HUBBLE SPACE TELESCOPE

WIDE FIELD CAMERA 3

CONTRACT END ITEM SPECIFICATION

(PART I)

April 7, 1999

Draft Version 2.00 (Two Channel WFC3)

This version is the first complete draft incorporating the Infrared
Channel. It contains the CCD channel specifications essentially
unchanged from the 15 March 1999 Version 1.00 Baseline Version.

The 1.00 Baseline version was a revision of the draft circulated within
the WFC3 Science Oversight Committee (SOC), the HST Project, and to Ball
Aerospace on 3 February. This draft was a revision of the 4 January
draft following comments from all parties. The 4 January draft was a
revision to the draft submitted to the Science Oversight Committee on 21
December 1998 and incorporated most of the changes suggested by the SOC
prior to 3 January 1998.

N.B. Starting with the 15 March version we have explicitly
[excluded]{.underline} requirements requested and endorsed by SOC at the
direction of the HST Flight Director. The CEI reflects those
requirements (pertaining to the operation of the CCD channel) as being
comparable to those planned or achieved for the ACS Science Instrument.
The requirements which exceed this \"ACS baseline\" are being submitted
simultaneously as Document Change Requests (DCRs).

Change bars on this draft reflect revisions to the 15 March 1999 draft.

0 ACRONYMS LIST [5](#acronyms-list)

1 SCOPE [7](#scope)

1.1 STRATEGIC OBJECTIVES [7](#strategic-objectives)

1.2 MAJOR SCIENTIFIC OBJECTIVES [7](#major-scientific-objectives)

2 APPLICABLE DOCUMENTS [8](#applicable-documents)

3 SCIENCE INSTRUMENT DEFINITION [9](#science-instrument-definition)

3.1 GENERAL DESCRIPTION [9](#general-description)

3.2 MISSION REQUIREMENTS [10](#mission-requirements)

CONCEPTUAL VIEW OF WFC3 [10](#conceptual-view-of-wfc3)

