~3 cm) mirror samples. We have chosen the alternate concept of two larger mirrors to 

provide a larger amount of coated surface area and perhaps better demonstrate the 

coating of large telescope mirrors. 

The case for thermal evaporation as the means of depositing coatings in space is 

discussed further in Section 3.4.4. Basically, thermal evaporation is known to provide 

smooth and uniform optical coatings with good adhesion properties. Although some 

thermal evaporation techniques (designed for ground laboratories) depend on gravity, 

evaporator designs exist which do not rely on gravity (21). 

Concerning the choice of constant broad-band ultraviolet light source for the measurement of reflectivity, we have selected the relatively simple expedient of using the Sun: 

an intense, more or less constant and reliable source to which the laboratory will have 

access most of the time. Table 2 shows some estimates of the short-term time 

variability (1 minute-1 hour) of the integrated flux from the disk of the Sun at various 

wavelengths (17, 184, 185, 186, 187). The coronal emission lines show the most 

variability, but even for these the whole Sun flux changes by < 10% in 24 hours and 

<-5% in one hour. Since in the concept we are describing, all reflectivity measurements come from ratios of measurements made a few minutes apart, the variability of 

the light source on longer time scales is not important. 

The concept sketched in Figure 28 is a 48 x 36 x 65-inch experiment housing mounted in 

a 2-axis gimbal mount. The experiment system is designed for the direction of 

atmospheric flow to always be within a few degrees of the vector shown. The sides 

marked A, B, C, D, have solid metal walls to block the flow of atmospheric gas. The 

rest of the assembly is well-vented to the "waket1 side of the flow. The side, bottom 

and back walls have a louvre baffle arrangement, C, to shield the interior from the bulk 

flow of the atmospheric gas and from major stray light sources (sunlit Earth, moon) 

while allowing outgas products from the experiment cannister to escape. Items E and F 

are molecular shields to shield the side and bottom walls and the optical aperture. A 

solar aspect sensor H senses the angular coordinates of the Sun with respect to the 

experiment cannister. 

56 
PERMIN-ELMER 

TABLE 2 

ESTIMATED VARIABILITY OF THE SUN 

Continuum Above = 2100 a 

Continuum 1520 A - 2100 8, 

C IV (1550 A) 

Continuum 1216 A - 1520 A 

Lyman -a (1216 

Continuum 800 a - 900 a 

Helium I 584 a 

Continuum 400 - 600 A 

Helium I1 30481 

ER-591 

< 1% 

< 1% 

< 5% 

4 1% 

4 1% 

< 5% 

< 5% 

4 5% 

< 5% 

57 
PERKIN-ELMER 

c 

I 

\\’\\\\\\\ 

\ 

G 

Figure 28. Sketch of Concept for an Orbiting Optical Coating 

Laboratory, with 2-Axis Gimbals for Orienting. 

The heavy arrow indicates the direction of atmospheric 

flow. Items E and F are shPelds to shadow the 

Laboratory from this flow. 
ER-591 PERMIN-ELMER 

It is important that this experiment chamber be mounted (on a space platform, free 

flyer, or on the end of a long arm from the Space Shuttle) so as to minimize or 

eliminate any direct lines of sight from any spacecraft surfaces which are exposed to 

the ram flow, through the baffles into the optical coating laboratory. Surfaces exposed 

to the ram flow of atmospheric gas become themselves-secondary sources of atomic 

oxygen flux and sources of contaminant gases. 

The interior is sketched in Figure 29. Two large flat mirrors, 1 and 2, provide a total of 

4 mirror surfaces (2x2) for coating experiments. The experiment cannister is divided 

into 3 separate compartments: the top coating chamber J, the bottom coating chamber 

K, and the optical measurement L. Each of these compartments is sealed off from each 

other with a solid wall but all three are well vented to the exterior towards the ltwakel1 

side. No combinations of lines of sight exist between the upper coating chamber and 

the lower coating chamber except via 3 or more bounces. 

Each of the two mirrors 1 and 2 can be rotated by 1800 around the axes shown, M, so as 

to turn either face A or face B towards the optical measurement chamber. The 

Itbutterfly valvet1 sealing rings, N, provide a geometrically tight (but not hermetically 

tight) seal around each mirror while still allowing the mirrors to rotate. The mirrors 

are driven by sealed DC torque motors. 

Reflectivity measurements are via a multiple bounce reflectometer, using the Sun as a 

source. The principle is illustrated in Figure 30. A small aperture, P, allows sunlight to 

illuminate the lower mirror. By tilting the assembly with respect to the Sun line over a 

total range of -220, any number between 1 and 6 reflections can be achieved from the 

two mirrors. The ratio of signals recorded with different numbers of reflections allows 

solving for R1, R2, R2, R2, and so on, where R1 and R2 are the reflectivity of the two 

mirrors, independent of the intensity of the source and the sensitivity of the detector. 

For the geometry shown, the angle of incidence on each of the parallel mirrors for n 

reflections is given by 

22 

59 
PERKIN-ELMER 

P 

I E;J 

IFigure 29. Cross-Section Through Interior of Orbiting 

Coating Laboratory, Showing Principal Components. 

Labeled items are defined in text. 

60 
PERKIN-ELMER 

1 

I 

h 

I 

cl 

Figure 30. Reflectivity Measurement Scheme Using 

Reflected Sunlight from Both of Two Mirrors. 

61 
PERKIN-ELMER ER-591 

The benefits of multiple reflections are (1) to allow solving for the individual 

reflectivities, (2) to increase the sensitivity to changes in reflectivity, and (3) to allow 

sampling other portions of the mirror surfaces. 

The reflected radiation is passed through the entrance aperture of a moveable objective 

grating monochromator, Q, whose plane of dispersion is close to the plane of incidence 

of the last reflection. The monochromator selects a spectral band of bandwidth 

Ah = 50-100 to be fed through an exit slit to a detector. The entrance aperture, exit 

slit and detector are all fixed inside the monochromator compartment, and the concave 

reflection grating rotates to scan the wavelength range. The entire monochromator 

assembly must have three degrees of freedom of motion: (1) pivoting through a range 

of N220 to accept the different multiply-reflected rays, (2) swivelling through 1800 to 

view each of the two mirrors, and (3) translation (perpendicular to the page in 

Figure 29) to sample different lateral positions on the test mirrors. 

Each of the two optical coating chambers contain a multi-source rotatable wheel of 

aluminum-loaded heater filaments (R), a coating mask (SI, motor drives (T) and a fast 

atom bombardment (FAB) neutral oxygen atom beam source (U) for the mirror cleaning 

(152, 196), all mounted on a base plate, Y. None of these devices requires a pressurized 

compartment to operate, so the coating compartments are fully vented to the outside. 

The items marked QC are temperature-controlled quartz crystal microbalances 

(TQCM'S) for monitoring the coating thickness immediately next to each mirror. 

Additional monitors QM in other locations serve to test for evaporant deposition in 

other parts of the chamber away from the mirror. 

Finally, in Figure 29, item V is a pressurized sphere of oxygen to supply the atom beam 

cleaning units, and item W is a microprocessor-based control unit and data processing 

unit. Item X in Figure 28 is a moveable door (containing the small aperture P) which 

can be swung open to illuminate a large fraction of both mirrors with one Sun, to test 

for solar-induced degradation. Small filters can also be conveniently located at 

location P. A thin fused silica filter here would allow separating the solar farultraviolet from the near-ultraviolet entering the system. 2 is an aperture that can be 

opened on command to expose mirror 2 to the flux of high kinetic energy (5 eV) atomic 

oxygen from the orbital flow. , 

62 
PERKIN-ELMER ER-591 

Not shown in Figure 29 are high-vacuum pressure monitors, sensitive over the range 

10-lo torr to 10-5 torr, in each of the three compartments. 

Figures 31 and 32 provide additional views of this arrangement. Figure 31 is a top view 

showing the projection of the two mirrors and the small aperture from the top, and 

showing a cross-section of one possible arrangement for baffles at the side and back 

walls. Figure 32 shows one of the interior solid separation walls, separating the optical 

measurement compartment from the lower coating chamber. Cables inside the hubs on 

which each mirror pivots carry power to controllable heaters for each mirror, so that 

substrate temperature can be controlled in experiments where this is desireable. 

3.4.3 Coating Materials 

What coating materials should an orbiting coating laboratory be prepared to evaluate? 

No single film material exists with a higher reflectivity over the broad far-ultraviolet 

region of interest to ultraviolet astronomy than pure aluminum. Hass and Hunter (59, 

63) have shown that iridium overcoated with 265 8, of unoxidized aluminum gives a 

significant boost to the 500-800 A reflectivity, over that of pure aluminum, while the 

reflectivity of this combination from h = 900 8, to 1500 A is not greatly reduced from 

that of pure aluminum. We have verified the results of Hass and Hunter using the 

program of Appendix B and the optical constants of Appendix C, finding an optimum 

aluminum thickness of ~280 A to maximize a "figure of merit" for far-ultraviolet 

astronomy. 

Unfortunately, iridium has a very high melting point and therefore would introduce 

difficulties including a much higher power requirement than aluminum. As there seems 

to be no compelling reason to apply iridium, tungsten, or the other refractory metals in 

space, we will not consider these further. 

Silicon carbide has recently received much attention as a high-reflectivity material for 

the far ultraviolet and extreme ultraviolet (44, 77, 88, 108, 109, 135, 201-205). It has a 

reflectivity over the A= 500-900 region (Figure 3) which compares well with the 

transition metals (202, 203) and it can form an extremely smooth surface (201). 

However, the process of deposition is complex and requires very high temperatures 

(204, 205). Although a fine mirror substrate material, Sic is not yet a viable coating 

material. 

63 
PERKIN-ELMER 

I 

F / 

/ 

\ 

\ 

- 

G 

I 

I 

-G 

Figure 31. Top View of Orbital Coating Laboratory, 

Showing Internal Baffle Arrangement. The 

Flow of Atmospheric Gas is from the Top. 

64 
PERKIN-ELMER 

Figure 32. Isometric Sketch of Interior of Orbiting Coating 

Laboratory, Showing One of the Solid Walls Separating 

Interior Compartments, in which is Mounted One of the 

Rotatable Test Mirrors. 

65 
PERKIN-ELMER ER-591 

Is there a "magic1* protective material which could be used, in a very thin film, over 

pure aluminum, which might retard the rate of aluminum oxidation somewhat without 

destroying the far ultraviolet reflectivity? We have not found such a material. Using 

the optical constants for lithium fluoride from Roessler and Walker (188) (Appendix C), 

we have found that even as little as 10 8, of LiF over aluminum spoils the "figure of 

merit" (page 43) by N35%. 

Because all fluorides and oxides will have similar deep absorption bands in the 

ultraviolet, such materials are unacceptable for protective coatings over aluminum. 

A thin metallic protective-overcoating, if one existed that did not decrease the net 

reflectivity of aluminum, would also be likely to diffuse together with the aluminum 

over a period of months, spoiling the advantage of the two-metal coating (62). 

3.4.4 Evaporators 

We have examined several options for depositing a clean, smooth aluminum coating of 

-500 A on mirrors of 16 to 19 inches in size: thermal evaporation, electron-beam 

evaporation, sputtering, and chemical reduction (2, 189). 

Thermal evaporation, the process of heating a crucible or a helix of tungsten wire until 

the aluminum melts and evaporates, is a well-understood technique which does not 

require gravity to be effective (19, 21). The power requirements are not severe. 

Electron-beam evaporation in principle might be more efficient than thermal evaporation because an electron beam can heat and vaporize a small section of the material at 

a time. However, the rate of evaporation cannot be controlled as well as for thermal 

evaporation, heat loss from the cruicible forces the power requirement up, the resulting 

coated surfaces are often not as smooth, and the required high voltage is an additional 

risk (150). 

Biassed sputtering involves ion bombardment of the target material. The disadvantage 

of this technique is that the coating thickness uniformity is never as good as for 

thermal evaporation. Sputtering works best with a small aperture (small solid angle) 

while a larger solid angle is required here. While conventional diode sputtering 

(involving two electrodes) is a very difficult technique to use for optical coating, a 

variation called plasma ion sputtering may be more viable. 

66 
PERKIN-ELMER ER-591 

However, it is our conclusion that thermal evaporation provides the highest reflectivity, 

the best smoothness, the best uniformity, and the highest degree of thickness control of 

the available techniques. Aluminum wets a hot tungsten ribbon very effectively and 

provides the opportunity for either slow or fast evaporation. 

How often can a tungsten wire be re-wetted with fresh aluminum and thereby re-used? 

Eventually the aluminum and tungsten will begin to alloy and the tungsten becomes 

brittle. The probable life of a tungsten coil is only 2 or 3 uses. Therefore we 

recommend a turntable of N 16 pre-loaded evaporators, each consisting of multistrand 

helical tungsten coils, and each of which would be used only once. As the turntable is 

rotated, a new tungsten filament is brought into position under a conical "coating gunf1 

and is connected to the power supply. 

Laboratory experimentation with optimizing the design of a coating gun is needed. A 

few concepts are sketched in Figure 33. If aluminum vapor were to specularly reflect 

from the walls of a coating gun (which it does not), then the "Winston cone" (compound 

parabolic concentrator, Figure 33(a) might provide the basis for a good coating gun 

design, as this figure provides a uniform beam which is spread uniformly over a desired 

solid angle with no rays outside this solid angle (190, 191, 192). Figure 33(b) shows a 

large solid angle conical gun with internal masks to define the area covered. 

Figure 33(c) shows a straight "gun barrel" design that might be appropriate for coating 

mirrors in-situ in a space telescope, when the coating guns could be placed at a large 

distance from the mirror. It is known that better smoothness and higher reflectivity 

(higher packing density of the coated material) are achieved when the evaporated 

material is incident on the substrate at near-normal incidence. 

3.4.5 Stray Light Control 

A major concern of those who have considered coating telescope mirrors in place in 

space has been whether or not the stray light characteristics of the telescope can be 

maintained after the telescope barrel has been filled with aluminum vapor. Inter-beam 

collisions of aluminum atoms in the vapor beam can lead to a diffuse distribution of a 

small fraction of the evaporant beam. In solar telescopes where the flux of visible light 

is orders of magnitude stronger than the flux of EUV radiation, and in celestial 

67 
PERKIN-ELMER 

m 

m 

a 

n 

68 
PERKIN-ELMER ER-591 

astronomy, where 26th magnitude stars are to be studied in the presence of a full moon 

300 away in the sky, the control of stray light requires painstaking care in design. 

This subject can certainly be studied by ground laboratory experiments. Information 

available today indicates that at pressures $10-6 torr, the sharpness of the edge of a 

shadow formed by a mask in a coating chamber is very fine. But we are not aware of 

experiments that have been aimed at characterizing the amount of scattered vapor or 

at optimizing the design of a coating system to minimize the amount of stray vapor at 

large angles from the desired direction. 

Aluminum coating in ground-based coating chambers is usually applied at a high 

deposition rate to minimize the amount of oxidation (92, 63, 145). It may be possible to 

achieve a significantly better and more oxygen -free vacuum in a space coating facility 

and therefore use much lower deposition rates. In this case, the inter-beam collisions 

are greatly reduced and the amount of stray vapor expected is much less. 

It is possible that a small amount of stray aluminum deposited on black baffles does 

very little harm in terms of scattered ultraviolet light, provided that the black surfaces 

are rough. The roughness of most black surfaces ensures that any deposited aluminum 

will be non-continuous and that any scattered light will still be trapped by the geometry 

of the rough surface (150). 

In the design of an orbital coating laboratory, TQCM's should be arranged to monitor 

the amount of stray aluminum received during the evaporation process in directions 

well away from the mirror being coated. 

The control of stray light in the actual reflectometer arrangement suggested in 

Figure 29 must also be considered. Since the Sun is much brighter than any other 

sources of possible light entering the optical measurement chamber, L, baffles like 

those sketched in Figures 28 and 31 should be sufficient protection for this chamber. 

The location most sensitive to stray light in reflectivity measurements is within the 

monochromator, Q, where a particular wavelength interval is fed to a detector.. 

Therefore the entire monochromator is enclosed in a light-tight box which accepts only 

light from the appropriate direction. 

