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DEPARTMENT OF THE AIR FORCE 

WASH I NGTON 

OFFICE OF THE SECRETARY 

MEMORANDUM FOR DR. FLAX 

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FEB 9 1967 

SECRET 

SUBJECT: Application of MOL to Astronomical Observations 

Attached is a letter I have just received from Homer 

Newell regarding the use of the DORIAN sensor for astronomical 

observations. Dr. Newell essentially confirms that the sensor 

is useful for planetary observations-:--,On this basis we shall 

fit planetary observations into our flight program on a noninterference basis. with the basic reconnaissance mission. 

I note that Dr. Newell considers that we should first 

collect planetary photography, and then work out any security 

procedures which may arise once the data can be examined and 

their relevance to NASA missions understood. I consider this 

reasonable. 

Dr. Newell also points out that significant benefits could 

be realized in NASA programs by adaptation of MOL telescope 

technology. I agree with this, and will refer the subject to 

the NRO for further action. 

I am not prepared at present to accept Dr. Newell's 

other comments relative to the use of the DORIAN sensor as 

an astronomical telescope. From our previous brief analysis, 

it does not appear to be unduly difficult and expensive to 

improve attitude reference, and broaden the spectral response 

capability of the instrument. However, I will pursue these 

points in more detail and advise you of results at a later time. 

ar 

HARRY f. EVANS 

Major General, USAF 

Vice Director, MOL Program 

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Major General Harry L. Evans, USAF 

Vice Director 

MOL Program Office 

Department of the Air Force 

Washington, D. C. 20330 

Dear General Evans: 

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NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 

WASHINGTON. D.C. 20516 

OFFICE OF THE ADMINISTRATOR 

FEB 7 1967 

 In response to your letter of August 4, 1966, a working 

 group was established to examine the suitability of MOL 

telescopes and flight missions for astronomical research. 

 This working group has met with personnel of your office 

 on several occasions, and has reviewed with me and my staff 

 their findings and recommendations relevant to your suggestion. 

 The application of MOL technology to astronomical research 

can be examined in four categories, as follows: 

(1) Use of existing design and equipment configuration, 

requiring no significant modification or addition to the basic 

instrumentation or operation plan. 

(2) Provision of an alternate image station in the 

current design of instrument, to accommodate specialized 

analytical detectors such as spectrometers, interferometers, 

photometers, and polarimeters. 

(3) Designing the following generation of instrumentation 

to provide capabilities for specialized astronomical observations. 

(4) Application of MOL technology (components, subsystems, 

procedures, etc.) to the development of NASA's cognate instrumentiation. 

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The high degree of specialization of the present MOL configuration 

severely restricts its potential for astronomical use. The 

limitation is most critical in the area of attitude control in 

the inertial reference system, and attitude stabilization 

commensurate with the optical resolution of the telescope, over 

a time scale as long as the orbital period. Precise attitude 

control is essential to direct the light of a selected star 

into the alit of a spectrometer, while wide field photography 

of faint objects requires steady guiding over lengthy integration 

times. 

In the framework of category (1) use, only bright objects, 

such as the moon and nearer planets, appear to be suitable 

targets. Useful observations of these objects can be made 

in the short exposure times available, and they are easily 

acquired by visual sighting or coarse attitude control. 

However, NASA's Lunar Orbiter and Apollo Mapping and Survey 

System Program are expected to provide superior observations 

of the moon sooner than MOL could. With respect to the planets, 

there is some rationale for securing random observations as the 

opportunity arises. The scientific interest in such observations 

is indicated in the attachment, "Use of a High Resolution Orbiting 

Telescope for Astronomical Observations by Direct Photography in 

Visible Light". 

Accordingly, I commend to you the acquisition of such observations 

of the planets as your missions can support on a non-interference 

basis. Since there exist no specific requirements for such 

observations, NASA can provide at this time no guidelines for 

selecting targets, modes of observations, or optimum times of 

observation. The principal uses of such data would be to support 

NASA planetary missions such as Mariner and Voyager flights. 

I suggest that security procedures relating to any eventual data 

should be worked out after the data can be examined, when their 

relevance to NASA missions can be better understood. 

The use of auxiliary equipment in conjunction with MOL telescopept, 

in the sense of Category (2) above, does not appear meritorious. 

High resolution analyzers of star light require lengthy integration • 

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exposures and precise guidance, and this would demand extensive 

modifications to the 14011. attitude control and stabilization 

systems. However, the potential gain, compared to existing 

ground-based telescopes, does not make this an attractive 

opportunity. 

The same reasoning applies even more forcibly to Category (3), 

the provision of astronomical observing functions in the basic 

design of follow-on systems. The cost of develOping.adequate 

guidance and control systems would be very high. We do not 

believe it would be a good investment unless accompanied by 

redesign of the optical system to permit observations below 

2900A°, In these respects, astronomical requirements appear 

to be in conflict with some of the requirements on MOIL hardware. Accordingly, I do not recommend pursuit of Category (3) 

developments. 

In considering the last category, adaptation of MOL technology 

. to NASA programs, it is clear that significant benefits can 

be realized. Much of the telescope technology could be directly 

beneficial to work planned in the NASA program. I therefore 

recommend that we continue to explore this category of cooperative 

effort, in order to identify particular items of technology that 

would be of benefit, and to create procedures which would allow 

their use by unclassified programs. 

Sincerely, 

00geHomer E. Newell 

Associate Administrator for 

Space Science and Applications 

Enclosure 

as stated 

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9 Dec. 1966 

Use of a High Resolution Orbiting Telescope for 

Astronomical Observations by Direct Photography 

in Visible Light. 