4 PERFORMANCE REQUIREMENTS [11](#performance-requirements)

4.1 CHANNEL DESCRIPTIONS [11](#__RefHeading___Toc448204471)

4.1.1 CCD Channel [11](#__RefHeading___Toc448204472)

4.1.2 IR Channel [11](#__RefHeading___Toc448204473)

4.2 SCIENCE PERFORMANCE METRICS [11](#science-performance-metrics)

4.3 OPTICAL PERFORMANCE [12](#optical-performance)

4.3.1 Optical Design Parameters [12](#optical-design-parameters)

4.3.2 Image Quality [13](#image-quality)

4.4 SPECTRAL PERFORMANCE [16](#spectral-performance)

4.4.1 Wavelength Range [16](#wavelength-range)

4.4.2 Optics Throughput. [16](#__RefHeading___Toc448204480)

4.4.3 Spectral Range Stability [17](#__RefHeading___Toc448204481)

4.4.4 Optical Coatings [17](#__RefHeading___Toc448204482)

4.4.5 CCD Channel Spectral Components [18](#__RefHeading___Toc448204483)

4.4.6 IR Channel Spectral Components [18](#__RefHeading___Toc448204484)

4.4.7 Channel Selection Mechanism Spectral Components
[19](#__RefHeading___Toc448204485)

4.5 CCD CHANNEL SHUTTER PERFORMANCE [19](#__RefHeading___Toc448204486)

4.5.1 Range of Exposure Times [19](#range-of-exposure-times)

4.5.2 Calibration of CCD Channel Shutter Operation
[20](#calibration-of-ccd-channel-shutter-operation)

4.6 CCD CHANNEL DETECTOR REQUIREMENTS [20](#__RefHeading___Toc448204489)

4.6.1 CCD Orientation (TBR) [20](#__RefHeading___Toc448204490)

4.6.2 CCD QE Sensitivity [20](#__RefHeading___Toc448204491)

4.6.3 CCD Detector Readout Noise [20](#__RefHeading___Toc448204492)

4.6.4 CCD Detector Dark Current [20](#__RefHeading___Toc448204493)

4.6.5 CCD Detector Internal Background
[21](#__RefHeading___Toc448204494)

4.6.6 CCD Detector Correlated Noise. [21](#__RefHeading___Toc448204495)

4.6.7 CCD Detector Full Well [21](#__RefHeading___Toc448204496)

4.6.8 CCD Detector Linearity and Dynamic Range
[21](#__RefHeading___Toc448204497)

4.6.9 CCD Detector Charge Transfer Efficiency and resistance to
radiation damage [21](#__RefHeading___Toc448204498)

4.6.10 CCD Detector QE stability [22](#__RefHeading___Toc448204499)

4.6.11 CCD Detector Flat Field Properties
[22](#__RefHeading___Toc448204500)

4.6.12 CCD Detector Overlight Response
[22](#__RefHeading___Toc448204501)

4.6.13 CCD Detector Pixel Response Function
[22](#__RefHeading___Toc448204502)

4.6.14 CCD Detector Bias Stability [23](#__RefHeading___Toc448204503)

4.6.15 CCD Detector Cosmic Ray Susceptibility
[23](#__RefHeading___Toc448204504)

4.7 CCD Detector Thermal Control [23](#__RefHeading___Toc448204505)

4.7.1 CCD Detector Cold Operation [23](#__RefHeading___Toc448204506)

4.7.2 CCD Detector Warm Operation [23](#__RefHeading___Toc448204507)

4.7.3 CCD Channel Thermal Transition Time
[24](#__RefHeading___Toc448204508)

4.7.4 CCD Channel Safe State Operation
[24](#__RefHeading___Toc448204509)

4.8 IR CHANNEL DETECTOR REQUIREMENTS [24](#__RefHeading___Toc448204510)

4.8.1 Orientation (TBR) [24](#__RefHeading___Toc448204511)

4.8.2 IR Detector QE Sensitivity [24](#__RefHeading___Toc448204512)

4.8.3 IR Detector Readout Noise [24](#__RefHeading___Toc448204513)

4.8.4 IR Detector Dark Current and Internal Background
[25](#__RefHeading___Toc448204514)

4.8.5 IR Detector Amplifier Emission (\"Amp Glow\") Contribution
[25](#__RefHeading___Toc448204515)

4.8.6 IR Detector Correlated Noise. [25](#__RefHeading___Toc448204516)

4.8.7 IR Detector Full Well [25](#__RefHeading___Toc448204517)

4.8.8 IR Detector Linearity and Dynamic Range
[25](#__RefHeading___Toc448204518)

4.8.9 IR Detector Resistance to Radiation Damage
[25](#__RefHeading___Toc448204519)

4.8.10 IR Detector QE stability [25](#__RefHeading___Toc448204520)

4.8.11 IR Detector Flat Field Properties
[26](#__RefHeading___Toc448204521)

4.8.12 IR Detector Overlight Response [26](#__RefHeading___Toc448204522)

4.8.13 IR Detector Pixel Response Function
[26](#__RefHeading___Toc448204523)

4.8.14 IR Detector Bias Stability [26](#__RefHeading___Toc448204524)

4.8.15 IR Detector Cosmic Ray Susceptibility
[27](#__RefHeading___Toc448204525)

4.9 IR Detector Thermal Control [27](#__RefHeading___Toc448204526)

4.9.1 Cold Operation [27](#__RefHeading___Toc448204527)

4.9.2 Warm Operation [27](#__RefHeading___Toc448204528)

4.9.3 IR Thermal Transition Time [27](#__RefHeading___Toc448204529)

4.9.4 Safe State Operation [27](#__RefHeading___Toc448204530)

4.10 OPERATIONAL REQUIREMENTS [28](#__RefHeading___Toc448204531)

4.10.1 Observation Modes [28](#observation-modes)

4.10.2 CCD Detector Operation Requirements
[29](#__RefHeading___Toc448204533)

4.10.3 IR Detector Operation Requirements
[30](#__RefHeading___Toc448204534)

4.10.4 Parallel Operations [30](#parallel-operations)

4.10.5 CCD Preflash Capability [30](#__RefHeading___Toc448204536)

4.11 CALIBRATION [31](#calibration)

4.11.1 Calibration Subsystem Purpose
[31](#calibration-subsystem-purpose)

4.11.2 Calibration Subsystem Spatial Uniformity
[31](#calibration-subsystem-spatial-uniformity)

4.11.3 Calibration Subsystem Temporal Stability
[31](#calibration-subsystem-temporal-stability)

4.11.4 Wavelength Coverage and Spectral Requirements
[31](#wavelength-coverage-and-spectral-requirements)

5 DESIGN REQUIREMENTS [31](#design-requirements)

5.1 SYSTEM [31](#system)

5.1.1 System Interfaces [31](#system-interfaces)

5.1.2 Useful Life [31](#useful-life)

5.1.3 Single Point Failure [32](#single-point-failure)

5.1.4 Fail-Safe and Redundancy [32](#fail-safe-and-redundancy)

5.1.5 Commonality [33](#commonality)

5.2 OPTICAL [33](#optical)

5.2.1 Optical Interfaces [33](#optical-interfaces)

5.2.2 Optical Design [33](#optical-design)

5.3 MECHANICAL AND STRUCTURAL [33](#mechanical-and-structural)

5.3.1 Mechanical Interfaces [33](#mechanical-interfaces)

5.3.2 Mechanical Interchangeability [33](#mechanical-interchangeability)

5.3.3 Loads [33](#loads)

5.3.4 Modal Characteristics [34](#modal-characteristics)

5.3.5 Mass Properties [34](#mass-properties)

5.3.6 Envelope [34](#envelope)

5.3.7 Mounting and Alignment [34](#mounting-and-alignment)

5.3.8 Venting [34](#venting)

5.3.9 Ground Refurbishment and Maintenance
[35](#ground-refurbishment-and-maintenance)

5.3.10 Orbital Replacement [35](#orbital-replacement)

5.3.11 SIPE Interface [35](#sipe-interface)

5.3.12 Pickoff Mirror Cover [35](#pickoff-mirror-cover)

5.3.13 CCD Detector Replacement Capability
[35](#ccd-detector-replacement-capability)

5.4 THERMAL [35](#thermal)

5.4.1 Thermal Interfaces [35](#thermal-interfaces)

5.4.2 Thermal Design [35](#thermal-design)

5.5 ELECTRICAL [36](#electrical)

5.5.1 Electrical Interfaces [36](#electrical-interfaces)

5.5.2 Electrical Design [36](#electrical-design)

5.5.3 Electrical Redundancy [37](#electrical-redundancy)

5.6 SOFTWARE [37](#software)

5.6.1 NSSC-1 Flight Software Interfaces
[37](#nssc-1-flight-software-interfaces)

5.6.2 WFC3 Internal Flight Software [38](#wfc3-internal-flight-software)

5.6.3 Software Design [38](#software-design)

5.7 OPERATIONS [39](#operations)

5.7.1 Operations Interfaces [39](#operations-interfaces)

5.7.2 Operations Design [39](#operations-design)

6 PERFORMANCE ASSURANCE [39](#performance-assurance)

6.1 FLIGHT ASSURANCE [40](#flight-assurance)

6.2 TEST AND VERIFICATION [40](#test-and-verification)

6.2.1 Performance Verification Plan [40](#performance-verification-plan)

6.2.2 Subsystem Testing [40](#subsystem-testing)

6.2.3 Life Testing [40](#life-testing)

6.2.4 Minimum Test Suite [40](#minimum-test-suite)

6.3 Calibration [41](#calibration-1)

6.4 CONTAMINATION CONTROL [41](#contamination-control)

6.5 MAINTAINABILITY [42](#maintainability)

6.6 CREW SYSTEMS [42](#crew-systems)

6.7 DESIGN AND CONTRUCTION STANDARDS
[42](#design-and-contruction-standards)

6.7.1 Electrical [43](#electrical-1)

6.7.2 Structural [43](#structural)

6.7.3 Materials [43](#materials)

6.7.4 Coordinate System [44](#coordinate-system)

6.7.5 Identification and Marking [44](#identification-and-marking)

6.8 Radiation Properties [44](#radiation-properties)

6.9 MAGNETIC PROPERTIES [44](#magnetic-properties)

6.10 TRANSPORTABILITY [44](#transportability)

6.11 SYSTEM SAFETY [45](#system-safety)

1.  Applicable Documents

2.  Reference Documents

2-3 Additional Required Documents

4-1 Encircled Energy Requirements

2.  Optics Throughout Requirements

3.  Throughput Stability Requirements

4.  WFC3 Spectral Elements

4-5 CCD Detector QE Requirements

4-6 CCD Detector CTE Requirements

# ACRONYMS LIST

ACS Advanced Camera for Surveys

AGN Active Galactic Nuclei

ASCS Aft Shroud Cooling System

C&DH Command and Data Handler

CCD Charge Coupled Device

CEI Contract End Item

COSTAR Corrective Optics Space Telescope Axial Replacement

COS Cosmic Origins Spectrograph

EEE Electrical, Electronic, and Electromechanical

EMC Electromagnetic Compatibility

EVA Extra-Vehicular Activity

FOC Faint Object Camera

FOV Field of View

FPA Focal Plane Assembly

FWHM Full Width at Half Maximum

GFE Government Furnished Equipment

GHRS Goddard High Resolution Spectrograph

GSFC Goddard Space Flight Center

GSSS Guide Star Selection System

HST Hubble Space Telescope

ICD Interface Control Document

IRD Interface Requirements Document

ISM Interstellar Medium

I&T Integration and Test

JPL Jet Propulsion Laboratory

LOS Line of Sight

mm Millimeter

MLI Multi-Layer Insulation

MSFC Marshall Space Flight Center

nm Nanometer

NICMOS Near Infrared Camera and Multi-Object Spectrometer

NSSC-1 NASA Standard Spacecraft Computer -- Model 1

ORI Orbital Replacement Unit

OTA Optical Telescope Assembly

PASS POCC Applications Software Support

PFU Protoflight Unit

PIXEL Picture Element

PSF Point Spread Function

QE Quantum Efficiency

RIU Remote Interface Unit

RMS Root Mean Square

ROM Read Only Memory

SAA South Atlantic Anomaly

SDF Science Data Formatter

SI Science Instrument

SI C&DH Science Instrument Control and Data Handling

SIPE Science Instrument Protective Enclosure

SMOV Servicing Mission Orbital Verification

SNR Signal to Noise Ratio

SOFA Selectable Optical Filter Assembly

SSE Space Support Equipment

SSM Systems Support Module

STD Standard

STIS Space Telescope Imaging Spectrograph

STR Space Telescope Requirements

STS Space Transportation System

TBD To Be Determined

TBR To Be Reviewed

TV Thermal Vacuum

UV Ultra-Violet

WF/PC-I Wide Field and Planetary Camera -I

WF/PC-II Wide Field and Planetary Camera --II

WFPC2 Wide Field and Planetary Camera 2

WFC3 Wide Field Camera 3

**[WFC3 CEI PART I SPECIFICATION]{.underline}**

# SCOPE

This document establishes the scientific objectives, the scientific
performance requirements, and the interface requirements for the Hubble
Space Telescope (HST) Wide Field Camera 3 (WFC3) scientific instrument
(SI). It provides a baseline for development of the Contract End Item
(CEI) Specification Part II (STE-50).

## STRATEGIC OBJECTIVES

The WFC3 shall be a general purpose facility instrument designed to
provide HST with a high quality imaging capability until the end of the
HST mission (nominally 2010). It shall take good advantage of the
available HST image quality with improved throughput, and sampling
compared to WFPC2. By replacing WFPC2, the WFC3 shall provide HST with
CCD detectors which will have experienced significantly less on-orbit
exposure to radiation than those in ACS or WFPC2 by the end of the HST
mission. Further, with the inclusion of an Infrared (IR) Channel, the
WFC3 will provide an enhanced near infrared imaging capability for HST
beyond NICMOS. The WFC3 shall be designed for installation in a radial
bay within the HST, during on-orbit extra-vehicular activity (EVA)
during the fourth servicing mission (SM4), presently planned for 2003.

## MAJOR SCIENTIFIC OBJECTIVES

Unlike previous HST science instruments, WFC3 is being developed as a
[facility class]{.underline} instrument. All previous HST instruments
(with the partial exception of the FOC) were solicited together with
scientific investigations and were developed under the leadership of a
science team led by a principal investigator who was also responsible
for the proposed scientific investigation. WFC3 is being developed by a
team drawn from the HST project for the general benefit of the HST user
community. As such, its scientific objectives are defined with less
specificity than those of science instruments proposed by PI teams.

In place of the PI team, NASA has formed an Integrated Product Team
(IPT) to develop WFC3. Further, a Science Oversight Committee (SOC) has
been selected by NASA to provide the IPT with scientific guidance and to
represent the views of the HST observer community to the WFC3 IPT and
the HST Project.

WFC3 has four components to its scientific objectives. First, and
foremost, it serves to provide redundancy for HST's visible light high
resolution imaging capabilities from SM4 until the end of the HST
mission (currently planned for 2010). Second, it offers the possibility
of providing additional and complementary imaging capabilities to the
ACS wide field channel including the provision of UV sensitivity (down
to 200nm) over a wide field and a different but partially redundant set
of filter elements. Third, the inclusion of an IR channel provide WFC3
with a high sensitivity imaging capability in the near Infrared
providing HST with a second generation infrared instrument. Fourth, the
WFC3 SOC and IPT are formulating a "Design Reference Mission" (DRM) of
*representative* scientific programs to guide the WFC3 development
process by providing both a vision of its potential scientific
contributions and a metric by which to measure the relative importance
of technical tradeoffs.