69 
PERKIN-ELMER ER-591 

3.4.6 Reflectometer 

The method of measuring reflectivity suggested in Section 3.4.2 and sketched in 

Figure 29 is to allow unfocused parallel sunlight from a small aperture to reflect from 

the one or two test mirrors and enter a concave objective reflection grating monochromator. The suggested configuration is a pseudo-Rowland circle configuration in 

which the grating is rocked to scan in wavelength but the total included angle, d+/C), is 

held constant (Figure 34). 

The entrance aperture to the monochromator is roughly the same size as the entrance 

aperture into the optical measurement chamber. With a grating of 600 lines/mm and a 

total included angle d+/3 = 350 and with a radius of curvature of 200 mm, the range of 

wavelengths 440 A to 2200 1$. can be scanned by rotating the grating through 100, with a 

dispersion of ~35 A/mm. A fixed exit slit of ~1.5 mm width is placed ahead of the 

detector, which could be a National Bureau of Standards windowless A1203 far 

ultraviolet photodiode (193, 194). This detector serves well from the shortest 

wavelengths to Lyman-d (1216 A). Longward of Lyman-o(, the efficiency of this 

detector falls off and an alternate detector might be required. 

The only moving part within the monochromator is the loo scan motion of the grating, 

controlled by a sealed DC stepper motor. However, three degrees of freedom of motion 

are required for the entire monochromator package: (1) rotation through a range of 

220 to change the line of sight, (2) 1800 inversion to face the other test mirror, and (3) 

a lateral motion to Scan different portions of the test mirrors. These motions are 

indicated schematically in Figure 35 and are also controlled by sealed DC stepper 

motors. 

3.4.7 Plasma Discharge Cleaning 

The usual means of preparing a substrate for optical coating is to establish a glow 

discharge in the vicinity of the optic by allowing a pressure of ~50 microns Hg (0.05 

torr) of argon or oxygen (49, 51, 57, 91, 153, 195). This procedure apparently oxidizes 

and vaporizes all oxidizable contaminants on the mirror surface. See Figures 15-17. 

The effect is to improve the adhesion of the coating and increase the reflectivity of the 

resultant coated mirror. 

70 
PERKIN-ELMER 

Figure 34. Schematic Diagram of Monochromator for 

Measuring Reflectivity. Parallel Sunlight 

from the Flat Mirrors Enters the Enclosure. 

The Concave Grating is Rocked about an Axis 

Perpendicular to the Page to Scan Wavelength. 

71 
PERKIN-ELMER 

c-) n 

ISO" 

Figure 35. Top View of the Monochromator Package Showing the 

Desired Three Degrees of Motion: (1) Rotation 

through % 22O to Change Line of Sight, (2) 180' 

Reversal, to View Other Mirror, (3) Sideways 

Motion to Change Strip of Mirror being Tested. 

72 
PERKIN-ELMER ER-591 

However, the need to pressurize the mirror compartment and the somewhat indiscriminant nature of the plasma cleaning process, which can attack other surfaces near the 

mirror, makes this technique unattractive for use in a space telescope. 

An alternative to the plasma discharge is the more highly controlled, high vacuum, 

technique of an argon or oxygen ion gun, defocused so as to spread the ion beam over an 

area on the mirror surface, which is then scanned over the entire mirror area, and 

removes contaminants by a sputtering mechanism. But again the presence of an intense 

level of ions may be incompatible with a sophisticated telescope environment. 

The cleaning technique which possibly offers the best advantage is the fast atom 

bombardment (FAB) gun technique (152, 196) in which a beam of high kinetic energy 

energetic neutral atoms of a chosen gas is directed at a target to be cleaned. This 

technique is used in the semiconductor industry where a concern for ion beam-induced 

substrate ion migration argues against ion glow discharge or ion gun techniques. In the 

FAB technique, atoms are ionized, accelerated and neutralized as they are emitted by 

the atom gun. The device is compact and uses only DC voltages. This device could be 

made to scan over an entire mirror surface area just as an ion gun. 

Oxygen is a preferred material for the FAB beam as its reactivity provides extra 

cleaning power over an argon beam. The required voltage is 500-2000 volts; the 

required current is 5 to 50 milliamperes. Therefore, the required power is only 2.5 to 

100 watts (152). 

. All of the above cleaning techniques remove only oxidizable or loosely-bound chemicals 

from a mirror surface. An aluminum oxide layer is very resistant to attack and is not 

removed by any of these techniques. Our approach here is to let the A1203 layer 

remain and clean this surface for subsequent aluminization. 

3.4.8 Atmospheric Oxygen Cleaning 

An interesting question is whether the high velocity (7.6 km sec-l; 4.8 electron volts) 

atomic oxygen flow streaming past a telescope in low earth orbit can be put to use in 

lieu of the above neutral atomic beam technique described above. This concept can be 

easily tested in the orbital coating laboratory configuration described here. When the 

small door shown (2) in Figure 29 on the forward side of the structure is opened to the 

73 
PERKIN-ELMER ER-59 1 

atmospheric flow, a beam of predominantly oxygen atoms is directed against one of the 

mirrors. The ability of the atmosphere itself to remove a polymerized organic film has 

in essence already been demonstrated by the materials studies carried out on the early 

Shuttle flights (Section 2.3). 

3.4.9 Liquid Cleaning 

Cleaning telescope mirrors by means of liquids seems quite incompatible with the insitu re-coating of telescope mirrors.. The absence of both gravity and air pressure 

makes the handling of liquids very awkward, and we will therefore not consider the use 

of liquids in an orbital coating laboratory. 

Liquid cleaning might possibly find a use in a separate dedicated orbital coating 

facility, in which a raw mirror blank is handled in a sealed container (2,3). 

The one type of cleaning in which liquids might be desireable is the removal of dust 

particles. Clearly the need for a dust-free substrate is just as important when a mirror 

is re-coated in space as when it is originally coated in a ground-based coating chamber. 

How may dust be removed in an orbiting telescope environment? This is a question thGt 

needs to be further studied. Anti-static sources such as ultraviolet light sources, 

piezoelectric crystals, alpha particle emitters may be considered. However, the best 

baseline plan would seem to be to avoid carrying dust into orbit at the beginning. 

3.4.10 Power Supplies 

Although the power requirements for evaporating aluminum in a space telescope may 

have been one factor deterring investigators from attempting optical coating in orbit in 

the past, the power is no longer a concern by the standards of todays' spacecraft and 

future space telescopes and space platforms. Since we are considering, for a space 

telescope, re-coating operations at very infrequent intervals (- 6 months or more), the 

average power is of course negligible. 

For the Orbital Coating Laboratory, the power estimate during each coating operation 

is 30 to 150 watts for a maximum of 2.5 minutes. The maximum current and voltage 

might beN30 amperes of unregulated power at 5 volts. The precision of the coating 

74 
PERKIN-ELMER 

thickness deposited is determined by the a e and cl 

ER-591 

je timing of a mask, and not by 

the control of power to the tungsten filaments. 

3.4.1 1 Pointing System 

The requirements for pointing the Orbital Coating Laboratory with respect to the flight 

vector and the Sun line have been discussed in the introductory paragraphs of section 

3.4. The need to avoid a high flux of atmospheric atomic oxygen into the laboratory 

requires that the "optical axis" of the laboratory lie within the 550-wide cone with 

respect to the instantaneous flight vector shown in Figure 36. Reflectivity measurements can only be made when the Sun is in the figure of revolution generated by this 

cone (that is, a 550-wide band around the sky). A high inclination orbit can satisfy this 

requirement for a larger fraction of the time. 

Of course, the celestial co-ordinate of the flight vector is constantly changing. 

Therefore, the Sun may not be visible by the reflectometer for more than N 15 minutes 

at a time. The pointing of the laboratory is controlled to track the Sun during 

reflectometer measurements (that is, to control the location of the spots illuminated on 

the two test mirrors). At other times, the pointing is controlled to track the flight 

vector. All of this pointing control is managed by the Orbital Coating Laboratory's 

microprocesso When the Sun is in view, the exact solar aspect is measured by a 2- 

dimensional imaging solar aspect telescope, co-aligned with the laboratory's "optical 

axis", which has a field of view of ~550 width. 

Since a set of reflectivity measurements covering the entire wavelength range 400 to 

2200 A takes only 10 minutes, the finite duration of the solar exposure is not a problem. 

The (e,$) tilt of the laboratory with respect to the Sun is controlled by the 2-axis gimbal 

arrangement shown in Figure 28. The pointing of the "windward" side of the laboratory 

with respect to the flight vector is controlled by the orientation of the vehicle carrying 

the laboratory, in this concept. 

3.5 ASTRONAUT INVOLVEMENT 

The concept for an Orbital Coating Laboratory that we have described is for a 

remotely-controlled laboratory in which scientists or payload specialists control the 

75 
PERKIN-ELMER 

Figure 36. Constraint on Pointing of Orbital Laboratory Due to 

Flux of Atmospheric Atomic Oxygen. 

of the Laboratory can Point into the Figure uf 

Revolution Generated by a 55O-wide Cone. 

Measurements can be Made Only when the Sun is Within 

this Allowed Range. 

The Optical Axis 

Reflectivity 

76 
_- 

PERKIN-ELMER ER-591 

experiments and receive the data in near-real time. The role of astronauts is largely in 

extra-vehicular activity (EVA) servicing. The most important need for astronaut 

involvement is in changing the two evaporant source disks, which are accessible through 

service doors just visible in Figure 28. Provision for these replaceable units will be 

useful for testing new coating materials or changing the quantity of evaporant loaded 

into the laboratory. 

Astronauts might also be required to deploy or modify the arrangement of a large 

external molecular shield, which could serve to reduce still further the oxygen atom 

flux in the vicinity of the laboratory in low Earth orbit (166, 174, 175, 177). 

77 
PERMIN-ELMER 

SECTION 4 

ER-591 

EXPERIMENTS WITH AN ORBITAL COATING LABORATORY 

Assuming that an optical coating laboratory in space similar to the concept described in 

the preceding sections is available, we now will discuss some of the demonstrations and 

experiments that can be carried out. In this section we will briefly describe the 

procedures to be followed for each experiment. 

4.1 RATE OF ALUMINUM OXIDATION 

A key experiment or series of experiments is the measurement of the rate of 

degradation of far ultraviolet reflectivity, as a function of wavelength and as a function 

of environmental conditions. 

A coating and reflectivity measurement is typically carried out as follows, assuming a 

clean aluminum or oxidized aluminum substrate is available: 

A. Coating Procedure 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

Position laboratory to optimize "molecular shield" geometry. 

aperture closed or pointed away from Sun. 

Rotate aluminum source wheel to position source in evaporation 

position. 

Rotate one or both of desired mirror test surfaces toward Coating 

Chambers. 

Set substrate temperature to desired temperature. 

Measure status of all thermistors and TQCM's. 

Pre-heat tungsten filament to outgas source, with mask over source 

gun. 

Full evaporation power to filament. 

Sun 

78 
PERMIN-ELMER ER-591 

8. 

9. 

10. 

11. 

12. 

13. 

Open and close mask for set period of time (typically 30 seconds). 

Filament power off. 

Measurement status of all thermistors and TQCM's. 

Substrate heater power run-down. 

Rotate freshly-coated mirror surface into optical measurement compartment (Sun aperture closed or pointed away from Sun). 

Allow entire laboratory to outgas in optimum "molecular shield" 

geometry for 30 minutes - 12 hours (depending on orbit). 

B. Reflectivity Measurement Procedure 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

Open Sun aperture. 

Fine-tune the angular position of mirrors 1 and 2 if desired. 

Point laboratory optical axis in (e,?) to the llR1ll, position (see 

Figure 30). 

Use solar aspect camera to lllock-onll to this orientation of laboratory. 

Position monochromator to the llR1ll position. 

Scan grating angle to record once-reflected solar spectrum. 

Re-point laboratory optical axis to the 11R1R211 position. 

Use solar aspect camera to lock-on to this orientation. 

Position monochromator to the 11RlR211 position. 

Scan grating to record twice-reflected solar spectrum. 

Compute reflectivities. Compare to previous measurements. 

2 22 Proceed to R1R2, R1R2 etc. positions if desired. 

The coating procedure is estimated to require 5 minutes. The above reflectivity 

measurements require about 6 minutes. Much of the above procedures is automatically 

controlled by the laboratory microprocessor to minimize the elapsed time. 

79 
PERMIN-ELMER ER-591 

The measurement of coating lifetime is then made by repeating the above reflectivity 

measurements at frequent intervals. The laboratory microprocessor records the 

pressure in the optical measurement compartment versus time and keeps a running 

measure of the ambient gas exposure age in Langmuirs (torr-seconds). The microprocessor is also, at all times, keeping arunning tally of the Sun exposure of each area 

element of all four optical test surfaces. 

This sequence of optical coating with aluminum followed by reflectivity measurements 

is the kernel of the in-orbit aluminizing demonstration that is one of the main purposes 

of this orbital coating laboratory . 

4.2 SHUTTLE/SPACE STATION RAM FLOW EFFECTS 

Another class of experiments that can be carried out with an Orbital Coating 

Laboratory is the examination of the effects of the highly asymmetric (non-isotropic) 

distribution of flux of atmospheric gas. What reduction in pressure can actually be 

achieved when the laboratory is shielded from the direct flow? How does the net 

pressure in the optical measurement compartment depend on the attitude of the 

laboratory with respect to the flight vector? The goal of these studies is to aid in the 

design of future bare aluminum telescopes. What latitude in pointing direction will such 

telescopes have, to avoid the risk of mirror oxidation? 

Two methods are available to answer the above question. One method is simply to 

measure pressure by an auxilliary ionization gauge located in the optical measurement 

compartment. This gauge would have a range of -10-4 to 10-10 torr. As different 

laboratory attitudes are samples (and altitudes as well, if this variable is available), the 

laboratory can be characterized in terms of its ability to shield the region inside from 

molecular flow coming from various directions. The second method, which could be 

used for net pressures in the range of -10-10 to 10-13 torr range, is to use the rate of 

oxidation of aluminum as a highly sensitive measure of the amount of oxygen reaching 

the mirrors. 

These experiments are intended to provide a real experimental check of the theoretical 

calculations of gas density in a shielded geometry (174, 175). At the same time, these 

measurements will aid in the characterization of the oxygen component of the 

atmosphere in the altitude range 400-1000 km. 

80 
PERMIN-ELMER ER-591 

Experiments in which the forward side aperture door (facing the atmospheric flow) is 

opened to allow the 5 eV atomic oxygen beam to directly irradiate a freshly aluminized 

mirror will allow testing the linearity condition (that a high flux for a short time 

produces the same oxidation as a low flux for a long time). The atmospheric atomic 

beam also provides an opportunity for studying basic surface physics questions that 

cannot easily be studied in ground laboratories. Does irradiation of pure aluminum by 

5 eV oxygen atoms lead only to oxidation, or is material actually removed by 

sputtering? Examining the scatter performance of the test mirrors may help to answer 

this question. (See Section 4.4). 

4.3 RATE OF PHOTOPOLYMERIZATION 

A secondary purpose of the Orbital Coating Laboratory is to characterize the rate of 

photopolymerization when sunlight is incident on a freshly-coated aluminum mirror in 

the presence of hydrocarbon gases. In a sense, this surface reaction is the opposite of 

oxidation, as it can occur in the complete absence of oxygen, and in fact may be cured 

by the addition of oxygen. This reaction is of interest for estimating the lifetime of a 

solar-pointed ultraviolet telescope using bare aluminum-coated mirrors. The photopolymerization reaction has been observed in solar space telescopes and in ground 

laboratory experiments and can be visualized as the formation of long-chain hydrocarbons formed on a mirror surface in the presence of both organic gases and intense 

ionizing radiation (16, 61, 65, 66, 69, 75, 110, 130, 72, 17, 49, 50, 56, 115). However, it 

is not known what role, if any, the substrate material plays in catalyzing this reaction. 

* 

Two experiments can be conducted. One experiment is to test for the build-up of a 

polymer film due to the natural outgassing of the laboratory and surrounding hardware. 

The second experiment is to introduce a known amount of a known compound (say, 

propane or butane) and thus provide a much better controlled experiment. The 

procedure might go as follows: 

1. Orient the laboratory to maximize "molecular shield" effect. 

2. 

3. Measure reflectivity versus wavelength according to the procedure on 

Coat both mirrors according to procedure on Page 78. 

Page 79. 