This report considers the usefulness of observations of astronomical 

objects by photographs in visible light with cameras capable of providing 

angular resolution between 0.2 and 0.3 arc seconds. Experience has shown 

that astronomical observations by direct photography can exceed nominal 

theoretical resolving powers (for certain classes of objects) for a given 

telescope when enough essentially redundant observations are available to 

Pt permit image averaging. Another muffed advantage is that the observational 

program will allow extended observations, approaching continuity, with 

picture rates ranging from a record every few minutes to several records 

per day over a time scale of a month or more. 

Mars an obvious. first choice for attention by the instrument under 

consideration. An obvious requirement is for cartographic survey maps 

of the entire planet. Only a few exceptional ground-based photographs 

have attained comparable resolution, but major areas of the planet's 

surface have not been so well studied. For example the Mariner '64 

pictures are not matched by highest resolution observations of the zone 

photographed during the fly-by. Time sequence photographs. of the surface' 

of Mars in visible light are highly desirable, especially at intervals of 

about 30 minutes. An important use of these observations is to determine 

whether the cloud surface velocity is what is claimed from quite rudimentary 

and scarcely adequate ground-based observations. Theory predicts that 

.erIg 

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surface winds on Mars must be of the order of hundreds of kilometers per 

hour. In point,

of fact, clouds appeared to move across the surface of the 

planet at lower velocities of the range 20 to 50 kilometers per hour. 

However, the observations are fragmentary and incomplete, so that the con* 

clusion is equivacable. Moreover, the limited resolution hitherto available 

has made the identification of a single cloud feature from one night to the 

next, conjectural, and in many cases dubious. 

Venus has been observed to show vague dark markings in the.cloud structure, 

especially in the near ultraviolet (between 3,000 and 4,000 angstroms). 

Observations by French astronomers indicate that the dark markings rotate 

retrograde with ileriod of about four years. This remarkable phenomenon • 

must be checked by observations which provide reliable high resolution 

and continuity over several four-day periods.' The investigation is quite 

difficult, however, since the visibility of these dark markings is maximum 

when they are near the terminator of the gibbons phase of the planet. 

Another program of Venus observations, would be the search for airglow on 

the darkened hemisphere of the planet. Conflicting observations of this 

alleged phenomeoservt- have been reported. The technical parameters of such an 

investigation are not clearly defined, but it is possible that a conventional 

telescope could contribute useful information. However, it is likely that 

a more refined, specialised instrument (such as a coronagraph) would be 

necessary to control the light of the much brighter sunlit portion of the 

disk, and to prevent it scattering into the optics of the telescope. 

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Jupiter is a very well marked planetary body, with numerous vividlycolored and photometrically well differentiated markings on its globe. 

Some of these markings appear to have very rapid proper motions relative to the average motions of the surface associated with diurnal rotation. 

A fraction of the observed structures is seen to appear or disappear in 

association with the famous large red spot. It is not known what observations achieving 0.2 arc seconds will reveal to us of the physical 

processes involved in the structural dynamics of Jupiter. The morphology 

of familiar markings suggests, however, that higher resolition would 

reveal another order of magnitude of physically interpretable phenomena. 

Such observations must be made consecutively, to permit observing periods 

up to a full rotation of a planet. Satellites of Jupiter in some cases 

show traces of an atmosphere. Uncertain observations in the past also 

suggest that there are traces of surface markings that would permit the 

establishment pf rotation periods. One of the Galilean satellites 

appeared to have a higher albedo after an eclipse of the sun%y Jupiter. 

High resolution observations should permit testing the hypothesi# that 

this change in albedo was the result of a snowfall after apparent sunset 

on the satellite. 

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Mercury has revealed to the most skillful observers some very faint, low 

contrast markings. However, these features have never been photographed. 

The observation of markings on Mercury is especially important as a wart* 

test the recent radar observations of the planet's rotation period. The 

classical surface observations indicated that the planet rotates in 

88 dayi; however, radar data have recently indicated with some certainty 

that the rotational period is only 59 days. 
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Comets do not present any specially challenging investigation topics for 

high resolution direct photography. Shape variations of comet tails near 

perihelion passage, 'under the influence of varying solar activity 

conditions, are a'well known phenomenon. However, the hydromagnetiC 

processes prevalent in defining the shape and extent of the comet's tail 

are not known to produce structures of the site significantly smaller than 

can be resolved by ground-based telescopes. A large, well-developed comet 

certainly ought to be observed by the proposed instrument to validate the 

assumptions made about scale length of interplanetary disturbances. 

Saturn still presents a fascinating object for astronomical research by 

direct photography. When Saturn's ring system tilts to include the earth 

in its plane, the ring, as seen from the earth, appears progressively 

thinner until its cross section almost vanishes. This extreme aspect of the 

ring occurred in. 1966. Measurements of the actual thickness of these rings 

will provide important clues to the dynamics and stability of the whole 

ring system. In addition, straigheforward studies of the zonal divisions 

in the rings will also contribute to our understanding of the nature of 

the rings and the mass distribution in the Saturnian system. , 

The outer planets (Uranus, Neptune and Pluto) are less well known, but very 

deserving of high resolution observations. The diameter of Pluto lies 

below the limit of measurements by ground-based telescopes, and should be 

examined visually if possible. Surface features of Uranus and Neptune are 

inconspicuous and little known. The low surface brightness of these remote 

bodies would, however, require longer exposures than would be needed for 

Mare or Venus. '

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