# APPLICABLE DOCUMENTS

The following documents (shown in Tables 2-1, 2-2 and 2-3), most recent
issue, form a part of this specification to the extent specified herein.
In the event of a conflict between these documents and the Statement of
Work, the Statement of Work shall take precedence. In the event of a
conflict between these documents and other detailed contents of this
specification, the detailed requirements herein shall take precedence
except for the referenced Interface Control Documents (ICD's). All
applicable documents and requirements specified in the following
documents shall form a part of this specification by incorporation
herein. Contractor specifications satisfying the intent of the following
documents may be used in lieu of the specifically listed document upon
review and approval by GSFC.

Table 2-1 Applicable Documents

  ----- --------------------------------------------------- -------------
  1     Hubble Space Telescope (HST): Space Telescope       STR-43
        Imaging Spectrograph (STIS), Near Infrared Camera   
        and Multi-Object Spectrometer (NICMOS), Performance 
        Assurance Requirements                              

  2     Second and Third Servicing Mission Orbital          SCM-1030
        Replacement Instrument (ORI) Data Requirements      
        Document                                            

  3     Space Telescope Scientific Instruments to           ST-ICD-08
        Scientific Instruments Control and Data Handling    
        System Interface Control Document (SI to SI C&DH    
        ICD)                                                

  4     HST Level Interface Control Document, Radial        ST-ICD-03
        Scientific Instruments to Optical Telescope         
        Assembly and Support Systems Module (Radial SI to   
        OTA and SSM)                                        

  5     HST Servicing Mission Contamination Control         STR-29
        Requirements                                        

  6     Hubble Space Telescope Level 1 Requirements         NASA HQ OSSA

  7     System Description and Design Data --               NSTS 07700,
        Extra-vehicular Activity                            Vol. XIV
  ----- --------------------------------------------------- -------------

Table 2-2 Reference Documents

  -------- ----------------------------------------------- ---------------
  1        The Hubble Space Telescope Wide Field Camera 3  Study Report
           Study Report, March 8, 1998                     

  2        HST Interface Control Document, Radial          ST-ICD-83
           Scientific Instrument to Space Support          
           Equipment                                       

  3        Configuration Management                        GMI 8040.1

  4        HST Flight Projects Configuration Management    SCM-1020
           Plan                                            

  5        HST Science Instrument Test System (SITS)       STE-27
           Specification                                   

  6        ST Command List                                 SDM-1001

  7        ST Instrumentation Program and Component List   SDM-1002

  8        HST Constraints and Restrictions                SMO-1020

  9        ST Mission Operations Functional Requirements   SMO-1000
           Document                                        

  10       HST Input to Project Data Base Interface        ST-ICD-26 Pt. 4
           Control Document                                
  -------- ----------------------------------------------- ---------------

Table 2-3 Additional Required Documents

  ----- ---------------------------------------------------- ------------
  1     SI Calibration Procedures                            AV-03

  2     SI Pre-Launch Calibration Data                       AV-04

  3     Scientific and Performance Assessment and            AV-05
        Calibration Report                                   

  4     SI Command Lists                                     DM-01

  5     SI Engineering Data List                             DM-02

  6     SI Command Development Handbook                      DM-05

  7     SI Science Data Format                               DM-06

  8     SI Engineering Telemetry Calibration List            DM-14

  9     SI Operations Requirements Document                  OP-01

  10    Inputs to SMOV Plans & Proposals Calibration and SI  OP-03
        Proposals                                            

  11    Limited Life Matrix                                  PA-17

  12    SI Systems Description and Users Handbook            SE-02

  13    SI FSW Documentation                                 DM-03

  14    SI Ground Software Documentation                     DM-04

  15    SI Software Test Plan                                DM-07

  16    SI Software Test Procedures and Reports              DM-08

  17    Inputs to the CARD, OLD and CL (Critical Limits)     OP-04

  18    Inputs to the SMIT                                   OP-05

  19    Support for Operations Contingency Planning          OP-06

  20    SM Aliveness and Functional Test Success Criteria    OP-07

  21    Performance Verification Plan                        AV-01

  22    Configuration Management Plan                        CM-01

  23    Management Plan                                      MA-01

  24    Systems Engineering Plan                             SE-01

  25    Requirements Verification Matrix                     
  ----- ---------------------------------------------------- ------------

# SCIENCE INSTRUMENT DEFINITION

## GENERAL DESCRIPTION

The WFC3 is one of five scientific instruments that will form part of
the Focal Plane Assembly (FPA). The Optical Telescope Assembly (OTA) and
Support systems Module (SSM) will provide the WFC3 with incoming light,
target acquisition and, via the SI Control and Data Handling (C&DH)
System, pointing control, data handling, communications, electrical
power, and other services that are common to all SI' s.

## MISSION REQUIREMENTS

The WFC3 shall be designed, built, and tested for launch, orbital
replacement, return to earth in the space shuttle, and operation in a
nominal circular earth orbit at orbital altitudes from 398 km to 593 km
at 28.8 degrees inclination. It shall be designed to be removed or
installed into a radial bay of HST or the Radial Scientific Instrument
Protective Enclosure (R-SIPE) in orbit by a suited astronaut performing
EVA, or by technicians working in a one-g environment. The SI will be
launched in the SIPE. The baseline bay assignment for the WFC3 shall be
the radial bay replacing the WFPC2. The total SI shall consist of one
integral package designed to survive handling and transportation loads
as defined in ST-ICD-03.

\[provision for attachment to external radiator is TBD. -- JWM\]

## CONCEPTUAL VIEW OF WFC3

Figure 3-1

The diagram in the Figure above provides a conceptual view of the WFC3
science instrument. In WFC3 the Pick Off mirror is a fixed element which
captures a portion of the HST focal plane and directs it into the WFC3.
The "optics" sub-system provides correction for the HST OTA spherical
aberration, brings WFC3 to a common focus with the other Science
Instruments using a focus and alignment mechanism, and provides the
required focal ratio at the CCD detector. The CCD filter elements are
contained in a selectable mechanism and provide bandpass limitation and
other science driven modifications to the incident light. The shutter
mechanism provides a means of defining the duration of an exposure. The
CCD detector converts photons into measured signal.

The optics train includes a \"channel selection mechanism\" to direct
light into the IR relay optics which provide re-imaging to the required
IR focal ratio. The IR Filter Elements are contained in a single wheel
which provides bandpass limitation and other science driven
modifications to the incident light. The IR detector converts photons
into measured signal and also provides, by electronic gating, the means
of defining the exposure duration. To achieve low internal background
flux incident upon the IR detector, its surroundings including the IR
filter elements and a \"cold stop\" are cooled.

WFC3 requires a thermal control subsystem to provide detector and
environmental cooling to reduce internal dark current in both detectors.
It also requires heating to control contamination and anneal radiation
damage in the CCD detector. A calibration subsystem is required to
provide simple internal illumination of the detectors for differential
calibration. Finally, a control and data handling subsystem provides
both control of each subsystem, telemetry, and handling of the science
data from the detectors.

# PERFORMANCE REQUIREMENTS

The WFC3 performance requirements shall be met after a suitable
commissioning period, which shall not exceed servicing mission orbital
verification (SMOV), during which focus and alignment settings and
on-orbit operating parameters shall be determined. This period shall
suffice to demonstrate that WFC3 conforms to all aspects of this
Specification Document when combined with measurements and test results
obtained during ground testing.

## CHANNEL DESCRIPTIONS

## 

## The WFC3 provides two science channels. Both channels view the same region in the HST focal plane. This region is selected by an external pick-off mirror (POM).

### CCD Channel

The CCD channel consists of an optical train capable of providing focus
adjustment and correction for the HST OTA spherical aberration, a filter
element selection mechanism, a shutter, and a CCD detector assembly.
These are supported by a thermal control subsystem and also by control
and data handling electronics subsystems. In general concept and
functionality, this channel is patterned on the ACS WFC channel.

### IR Channel

The IR Channel consists of a selection mechanism to divert light from
the CCD channel (after the HST OTA spherical aberration), a filter
element selection mechanism, and an IR detector assembly. These are
supported by a thermal control subsystem and also by control and data
handling electronics subsystems. This channel is cooled with TEC devices
in a manner similar to the ACS WFC channel and it operated in a similar
fashion to the NICMOS detectors.

## SCIENCE PERFORMANCE METRICS

The WFC3 is intended as a facility science instrument will broad
capabilities to support the community\'s needs for imaging science from
HST. To capture a representative range of science capabilities, the DRM
was constructed by the SOC and the Science IPT based upon science
programs originated by SOC members.

The DRM is supported by an Exposure Time Calculator (ETC) developed by
the Science IPT and a database estimating the observing time required to
complete the DRM. One metric available to access the science performance
of WFC3 is the relative time required to complete the DRM program.

##  OPTICAL PERFORMANCE

The optical performance of the WFC3 shall be met when provided with
light from the HST in accordance with the optical parameters of
ST-ICD-03. Correction for HST aberration shall be contained within the
WFC3 including provision for on-orbit optical alignment capability.