4. Point the laboratory optical axis to the Sun. 

81 
PERKIN-ELMER ER-591 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

Open the large aperture door to illuminate a maximum area of both mirrors. 

Expose mirrors for ~1 hour of integrated solar exposure. 

Switch to small solar aperture. 

Measure reflectivity versus A. 

Open large solar aperture door to the Sun. 

Introduce a small flow, say 10-1 standard cm3 per minute, of hydrocarbon 

gas from storage bottle. 

Monitor temperature of substrate versus time. 

Measure reflectivity every h4 hours. 

If degradation in reflectivity is observed, then one must determine whether it is due to 

oxidation or to the deposition of an absorbing contaminant. One test is the particular 

shape of the degraded reflectivity curve, which tends to be quite different from that of 

Al2O3. Figures 37 (16) and 38 (130) show examples of the short-wavelength degradation of two solar-pointed space telescopes. Note that the loss of throughput at 

= 1200 A is a remarkable 3 to 4 orders of magnitude. 

The second test of the source of an observed degradation is to put the mirrods) in 

question through the atom beam cleaning procedure described on Page 91. If the 

reflectivity partially recovers or converts to the A1203 curve, then the original 

degradation was not simply due to oxidiation. 

Figure 39 shows the effect on reflectivity at h = 1236 % of thin films of various 

common oils found in manufacturing areas (168). Figure 40 shows that the equilibrium 

thickness of one of these oils (without polymerization) is a strong function of substrate 

temperature, and may approach a monolayer at a sufficiently high temperature (168). 

4.4 RE-ALUMINIZING DEMONSTRATION 

The purpose of this experiment is to demonstrate the repetitive process of cleaning and 

re-aluminizing a mirror and to measure the cumulative degradation, if any, that occurs 

when this re-coating process is repeated several times. This experiment is a key one to 

the coating-in-space concept. Although this experiment can (and should) be first 

82 
PERKIN-ELMER 

1 

14’ 

LYMAN ALPHA 

LYMAN BETA 

0 BO 160 240 320 400 480 560 640 

CALENDAR DAY 

Figure 37. Variations of the Sensitivity of the Solar Pointed LPSP 

(Laboratoire de Physique Stellaire et Planetaire) 

Instrument on OSO-8 Versus Time After Launch in Days. 

Lyman Beta = 1025g 

Ca I1 = 3950A. 

attributed to Molecular Contamination (16) . 

Lyman Alpha = 12162 Mg I1 = 28008, 

0 

At least part of this degradation is 

83 
WAVELENGTH (8) 

Figure 38. Deterioratzon of the Sensitivity of the University of 

Colorado Solar-Pointed Telescope on OSO-8 with Time. 

The date 75-172 is Day 172 of 1975. Part of this 

degradation is assumed to be due to the build-up of 

molecular contaminants on the telescope mirrors (130). 

84 
PERKIN-ELMER 

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PERMIN-ELMER ER-591 

conducted in a ground laboratory, the impurity-free, ultra-high vacuum of the space 

laboratory could conceivably lead to quite different results. 

The procedure to be followed is a simple combination of the cleaning, coating, and 

reflectivity measurement procedures described elsewhere in this chapter. If the 

orbiting laboratory is in a sufficiently high orbit that oxygen is very sparse, the 

oxidation may be accelerated by tipping the laboratory vents toward the flight vector 

or by opening the "oxygen beam door" on the forward wall (Figure 29). 

Suppose that 495 a of fresh aluminum are deposited with each coating, of which 45 

oxidizes to A1203 leaving a sandwich of 450 A of aluminum and 45 8, of Al-203. We 

have run the I1OPTCOATf1 program of Appendix B, using optical constants for A1203 

from Reference 170 and for aluminum from Reference 169, to predict the net effect of 

this sequence of layers on the reflectivity of a mirror. The surprising result is that this 

multilayer actually has a normal-incidence reflectivity "figure of merit" for far 

ultraviolet astronomy which is slightly higher than that of pure aluminum. The data are 

included here on the following pages (Table 3). 

One important test for the re-coating concept is whether the level of scatter from the 

mirror surface signifgicantly worsens after a few re-coatings. Scattered light can be 

measured by the apparatus described here as follows: 

As seen in Figure 41, the aperture to the optical measurement compartment of the 

laboratory is slighty smaller than the aperture to the monochromator. The pool of light 

with little or no scattered light falls within the aperture of the monochromator and is 

analyzed. But with larger amounts of scattering the pool of light reaching the 

monochromator is spread over a larger area. This is tested by tilting one of the mirrors 

(or the entire line of sight) slightly so as to displace the monochromator entrance 

aperture with respect to the reflected beam of light (dashed lines in Figure 41). A nonzero measurement here is a measure of the scattered light. 

4.5 ATOM BEAM CLEANING DEMONSTRATION 

In Section 3.4.7, we described one technique for an high velocity impact oxidation 

reaction cleaning which does not require pressurizing the compartment containing the 

mirror. The procedure for this atom beam cleaning demonstration is as follows: 

a7 
PERKIN-ELMER 

Table 3 

Reflectivity of Aluminum Over ......... . .- . ._ .- . .... .............. 

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PERKIN-ELMER 

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90 
PERKIN-EL ER-591 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

Allow one mirror surface to become contaminated with a molecular film, by 

exposure to solar ultraviolet and an organic gaseous contaminant simultaneously, or by some other method.* 

Measure reflectivity versus wavelength. 

Rotate mirror surface to face atom beam gun. 

Monitor all TQCM's. 

Turn on atom beam gun. 

Raster scan atom beam gun over surface of mirror. 

Turn off atom beam. 

Monitor all TQCM's. 

Rotate clean mirror surface to optical measurement compartment. 

Re-measure reflectivity versus wavelength. 

An even more dramatic demonstration of the atom beam cleaning method would be to 

remove a contaminant film which had failed to evaporate follovhg a long heating of 

the contaminated substrate. 

4.6 CONCLUSIONS AND RECOMMENDATIONS 

We have described a conceptual design for an orbital laboratory which features the 

capability to demonstrate in-orbit optical coating, particulary for pure aluminum, and 

also allows for a variety of basic experiments which are stepping-stones to the in-situ 

coating of future large space telescopes. 

The design we have described makes use of the highest level of contaminant-free 

vacuum available in a near-Earth orbit. Alternate designs or refinements to this design 

are certainly possible. The major disadvantage of the design sketched in this chapter is 

* Concentrated solar ultraviolet is known to accelerate the rate of degradation due to 

photopolymerization. A uv-transmitting lens built into this orbital laboratory could 

therefore serve to accelerate the build-up of a contaminant film on one illuminated 

area, by providing a factor - 5- 10 concentration of the sunlight. 

91 
PERMIN-ELMER ER-591 

the number of moving parts, always an element of risk in any design. The advantages of 

the design include a considerable level of versatility, so that experiments even beyond 

those described in this chapter could be attempted. 

There is nothing that is technically very difficult about building the instrumentation 

described here. This laboratory could be flown today. The most difficult aspect of the 

construction of this hardware would probably be the selection of acceptable materials 

to minimize the outgassing of oxygen, water or organic gases in space. 

A logical plan for the initial launch of this experimentation would be to launch both 

mirrors with an initial coating of iridium. Iridium has a high FUV reflectivity and is not 

subject to atomic oxygen effects. Therefore the initial response of the system would be 

calibrated. An initial "heat soak1* of the laboratory and an outgassing period of a few 

days after reaching orbit before opening the aperture to the Sun is advisable. 

This orbital coating laboratory would be best flown on an unmanned Space Platform at 

an altitude of 600-1000 km which is periodically visited by astronauts. The astronauts 

serve to replace key components such as the evaporators and the contamination 

monitors. 

An orbiting laboratory of the kind described here needs to be located at a remote 

corner of the platform, away from all sources of outgassing or contamination, 

particularly sources of oxygen, water, other oxidants, or compounds which could 

decompose into 0 or OH ions, as these are the substances which will most severely 

shorten the life of a highly reactive aluminum mirror. A location on the end of an 

"outrigger" beam on a Space Platform would be appropriate (Figure 42). This laboratory 

also requires a particular controlled alignment with respect to the vehicle flight vector, 

and in addition a frequent controlled alignment with respect to the Earth-Sun line. 

These motions could be accommodated by swivelled stage holding a two-axis gimbal 

mount for the laboratory payload. 

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SOLAR ARRAYS 

SUN VECl 

\-SYSTEMS MODULE 

BOOM 

r MOLECU LAR 

. - - . -. - I EARTH RADIAL 

Figure 42. Concept for a High-Vacuum Orbital 

Laboratory, with Molecular Shield, 

Located on Long Boom Extending from 

Free-Flyer Platform (from Reference 166). 

93 
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SECTION 5 

ER-592 

A SPACE STATION COATING FACILITY 

Much of what has been discussed so far in this report constitutes a technological 

appraisal of the steps required to approach the goal of in-situ optical coating of the 

optical elements of a remote telescope in space. A quite different approach to recoating mirrors in space, and one which will be the more viable route for certain large 

systems where in-situ coating is ruled out, is the concept for an optical coating facility, 

possibly an adjunct to a manned space station in low or moderately low Earth orbit. 

This facility could be a general-purpose operation capable of handling a variety of 

ultraviolet, infrared or special-purpose coating materials, toxic materials such as 

osmium, and capable of repairing damaged mirrors by completely stripping their 

existing coatings. Such a facility would be a generalized and updated version of the 

Orbital Mirror Recoating Facility conceived in 1967 (Reference 2) to be a part of the 

Apollo Applications Program Orbital Workshop. See Figure 6. 

Figure 43 is a block (or task structure) diagram indicating the general organization and 

makeup of an envisioned 21st century Space Station Coating Facility. The diagram is 

intended to represent all of the principal subsystems making up the SSCF, and their 

capabilities and interrelationships. Such a diagram can serve as a guide in planning the 

engineering design of the SSCF and in extending or modifying its specifications. The 

following is a brief discourse on each element of the system as presently envisioned. 

5.1 SPACE STATION INTEGRATION (010) 

The SSCF is considered to be an integral or adjunct part of a permanent Manned Space 

Station (MSS) in Earth orbit at an altitude of about 600 km (See Figure 44). Optical 

components of up to 2 meters in size would be brought to the SSCF by a space transport 

craft, introduced into the SSCF through an interlock port, tested, stripped, cleaned, 

recoated with aluminum or another coating, and then returned to use in high orbital 

space observatories. The principal motivation for establishing the SSCF is to eliminate 

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m 

U 

a, 

Li 

7 

M 

.rl 

Fr 

95 
Figure 44. Artist's Concept for a Future Space Station 

Including Materials Processing Facilities 

such as an Optical Coating Facility. 

(Johnson Space Center drawing, Reference 206). 

96 
PERKIN-ELMER ER-591 

the expense of returning space observatory optical components to Earth for periodic 

recoating, and to take advantage of the vacuum of space to produce pure aluminum 

coatings with high reflectance in the extreme Ultraviolet. An objective of the overall 

SSCF design is to achieve a processing turnaround time of less than the lifetime of a 

pure aluminum coating at the altitude of the SSCF - about 16 days. 

The MSS is assumed equipped with ali necessary primary electrical power sources, a 

clean room interior environment, access ports and air locks, and astronauts equipped for 

EVA as necessary. Some of the activity of the SSCF is conducted inside the MSS in a 1 

atmosphere air environment. Actual coating of mirrors will be conducted externally to 

the MSS under remote control from operating centers in the SSCF. The detailed 

arrangement of the MSS is not now known. It is possible that some of the subsystems 

envisioned as part of the SSCF will already be provided by the MSS itself. For example, 

the MSS may have a liquid handling system (or chemical storage and recovery facility) 

that would be sufficient for the needs of the SSCF. However, this this not assumed in 

the present discourse. Also, the MSS may provide artificial gravity. In the following, 

however, operations are assumed to take place in a zero gravity environment in which 

special procedures are required, for example, in the handling of liquids. 

The Space Station Coating Facility should be located on the Space Station at a remote 

end of the structure, both so that the coating chamber is removed from sources of 

outgassing elsewhere in the MSS, including leading-edge surfaces facing the ram flow, 

and also so that its own effluent gases are dissipated away from other parts of the 

Space Station. 

5.2 TRANSIT CONTAINER (110) 

An important requirement of the SSCF is the design of the containers used to transport 

mirrors (or other optical components) back and forth between the SSCF and their parent 

spacecraft. The transit container must be configured to fit and hold securely a 

particular component. The container must be made of a material whose outgassing will 

not damage the newly coated mirror in the return voyage to the parent spacecraft. The 

container must be able to be handled and docked at the SSCF. A number of tasks are 

envisioned in designing and developing these containers. 

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Material Selection - Outgassing Requirements (1 11) 

The material must not introduce reactive (oxidizing or UV-absorbing) contamination in 

the course of a voyage. The material may have to be capable of being baked if the 

container handling involves exposure to the interior environment of the MSS. 

Mirror Assembly Mounting Interface (1 12) 

The container must have hold-down fasteners for the optical component or assembly it 

carries. In some cases, a mirror will have attached metal mounting hardware of some 

kind which practically cannot be detached; the particular component configuration will 

dictate the detailed-design of the mounting interface. 

Transit Container Seals (1 13) 

Seals for the cover of the container must be operable by an astronaut during EVA and 

must provide a seal against contamination during a return voyage. 

Docking Adaptor at SSCF (1 14) 

The container will be reloaded externally to the SSCF immediately after a mirror is recoated. This external EVA is required in order to avoid damage (oxidation or 

contamination) of the mirror in the MSS. Thus, the container is envisioned to be docked 

securely outside the SSCF. 

Bakeout Requirements (1 15) 

In case it is impossible to avoid an objectionable amount of contamination of the 

container, bakeout may be a requirement prior to a return voyage. This may take place 

in a bakeout oven belonging to the SSCF. Alternatively, the container may have a selfbaking capability when furnished with external electrical power. 

5.3 CHEMICAL STORAGE AND RECLAMATION FACILITY (120) 

The use of liquids appears difficult to avoid in the processing (stripping and cleaning in 

preparation for recoating) of mirrors. In some cases, new coatings might be applied to 

previously uncoated mirrors or new coatings might be laid down over old ones without 

necessarily requiring the use of liquids. In general, however, the best results will be 

obtained if standard reagents (and distilled water) can be used. (See Reference 125.) 

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Distilled Water (121) 

Distilled water would be used in final stages of mirror preparation after stripping. 

Relatively large quantities of distilled water (5-10 gallons or more) could be required in 

the preparation of a 2 meter mirror for coating. The consumption of water may 

necessitate a reclamation (re-distillation and re-use) processing facility (such a facility 

may already be provided by the MSS). 

Stripping Solution (HCI + CUSO~) (122) 

Up to a gallon of stripping solution may be consumed per mirror. Suitable conditions 

and facilities for handling of this chemical are a requirement. Possible reclamation and 

re-use of the solution or its ingredients should be investigated. 

Organic Solvents (123) 

Organic solvents (acetone, alcohol, and various composite organic solvents) are used to 

remove hydrocarbon (oil, etc.) contaminants which are not dissolved by other means. 

Means for safe transport to the MSS and for storage, use, and possible reclamation in 

the MSS should be considered. Possible contamination of the MSS atmosphere could 

pose a hazard. 

Dry Nitrogen (124) 

Used for flushing the stripping and cleaning units. 

Chemical Disposal Requirements (125) 

In case it is not possible to reclaim and recycle reagents various methods of containing 

or disposing of them must be considered, including, possibly, ejection into high orbit, 

ejecting them locally, or returning canisters to the ground. 

5.4 PROTECTIVE MASKING REQUIREMENTS (130) 

In some instances parts of a mirror (such as metal mounting hardware cemented to the 

mirror) must be protected from exposure to liquids (especially corrosive liquids). 

Possibly the necessary masking can make use of an impregnable fabric that can be 

fastened and sealed (with an adhesive) to the edge of a mirror. 

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PERMIN-ELMER ER-591 

5.5 FILM STRIPPING UNIT (140) 

The FSU is envisioned as a sealed (probably lightweight stainless steel or suitable 

plastic) vessel within which a mirror can be stripped and washed by personnel of the 

SSCF. The FSU would operate with an internal air atmosphere at close to the MSS 

atmospheric pressure. It would have a window, and (possibly) an internal manipulator or 

operator gloves extending into the vessel enabling the operator to perform various 

stripping and cleaning actions. The FSU will have a water dispensing and flushing 

system. and a purging system capable of eliminating all unwanted liquids and vapors 

prior to reopening the vessel. Several necessary design considerations are envisioned. 