### Optical Design Parameters

#### 

#### Pixel Spacing. 

##### CCD Channel

The nominal pixel center-to-center spacing of the CCD channel shall be
0.039 arc seconds.

##### IR Channel

The nominal pixel center-to-center spacing of the IR channel shall be
0.080 arc seconds

#### Field of View.

The unvignetted (\>95% throughput) angular field of view projected onto
the sky for the WFC3 shall be lie between 155 and 170 arc seconds on a
side. Within these limits, it should be as large as practical without
vignetting the FOVs of any axial bay science instrument(s).

#### Field of View Distortion.

The field of view shall be square within 5% (and also provide an
allowance for any asymmetric gap(s) in the CCD mosaic not to exceed 2%)
and oriented at a 45 degree angle (+/- 10 degrees) from the HST focal
plane's V2-V3 coordinate system.

#### Wavefront Error.

The optical design shall provide essentially diffraction-limited
performance over the FOV for λ \> TBD. The Root Mean Square (RMS)
wavefront error introduced by the combination of the HST optics and the
WFC3 optical system in filter mode shall be less than λ/11.75 at 633nm
with a goal of λ/13.33 at 633nm, at the center FOV position when used
with an input wavefront which conforms to the following OTA
characteristics:

Primary Conic Constant: K = -1.0139

Intervertex Distance: 4907.0100

These values shall apply over a square region (inscribed within the
square field of view) whose corners are the center of the edges of the
field of view, as a minimum.

##### Ultraviolet Wavefront Specification.

At λ \< TBD (the near ultraviolet), the HST OTA introduces wavefront
errors which significantly exceed diffraction limited performance. WFC3
shall not increase these errors by more than TBD percent corresponding
to an instrumental wavefront error of no more than λ/TBD between 200nm
and TBD.

##### Visible Wavefront Specification

##### Infrared Wavefront Specification

#### Geometric Distortion.

The magnitude and stability of the WFC3 geometric distortion shall be
such that the relative positions of stellar images shall be determinable
to within 0.2 pixel over the entire image by application of a correction
function. This shall apply to point sources exposed to between 0.1 and
0.5 of detector linear full well and shall remain within tolerance over
a period of at least 1 month.

#### Polarization Sensitivity.

The maximum value for induced polarization, assuming unpolarized
incoming light, is 6.5 percent over the range 220 -- 1000nm with a goal
of \< 5%.

\[need IR specification -- JWM\]

### Image Quality

#### CCD Channel Point Source Profile.

The WFC3 image quality requirement for the CCD channel in filter mode
shall be the encircled energy as presented in Table 4-1. The image
quality shall be achievable for the range of uncertainty in on-orbit
conic constant and shall include all internal WFC3 effects due to
thermal, mechanical, and optical contributions, but not those due to
spacecraft jitter or guiding errors. Image quality is specified at both
the center of the FOV and at the edge (where \"corner\" is taken to be
50 active pixels in both X and Y from the corners of the detector).

Table 4-1 Encircled Energy Requirements

  ---------------------------------- ------------------ ------------------
  Specification                      Center of FOV      Corner of FOV

  Core @ 633nm in 0.25 arc sec       \>75% Goal: \>80%  \>75% Goal: \>80%
  diameter                                              

  Core @ 250nm in 0.20 arc sec       \>75% Goal: \>80%  \>75% Goal: \>80%
  diameter                                              

                                                        

  Wing @ 633 nm 0.5 arc sec radius   \< TBD% peak       \< TBD% peak

  Wing @ 633 nm 1.0 arc sec radius   \< TBD% peak       \< TBD% peak

  Wing @ 633 nm 2.0 arc sec radius   \< TBD% peak       \< TBD% peak

  Wing @ 633 nm 3.0 arc sec radius   \< TBD% peak       \< TBD% peak

                                                        

  Wing @ 250 nm 0.5 arc sec radius   \< TBD% peak       \< TBD% peak

  Wing @ 250nm 1.0 arc sec radius    \< TBD% peak       \< TBD% peak

  Wing @ 250 nm 2.0 arc sec radius   \< TBD% peak       \< TBD% peak

  Wing @ 250 nm 3.0 arc sec radius   \< TBD% peak       \< TBD% peak
  ---------------------------------- ------------------ ------------------

#### IR Channel Point Source Profile.

The WFC3 image quality requirement for the IR channel in filter mode
shall be the encircled energy as presented in Table 4-2. The image
quality shall be achievable for the range of uncertainty in on-orbit
conic constant and shall include all internal WFC3 effects due to
thermal, mechanical, and optical contributions, but not those due to
spacecraft jitter or guiding errors. Image quality is specified at both
the center of the FOV and at the edge (where \"corner\" is taken to be
50 active pixels in both X and Y from the corners of the detector).

Table 4-2 Encircled Energy Requirements

  ---------------------------------- ------------------ ------------------
  Specification                      Center of FOV      Corner of FOV

  Core @ TBD nm in 0.25 arc sec      \>75% Goal: \>80%  \>75% Goal: \>80%
  diameter                                              

  Core @ TBD nm in 0.TBD arc sec     \>75% Goal: \>80%  \>75% Goal: \>80%
  diameter                                              

                                                        

  Wing @ 633 nm 0.5 arc sec radius   \< TBD% peak       \< TBD% peak

  Wing @ 633 nm 1.0 arc sec radius   \< TBD% peak       \< TBD% peak

  Wing @ 633 nm 2.0 arc sec radius   \< TBD% peak       \< TBD% peak

  Wing @ 633 nm 3.0 arc sec radius   \< TBD% peak       \< TBD% peak

                                                        

  Wing @ 250 nm 0.5 arc sec radius   \< TBD% peak       \< TBD% peak

  Wing @ 250nm 1.0 arc sec radius    \< TBD% peak       \< TBD% peak

  Wing @ 250 nm 2.0 arc sec radius   \< TBD% peak       \< TBD% peak

  Wing @ 250 nm 3.0 arc sec radius   \< TBD% peak       \< TBD% peak
  ---------------------------------- ------------------ ------------------

#### Uniformity of Image Quality.

#### At no position in the FOV may the image quality be worse than the \"corner\" specifications in Tables 4-1, and 4-2 for the appropriate channel. Further, a high degree of uniformity in the PSF is an important goal. {#at-no-position-in-the-fov-may-the-image-quality-be-worse-than-the-corner-specifications-in-tables-4-1-and-4-2-for-the-appropriate-channel.-further-a-high-degree-of-uniformity-in-the-psf-is-an-important-goal. .unnumbered}

#### Image Jitter.

The internal image jitter introduced by the WFC3 itself shall be less
than 3 milli-arcseconds (1 sigma) (with a goal of less than 1
milli-arcsecond) for any integration interval up to 1300 seconds. This
requirement may be satisfied by design on the ground and verified
on-orbit.

#### Image Drift.

##### CCD Channel

The image drift within the WFC3 CCD Channel shall be less than 10
milli-arcseconds peak-to-peak over two orbits relative to the FGS frame.
The long-term stability shall allow consecutive exposures to be
successfully co-added by exposure registration for elapsed periods of up
to 24 hours without re-pointing the telescope or adjusting the WFC3.
Registration to 0.25 pixels RMS is required for successful co-addition.
This requirement may be satisfied by design on the ground and verified
on-orbit.

##### IR Channel

The image drift within the WFC3 IR Channel shall be less than 20
milli-arcseconds peak-to-peak over two orbits relative to the FGS frame.
The long-term stability shall allow consecutive exposures to be
successfully co-added by exposure registration for elapsed periods of up
to 24 hours without re-pointing the telescope or adjusting the WFC3.
Registration to 0.25 pixels RMS is required for successful co-addition.
This requirement may be satisfied by design on the ground and verified
on-orbit.

Ghost Images.

Stray light due to reflected scatter in the optical train, including
spectral defining elements, from a point source shall result in less
than 0.1% of the total incident light within a discrete ghost image.

#### Large Angle Stray Light.

Stray light per pixel more than 30 arc seconds from a point source shall
not exceed TBD % of the total brightness of the point source. This
includes effects of the OTA.

## SPECTRAL PERFORMANCE

### Wavelength Range

#### CCD Channel

The nominal wavelength range of the WFC3 CCD channel shall be
200-1000nm, with special emphasis given to the 200-400nm range.
Performance in this preferred spectral interval shall have priority in
performing design trades.

#### IR Channel

The nominal wavelength range of the WFC3 IR channel shall be 850-1700nm,
with a goal of 700 -- 1900nm. Performance in the 1000 -- 1600nm spectral
interval shall have priority in performing design trades.

[]{#__RefHeading___Toc448204480 .anchor}Optics Throughput.

#### CCD Channel Optics Throughput

The optics, exclusive of OTA, spectral Elements, and detector response,
shall provide throughput exceeding the values in Table 4-3 for the CCD
Channel

Table 4-3 CCD Channel Optics Throughput Requirements

  ---------------------------- ------------------------------------------
  Wavelength (microns)         Optics Throughput

  0.18                         TBD

  0.2                          0.59

  0.25                         0.59

  0.3                          0.61

  0.35                         0.60

  0.4                          0.60

  0.45                         0.62

  0.5                          0.62

  0.55                         0.62

  0.6                          0.62

  0.7                          0.60

  0.8                          0.52

  0.9                          0.59

  1                            0.72
  ---------------------------- ------------------------------------------

#### IR Channel Optics Throughput

The optics, exclusive of OTA, spectral Elements, and detector response,
shall provide throughput exceeding the values in Table 4-4 for the IR
Channel

Table 4-4 IR Channel Optics Throughput Requirements

  ---------------------------- ------------------------------------------
  Wavelength (microns)         Optics Throughput

  0.60                         TBD

  0.70                         TBD

  0.80                         TBD

  0.90                         TBD

  1.00                         TBD

  1.10                         TBD

  1.20                         TBD

  1.30                         TBD

  1.40                         TBD

  1.50                         TBD

  1.60                         TBD

  1.70                         TBD

  1.80                         TBD

  1.90                         TBD
  ---------------------------- ------------------------------------------

[]{#__RefHeading___Toc448204481 .anchor}Spectral Range Stability

Photometric capabilities are an important aspect of the WFC3 scientific
goals. Stability in throughput over the entire spectral range is
essential to these goals. Table 4-3 establishes requirements for
throughput stability. These specifications are for any one month period
(after the first 3 months in orbit). These include all components
including detectors after calibration.

In addition, all variations in excess of 3% per year shall be
recoverable by decontamination procedure(s).

Table 4-3 Throughput Stability Requirements

  ----------------------------- -----------------------------------------
  Wavelength Range              Throughput Stability

  200 -- 300 nm                 \<5 % per month (\<1% goal)

  300 -- 400 nm                 \<3% per month (\<1 % goal)

  400 -- 600 nm                 \<1% per month ( \<0.5% goal)

  600 -- 1000 nm                \<1% per month ( \<0.5% goal)

  1000 -- 2000nm                \<1% per month (\<0.5% goal)
  ----------------------------- -----------------------------------------

[]{#__RefHeading___Toc448204482 .anchor}Optical Coatings

#### CCD Channel Optical Coatings

Optical coatings on optics and filter elements within the CCD Channel
shall be designed to maximize efficiency with an emphasis on the 200 --
400nm wavelength region. No individual coating surface shall decrease in
throughput by more than 0.6 percent by delivery or 1.0 percent over 5
years.

#### IR Channel Optical Coatings

Optical coatings on optics unique to the IR Channel shall be designed to
minimize emission of thermal radiation between 1.4 and 2.0 microns.
Consistent with this requirement, high reflectivity is desired. Further,
no individual coating surface shall decrease in throughput by more than
0.6 percent by delivery or 1.0 percent over 5 years.

### CCD Channel Spectral Components

#### Number of Spectral Elements

The WFC3 CCD channel shall contain at least 48 selectable spectral
defining elements. As a minimum, the spectral elements defined in Table
4-5 will be included.

#### Types of Spectral Elements

Provision to support spectral filters, polarizers, prisms, grisms, and
ramp filters must be provided in the CCD channel. These spectral
elements must be located in the unaberrated beam.

#### Spectral Elements Selection Mechanism

The mechanism to support spectral element selection for the CCD channel
shall be the refurbished WF/PC-1 SOFA mechanism.

Table 4-4 WFC3 CCD Channel Spectral Elements

  ----------------------------------- -----------------------------------
  TBD                                 TBD

  TBD                                 TBD
  ----------------------------------- -----------------------------------

### IR Channel Spectral Components

#### Number of Spectral Elements

The WFC3 IR channel shall contain at least 10 selectable spectral
defining elements (with a goal of 20 elements). As a minimum, the
spectral elements defined in Table 4-6 will be included.

#### Types of Spectral Elements

Provision to support spectral filters, polarizers, prisms, and grisms in
the IR channel must be provided. These spectral elements must be located
in the unaberrated beam.

#### IR Spectral Elements Selection Mechanism

The IR spectral elements selection mechanism must be capable of
selecting any element in less than 60 seconds. Operational lifetime must
be consistent with both the DRM and the requirement for at least three
motions (any element position to any other element position) per orbit
over the design life of WFC3. The IR spectral element selection
mechanism must provide a means of fully blocking the path of light to
the detector.

Table 4-6 WFC3 IR Channel Spectral Elements

  ----------------------------------- -----------------------------------
  TBD                                 TBD

  TBD                                 TBD
  ----------------------------------- -----------------------------------

### Channel Selection Mechanism Spectral Components

#### Number of Spectral Elements

The WFC3 channel selection mechanism shall contain at least 4 selectable
spectral defining components. As a minimum, the spectral elements
defined in Table 4-7 will be included.

#### Types of Spectral Elements

Provision to support transmission to the CCD channel, reflection to the
IR channel, and at least two beam splitting filters must be provided.

#### Spectral Elements Selection Mechanism

The channel selection mechanism must be capable of selecting any element
in less than 60 seconds. Operational lifetime must be consistent with
both the DRM and the requirement for at least three motions (any element
position to any other element position) per orbit over the design life
of WFC3.

Table 4-7 WFC3 Channel Selection Mechanism Spectral Elements

  ----------------------------------- -----------------------------------
  Clear (UV optimized)                Mirror (IR optimized)

  TBD---beamsplitter                  TBD---beamsplitter
  ----------------------------------- -----------------------------------

## CCD CHANNEL SHUTTER PERFORMANCE

### Range of Exposure Times

WFC3 CCD Channel shall be equipped with a shutter capable of providing
timed exposures from 0.10 seconds to \>6000 seconds. Selectable
integration times shall be supported in increments of 0.10 seconds from
a minimum of 0.1 sec to at least 100 minutes. For exposures longer than
10 seconds these may be supported in increments of 1 second. For
exposures longer than 100 seconds these may be supported in increments
of 10 seconds.

### Calibration of CCD Channel Shutter Operation

The CCD Channel shutter shall be repeatable to better than 0.01 seconds.
For exposures greater than 1.0 seconds, shading (uncorrected) shall be
less than 1%. \[TBR ---JWM\].

## CCD CHANNEL DETECTOR REQUIREMENTS

### CCD Orientation (TBR)

The orientation of the WFC3 CCD array is driven by the FOV of the
pickoff mirror. The orientation of the optical FOV is specified in
4.3.1.3.

### CCD QE Sensitivity

The WFC3 CCD detector sensitivity shall be optimized for the spectral
interval 200-400nm and meet the following QE requirements, specified at
several key wavelengths in Table 4-5. QEmin is to be taken as the
minimum allowable monochromatic detector QE within the specified
wavelength interval (with the exception of the 200-300nm region where it
shall be taken as the average QE within that interval). These
requirements apply to a detector without window and operating at --83C.

Table 4-5 CCD Detector QE Requirements

  ----------------------------- -------------------- ---------------------
  Wavelength range              QE min               QE Goal

  200--300nm                    30%                  65%

  300-400nm                     40%                  65%

  400-600nm                     50%                  80%

  600-800nm                     50%                  70%

  800-950nm                     30%                  40%
  ----------------------------- -------------------- ---------------------

\[TBR: these were obtained from the SITe blue HRC device for the QEmin
values and the best Lesser (blue or red detectors for the \"QE Goal\"
values--JWM\]

The selection of anti-reflective coatings applied to the CCD detector
shall emphasize the 200-400nm range.

### CCD Detector Readout Noise

The CCD detector read noise shall not exceed 4.0 electrons per pixel
(with a goal of 3 electrons) at 30,000 pixels/second readout rate.

### CCD Detector Dark Current

The detector dark current shall not exceed 10 electrons per pixel per
hour at --90C.

### CCD Detector Internal Background

Any detector emission or emission from the detector assembly windows
(e.g. due to SAA passage) shall not exceed 10 electrons per pixel per
hour.

### CCD Detector Correlated Noise.

Noise in any image due to electrical interference shall be limited such
that a one dimensional Fourier analysis of the pixel readouts contains
no spectral components having more than 50 percent (TBR) higher power
density than the background random noise spectrum.

### CCD Detector Full Well

The Full Well capacity shall be a minimum of 50,000 electrons per pixel
with a goal of 85,000 electrons.

### CCD Detector Linearity and Dynamic Range

The response shall be linear with input signal to \<5% (correctable to
\<0.3%) over the range 100 to 50,000 electrons and shall be independent
of exposure time.

### CCD Detector Charge Transfer Efficiency and resistance to radiation damage

CTE testing shall be performed both with radioactive (on the ground) and
light sources. Performance requirements are specified in Table 4-6. The
required charge losses are across 2048 pixels under zero background
conditions (i.e. independent of the number of sources on the detector).