Vessel Design and Material Selection (141) 

Design objectives include lightweight construction and resistance to damage by the 

reagents used. 

Access Ports and Handling Devices (142) 

Design objectives include suitability for a wide range in size and configuration of 

mirrors to be processed, and ease of operation by facility personnel. 

Liquid Handling System (143) 

The system must be suited to handing of liquids (including corrosive liquids) in a zero 

gravity environment. The possible use of a centrifuge system should be considered. 

Vapor Handling System (1 44) 

The vapor handling system is the interface between the atmosphere within the FSU and 

the MSS atmosphere. 

Metal Mirror Requirements (145) 

Metal mirrors cannot be stripped by the same methods used for glass or ceramic 

mirrors. Metal (for example, aluminum) mirrors are often used for heat rejection in 

solar instrumentation. Such mirrors are usually nickel- and chromium-plated to form a 

substrate suitable for adherence of the aluminum film. Development of a suitable 

stripping procedure for such mirrors may become a requirement for the SSCF. 

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5.6 CHEMICAL CLEANING UNIT (150) 

ER-591 

The CCU provides an enclosed atmosphere for final cleaning of the mirror with distilled 

water and various organic solvents. This unit might possibly be virtually identical to 

the FSU except as modified for the handling of the particular chemicals used. 

Separation of the CCU and FSU is considered necessary to prevent cross-contamination 

between the stripping and final cleaning materials. Possibly (especially in the interest 

of economy and weight-saving) procedures will be devised that enable only one 

processing unit to be called for. 

Vessel Design and Material Selection (151) 

As required for the use of organic solvents. 

Access Ports and Handling Devices (152) 

Operation in principle the same as for the FSU. 

Liquid Handling System (1 53) 

Appropriate for Organic solvents and distilled water. 

Vapor Handling System (1 54) 

Special precautions are needed to control possible explosion hazard from organic 

vapors. 

5.7 MIRROR ASSEMBLY COATING STATION (160) 

Actual coating of the stripped and cleaned mirror will necessarily be done in free space 

outside the MSS to prevent immediate contamination of the fresh aluminum by 

outgassing products. The MACS is considered to consist of a structure for holding the 

mirror during the coating operation, together with any necessary shields or baffles to 

contain the evaporated aluminum stream and protect the mirror from the ram flow of 

upper atmospheric gas. 

Mirror Mounting Interface (161) 

Standard or customer designed jigs or other tooling will attach the mirror to the MACS. 

101 
PERMIN-ELMER ER-591 

Environmental Requirements (162) 

Consideration must be given to the effect of the proximity of the MSS or other 

spacecraft at the time of coating. The mirror should face away from the ram direction 

during and after coating. Stray evaporated aluminum must not coat the spacecraft 

(particularly windows, electrical or communications devices, solar panels). 

Deployment System (1 63) 

The deployment system carries the mirror from final processing inside the SSCF to the 

external Coating Station and, after coating, places the mirror into its transit container 

under remote control without astronaut EVA. 

5.8 PLASMA CLEANING SYSTEM (170) 

The PCS is the SSCF equivalent of the gas discharge cleaning cycle used in groundbased coating facilties. It is envisioned as consisting of a plasma source (ejecting a 

stream of oxygen ions directed at the mirror) and associated monitor/control instrumentation. The plasma cleaning cycle will be performed with the mirror attached to 

the Mirror Assembly Coating Station. 

Plasma Source (171) 

Ion density, particle kinetic energy, geometry, cycle duration TBD. 

Electrical Requirements (1 72) 

The design must include consideration of possible effects on MSS communications. 

5.9 COATING SYSTEM (180) 

The coating system is considered to consist of the evaporators for aluminum, and 

associated control system within the SSCF. The evaporator may have either a tungsten 

filament source or an electron beam source. A tungsten source might possibly 

introduce contamination that would be objectionable in the EUV. An electron beam 

source could utilize billets of pure aluminum and might best serve for depositing large 

amounts of aluminum in repeated coatings. 

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Tungsten Filament Source (181) 

Wire gauge, aluminum charge weight, loading procedure and tooling, melt-in requirements TBD. 

Electron Beam Source (1 82) 

Beam source, geometry (bending magnet), boat design, electrical requirements TBD. 

Control System (183) 

Must monitor beam or filament current, voltages, and possibly interact with film 

thickness monitor. 

5.10 FILM THICKNESS MEASURING SYSTEM (1 90) 

Because the coatings of primary interest are opaque aluminum, film thicknesses will be 

monitored by a piezoelectric transducer system. The transducer (along with possible 

witness samples) will be deployed with the mirror at the coating station. Such 

equipment is standard in ground based coating facilities, but must be hardened as 

necessary for the SSCF. Requirements include consideration of the following: 

Transducer Design (1 91) 

Sensitivity, accuracy, signal-to-noise. 

Data Monitor (192) 

Provides operator real time information on progress of coating operation. 

Process Control Interface (193) 

Possible automation of the coating cycle should be considered. 

5.1 1 REFLECTANCE MEASURING SYSTEM (200) 

The RMS must be capable of reflectance measurement (to about 1 percent accuracy if 

possible) as a function of wavelength over a minimum bandwidth extending from 800 

to 1200 A (and probably into the visible and near infrared range as well). The system 

should be capable of evaluating mirrors of arbitrary size, shape, and surface figure, 

both before and after recoating. Probably the RMS must be deployed outside the SSCF 

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for this purpose. The RMS is considered to include the following subassemblies and 

components. 

Light Sources (201) 

Selection of artificial EUV light sources TBD. The Sun could possibly serve as a source 

for reflectance measurement in some spectral regions. The entire surface of a mirror 

would not necessarily have to be illuminated for a reflectance measurement. Thus, a 

suitable shield or baffle could allow a relatively narrow beam of sunlight to strike the 

mirror under test. Similarly sunlight might be admitted into the SSCF for a secondary 

RMS that might be located there. 

Spectrometer (202) 

A Spectrometer suitable for use in measuring the reflectance of aluminum could have a 

relatively wide bandwidth (assuming there are no narrow reflectance anomalies of 

interest). A grazing incidence optical system is probably necessary. 

Control System (203) 

The RMS will be operated remotely by personnel within the SSCF. 

Data Acquisition and Processing System (204) 

Permanent record-keeping and data analysis by computer is assumed. 

Expendable Supplies (300) 

A considerable store of expendable supplies specifically needed for the SSCF can be 

envisioned. 

5.12 OPERATION OF A SPACE STATION COATING FACILITY 

To summarize the handling and processing tasks involved in re-coating a large telescope 

mirror or mirror segment in this facility, the following key steps are involved: 

1. 

2. 

Receive and dock transit container. Astronaut EVA may be required. 

Transfer optical assembly (eg. mirror segment) to MSS/SSCF. 

3. Inspection of optical component: Visual; Physical; Optical Measurements. 

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4. Preparation and application of protective masking, if necessary. 

5. Stripping of coating: 

Pre-clean (water and detergent are possible agents) 

Strip/Swab 

Rinse/Flush 

Purge the Film Stripping Unit 

6. Chemical cleaning: 

Rinse/Swab/Flush 

Purge the Chemical Cleaning Unit 

7. Move cleaned optic to coating station. 

8. Vent all gas from the coating station. 

9. Plasma cleaning. 

10. Coating operation. w 

1 I. Re-install mirror in high-vacuum transit container. 

5.13 SUMMARY 

The above description of a Space Station Coating Facility is based on the anticipated 

requirement to perform the same general-purpose coating facility operations that are 

presently handled in ground laboratories. The key elements of the Space Station 

facility are 

o 

o 

o 

Avoidance of costly return to Earth of large optical components, 

Using the vacuum of space as a clean "roughing pump", 

Permitting the application of reactive coatings such as bare aluminum, 

which can then be quickly ferried to higher orbit. 

The design of the transit container would be a challenging aspect of this concept. To be 

able to carry aluminum-coated mirrors without a measureable amount of oxidation, it 

I05 
PERKIN-ELMER ER-59 1 

may require an internal vacuum which is better than that of the surrounding space in 

low Earth orbit. 

A manned space station facility of the kind described here also offers a tremendous 

opportunity for research. When senior scientists can travel at reasonable cost and 

comfort to a space station to supervise or conduct experiments, then research which 

utilizes the unique benefits of the space environment will have advanced to a new era, 

and a resulting enhancement of scientific yield may be expected. 

LO6 
PERMIN-ELMER 

SECTON 6 

ER-591 

IN-SITU COATING OF LARGE SPACE TELWOPE MIRRORS 

The final phase of an experimental space coating program will be in-situ application of 

an aluminum film to a large primary mirror and its associated secondary mirror. The 

advantages of this approach have been discussed earlier in this report. Experimental 

verification of the technique during the previous phases of the program will prove 

feasibility . 

In-situ coating capability for a large astronomical telescope system in space would have 

to be incorporated into the design of the system during the early conceptual phases. 

Baffling, power systems and on-board instrumentation would all have to be compatible 

with this process. Proper integration of a coating system into the telescope assembly 

would make coating in space both feasible and practical in applications where optical 

throughput in the vacuum ultraviolet must be maintained for extended periods of time. 

Several assumptions will serve as guidelines for this study. Our system will be in 

geosynchronous orbit where ambient pressures will be torr or lower. At this 

pressure a bare aluminum film without a protective overcoat will be sufficient. We also 

assume that all coating work is to be performed automatically. Astronauts will not be 

available to manipulate mirrors, sources or baffles. 

6.1 SYSTEM DESCRIPTION 

For our telescope we will choose a design similar to the Space Telescope - a 100 inch 

primary mirror with a 15 inch secondary (Figure 45). Located at the outer diameter of 

both mirrors are stray light baffles. The primary mirror also has a central baffle 

located at approximately a 24 inch diameter. The surfaces of the primary mirror and 

secondary are separated by approximately 20 feet. These are the only optics in the 

system that we will consider coating. We will also consider recoating of these optics 

several times. 

10 7 
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6.2 EVA PO R A TO R DESCRIPTION 

The type of evaporators and their location are critical to the feasibility of this 

approach. Power requirements play a primary role in determining evaporator type and 

size. The location and number of evaporators determine film uniformity. 

There are two types of sources which may be used to thermally evaporate aluminum: 

resistance heating and electron beam gun heating. We will not consider electron beam 

gun sources because of the large powers required (several kilowatts). Resistance 

sources can be designed to operate at low voltages and therefore low powers (tens of 

watts). In addition resistance sources can be pre-shaped and pre-charged to give a wide 

range of vapor distribution patterns and pre-determined mechanical thickness. A large 

number of sources can be arranged in a distributed geometry to simulate an extended 

source. 

Tungsten stranded wire can be formed into large helical coils and precharged with 

aluminum (Figure 46). This geometry gives excellent uniformity in two directions. The 

source can be made simple, compact and mechanically sound. The tungsten filaments 

can be pre-charged with aluminum prior to launch. Multiple evaporation can be 

accommodated by using several sources with a multiple tap switching mechanism. This 

technique is used routinely in conventional deposition systems. 

6.3 UNIFORMITY AND THICKNESS CONSIDERATIONS 

The performance of the telescope system is very dependent upon the uniformity and 

thickness of the aluminum film applied to the optical surfaces. A non-uniform film on 

either the primary or secondary mirror can seriously degrade the optical figure. The 

mechanical thickness of aluminum specified will be 600 A. This value is a lower limit. 

Thicker films (4 1000 A) can be used without a serious increase in surface roughness. 

If telescope mirrors or other components to be coated were to be used at other than 

normal incidence, special care would be required in choosing the thickness of aluminum 

in order to prevent unwanted polarization effects. 

The sources for the primary mirror coating are arranged on a circumference outside the 

clear aperture of the main baffle (Figure 47). Shielding and baffle opening are such 

that only the mirror surface is in the line of sight of the source. The angle& is a 

109 
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ER-591 PERMIN-ELMER 

function of the source distance from the primary mirror plane. The further away the 

source is from this plane the smaller is and the better the uniformity across the 

mirror in the radial direction. However, the tradeoff in locating sources far from the 

primary mirror is in the amount of energy which must be expended. More aluminum 

must be evaporated as the solid angle coverage decreases. For a continuous ring source 

the azimuthal uniformity is very good. Since discrete sources must be used, azimuthal 

uniformity deteriorates. A tradeoff study must again be made to determine acceptable 

uniformity versus power expenditures. 

The secondary mirror presents more of a problem than the primary mirror because of 

the difficulty in locating the sources in a position which will not obscure the optical 

path. One possibility (Figure 48) is to locate the evaporators at the extreme end of the 

primary mirror central baffle. This position is far enough away from the secondary 

mirror to insure a uniform coating yet in a position that would not present a large 

obscuration to the optical path. 

Proper thickness control can be achieved by evaporating to completion a pre-set charge 

of aluminum. This technique can be used as long ?is the evaporators are used once. For 

multiple evaporations new sources are switched in sequentially. If sources are to be 

used more than once, it will be necessary to monitor the deposition for thickness 

control. One simple method is to photometrically monitor the system throughput at 

1216 8. As the aluminum film is deposited, throughput will increase to a value limited 

by the film reflectance at 1216 A. When throughput ceases to increase the deposition 

can be terminated. It is a simple technique which would require no additional 

instrumentation. 

6.4 SUMMARY 

In-situ coating of large optical systems appears to be very feasible. Detailed work must 

be performed to accurately determine film uniformity requirements for the mirrors and 

the source geometry necessary to achieve these uniformities. Power requirements do 

not seem to be severe and process monitoring does not appear to be critical. If the 

early experiments on coating in space prove successful the application of this 

technology to a large system would be the next logical step. 

112 
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PERMIN-ELMER ER-591 

SECTION 7 

CONCLUSIONS AND RECOMMENDATIONS 

In this study we have given some thought to the steps required to approach the goal of 

in-situ optical coating, cleaning and re -coating the optical elements of a space 

telescope. We have concentrated our attention on the desire to achieve high 

reflectivity with normal incidence telescope mirrors. In general, grazing incidence 

mirrors such as are used for X-ray and EUV astronomy (7, 135, 138, 139, 147) are more 

tolerant of small amounts of surface contamination and there is therefore less gained 

by coating these in space. In particular, we have considered the case of bare aluminum 

coatings, which offer a tremendous advantage to far ultraviolet astronomy. We have 

suggested some design ideas for an optical coating laboratory in space, flown either on 

a space platform or as a 5partant1-type free flyer, for conducting experiments and 

demonstrations that can set the stage for a future telescope with built-in aluminum 

evaporators. 

Some prerequisite experiments should be carried out in ground-based laboratories 

before a final design of an orbital coating laboratory can be made. The recommended 

work is listed here: 

1. Experimental tests of evaporator gun design. A design for a vapor 

collimator must be found that provides an optimum "top-hat function" 

(uniform distribution over an area and zero vapour outside that area) and 

that does not clog up with condensed aluminum after multiple uses. 

2. Measurements of the angular distribution of the evaporant as received on a 

substrate behind a mask, as a function of evaporation rate and local 

pressure. This data is needed to find the optimum deposition rate and the 

maximum allowable chamber pressure to avoid stray vapor beyond the 

desired target areas. 

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3. Measurements of the amount of stray vapor scattered at large angles out of 

a thermally evaporated aluminum beam. 

4. Experiments on repeated coating, oxidation, and recoating of aluminum 

mirror surfaces. How does the scattered light performance change with 

increasing number of Al2O3/Al layers? How many repetitions of this 

process can be allowed before a mirror is no longer satisfactory? 

5. Measurements of the adhesion of new aluminum layers over oxidized 

aluminum as a function of various parameters such as temperature, 

deposition rate. 

Experiments on ways to remove dust from a mirror in a vacuum by an 

automated, remote technique. 

6. 

7. Search for a "magic" material that, when deposited as a very thin film over 

pure aluminum, retards the rate of oxidation of aluminum without significantly losing the advantage of high far-ultraviolet reflectivity that 

aluminum offers. 

8. Experiments with fast atom beam cleaning of polymerized hydrocarbon 

films on coated mirrors, using rieutral oxygen atoms in high vacuum. 