Table 4-6 CCD Detector CTE Requirements

  -------------- -------------- ------------- --------------- -------------
                 At Launch                    After 5 Years   

  Signal Level   Uncorrected    Correctable   Uncorrected     Correctable
                 loss           to            loss            to

  300 e-/pixel   \<3%           1%            \<10%           2%

  3,000 e-/pixel \<2%           \<1%          \<5%            1%

  30,000         \<1%           \<1%          \<3%            \<1%
  e-/pixel                                                    

  1620 e-/pixel  .99999/pixel                 .99995/pixel    
                                              (at 2.5 years)  
  -------------- -------------- ------------- --------------- -------------

In addition, ground testing shall characterize the performance at 50 and
100 electrons per pixel signal levels.

### CCD Detector QE stability

Absolute QE stability (peak-to-peak) /hour shall be better than +/-
0.5%, and the QE stability (peak-to-peak) /month shall be better than
+/- 1% (2% shortwards of 300 nm). Pixel-to-pixel stability (1σ )/hour
shall be better than 0.2%. It shall be satisfactory to demonstrate short
term stability requirements during ground test.

### CCD Detector Flat Field Properties

#### CCD Detector Uniformity

The CCD detector shall be correctable to a uniform gain per pixel to
\<2% at all wavelengths and \<1% between 400nm and 850nm (goal less than
0.5%). No more than 5% of all pixels shall have response outside the
range of 90 -- 110% of the mean response. Goal to have \<1% of pixels
outside range of 95 -- 105%.

#### CCD Detector Low Spatial Frequency Flat Field Structure

Large scale flat field non-uniformities shall not exceed 3% peak-to-peak
including the WFC3 optical system. The large scale non-unformity shall
be correctable to \<2%.

#### CCD Detector Non-functional Pixels

No more than 1% of the pixels may be non-functional. Non-functional
pixels include dead pixels, hot pixels (exceeding 100 time the mean dark
current or 0.1 e-/s/pixel which ever is larger), pixels with uncorrected
QE's less than 50% or more than 200% of the mean QE.

#### CCD Detector Flat Field Stability

The difference between two flat fields taken 60 days apart using the
same instrument configuration shall not exceed 1% rms (0.5% goal).
Further, no more than 5% of the field of view shall exceed 5% variation.

### CCD Detector Overlight Response

The CCD detector array shall not be harmed by exposure to any light
levels (other than direct solar radiation). Exposures of less than 2
times full well should not result in blooming and exposures of less than
100 times full well may only bloom in the detector columns containing
the overlight pixels. Residual images from 100 times full well overlight
conditions shall not exceed 1 electron per second per pixel after 96
minutes.

### CCD Detector Pixel Response Function

The CCD detector shall be backside illuminated and shall have
inter-pixel gaps which do not exceed TBD percent of the pixel width
(where gaps are defined to be regions with less than 50% of the response
at the pixel centers). Pixel to pixel cross talk shall be sufficiently
small that 90% of the energy from a 5 micron diameter spot centered on a
pixel shall be detected within that pixel. It is expected that backside
illuminated detectors will meet this specification. It shall be
satisfactory to demonstrate compliance with measurements on detectors
from the same lot.

### CCD Detector Bias Stability

The detector bias (zero) level over a single row shall be stable during
array readout to at least 2 electrons RMS. The bias level for the entire
array shall be correctable to at least 1 electron RMS.

### CCD Detector Cosmic Ray Susceptibility

The median energy deposited per charged particle event shall not exceed
2000 electrons. The median number of pixels containing more than 5% of
the total event energy shall not exceed 6. These values correspond to a
detector effective thickness of approximately 25 microns.

## CCD Detector Thermal Control

\[NOTE: all 4.7 values should be considered TBD pending engineering
study.\]

### CCD Detector Cold Operation

#### CCD Operating Temperatures

The nominal operating temperature for the WFC3 CCD is -83°C (with a goal
of --90C). Provision for cooling using thermal electric coolers and
rejection of waste heat via the WFC3 external radiation shall be
provided. . Indefinite operation at cold set-points is required.

#### CCD Temperature Regulation

Regulation via set-points at intervals no greater than 5 degree C shall
be provided. Regulation sufficient to meet the QE stability requirement
(4.6.10) over 24 hours is required.

#### CCD Temperature Measurement

Absolute temperature measurement to 1 degree C is required.

### CCD Detector Warm Operation

#### Range of CCD Detector Warm Operating Temperatures

The thermal control system shall be designed to permit periodic warming
of the CCD detector to at least -5 degrees C (with a goal of +5 degrees
C). Operation at warm temperatures is necessary to permit annealing hot
or warm pixels.

Operation of the WFC3 CCD detector at its warmest set-point for at least
48 hours shall be permitted.

### CCD Channel Thermal Transition Time

It shall be possible to transition from nominal operate temperature to
anneal temperature and return to operating temperature in less than 24
hours exclusive of the time spent at the warm (anneal) temperature.

### CCD Channel Safe State Operation

Operation at to maintain the CCD detector external window above the
ambient temperature in the instrument enclosure is necessary to provide
a contamination safe state for instrument hold.

## IR CHANNEL DETECTOR REQUIREMENTS

### Orientation (TBR)

The orientation of the WFC3 IR array is driven by the FOV of the pickoff
mirror. The orientation of the optical FOV is specified in 4.3.1.3.

### IR Detector QE Sensitivity

The WFC3 IR detector sensitivity meet the following QE requirements,
specified at several key wavelengths in Table 4-5. QEmin is to be taken
as the minimum allowable monochromatic detector QE within the specified
wavelength interval (with the exception of the 600-800nm and 1800-1900nm
where these should be the average values). These requirements apply to a
detector without window and operating at 150K.

Table 4-5 IR Detector QE Requirements

  ----------------------------- -------------------- ---------------------
  Wavelength range              QE min               QE Goal

  600-800nm                                          

  800-1000nm                                         

  1000-1200nm                                        

  1200-1400nm                                        

  1400-1600nm                                        

  1600-1800nm                                        

  1800-1900nm                                        

  1900-10000nm                  0%                   0%
  ----------------------------- -------------------- ---------------------

### IR Detector Readout Noise

The single read pair IR detector read noise shall not exceed 15.0
electrons per pixel (with a goal of 10 electrons per pixel) at TBD
pixels/second readout rate. The achievable readout noise from a sequence
of 10 non-destructive readouts shall not exceed 10 electronics per pixel
(with a goal of 7 electrons per pixel) at the same readout rate.

### IR Detector Dark Current and Internal Background

The combined IR detector dark current and signal from radiation
generated internal to the WFC3 and HST shall not exceed 0.4 electrons
per pixel per second at the nominal operating temperatures with a goal
of 0.1 electrons per pixel per second. This specification does not
include the emission contribution from the amplifiers on the detector.

\[\*\*\*we need to review this carefully. This is reasonable for the
detector and probably the interior of the WFC3...but a calculation of
the OTA contribution and, by implication, the effectiveness of the cold
stop, is required.---JWM\]

### IR Detector Amplifier Emission (\"Amp Glow\") Contribution

The additional signal from IR detector amplifier emission beyond the
limits in 4.8.4 shall not exceed TBD electrons at the detector center
and TBD electrons for more than 5% of the pixels on the detector.

### IR Detector Correlated Noise.

Noise in any image due to electrical interference shall be limited such
that a one dimensional Fourier analysis of the pixel readouts contains
no spectral components having more than 50 percent (TBR) higher power
density than the background random noise spectrum.

### IR Detector Full Well

The Full Well capacity shall be a minimum of TBD electrons per pixel
with a goal of TBD electrons.

### IR Detector Linearity and Dynamic Range

The response shall be linear with input signal to \<5% (correctable to
\<0.3%) over the range 100 to TBD electrons and shall be independent of
exposure time.

### IR Detector Resistance to Radiation Damage

TBD. (also spec for SAA afterglow!)

### IR Detector QE stability

Absolute QE stability (peak-to-peak) /hour shall be better than +/-
0.5%, and the QE stability (peak-to-peak) /month shall be better than
+/- 1%. Pixel-to-pixel stability (1σ)/hour shall be better than 0.2%. It
shall be satisfactory to demonstrate short-term stability requirements
during ground test.

### IR Detector Flat Field Properties

#### Detector Uniformity

The IR detector shall be correctable to a uniform gain per pixel to \<2%
at all usable wavelengths and \<1% between 1000-1800nm (goal less than
0.5%). No more than 5% of all pixels shall have response outside the
range of 50 -- 200% of the mean response. Goal to have \<1% of pixels
outside range of 95 -- 105%.\*\*\*TBR\*\*\*

#### IR Channel Low Spatial Frequency Flat Field Structure

Large-scale flat field non-uniformities shall be correctable to \<2%.