However, ground-based experiments cannot replace experiments and observations made 

directly outside the Earth's atmosphere. The true test of the techniques considered 

here for coating in outer space can only be made on a spacecraft, and best on a 

platform which samples various orbital altitudes over a period of time. 

In all likelihood, the coating of large optics in space is the approach that will in fact be 

taken for the next generation of large space telescopes in the twenty-first century. 

The technology exists to develop this approach today. 

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SECTION 8 

REFERENCES 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

-’ Princeton Advanced Satellite Study, Perkin-Elmer Report No. 8346, 

pps. 2-20, May 1966. 

-’ Optical Technology Apollo Extension System (OTES) Phase A Study 

Final Report, Perkin-Elmer/Lockheed, Perkin-Elmer Engineering Report ER8900, October 1967. 

-’ Large Telescope Experiment Program (LTEP), Perkin-Elmer 

Engineering Report No. ER-9800, April 1970. 

-’ Spacecraft Contamination Under Simulated Orbital Environment, 

Interim Report, Aerospace Corp., SAMSO-TR-77-130, July 1977. 

-’ Presentation Material Volume, NASA Shuttle Environment Workshop, 

Calverton, MD, October 5-7, 1982. 

-’ Shuttle Mission 5 to Study Orbiter Glow Phenomenon, Av. Week & 

Space Tech., November 1, 1982, p. 64. 

-’ The Final Report of the Science Working Group for the Far Ultraviolet 

Spectroscopic Explorer, April 1983. 

R.J. Adornato, Retrieval and Servicing of Contamination Sensitive Satellites, 

AIAA Conference on Technology for Space Astrophysics: The Next 30 Years, 

Danbury, Conn. October 4, 1982. 

M.R. Adriaens and B. Feuerbacher, Improved LiF and MgF2 Overcoated 

Aluminum Mirrors for Vacuum Ultraviolet Astronomy, Appl. Opt. 10, 958 

(1 971). 

D.W. Angel, W.R. Hunter and R. Tousey, Extreme Ultraviolet Reflectance of 

LiF-Coated Aluminum Mirrors, J.O.S.A. - 51, 913 (1961). 

J.D. Austin, Test Program on the Contamination of Ultraviolet-Region Mirrors 

by Apollo Telescope Mount Materials, Ball Brothers Research Corp., Final 

Report, NASA-CR-120516, January 1974. 

P.M. Banks, et. al., Space Shuttle Glow Observations, Geophys. Res. Letters 

-’ 10 118, (1983). 

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13. 

14. 

15. 

16. 

17. 

18. 

19. 

20. 

21. 

22. 

23. 

24. 

25. 

26. 

27. 

28. 

R.A. Becker, Optical Material Problems of Interplanetary Space, Appl. Opt. - 6, 

955 (1967). 

J.A. Berning and J.P.H. Berning, Thin Film Calculations Using the IBM 650 

Electronic Calculator, J.O.S.A. 50, 813 (1960) 

A. Boggess, The International Ultraviolet Explorer, Proc. SPIE 279, 168 (1981). 

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Overview, AIAA 19th Aerospace Sciences Meeting, Paper No. AIAA-81-0339, 

January 1981. 

Aviation Week and Space Technology, August 10, 1981, page 52. 

D.J. Olney and R.G. Cruddace, Free Flying Shuttle Payloads, An extrapolation 

of Sounding Rocketry into the Shuttle Era, AIAA Paper No. AIAA-79-0485 

(1 979). , 

P. H. Lissberger, An Analytical Model of the Performance of Multilayer 

Fabry-Perot Filter Coatings Subject to Interfacial Roughness, Optica Acta 30, 

981 (1983). 

M.E. VanHoosier and G.E. Brueckner, Design, Calibration of the Solar 

Ultraviolet Spectral Irradiance Monitor, Proc. of the Fifth Workshop on the 

VUV Radiometric Calibration of Space Experiments, NCAR, Boulder, 

Colorado, March 1979. 

S. Sofia, Editor, Variations of the Solar Constant, NASA Conference 

Publication 2191 (1981). 

J.-D. Bartoe, Naval Research Laboratory, private communication, 1983. 

The Solar Output and its Variation, 0. White, editor, Proceedings of Workshop, 

Univ. of Colorado (1977). 

D.M. Roessler and W.C. Walker, Optical Constants of Magnesium Oxide and . Lithium Fluoride in the Far Ultraviolet, J.O.S.A. - 57, 835 (1967). 

H. A. MacLeod, Thin Film Optical Filters, N.Y. Am. Elsevier (1969). 

W.T. Welford and R. Winston, The Optics of Nonimaging Concentrators, 

Academic Press, New York (1978). 

A. Rabl and R. Winston, Appl. Optics 15, 2880 (1976). 

W.L. Eichhorn, Appl. Optics 2, 3887 (1982). 

L.R. Canfield, National Bureau of Standards, Washington, private 

communication (1983). 

Proceedings of the Fifth Workshop on the VUV Radiometric Calibration of 

Space Experiments, NCAR, Boulder, Colorado, March, 1979. 

J. Strong, The Evaporation Process and its Application to the Aluminizing of 

Large Telescope Mirrors, Astrophys. Jour. 83, 401 (1936). 

Technical literature, Ion Tech, Ltd., 2 Park Street, Teddington, Middlesex, 

TW 11-OLT, England (1983). 

128 
PERKIN-ELMER ER-591 

197. 

198. 

199. 

200. 

201. 

202. 

203. 

204. 

205. 

206. 

207. 

R. Kato, Optical Constants of LiF in the Extreme Ultraviolet, Jour. Physical 

SOC. Japan 16, 1476 (1961). 

R. Kato, Optical Properties of LiF in the Extreme Ultraviolet, Jour. Physical 

SOC. Japan 16, 2525 (1961). 

Michael Hettrick, University of California, Berkeley, private communication 

(1 983). 

NASA Space Transportation Systems Advanced Concepts - Space Platform, 

NASA Program Summary, August 1981. 

V. Rehn et al., Applied Optics 16, 1111 (1977). 

W. J. Choyke et al., Applied Optics 16, 2013 (1977). 

J. C. Rife and J. F. Osantowski, Optical Constants in the Extreme Ultraviolet 

and Soft X-ray Region, Proc. SPIE, 315, 103 (1981). 

R. E. Engdahl, Chemical Vapor Deposited (CVD) Silicon Carbide Mirror 

Technology, SPIE 315, 123 (1981). 

R. L. Gentilman and E. A. Maguire, Chemical Vapor Deposition of Silicon 

Carbide for Large Area Mirrors, Proc. SPIE 315, 131 (1981). 

"Consensus Nearing on Orbital Facilities", Aviation Week and Space 

Technology, February 13, 1982, page 1 19. 

J. J. Scialdone, Estimates of Internal Pressures and Contamination of the 

Space Telescope, NASA GSFC Memo (1982). 

129 
PERKIN-ELMER ER-591 

AE 

ATS 

ATM 

ccu 

CVD 

ESA 

EUV 

EVA 

FSU 

FUSE 

FUV 

GAS 

GRIST 

HUT 

JPL 

LDEF 

LPSP 

MACS 

M SFC 

M SS 

NRL 

OAO 

OMRF 

os0 

oss 

OST 

APPENDIX A 

DICTIONARY OF ACRONYMS 

Atmospheric Explorer 

Applications Technology Satellite 

Apollo Telescope Mount (on Skylab) 

Chemical Cleaning Unit 

Chemically Vapor Deposited 

European Space Agency 

Extreme Ultra-violet .Wavelength range from N 100 

Extra-vehicular Activity 

Film Stripping Unit 

Far Ultraviolet Spectroscopic Explorer 

Far Ultraviolet. Wavelength range from -900 

Get Away Special (NASA cannister for self-contained Space Shuttle 

experiments) 

Grazing Incidence Solar Telescope (ESA program) 

Hopkins Ultraviolet Telesope (Johns Hopkins University) 

Jet Propulsion Laboratory 

Long Duration Exposure Facility 

Laboratoire de Physique Stellaire et Planetaire (C.N.R.S., France) 

Mirror Assembly Coating Station 

Marshall Space Flight Center 

Manned Space Station 

Naval Research Laboratory 

Orbiting Astronomical Observatory 

Orbital Mirror Recoating Facility 

Orbiting Solar Observatory 

Office of Space Science (NASA office) 

Orbiting Solar Telescope (on Salyut 4) 

to 1000 A 

to 1800 A. 

13 0 
PERKIN-ELMER 

PCS 

REVAP 

SOT 

SPARTAN 

SSCF 

ST 

STS 

TBD 

TQCM 

uvso 

vuv 

xuv 

ER-591 

Plasma Cleaning Sation 

Removeable Volatile Aluminum Protection 

Solar Optical Telescope 

Shuttle Pointed Autonomous Research Tool for Astronomy (free flying 

payload dropped and retrieved by Shuttle) 

Space Station Coating Facility 

Space Telescope 

Space Transportation System (Space Shuttle) 

To Be Determined 

Temperature Controlled Quartz Crystal Microbalance 

Ultraviolet Space Observatory (U.K. proposal) 

Vacuum Ultraviolet. Wavelength range from -900 A to 2000 A. 

Extreme Ultraviolet. Wavelength range from -100 to 1200 A. 

13 1 
PERKIN-ELMER ER-591 

APPENDIX B 

FORTRAN OPTICAL COATING REFLECTIVITY PROGRAM 

The program "OPTCOAT" which is listed on the following pages, was created to 

compute the reflectivity versus wavelength of a multi-layer coating at any desired 

angle of incidence. The program assumes that data files exist containing lists of 

wavelength (in microns) and n and k values, where the complex index of refraction is 

g = n - ik. 

The program also assumes, for multilayer calculations, that there is a one-to-one 

correspondence of the wavelengths in each list of optical constants being used, in other 

words, that the data files for each material have the same number of entries and are 

"synchronized" in wavelength. 

The input data are: Mode (different printout options), Number of films (above the 

substrate material), the angle of incidence in degrees, and the physical thickness of 

each layer in Angstroms, starting with the layer adjacent to the substrate. 

The output data include wavelength (in microns), s-polarization and p-polarization 

reflectivities, average reflectivity, transmittance and absorptance. 

This program is adapted from one of John S. Loomis, Air Force Weapons Lab, Kirtland 

Air Force Base (reference 90). We gratefully acknowledge this help. 

As examples of runs made with this program, a computation of the normal incidence 

reflectivity of pure aluminum, using the optical constants of Appendix C, and the 

normal incidence reflectivity of 280 A aluminum over an iridium substrate, follows the 

Fortran program listing. (A plot of this pure aluminum data appears in Figure 3). 

13 2 
PERKIN-ELMER 

... 

.. .. 

.. 

4 .. .. .. 

..., 

,. 

.. 

4 :> .. 

.. 

... 

., 

.. 

.. T 

.. .... 

'I ''.. 

.... 

.... 

... 

.. 

. /. 

.. .... 

1 .:_ .. 

.... 

Program "OPTCOAT" Fortran Listing 

...... . 1: , .< 

........... 

... . .. , :! 'r . ., .? ,. ? ..... <',; '1 : .. :: , .. 2. 

... -;,: ,.. 

: ..: , 

133 
PERKIN-ELMER 

.. ,... . .. . .. .. 

-. .( 

. .. . 

, . .. 2, .. , 

.! ,>' .- :. .i,_ I .... i 

f :.:) .& ... i 

.... .-. .. ._> ... .- . .. 

>,! ::. c z ..z 

! .::: 

c: ;., ."., 2. .... .;.. 

.... , i . \.. 

..,, 

134 
PERKIN-ELMER 

135 
PERKIN-ELMER 

13 6 
PERKIN-ELMER 

.. 

,-/ 

.. 

I, 'I .. ! 

. . .. 

13 7 
.. . . ... .... .. ... ... ".( 

I 

.I 

..I I 

._., 

.. 

13 8 
PERKIN-ELMER 

.. 

...... 1. 

.7 .( .y 

.. 

i' 

i'; 

13 9 
PERKIN-ELMER 

WAVELENGTH 

nrcRoNs 

0.0113000 

0.0495920 

0+0506040 

0 t 05 16580 

0 + 0523120 

0 ,0535340 

0 0529830 

0*0532100 

0 + 0534400 

0536710 6 0537870 

0+0539040 

0 t 0540220 

0 t 0541400 

0 t 0343770 

0.0548580 

0 t 0553480 

0.0558470 

0 6 0563550 

0 t 0568720 

0.0573980 

0 0579350 

0 0590380 

o ,0604780 

0 + 061 9900 

0 0635790 

0 + 0652530 

0 0666560 

0 +06.70159 

0.0673800 

o 0688780 

0 t 0677490 

0 + 0700450 

0 t 0704430 

0 * 0708460 ' 0712529 

0 +0716650 

0+0733610 

0 0755979 

0 *0765310 

0 + 0770060 

0,0774879 

0.0784680 

0.0799870 

0.0779750 

0 0789680 

REFLT 

AVERAGE 

0,0073 

1 t 1246 

1 + 2582 

1.4022 

1 + 5240 

1.5398 

1.6196 

1 6358 

1,7018 

1 e 7355 

1,7525 

1 + 7696 

1.7866 

1.8211 

1 * 8559 

1,9630 

2 t 0552 

2.1694 

2.2681 

2 t 3900 

2,5158 

2.6458 

2 t 9654 

3,4116 

3.9869 

9,6530 

545346 

6.4044 

6 4 6463 

6.8949 

7 + 1923 

0.0948 

9 t 0220 

9,5436 

10,0285 

10 + 2504 

11,2321 

13 4797 

17 ,8669 

20 3114 

21 + 6780 

23.2284 

24 t 9802 

26 9532 

29 1936 

35,0391 

Table 4 

Normal Incidence Reflectivity of Pure Aluminum 

ANGLE= 0.0 DEGREES 

TRANS 

AVERAGE 

99 9928 

98.8755 

98.7418 

98 + 5979 

98 + 4761 

98,4602 

98,3ao4 

98 2645 

98 t 3642 

98 t 2982 

98 + 2475 

98 t 2304 

98.2134 

98.1790 

9841441 

98 + 0370 

97 +9448 

97,8306 

97 + 7318 

97,6100 

97 + 4842 

97,3542 

97 + 0346 

96.5884 

96,0132 

95.3470 

94.4654 

93,5957 

93.3537 

93.1053 

92.8078 

91,9053 

90 9773 

90,4566 

89,9715 

89,7497 

88.7679 

86,5204 

82.1331 

79.6887 

78.3222 

76.7717 

75 6 0200 

73 0468 

70 t 8065 

64,9610 

ABSORP 

AVERAGE 

-0 0000 

-0,0001 

-0.0000 

-0 * 0000 

-0.0001 

0 0 0000 

0.0 

-0.0000 

-0.0000 

-0.0001 

-0.0000 

-0.0000 

-0.0000 

-0.000 1 

-0 0000 

-0.0000 

-0.0000 

-0,0000 

-0 t 0000 

-o*oooo 

-0 .oooo 

0.b 

-0.000 1 

-0,0001 

0.0000 

-0 + 0000 

-0.0001 

-0.0001 

-0 * 0002 

-0 t 0002 

-0 t 0001 

-0.0001 

-0,0001 

-0.0001 

-0 t 0000 

-0.0000 

-0~0001 

-0 t 0001 

-0.0002 

-0 t 0002 

-0.0001 

-0.0002 

-0 0000 

-0.0001 

-0.0001 

0.0 

REFLT 

S-POL 

0 + 0073 

1 t 1246 

1 I) 2582 

1 t 4022 

1 tX40 

1.5398 

1 + 6358 

1,6196 

1.7018 

1 t 7355 

1 7525 

1.7696 

'1 7866 

1.8211 

1 8559 

1.9630 

2,0552 

2 + 1694 

2,2682 

2,3900 

2,5158 

2 + 6458 

2 9654 

3.4116 

3,9869 

4 + 6530 

5 t 5346 

6.4044 

6 + 6463 

6. a949 

a. 0948 

7 1923 

9 t 0228 

9 + 5436 

10 0285 

10.2504 

11,2321 

13.4797 

17,8669 

20.3114 

21 + 6780 

23.2204 

24.9002 

26 9532 

29 t 1936 

35,0391 

TRANS 

S-POL 

99 9928 

98 8755 

98.7418 

98,5979 

98 .. 4602 

98.4761 

98 t 3804 

98 + 3642 

98 2982 

98.2645 

98.2475 

98,2304 

98.2134 

98.1790 

98.1441 

98 * 0370 

97 s 9448 

97 + 8306 

97,7318 

97,6100 

97 + 4842 

97.3542 

97 s 0346 

96 5884 

96 + 0132 

95 t 3470 

94 + 4654 

93.3957 

93.3537 

93 $1053 

92 .a078 

91 +9053 

90.9773 

90.4566 

89.9713 

89.7497 

az.1331 

79.6887 

8817679 

86,5204 

78 3222 

76.7717 

75 + 0200 

73 t 0468 

70.8065 

64,9610 

ABSORP 

S-POL 

-0.0000 

-0.0001 

-0 t 0000 

-0 * 0000 

-0 * 0001 

0.0000 

0.0 

-0 .oooo 

-0.0000 

-0 * 0001 

-0.0000 

-o*oooo 

-0 .oooo 

-0.0001 

-0.0000 

-0 t 0000 

-0 0000 

-0 t 0000 

-0 + 0000 

-0 + 0000 

-0.0000 

-0.000 1 

-0.0001 

0 * 0000 

-0 * 0000 

-0.0001 

-0.0001 

-0.0002 

-0 t 0002 

-0.0001 

-0 + 0001 

-0.0001 

-0.0001 

-0.0000 

-0 t 0000 

-0,0001 

-0 * 0001 

-0.000z 

-0,0002 

-0 0001 

-0.0002 

-0.0000 

-0.0001 

-0.0001 

0.0 

0.0 

REFLT 

P-POL 

0 0073 

1 1246 

1 2'182 

1 t 4022 

1 *5240 

1.5398 

1,6196 

1 6358 

1.7010 

1,7355 

1 t 7525 

1 7696 

1 7866 

1.8211 

1 8559 

1 + 9630 

2 t 0552 

24 1694 

2 2682 

2 t 3900 

2.5158 

2,9654 

3.4116 

3 + 9869 

4 6530 

5.5346 

6 4044 

6.6463 

7 + 1923 

2.6458 

6 + a949 

8.0948 

9 0228 

9.3436 

10.0285 

10 + 2504 

11.2321 

13,4797 

17.8669 

20 t 3114 

21 + 6780 

23,2284 

24.9802 

26 9532 

29 1936 

35 *0391 

TRANS 

P-POL 

99 9928 

98 t 8755 

98 t 7418 

98 ,5979 

98 ,3804 

98.3642 

98.2649 

98.4761 

98 t 4602 

98 2982 

98 2475 

98,2304 

98,2134 

98 t 1790 

98.1441 

98 t 0370 

97,9448 

97 t 8306 

97.7318 

97.6100 

97 *4842 

97.3542 

97 + 0346 

96.5884 

96.0132 

95.3470 

94 + 4654 

93 t 5957 

93.3537 

93 t 1053 

92 t 8078 

91 + 9053 

90 t 9773 

90 + 4566 

89 e9715 

89.7497 

86,5204 

79.6807 

88,7679 

82 t 1331 

78 t 3222 

76 + 7717 

75 t 0200 

73,046a 

70 t 8065 

64 t 9610 

ABSORP 

P-POL 

-0.0009 

-0.0001 

-0 0000 

-0*@000 

-0.@001 

0.0000 

0.0 

-0 .oooo 

-0.0001 

-0 +0000 

-0 t 0000 

-0,0001 

-0 .oooo 

-0. oaoo 

-0. ooao 

-0 .a000 

0.0 

-0 t 0000 

-o*oooo 

-0 t 0000 

-0 *oooo 

-0.0000 

-0 +0001 

-0 t 0001 

0.0000 

-0 0000 

-0.000 1 

-0 t 0001 

-0 ,0002 

-0 0002 

-0 t 0001 

-0.0001 

-0+0001 

-0 t 0001 

-0.0000 

-0 t 0000 

-0 * 0001 

-0.0002 

-0.0002 

-0 t 000 1 

-0 t 0002 

-0.0000 

-0.0001 

-0 t 000 1 

0.0 

-0. ooai 

140 
PERKIN-ELMER 

Table 4. (Continued) 

0.0810330 

0 +OS21060 

0 t 081,6530 

0 0832080 

9 t 9843400 

0*0849180 

0 t 0855030 

0 t 0360969 

0 t 0866989 

0 *OS73100 

0 t 0979290 

0 + 0985569 

0 + 0888750 

0+0891940 

~ 0895160 '. .OS90409 

0+0901670 

0.0904959 

0 + 0900279 

O+O911620 

0.0914980 

0.0913370 

0 t 0921780 

0 t 0925220 

0 + 3??B690 

0.O935700 

0 .O942910 

-. 0746410 ',. . 0750040 

0.0953590 

0+0932180 

0 +O93?240 

Q + 0957370 

0+0961090 

0+0964020 

0 ,0968590 

0 + 0972390 

0 t 0976220 

0 t 0980000 

0.0933970 

0 + 0991040 

0 t 0999840 

9 t 1007970 

0,1016230 

0 t 1026000 

0,1033170 

0.1055149 

0 1064000 

0.1100000 

0+1102040 

0 t 1127090 

0.1149999 

0.1180760 

Ot 1216000 

0.107aoa9 

1239800 

0 t 1300000 

0 1377560 

0 t 1400000 

0 + 1549750 

0 t 1600000 

43.5077 

54 9653 

61.2112 

66 * 7621 

75 t 0754 

77,9065 

79 t 6463 

81+0813 

82 * 1940 

83.0120 

84.9081 

85.0732 

84.1084 

85 + 5094 

85 9040 

86.3156 

86.5542 

87.0849 

97.3388 

86 + 5202 

87 t 6005 

87.8607 

88,0584 

88,2551 

88,4507 

98,6451 

88.8382 

88 + 9730 

89 t IO70 

89.2404 

89 4 3732 

89 5052 

a9.7143 

89,9217 

90.1018 

90 t 2292 

90 4066 

90 + 5823 

90 7647 

90.9372 

91,2774 

91 + 4662 

91.6523 

91 t 8359 

92.0317 

92 2022 

92,5325 

92 t 6799 

92 + 8524 

92,9347 

92.9125 

92.a~~ 

92. a574 

92 a721 

92.0551 

92.8964 

92 t 8036 

92 7290 

92.7275 

92.6432 

92 + 6326 

54 4924 

45 + 0349 

38,7887 

33.23ai 

20,3538 

ia.9iaa 

i7.ao62 

16 9880 

15.a916 

24 t 1247 

22,0937 

15.0921 

14 9269 

14 +4907 

14.0960 

13.6045 

13,4458 

13.1798 

12.9151 

12.6614 

12 3996 

12,1394 

11.9417 

11.7450 

11.5494 

11 + 3550 

11.1619 

11 t 0272 

10,8931 

10 + 7597 

10 e 6269 

10,4949 

10.2857 

i0.07a3 

9.7708 

9 + 8984 

9.5935 

9.4178 

9 2354 

9 0629 

a ,7227 

a + 5339 

13.3477 

7,9684 

8,1641 

7.7979 

7.4675 

7,3201 

7.1476 

7 0654 

7 1246 

7 .oa75 

7.1280 

7,1426 

7 1449 

7 1036 

7.1164 

7,2710 

7.2725 

7 +3674 

7.3568 

0+1771140 92.5945 7.4055 

108 WAVELNGTHS? SUH OF REFL- 

-0.0000 

-0 t 0002 

0 t 0000 

-0.0002 

-0.0001 

-0.0002 

-0 0002 

-0.0001 

-0 0002 

-0.0001 

-0'0001 

-0.0002 

-0.0001 

-0.0002 

-0.0001 

-0.0000 

-0.0002 

-0.0001 

-0,0002 

-0 t 0000 

-0 t 0001 

-0,0001 

-0 f 0002 

-0.0001 

-0.0002 

-0.0001 

-0.000 1 

-0.0001 

-0.0001 

-0.0001 

-0.0001 

-0.0002 

-0 0000 

-0.0002 

-0.000 1 

-0.0001 

-0.0001 

-0.0001 

-0 t 0001 

-0.0000 

-0.0000 

-0 t 0001 

-0 t 0000 

-0 0000 

-0.0000 

0.0000 

-0.0001 

-0.0001 

-0*0001 

-0*0001 

-0.0000 

-0.0000 

-0.0000 

-0.0000 

0.0001 

-0 0000 

0.0000 

0.0000 

0.0000 

9264 + 55 

0.0 

0.0 

0.0 

43 SO77 

54 + 9653 

61,2112 

66 9 7621 

75. a754 

ai .oa13 

83.0120 

a4.1084 

84.90a1 

85 + 0732 

8s. 5094 

86.3156 

86. 8202 

87,0849 

97.33a8 

87.a607 

8a.0584 

88,4507 

sa 8382 

58.9730 

77.9065 

79 t 6463 

82 1940 

85 t 9040 

06,5542 

07 + 6005 

88.2551 

88 + 6451 

89 1070 

89 2404 

09 t 3732 

89.5052 

09 * 7143 

89.9217 

90 + 1018 

90 t 2292 

90 t 4066 

90 5823 

90 7647 

90 4 9372 

91.2774 

91 4562 

91 + 6523 

91 8359 

92.0317 

92 2022 

92.5325 

92 t 6799 

92 * 8524 

92 9347 

92 + 0755 

92 + 9125 

92 .a574 

92.ass1 

92.8721 

92 ,8836 

92 0964 

92.7290 

92 7275 

92 t 6432 

92 6326 

92.5945 

9 FIG OF HR 

56.4924 

45.0349 

38.7807 

33.23ai 

24 1247 

22 0937 

20 + 3530 

17 + 0062 

ia.9iaa 

i6.9aao 

15.8916 

15 t 0921 

14 9269 

14.4907 

14.0960 

13.6045 

13.4458 

13.17913 

12,9151 

12.6614 

12 3996 

12,1394 

11 3417 

11.7450 

11 9 5494 

11+3550 

11 + 1619 

11.0272 

10.8931 

10.7597 

10 6269 

10 4949 

10.2857 

io 0753 

9.8984 

9.7708 

9.4i7a 

8.7227 

8.5339 

9.5935 

9 t 2354 

9.0529 

8.3477 

8,1641 

7.7979 

7 4675 

7,3201 

7.1476 

7 0654 

7 1246 

7,9684 

7.0875 

7,1280 

7.1426 

7.1449 

7 1036 

7*1164 

7.2710 

7.2725 

7 + 3548 

7.3674 

7 + 4055 

:T= 85.7 

141 

-0 0000 

-0.0002 

0 .oooo 

-0.0002 

-0 000 1 

-0.0002 

-0.0002 

-0.0001 

-0.0002 

-0 * 000 1 

-0.0001 

-0.0002 

-0.0001 

-0 t 0002 

-0.0000 

-0.000 1 

-0 .oooo 

-0 .oooo 

-0 * 0000 

-0 t 0002 

-0.0001 

-0,0002 

-0 t 0000 

-0.0001 

-0.0001 

-0.0002 

-0.000 1 

-0 t 0002 

-0,0001 

-0 + 0001 

-0.0001 

'0.0001 

-0 0001 

-0 000 1 

-d. 0002 

-0.0000 

-0 t 0002 

-0.0001 

-0.0001 

-0.0001 

-0,0001 

-0.0001 

-0.0000 

-0.0000 

-0 0001 

-0 0000 

-0 t 0000 

-0.0000 

0.0000 

-0.0001 

-0.0001 

-0.0001 

-0.0001 

-0 t 0000 

-0 .oooo 

-0.0000 

-0 .oooo 

0,0001 

-0 0000 

0.0000 

0 .oooo 

0.0000 

83 

43 + SO77 

54 9653 

61+2112 

66 7621 

75.8754 

ai.0813 

a2 1940 

83.0120 

84.1084 

a4.9081 

as ,0732 

as .so94 

96,3156 

86,5542 

86. a202 

87 + 0849 

87.6005 

a7 ,8607 

8ti.0584 

aa.2551 

a8.4507 

aa.6451 

88. 8382 

aa ,9730 

a9.1070 

a9 3732 

a9.5052 

a9.9217 

77 9065 

79 6463 

85 + 9040 

07 3388 

89 + 2404 

89.7143 

90. ioia 

90 t 2292 

90 t 4066 

90,7647 

90 9372 

91 + 2774 

91 4662 

91,6523 

90,5823 

91,9359 

92 + 0317 

92 t 2022 

92.5325 

92 t 6799 

92.8524 

92.8755 

92.8574 

92.assi 

92.8721 

92,8838 

92 9347 

92 t 912s 

92 + 0964 

92 + 7290 

92 727s 

92,6432 

92 6326 

92,5945 

56.4924 

45 + 0349 

38.7887 

33.2381 

24 1247 

22 t 0937 

20.3538 

ia.9iaa 

17. a062 

16 + 9880 

15.0916 

15+0921 

14 9269 

14 4907 

14.0960 

13 6045 

13,4458 

13.1798 

12.9151 

12 + 6614 

12.3996 

12.1394 

11,9417 

11,7450 

t1.5494 

11.3550 

11 t 1619 

f 1 t 0272 

io.a93i 

IO + 7597 

IO + 6269 

10 4949 

io.2a57 

so. 0783 

9,8984 

9 7708 

9.4178 

a + 7227 

a. 5339 

a 3477 

9 5935 

9.2354 

9 t 0629 

8,1641 

7 t 9604 

7 7979 

7 4675 

7,3201 

7.1476 

7 0654 

7 1246 

7.0875 

7,1280 

7.1426 

7 1449 

7 + 1036 

7,1164 

7.2710 

7 t 2725 

7 + ?&74 

7 4055 

7 +356a 

-0.0000 

-0,0002 

0 * 0000 

-0.0002 

-0.0001 

-0.0002 

-0,0002 

-010001 

-0 0002 

-0,0001 

-0*0001 

-0 6 0002 

-0 * 0001 

-0 t 0002 

-0 .oooo 

-010001 

-0 .oooo 

-0 .0000 

-0 0000 

-0.0002 

-0 0001 

-0.0002 

-0 t 0000 

-0.0001 

-0.0001 

-0,0002 

-0.0001 

-0.0002 

-0.0001 

-0.000 1 

-0.0001 

-0.000 1 

-0,0001 

-0.0001 

-0 t 0002 

-0.0000 

-0 t 0002 

-0.0001 

-0.0001 

-0 * 000 1 

-0.0001 

-0.0001 

-0 + 0000 

-0.0000 

-0.0001 

-0.0000 

-0 .oooo 

-0 .oooo 

0.0000 

-0.0001 

-0.0001 

-0,0001 

-0 0001 

-0 0000 

-0 * 0000 

-0.0000 

-0 * 0000 

0.0001 

-0.0000 

0 0000 

0 0000 

0.0000 
PERKIN-ELMER 

Table 5 

Computation of Reflectivity of 280A Aluminum Over Iridium 

15:27:02 >OPTCT2 

FI 10 DISK IRRID2 OFTCON A1 RECFM FB LRECL 80 BLKSIZ 800 DISP HOD PERM ) 

FJ 11 DISK ALUH2 OPTCON A1 ( RECFH FB LRECL 80 BLKSIZ 800 DISP HOD PERH 

F( 12 DISK LIF OPTCON A1 ( RECFH FB LRECL 80 BLKSIZ 800 DISP MOD PERM ) 

Ff 8 PRT 

FI 6 TERHINAL 

LOAD OPTCOAT ( CLEAR 

START ~ EXECUTION: 

OPTICAL PROPERTIES OF THIN FILMS OVER SUBSTRATE 

MOnE=l FOR SHORT PRINT OUT 

MODE=2 FOR SPECTRAL SCAN ONLY 

HODE=3 FOR ANGLE SCAN ONLY 

MODE=4 FOR FULL PRINT OUT 

ENTER HODErDESIGN.WLrOPERATING WLpWL STEP, NO. OF FILHS 8 ANGLE OF INC 

>2, 0.9 0.9 o., 1, 0.9 

*HAVE HODE= 2 0.0 0.0 0.0 NFL= 1 ANGLE= 0.0 

SUBSTRATE IS IRRI N AND Kr 108 VALUES, 113-1771 A 

HAVE READ IN 108 LINES FOR SUBSTRATE 

COAT NO. 1 IS ALUH N AND Kr 108 VALUES, 113-1771 A 

INPUT PHYSICAL THICKNESS OF THIS LAYER IN ANGSTROHS AND NAME 

HAVE READ IN 108 LINES FOR COATING 

>280*rALUH I 

ANGLE= 0.0 DEGREES 

WAVELENGTH 

c .E;::: 