#### IR Detector Non-functional Pixels

No more than TBD% of the pixels may be non-functional. Non-functional
pixels include dead pixels, hot pixels (exceeding 100 time the mean dark
current), pixels with uncorrected QE's less than 25% or more than 400%
of the mean QE.

#### IR Detector Flat Field Stability

The difference between two flat fields taken 60 days apart using the
same instrument configuration shall not exceed 1% rms (0.5% goal).
Further, no more than 5% of the field of view shall exceed 5% variation.

### IR Detector Overlight Response

The IR detector shall not be harmed by exposure to any light levels
(other than direct solar radiation). Exposures of less than 2 times full
well should not result in blooming and exposures of less than 100 times
full well may only bloom to a radius of TBD pixels. Residual images from
100 times full well over-light conditions shall not exceed 1 electron
per second per pixel after 96 minutes.

### IR Detector Pixel Response Function

The IR detector inter-pixel gaps shall not exceed TBD percent of the
pixel width (where gaps are defined to be regions with less than 50% of
the response at the pixel centers). Pixel to pixel cross talk shall be
sufficiently small that 90% of the energy from a 5 micron diameter spot
centered on a pixel shall be detected within that pixel. It shall be
satisfactory to demonstrate compliance with measurements on detectors
from the same lot.

### IR Detector Bias Stability

The detector bias (zero) level over a single quadrant shall be
correctable to better than 3 electrons RMS with a goal of 1 electron
RMS. The difference in bias level between any pair of readouts in an
exposure shall be determinable to less than 3 electrons with a goal of 1
electron.

### IR Detector Cosmic Ray Susceptibility

The median energy deposited per charged particle event shall not exceed
TBD electrons.

TBD: spec on SAA afterglow goes here

## IR Detector Thermal Control

\[NOTE: all 4.9 values should be considered TBD pending engineering
study.\]

### Cold Operation

#### Operating Temperatures

The nominal operating temperature for the WFC3 CCD is 150°K. Provision
for cooling using thermal electric coolers and rejection of waste heat
via the WFC3 external radiation (or other radiators) shall be provided.
. Indefinite operation at cold set-points is required.

#### Temperature Regulation

Regulation via set-points at intervals no greater than 2 degrees C shall
be provided. Regulation sufficient to meet the QE stability requirement
(4.6.10) over 24 hours is required.

#### Temperature Measurement

Absolute temperature measurement to 1 degree C is required.

### Warm Operation

#### Range of Warm Operating Temperatures

The thermal control system shall be designed to permit periodic warming
of the IR detector to at least -30 degrees C (with a goal of +5 degrees
C). Operation at warm temperatures is desired to remove potential
contamination and to offset radiation damage.

Operation of the IR detector at its warmest set-point for at least 48
hours shall be permitted.

### IR Thermal Transition Time

It shall be possible to transition between the nominal operate and warm
temperatures in less than 24 hours.

### Safe State Operation

Operation at to maintain the IR detector external window above the
ambient temperature in the instrument enclosure is necessary to provide
a contamination safe state for instrument hold. \--\*\*\* this
requirement is TBD for the IR detector---JWM

[]{#__RefHeading___Toc448204531 .anchor}OPERATIONAL REQUIREMENTS

### Observation Modes

The WFC3 shall support the following observation modes:

\[This section needs revision to support IR channel parallel and
sequential operations.---JWM\]

#### Observe Modes

##### CCD Observe Mode

This shall be the standard science (and external calibration) data
taking mode. The exposure time, the state of the shutter (active or
closed), and the filter element selected must be specified. Bias
exposures (zero exposure time) shall result in no shutter movement.

This shall be equivalent to the ACS/WFC IMAGE mode.

##### IR Observe Mode

This shall be the standard science (and external calibration) data
taking mode. A sequence of up to 9 monotonically increasing exposure
times and the filter element selected must be specified. The exposure
sequence consists on an initial detector reset, a detector readout (zero
read), and then 1 or more additional readouts at times subsequent to the
zero read as specified in the exposure command.

This shall be equivalent to the NICMOS MULTACCUM mode.

Internal Calibration Lamp Mode

Observe mode exposures with the internal calibration lamp activated
shall be supported. This mode provides control of the lamp sub-system
(see 4.11).

#### Anneal Mode

Performs a pre-determined warm-up sequence, hold at a warm temperature
set-point, and then returns WFC3 to operating temperature.

#### Operate Mode

Maintains WFC3 in a state ready to take data (i.e. transition to OBSERVE
mode). This should be suitable for passage(s) through the SAA.

#### Hold Mode

Places the WFC3 is a state suitable for longer term inactivity than
OPERATE mode.

#### Safe Mode

Places WFC3 in a safe state where minimal NSSC-1 and ground monitoring
is require[d.]{.underline} Places WFC3 in a safe state with the maximum
contamination protection and thermal safety. Primary goal is to minimize
spacecraft power consumption.

### CCD Detector Operation Requirements

#### Detector Readout

For a single 2048 x 4096 CCD chip, readout may be made through either
one or two amplifiers to one or two independent sectors of memory,
respectively. For a monolithic 4096 x 4096 detector, readout may be made
from any of four amplifiers. Maximum read-out time for either array with
four amplifier operation shall be two minutes or less.

#### Low Noise Readout Mode

TBD

#### Subarray Readout Capability

TBD

#### Selectable Gain Settings

Four gains shall be selectable in increments from 1, 2, 4, and 8
electrons /bit.

#### On chip Binning

TBD

#### Non-integrating Requirements

Basic flush operations shall be provided to condition the CCD.
Continuous flushing shall be the normal mode while not integrating or
reading out, except in Safe Mode (TBR -- what about HOLD mode?).

#### Readout electronics requirements

Readout electronics shall have the capability to reduce the VDD bias to
ground potential to eliminate amplifier glow.

Clock phasing and critical voltages shall be variable and selectable to
compensate for any possible on-orbit radiation damage.

#### Overscan Data requirement

Overscan shall be provided to determine line-to-line variations.

### IR Detector Operation Requirements

#### Detector Readout

IR detector array readout shall be made through all 4 quadrants. Maximum
read-out time shall be TBD seconds or less for a single readout.
Provision for up to ten non-destructive readouts shall be made within a
single exposure.

#### Subarray Readout Capability

TBD

#### Selectable Gain Settings

Four gains shall be selectable in increments from 2, 4, 8, and 16
electrons /bit.

#### Non-integrating Requirements

Basic flush operations shall be provided to condition the IR detector.
Continuous flushing shall be the normal mode while not integrating or
reading out, except in Safe Mode (TBR -- what about HOLD mode?).

#### Readout electronics requirements

Readout electronics shall provide a bias reference voltage and/or
provide a differential signal referenced to that voltage to ensure a
well defined and stable zero-point for the data.

Clock phasing and critical voltages shall be variable and selectable to
compensate for any possible on-orbit radiation damage or deterioration
in the electronics.

### Parallel Operations

#### External Parallel Operations

WFC3 shall support parallel operation with other science instruments on
HST within the constraints of the HST on-board data processing system.
Provision to store 2 uncompressed images in internal memory to minimize
scheduling demands on the SDF shall be made. This requirement shall, as
a goal, extend to the operation of the WFC3 internal calibration lamp
subsystem.

#### Internal Parallel Operations

TBD

### CCD Preflash Capability

TBD

## CALIBRATION

### Calibration Subsystem Purpose

The WFC3 shall contain an on-board optical stimulation/calibration
capability. This capability shall provide illumination of the entire
field of both the CCD and IR detectors with light which passes through
their filter assemblies. This calibration sub-system is intended to
provide a calibration monitoring capability and a means of assessing
correct operation of key instrument sub-systems (e.g. filter selection,
shutter, detector gain, linearity, and cosmetics). Also, it provides a
path to "bootstrap" the ground calibrations onto an initial set of
on-orbit calibrations.

### Calibration Subsystem Spatial Uniformity

Illumination shall be uniform to better than a factor of 2 over the
field of view.

### Calibration Subsystem Temporal Stability

Stability (\<1%) per pixel is required over 1 hour and \<5% over 1 year.
Lamp color temperature stability (over 1 hour) and repeatability (over 1
year) to 50 degrees K (TBR---JWM).

### Wavelength Coverage and Spectral Requirements

The calibration subsystem shall provide usable flux from 200 -- 2000nm
with no more than 20% out of band flux in any spectral element. The
calibration subsystem shall provide both red (cool) and a blue (hot)
continuum sources.

# DESIGN REQUIREMENTS

## SYSTEM

### System Interfaces

The WFC3 shall meet all interface requirements specified in the
Applicable Documents, including requirements to interface with the
OTA/SSM and the SI C&DH as defined in ST-ICD-03 and ST-ICD-08,
respectively.

### Useful Life

The WFC3 shall be designed for a minimum of five years (goal of 8 years)
on-orbit operating life and a minimum of seven years calendar life.
Calendar life is defined as the period during which an item can retain
its desired performance and reliability characteristics while in storage
or installed, operating or non-operating, before being refurbished or
re-certified.