0.0495920 

0 0506040 

0 0516580 

0+0523120 

0 t 0525340 

0 t 0529830 

0.0532100 

0 OS34400 

0*0536710 

0 t 0537870 

0.0539040 

0 + 0540220 

0 +0541400 

0 t 0543770 

0+0548580 

0 + 0553480 

0 0558470 

0 0563550 

0 t 0568720 

0 t 0573980 

0 + 0579350 

0 t 0590380 

0 0604780 

0619900 

0635790 t 4 0652530 

0 t 0666560 

0 + 0670159 

0 t 0673800 

0 + 0677490 

0 0688780 

0 + 0700450 

0 t 0704430 

REFLT 

AVERAGE 

0 + 0583 

12.1521 

11.8196 

10 + 981 1 

10.7891 

10 8376 

10 8557 

10,9405 

10 8909 

10 9855 

11.0949 

11 + 1589 

11 t 2068 

11.2653 

11,4086 

11 +8100 

12 2488 

12.7467 

13.2252 

14,0696 

15+0518 

16.1589 

18,9206 

22.6916 

26 

31 

35 

38 

39 

40 

41 

43 

44 

45 

9370 

0421 

3918 

7276 

5141 

2630 

1461 

3044 

9569 

6770 

0.0708460 46.5145 

0,0712529 46.7425 

0~0716650 48,2959 

Oe0733610 51.0468 

0+0755979 55.1186 

0.0765310 56,6789 

TRANS 

AVER AGE 

68 t 7663 

72.1912 

71 9426 

71 + 4551 

70.7369 

70.4402 

69 8588 

69 + 6358 

69,3143 

6a .9786 

68.7326 

68.5517 

68 t 4910 

68 3954 

68 t 2364 

67 4 6981 

67.2169 

66 6481 

65 + 8247 

64 8016 

63 6901 

62 t 5030 

59.7424 

56 3264 

52,1473 

49 + 21 10 

45.7153 

43 3062 

42 t 7034 

42 + 0996 

41 + 5098 

39.8512 

39 0452 

38 + 3567 

37 t 8367 

37 7631 

36 6238 

34 5329 

31 e4227 

29 + 9963 

ABSORP 

AVERAGE 

31 1754 

15 6566 

16,2379 

17 5638 

18 4740 

18.7222 

19 2855 

19 t 4236 

19,7948 

20 t 0359 

20 1726 

20 e2894 

20 3022 

20.3394 

20 3550 

20.4919 

20 5343 

20 + 6051 

20+9501 

21 + 1288 

21 +2581 

21 + 3381 

21 + 3370 

20 + 9820 

20,9156 

19 t 7469 

18,8929 

17.9662 

17 + 7825 

17.6374 

17.3441 

16 + 8444 

15 9979 

15 t 9664 

15 t 6487 

15.4944 

15 0803 

14 t 4203 

13 + 4587 

13.3248 

REFLT 

s-POL 

0 0583 

12.1521 

11.8196 

10 981 1 

10 7891 

1018376 

10 + 8557 

10 9405 

10.8909 

10 e 9855 

11.0949 

11.1589 

11 t 2068 

11.2653 

11 4086 

11+8100 

12 2408 

12.7467 

13.2252 

14,0696 

15 0518 

16.1589 

18 9206 

22 t 6916 

26 t 9370 

31.0421 

35,3918 

38 $7276 

39,5141 

40 2630 

41 1461 

43 3044 

44 9569 

45.6770 

46 15145 

46 *7425 

48.2959 

51 e 0468 

55,1186 

56 6789 

142 

TRANS 

s-POL 

68 t 7663 

72.1912 

71 e9426 

71,4551 

70 7369 

70 t 4402 

69 * 8580 

69 6358 

69,3143 

68 t 9786 

68 + 7326 

68.5517 

68,4910 

68 t 3954 

68,2364 

67.6981 

67,2169 

66.6481 

65 t 8247 

64.8016 

63,6901 

62 t SO30 

59.7424 

56 3264 

52 1473 

49.2110 

45,7153 

43 + 3062 

42 7034 

42 t 0996 

41 5098 

39.8512 

39 t 0452 

38 3567 

37 8367 

37 + 7631 

36 + 6238 

34.5329 

31,4227 

29.9963 

ABSORP 

s-POL 

31 t 1794 

15.6566 

16 2379 

17 + 5638 

18,4740 

18,7222 

19.2855 

19,4236 

19.7948 

20.0358 

20 1726 

20 t 2894 

20+3021 

20 t 3394 

20 + 3550 

20.4919 

20.5343 

20 +SO51 

20 + 9501 

21 e 1288 

21 ,2581 

21,3381 

21,3370 

20 + 9820 

20*9156 

19,7469 

18.8929 

17 9662 

17,7829 

17.6374 

17.3441 

16.8444 

15.9979 

15 t 9664 

15 t 6487 

15.4944 

15 0803 

14 4203 

13 + 4587 

13 3248 

IN DEGREES 

REFLT 

F-POL 

0 t 0583 

12,1521 

11.8196 

10,9811 

10.7891 

10 8376 

10 t 8557 

10,9405 

10*8909 

10 9855 

11,0949 

11.1589 

11,2068 

11,2653 

11 + 4086 

11+8100 

12 2488 

12 7467 

13 t 2252 

14 0696 

15,0518 

16.1589 

18,9206 

22 t 6916 

26 e9370 

31,0421 

35 9 3918 

38 t 7276 

39.5141 

40 + 2630 

41.1461 

43 + 3044 

44 + 9569 

45 t 6770 

46.5145 

46 + 7425 

48 2959 

51.0468 

55.1186 

56 t 6789 

TRANS 

P-POL 

68 t 7663 

72.1912 

71 + 9426 

71,4551 

70,7369 

70 4402 

69 t 8588 

69 + 6358 

69,3143 

68 9786 

68 + 7326 

68.5517 

68.4910 

68 e3954 

68 + 2364 

67,6981 

67.2169 

66+6481 

65 + 8247 

64,8016 

63.6901 

62 + 5030 

59 * 7424 

56 e3264 

52 1473 

49 t 2110 

45 e7153 

43 + 3062 

42 7034 

42 t 0996 

41 5098 

39 + 8512 

39 t 0452 

38 t 3567 

37 + 8367 

37 7631 

36 + 6238 

34.5329 

31 t 4227 

29 t 9963 

ABSORP 

P-POL 

31 t 1754 

15.6566 

16,2379 

17,5638 

18 9 4740 

18 t 7222 

19.2855 

19 t 4236 

19.7948 

20 + 0358 

20 I 1726 

20 t 2894 

20 3021 

20 t 3394 

20 e 3550 

20,4919 

20 + 5343 

20 + 6051 

20 9501 

21 + 1288 

21 ,2581 

21,3381 

21,3370 

20 + 9820 

20.9156 

19.7469 

18 + 8929 

17+9632 

17,7825 

17,6374 

17.3441 

16,8444 

15 t 9979 

15.9664 

15 t 6487 

15 4944 

15 + 0893 

14.4203 

13,4587 

13.3248 
PERKIN-ELMER 

0770060 

0 t 0774879 

0 t 0779750 

0 0784680 

0 + 0709680 

0.0799870 

o+oai0330 

0 *0821060 

0 + 0826530 

0 t 0832080 

0 0843400 

o .0549180 

o + 05.50959 

o ,0866989 

0 t 0855030 

0 t 0373 100 

0 t 0879290 

0 ,0385559 

0 + 0888750 

0+0391940 

0+0895160 

0.08?8409 

0,0901670 

0 0904959 

0.0908179 

lp 0911620 

. .0914980 

0+0918370 

0.0921780 

0 t 0925120 

0 0928690 

0.0932180 

0.0935700 

0 t 0939240 

0,0942810 

0 + 09 96410 

0 + 0950040 

0 t 0953690 

0 + 9957370 

0,0961090 

0.0964020 

0 0968590 

0 t 0972390 

0 + 0976210 

0 0980080 

0.0983970 

0.0991840 

0,0999840 

01 1007970 

0 t 1016230 

0 t 1026000 

< 1033170 

0.1055149 

0 t 1064000 

0 1078009 

0.1100000 

0.1102040 

0.1127090 

0 1149999 

0.1190760 

01 1216000 

ot 1239800 

0 t 1300000 

0 t 1377560 

0+1400000 

Q+ 1549750 

f 1600000 

0.1771 140 

57 L 5309 

sa 3125 

59.1106 

60 e 0791 

60 t 8541 

62 + 7822 

64 t 6598 

66 4664 

67 t 3737 

68 +3135 

70.3871 

70,9787 

72,8724 

74.8153 

71,5994 

72 1342 

73,4318 

74 t 1753 

74,9527 

75.3913 

75 7546 

76,1166 

76 + 3951 

76 t 6920 

76.9923 

77 2693 

77 4 5647 

77 + 3627 

78.1168 

78,3599 

78.6167 

70,9752 

79 1322 

79.3397 

79.5574 

79.7751 

79 9907 

80,1990 

80 4657 

80,7231 

80.9731 

ai ,1872 

ai ,6936 

82,2217 

a3.107a 

83, 8202 

84 ,Zoos 

84,5332 

85.3259 

as ,6904 

86.4290 

86 ,8977 

87.0551 

87.4111 

a7 9242 

88.2686 

88. 4860 

89.5651 

81.4421 

81 o 9727 

82.7177 

83 + 4693 

86.0263 

86.3864 

86.7332 

87 2289 

89 t 9341 

90,8166 

29,3915 

28 7249 

28.1413 

27 + 6427 

27.0831 

25.9106 

24 8240 

23,5077 

22.9066 

22 3093 

21 1479 

20 + 5069 

19 t 9277 

19.3631 

18,7947 

18.2209 

17 t 6705 

17.1336 

17 0300 

16.6205 

16.33ai 

15.5818 

16.0915 

15 t 8347 

15.3310 

15,1168 

14.8808 

14 t 6469 

14 4299 

14.2286 

14.0156 

13.8045 

13.5990 

13 t 4107 

i3.2i4a 

13.0211 

12.8331 

12 t 6532 

12.4712 

i2.300a 

12+1215 

11.9450 

11,7655 

11.5919 

11+39OO 

11.2221 

10+8910 

10 5625 

10,2689 

9.9890 

9 t 6910 

9 9 4299 

8 7573 

8 t 4575 

a 2084 

7 t 7756 

7.7691 

7.3641 

7 0644 

6 825s 

6 t 5623 

6.3376 

5 6331 

4 + 9796 

4.7088 

it 8892 

3 3170 

2.8796 

Table 5. 

13 + 0776 

12.9626 

12.7481 

12 t 2782 

12 0628 

11.3072 

10,5162 

10.0259 

9.7197 

9.3773 

8,5143 

8 + 4728 

8 t 4027 

8 3329 

a. 4650 

a .3474 

a.1462 

7,9883 

8.0511 

8.0174 

7.9073 

7 7920 

7 t 7703 

7 7263 

7 + 6767 

7,6138 

7 t 5545 

7 * 4904 

7 4534 

7.4117 

7 3676 

7 -320% 

7 2496 

7 2279 

7,1762 

7 2688 

7,2038 

7.1478 

7 + 0630 

6.9761 

6 9054 

6 .a679 

6 + 7924 

6.7145 

6 6373 

6 5562 

6,3913 

6 3297 

6,2618 

6.1907 

6 1003 

6 0370 

5.8522 

5 + 7653 

5.7954 

5 9027 

5.916a 

5.8445 

6.0380 

6.20aa 

6.75ia 

7.1863 

6.1195 

6.2513 

6 + 4427 

6 8052 

7.1179 

7 2942 

57 5309 

sa. 3125 

60.a541 

59.1106 

60.0791 

62 7822 

64 e 6598 

66 + 4664 

67 3737 

68.3135 

70.3a7i 

70.9787 

71.5994 

72 t 2342 

72 t 8724 

73.4318 

74 t 1753 

74.8153 

74 t 9527 

75.3913 

75.7546 

76,1166 

76 + 3951 

76 6920 

76.9923 

77 t 2693 

77 t 5647 

77 8627 

78, i 168 

78.3598 

78.a752 

78 + 6167 

79 1322 

79.3397 

79 5574 

79.7751 

79.9907 

80.1990 

80,7231 

80 4657 

80 9731 

81 t 1872 

81.4421 

81.6936 

81 + 9727 

82.2217 

82.7177 

83.1078 

83. a202 

84 2008 

85.3259 

85.6904 

86.0263 

86.4290 

86.3864 

7332 

ab. a977 

a7.4111 

87.9242 

88 ,2686 

8a.4a60 

83 t 4693 

84,5332 

87 0551 

87 t 2289 

89,9651 

89.9341 

(Continued) 

2943915 

28.7249 

2a.1413 

27 6427 

27 * 0831 

25,9106 

24.8240 

23 5077 

22 9066 

22.3093 

21 + 1479 

20 t 5069 

19 9277 

19.3631 

ia.7947 

ia.2209 

i7.67a5 

17.1336 

17 0300 

16 + 6205 

16 3381 

16.0915 

15.8347 

is. 5818 

14.88oa 

14.2286 

15.3310 

1511168 

14.6469 

14.4299 

14.0156 

13 + 8045 

13 5990 

13,4107 

i3.2i4a 

13 021 1 

12 8331 

12.6532 

12 4712 

12 3008 

12.1215 

11.9450 

11,7655 

11.5919 

11.3900 

11*2221 

10*8910 

10.5625 

10 t 2689 

9 t 9090 

9.6910 

9 + 4299 

a ,7573 

a + 4575 

a. 2084 

7 t 7756 

7.7691 

7.3641 

7 0644 

6,a255 

6 5623 

6 3376 

5.6331 

4 + 9796 

4.7088 

2.8796 

3.3170 

13.0776 

12 + 9626 

12.7481 

12.2782 

12.0628 

11.3072 

10 5162 

1010259 

9.7197 

9 t 3773 

8.5143 

8 + 4728 

a. 4650 

a. 4027 

a. 3474 

8 3329 

8,1462 

8,0511 

8 + 0174 

7.9883 

7 t 9073 

7,7920 

7 7703 

7 t 7263 

7 9 6767 

7.6138 

7 t 5545 

7 + 4904 

7.4534 

7,4117 

7,3676 

7.3203 

7.2688 

7 + 2496 

7.2279 

7.2038 

7 + 1762 

7.147% 

7 0630 

6,9761 

6 + 9054 

6.8679 

6.7924 

6.7145 

6 6373 

6 + 5562 

6.3912 

6 t 3297 

6.26ia 

6,1907 

6 + 1083 

6 0370 

5.9168 

5. 8522 

5.7653 

5 t 7954 

5 t 8445 

5 9027 

6 t 0380 

6.1195 

6.2088 

6,751a 

6. 8052 

7.1863 

6.2513 

6 4427 

7.1179 

7 t 2942 

57 t 5309 

5a.3125 

60. a541 

62,7822 

64.6598 

6a.3135 

90.3a7i 

70.97a7 

59,1106 

60+0791 

66 4664 

67 + 3737 

71 45994 

72 t 2342 

72 8724 

73.4318 

74,8153 

74 e 1753 

74.9527 

75.3913 

75 t 7546 

76.1166 

76,3951 

76 t 6920 

76+9923 

77 t 2693 

77 .L 5647 

77.8627 

78,3598 

78.8752 

78 t 1168 

78 + 6167 

79 1322 

79,3397 

79.5574 

79 t 7751 

79,9907 

ao. 1990 

ao.7231 

ai.ia72 

80.4657 

80 + 9731 

81.4421 

81.6936 

81 t 9727 

82 + 221 7 

82,7177 

83 1078 

83,4693 

83.8202 

84.5332 

85 6904 

86.4290 

86 .a977 

87.0551 

87,2289 

88,2686 

88. 4860 

89.5651 

a9.9341 

9o.ai66 

84 2008 

85.3259 

86 t 0263 

86 t 3864 

96.7332 

87.411 1 

07.9242 

29 + 3915 

$8 + 7249 

2a.1413 

27 t 6427 

37.0031 

25.9106 

34 8240 

33 5077 

22.9066 

32 3093 

21.1479 

40 .SO69 

19 9277 

19,3631 

18.7947 

18 ,2209 

17,6785 

17,1336 

17.0300 

16 6205 

i6.33ai 

15,5818 

i4.88oa 

16+0915 

15 t 8347 

15.3310 

15.1168 

14.6469 

14.4299 

14.2286 

14.0156 

13 + 8045 

13.5990 

13.4107 

13.2148 

13.0211 

12,8331 

12 6532 

12.4712 

12.1215 

f 1 9450 

11.7655 

11.5919 

11,3900 

11,2221 

10.8910 

10,5625 

10.2689 

9 9890 

9.6910 

9 * 4299 

i2.3ooa 

'8 t7573 

; 8,4575 

8 2084 

,7 t 7756 

,7+7691 

7.3641 

7 + 0644 

6. 825s 

6.5623 

6 3376 

5.6331 

4 + 9796 

'4.70aa 

1. 8892 

3.3170 

2.8796 

13.0776 

12 t 9626 

12.7481 

12 2782 

12.0628 

11,3072 

10.5162 

10.0259 

9,7197 

9.3773 

a. 4650 

8.5143 

a + 4728 

8. 3329 

8 t 4027 

8.3474 

8.1462 

8.0511 

8.0174 

7.9883 

7.9073 

7 t 7920 

7 7703 

7 + 7263 

7.6767 

715545 

7 + 4904 

7.4534 

7.4117 

7 3676 

7 t 3203 

7.6138 

7.2688 

7 t 2496 

7,2279 

7 203% 

7 1762 

7.1478 

7.0630 

6,9761 

6 9054 

6.8679 

6.7924 

6,7145 

6 6373 

6 t 5562 

6 + 3912 

6.3297 

6.2618 

6 1907 

6 1083 

6 0370 

5.9168 

5 * 8522 

5.7653 

5.7954 

5.8445 

5 t 9027 

.5 .ma0 

6.208a 

6,7518 

7 1863 

6.1195 

6,2513 

6 4427 

6 8052 

7.1179 

7 + 2942 

ioa WAVELNGTHS, sun OF REFL= 
PERKIN-ELMER 

APPENDLX C 

ER-591 

TABLES OF OPTICAL CONSTANT 

The tables on the following pages list the optical constants n and k for coating 

materials that we have considered in this study, aluminum, aluminum oxide (Al203), 

iridium and lithium fluoride, for wavelengths from to 1771 A (7 eV to 110 eV), 

with frequent values given for = 500 1 to 1200 A. The data for aluminum is from 

Physics Data, Volume 2 (169), with some interpolations. The data for AI203 and for 

iridium are from a 1982-83 compilation by Michael Hettrick (University of California, 

Berkeley) based on an exhaustive survey of experimental and theoretical literature (71, 

199). We are grateful to Hettrick for this data. The constants for lithium fluoride are 

largely from Roessler and Walker (1881, with some interpolations, and are based on bulk 

LiF rather than thin film data. This data was considered more reliable than that of 

Kat0 (197, 198). 

= 113 

Although not tabulated in this Appendix, we have also used n and k data for magnesium 

fluoride (MgF2) from Gillette (50) and from a Perkin-Elmer optical constant data file. 

The complex index of refraction g = n - ik is related to other commonly used optical 

constants by the following inter-relationships: 

real index of refraction 

extinction coefficient or absorption index 

complex dielectric constant = (1-6 -ik)2 

€1 +iE2 

absorption coefficient (cm-1) 

(1-612 - k2 

- 2k(l-6) 

4WX 

1 -n 

144 
PERKIN-ELMER 
PERKIN-ELMER 

Table 6. (Continued) 
PERKIN-ELMER 

Table 7 

Optical Constants of Aluminum Oxide (Al203) in Far Ultraviolet 

-i 1- 

-. . ...... .i.. ... .. ....... i ". ............ ..* I 

,. 

). _.I,_ .- :_._I .Ai .? , 

.... ... .. .?,i 

............... 

.. 

147 

... 
PERKIN-ELMER 
PERKIN-ELMER 
PIERKlN-ELMER 

Table 8. (Continued) 
PERKIN-ELMER 

, .. 
PERKIN-ELMER 
PERKIN-ELMER 

APPENDIX D 

ER-591 

FORTRAN MOLECULAR FLUX PROGRAM 

A simple Fortran program for computing the (non-Maxwellian) velocity distribution of a 

Maxwellian gas moving at a constant drift speed Vo is listed on the following pages. 

The program integrates this probability distribution over all possible directions in space 

and all possible speeds to derive the net flux of particles reaching a particular point 

from a given range of directions. That is, if a target point is shielded from a given 

range of directions (defined in terms of "latitude1' and 'Yongitude") the program sums, 

over all possible remaining directions and velocities, the probability that an atom from 

that direction at that velocity would exist. The resulting sum is proportional to the 

total mass flux or particles (cm3 sec1-l passing through the test point. 

All atoms are assumed to be oxygen atoms. The mass of the oxygen atom and 

Boltzmann's constant are written into the program. Input data include the drift 

velocity (km/sec), grid spacing for the numerical integrations (degrees), velocity 

spacing for the numerical integration and the number of velocity increments to make, 

the gas temperature, and the size and shape of the latitude, longitude region from 

which to accept atomic trajectories. Straight-line trajectories are assumed, that is, the 

mean-free path is assumed much larger than the size of the experimental target region, 

and no return flux or outgassing is added. 

The gas is assumed to be approaching from the direction of of latitude = Oo, longitude = 

1800. 

Therefore the program can calculate a number proportional to the pressure in a space 

shielded from a drifting Maxwellian gas by a shield of arbitrary size and shape. To 

normalize the calculation to absolute numbers, the numerical integrations must be 

repeated over 4 '~t steradians. 

The absolute density of major constituents of the ambient neutral atmosphere are 

shown in Figure 49, as functions of solar activity (105). 

153 
PERKIN-ELMER 

Program "MOFLUX" Fortran Listing 

.... 

.: . 

. I_ ..i 

. ... 

i I 

. .. .a. ii 

, .... 

I. .. 

. .. 3. . 

I. :L 

.. 

": I /.. .1. 

. .,. .- -i: i 

154 
.- 

PERKIN-ELMER 

.- . I.> . 

., .. 

_.: 

, L. 

. . ., 

. .. ... ... I 2. 

.. 

.- . a., .. I- .; 

“l I 

._ _* 

.: , ,’( .i .I 

. . . .. .. 

155 
PERKIN-ELMER 

1'00l\ 

'300 

800 

700 

GO@ 

5 00 

400 

300 

200 

100 

0 

lo2 1 o4 1 o6 1 o8 1o1O 10l2 10 1 

CONCENTRATION (~rn-~) 

Figure 49. Distribution of Major Constituents 

of Neutral Atmosphere at Extremes 

of Solar Activity (105). 

156 
PERKIN-ELMER 

APPENDIX E 

BIBLIOGRAPHY ON THE CONTAMINATION AND DEGRADATION OF 

MIRRORS AND OPTICAL ELEMENTS IN A SPACE ENVIRONMENT 

Alan N. Bunner 

Perkin-Elmer 

October 14, 1983 

The attached bibliography, arranged alphabetically by author, covers primarily 

published papers and reports related to mirrors used for ultraviolet wavelengths in a 

space environment and considerations related to the degradation of their reflectivity. 

The subject matter categories provide a key for a selection of references that may be 

useful for a particular question. In this key, degradation means loss of reflectivity or 

transmissivity; contamination means the deposition of foreign material; optical coatings 

means thin films; ultraviolet includes EUV wavelengths. Very few references on 

infrared reflectivity or the degradation of infrared mirrors are included. 

Subject Matter Categories 

A. 

B. 

C. 

D. 

E. 

F. 

G. 

H. 

I. 

J. 

K. 

L. 

MI 

Ultraviolet 

Reflectivity 

Optical Constants 

Mirrors 

Degradation 

Contamination 

Optical Coatings 

Cleaning 

Radiation Damage 

Transmitting Elements 

Thermal Coatings 

Coating in Space 

Upper Atmospheric Oxygen 

157 
PERWN-ELMER 

1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

-9 Princeton Advanced Satellite Study, 

Perkin-Elmer Report No. 8346, pps. 2-20, 

May 1966. 

-’ Optical Technology Apollo Extension 

System (OTES) Phase A Study Final Report, 

Perkin-Elmer/Lockheed, Perkin-Elmer Engineering Report ER-8900, October 1967. 

, Large Telescope Experiment Program 

Imp), Perkin-Elmer Engineering Report No. 

ER-9800, April 1970. 

, Spacecraft Contamination Under Simulated Orbital Environment, Interim Report, 

Aerospace Corp., SAMSO-TR-77-130, July 

1977. 

-’ Presentation Material Volume, NASA 

Shuttle Environment Workshop, Calverton, 

MD, October 5-7, 1982. 

-7 Shuttle Mission 5 to Study Orbiter Glow 

Phenomenon, Av. Week & Space Tech., 

November 1, 1982, p. 64. 

-’ The Final Report of the Science 

Working Group for the Far Ultraviolet 

Spectroscopic Explorer, April 1983. 

R.J. Adornato, Retrieval and Servicing of 

Contamination Sensitive Satellites, AIAA 

Conference on Technology for Space 

Astrophysics: The Next 30 Years, Danbury, 

Conn. October 4, 1982. 

M.R. Adriaens and B. Feuerbacher, Improved 

LiF and MgF2 Overcoated Aluminum Mirrors 

for Vacuum Ultraviolet Astronomy, Appl. Opt. -’ 10 958 (1971). 

D.W. Angel, W.R. Hunter and R. Tousey, Extreme Ultraviolet Reflectance of LiF-Coated 

Aluminum Mirrors, J.O.S.A. 2, 913 (1961). 

J.D. Austin, Test Program on the Contamination of Ultraviolet-Region Mirrors by Apollo 

Telescope Mount Materials, Ball Brothers Research Corp., Final Report, NASA-CR-120516, 

January 1974. 

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DEFG I 

DE GH 

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JKLM 

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158 
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12. 

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23. 

24. 

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the Understanding of Solar Variability, Solar 

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A.P. Bradford, et. al., Preparation of Mirror 

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Station Salyut-4, Bull. Crimean Astrophys. 

Obs. - 59, 31 (1979). 

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Appl. Physics 16, L129 (1983). 

W.M. Burton, High Reflectance Mirrors for 

EUV Space Instrumentation, Proc. SPIE 445, 

(1 983). 

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Studies on MgF2-Overcoated Aluminum 

Mirrors with Highest Reflectance in the 

Vacuum Ultraviolet, AppLOpt. 5, 45 (1966) 

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Haze, Aerospace Corp. Report No. TR-0081 

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Technical Memo NASA-TM-80551, August 

1979- 

J.T. Cox, G. Hass and J.E. Waylonis, Further 

Studies on LiF-Overcoated Aluminum Mirrors 

With Highest Reflectance in the Vacuum 

Ultraviolet, Appl. Opt. - 7, 1535 (1968) 

J.T. Cox et al., Reflectance and Optical Constants of Evaporated Osmium in- the Vacuum 

Ultraviolet- from 300 to 2000 #,J.O.S.A. -7 63 

435 (1973). 

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8 and 1400 8, C.R. Acad. Sci. B (France), -9 269 

901 (1969). 

A. Daude and S. Robin, Apparatus to Determine the Optical Properties in the Extreme 

Ultraviolet of Films which are Evaporated and 

Stored in Ultra-High Vacuum torr), 

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C.C. Edwards and 3.R. Day, Method for Providing Mirror Surfaces with Protective Strippable Polymeric Film, U.S. Patent No. PATAPPL-6-024 340, filed 22 March 1979. 

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42. L.B. Fogdall and S.S. Cannaday, Radiation 

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43. L.B. Fogdall et ai., Radiation Effects in 

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44. A. Franks et. al., Effects of Synchrotron 

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45. G.H. Freeman and M.A. Rejman, The Vacuum 

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Physical laboratory (U.K.) Report No. NPLQU-12, August 1970. 

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Studies of the Reaction of Clean Metals (Mg, 

Al, Cr, Mn) with Oxygen and Water Vapor, 

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Effects on Solar Concentrator Reflective Surfaces, NASA-CR-1024, May 1968. 

49. R.B. Gillette and B.A. Kenyon, Proton-Induced 

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Proton-Induced Effects on Reflective Surfaces 

of Space Mirrors, Boeing Go., Report No. 

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Device, Final Report, Boeing Aerospace, 

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R. Shannon, R. Gillette and G. Crut, Active 

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124. 

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L. Spitzer, Sensitivity Loss in Copernicus, AB DEFG I J M 

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M.R. Torr et al., Intercalibration of Airglow 

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APPENDIX F 

Adhesion 

Apollo Telescope Mount 

Astronaut Participation 

Atomic Oxygen 

Bakeout 

C leaning 

Contamination 

Deposition Rate 

Diode Detector Ir 

Dust Contamination 

Electron Beam Evaporation 

Extra-Vehicular Activity 

Fast Atom Bombardment 

Figure of Merit 

Filters 

Flight Vector 

Fluence 

FUSE 

Geosynchronous Orbit 

Grazing Incidence 

Heaters 

International Ultraviolet 

Explorer 

9, 42, 56, 70, 115 

15, 38 

1, 2, 76-77, 11, 75, 92, 94, 

106 

27, 32, 38, 40, 47, 48-50, 

62, 73, 75, 81, 152, 156 

27, 40, 91 

9, 41, 70, 87, 99-102, 105 

See Dust Contamination, 

Molecular Contamination 

27, 28, 69, 114 

70, 71 

74 

55-56, 66, 102-103, 109 

77, 92, 98 

27, 62, 73, 82, 87, 91, 115 

43, 66, 87 

17, 62 

39, 40, 51, 52, 56, 58, 75, 

76, 80, 87, 153 

39 

4) 21 

8, 17, 46 

4, 104, 114 

27, 54, 78, 91 

2 
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Ionization Gauge 

Iridium 

Langmuir 

Li f e t ime 

Liquids 

Manned Mission 

Mean Free Path 

Molecular Contamination 

Molecular Shield 

OAO Ocopernicus 

Optical Constants 

Orbit 

Osmium 

Outgassing 

Oxidation 

Photopolymerization 

Plasma Cleaning 

Polarization 

Power Supplies 

Reaction Rate 

REVAP, Re-evaporation 

Process 

Scattering 

Silicon Carbide 

Skylab 

Solar Activity 

- 55, 63, 80 

- 9, 10, 39, 63, 132, 142-143, 149 

- 80, 43 

- 10, 15, 41, 46, 80 

- 27, 74, 97-99 

- See Astronaut Participation 

- 51, 153 

- 17, 27, 29-31, 39, 41, 81-86, 91, 111 

- 48-53, 77, 93, 153 

- 2, 6, 14, 49 

- 43, 87, 132, 144-152 

- 32, 38, 42, 46-48, 75 

- 6, 39, 40 

- 11, 36, 40, 51, 55, 79, 81, 

92, 98 

- 4, 10, 14, 17, 23-36, 39, 

44-46, 78, 80, 115 

- 4, 8, 17, 27, 42, 48, 81-82, 

91 

- 17, 27, 29-31, 70, 73, 102 

- 109, 132 

- 14, 73, 74, 109 

- 23, 24, 39, 41, 43, 78, 81, 

115 

- 21, 22, 23 

- 9, 11, 21, 55, 66-67, 87, 

90, 115 

- 6, 63 

- 15, 38 

- 48-50 

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Solar Optical Telescope 

Solar Telescopes 

Solar Variability 

Space Platform 

Space Telescope 

"Spartan" Payload 

Sputtering 

Sticking Efficiency 

Transition Metals 

Tungsten Filament 

Ultraviolet Space 

Observatory (UVSO) 

Vacuum Research Facility 

- 42 

- 8, 32-38, 67, 81, 83, 84 

- 48, 50, 56-57 

- 1, 54, 59, 92, 114 

- 6, 10, 15, 17, 49, 51 

- 54, 114 

- 17, 38, 66 

- 15, 43, 45 

- 7, 63 

- 62, 66-67, 78, 102-103, 109- 

110 

- 4, 17 -21 

- 93, 42, 48 

173