### Single Point Failure

The WFC3 shall be designed such that no single failure (other than the
loss of the POM) shall violate the following for either channel:

#### Unvignetted Throughput

For any single failure, unvignetted throughput shall be available.

#### Fraction of Data

For any single failure, the majority of the data shall be unaffected.

For any single failure (except failure of the CCD shutters or
thermo-electric coolers), data from at least half of the data field in
each channel shall be unaffected.

#### Redundancy

Provision shall be taken to minimize the probability that redundant
items will fail due to a single cause or event and to isolate redundant
critical items to the maximum extent possible.

#### Impact on HST

The WFC3 shall have no single point failure that affects recovery of the
HST. No single point failure shall result in total loss of command,
engineering or scientific capability. No single point failure shall
simultaneously blow both the primary and redundant bus fuses.

### Fail-Safe and Redundancy

#### General Mechanism Redundancy

Mechanisms shall contain redundant drive motors in the event of failure.

#### CCD Channel Shutter

The CCD Channel shutter shall consist either of two blades, each of
which is driven by independent motors or a single blade driven by a
redundant motor.

#### Selectable Optical Filter Assembly

The SOFA shall contain redundant drive motors for each filter wheel
contained within.

#### IR Optical Element Selection Mechanism

The IR optical element selection mechanism (filter wheel) shall have a
redundant drive motor.

#### Channel Selection Mechanism

The channel selection mechanism shall have a redundant drive motor.

#### Corrective Optics Alignment and Focus Mechanism

The corrector mechanism shall contain redundant drive motors.

### Commonality

The WFC3 shall make optimal use of hardware and software design
commonality with the Wide Field and Planetary Camera 2 (WFPC2), the
Advanced Camera for Surveys (ACS), the Space Telescope Imaging
Spectrograph (STIS), and the Near Infrared Camera and Multi-Object
Spectrometer (NICMOS) to the maximum extent practicable, consistent with
the WFC3 scientific objectives.

## OPTICAL

### Optical Interfaces

The WFC3 shall meet the performance requirements of this specification
when presented with optical input from HST that is in accordance with
ST-ICD-03.

### Optical Design

The WFC3 shall correct for the as-built HST spherical aberration, as
well as off-axis aberrations. Focus control shall be provided to
compensate for uncertainties in location of the SI with respect to the
HST focus after insertion in orbit and to compensate for uncertainties
in the definition of HST focus.

## MECHANICAL AND STRUCTURAL

### Mechanical Interfaces

The WFC3 shall meet all mechanical interface requirements specified in
the Applicable Documents, including requirements to interface with the
OTA/SSM and the Remote Interface Units (RIU's) as defined in ST-ICD-03
and ST-ICD-08, respectively.

### Mechanical Interchangeability

The WFC3 shall be designed for mechanical compatibility and mounting
into the specific WFPC-II radial instrument bay. The WFC3 design will
include the pick-off mirror assembly necessary to divert the OTA beam
into the radial bay science instrument.

### Loads

The WFC3 shall operate within specification after exposure to ground,
launch, ascent, in-orbit, and landing loads as specified in ST-ICD-03.

### Modal Characteristics

The WFC3 shall meet the stiffness and modal frequency requirements
specified in ST-ICD-03.

### Mass Properties

#### Maximum Allowable Mass Limits

The maximum allowable weight shall be TBD lbs(without GFE hardware) and
TBDlbs(with GFE hardware). (This allowable weight requirement shall be
determined by the variation from the specified center of gravity
location as per ST-ICD-03).

#### RIU\'s

Two SI C&DH Remote Interface Units (RIU's) shall be included in the
weight requirement. Other Government Furnished Equipment (GFE), as
defined in ST-ICD-03, are not included in the weight budget; however,
they shall be included in the WFC3 mass properties.

#### Center of Gravity and Moments

The center of gravity and moments of inertia of the complete SI end item
shall be determined to the accuracies specified in ST-ICD-03.

### Envelope

The WFC3 outer dimensions shall be as specified in ST-ICD-03. The Remote
Interface Units (RIU's) shall be mounted within the envelope dimensions
specified in ST-ICD-03.

### Mounting and Alignment

The WFC3 shall be designed for installation into, and safe removal from,
the Focal Plane Assembly per ST-ICD-03. The WFC3 will be transported to
orbit in a Scientific Instrument Protective Enclosure (SIPE)
(ST-ICD-91). The WFC3 design shall not preclude installation into, and
safe removal from, the SIPE. The GFE latching mechanisms and crew aids
shall be installed prior to completion of the WFC3.

### Venting

The WFC3 shall meet the venting requirements of ST-ICD-03. The venting
shall be adequate to permit sufficient outgassing to ensure normal
instrument operating conditions in orbit during SMOV. Adequate
structural margins shall be maintained to ensure protection during
ascent and descent. Designs shall minimize flow over optical surfaces
and shall ensure that the SI is not contaminated during test, ascent, or
return in the SIPE. Provision shall also be made to permit purging of
the SI when fully assembled. Vent port and entrance aperture covers
shall also be provided.

### Ground Refurbishment and Maintenance

The WFC3 design shall provide ease of ground maintenance and ground
replacement of a subsystem or component if necessary.

### Orbital Replacement

The WFC3 shall be designed for in-orbit installation into, and removal
from, HST or the SIPE by suited astronauts performing Extravehicular
Activity (EVA). EVA handrails shall be provided assist in handling and
inserting the WFC3 into the designated radial bay on HST. The design and
implementation shall be consistent with that used for WFPC2 on SM1 and
shall incorporate any lessons learned from that Servicing Mission.

### SIPE Interface

The WFC3 will be transported to the HST as an ORU enclosed in the SIPE.
The SIPE's mechanical interface with the WFC3 will be in accordance with
and satisfy the requirements of ST-ICD-83.

### Pickoff Mirror Cover

A pickoff mirror cover shall be designed, built, tested and delivered as
part of the instrument. The mirror cover will protect the mirror during
EVA. The mirror cover will be installed on the instrument prior to
flight and will be red-tagged for removal by the astronaut immediately
prior to insertion into the radial instrument bay on the HST.

### CCD Detector Replacement Capability

The WFC3 shall be designed to allow replacement of the WFC CCD detector
package at any stage of instrument assembly prior to launch without
significant de-integration.

## THERMAL

### Thermal Interfaces

The WFC3 shall meet the thermal interface requirements of ST-ICD-03.

### Thermal Design

#### Overall Goals

A passive thermal design shall be used, as far as practical, to achieve
WFC3 temperature control and stability.

#### Multi-Layer Insulation

All MLI shall be protected to resist abrasion and crushing.

#### Thermal Control

The thermal control will ensure that the instrument remains within
acceptable operational temperature limits for all parts of the HST
mission in which the HST is within ICD limits. Short-term temperature
changes (up to 1 hour) under any HST operation condition shall not
adversely impact the WFC3 performance during an observation. Long-term
effects (greater that 24 hours) shall not result in permanent
misalignment of the WFC3.

#### Ground Operation

All heat pipes used in the WFC3 will be located such that the detector
may be operated and tested on the ground.

#### Servicing Mission Specific Requirements

The thermal interface with the SIPE shall be by conduction, convection
(while inert gasses are present) and radiation. No special coatings or
heaters will be required to be added to the WFC3 to cool or heat it
during any part of the maintenance missions.

## ELECTRICAL

### Electrical Interfaces

The electrical and command/data systems interfaces shall be in
accordance with ST-ICD-03 and ST-ICD-08. Power conditions and allotments
for average, peak, and hold power shall be as described in ST-ICD-03.
The RIU power budget, as given in ST-ICD-08, shall be charged to the
WFC3 power allotment.

### Electrical Design

#### Scope of Design

The WFC3 electrical design shall be capable of exercising the instrument
in all modes as defined by this specification. It shall include all
elements required to support the WFC3, including spacecraft interface,
command and control, engineering and science data collection, thermal
control, power configuration, electronic configuration, and redundancy.

#### RIU Interface

The WFC3 electrical design shall incorporate the SI C&DH Remote
Interface Unit (RIU) and shall contain sufficient design margin to meet
the life requirements of this specification.

#### Science Data

The WFC3 shall provide for the acquisition, formatting, buffering,
annotation, and control of science data through the Science Data
Formatter (SDF) interface as specified in ST-ICD-08. The science data
shall include, as a minimum, observation data and engineering data
required to annotate, calibrate, categorize, and clearly identify the
telemetered science data.

#### Software Modifications

The WFC3 shall have the capability to receive time code updates from the
spacecraft clock when commanded.

#### Engineering Data and Monitoring

The WFC3 instrumentation shall provide the necessary engineering data to
enable monitoring and evaluation of instrument status through the RIU
interface as specified in ST-ICD-08. It shall provide continuous,
on-board, real-time monitoring of critical elements and the ability to
switch the instrument to a safe condition, without real-time ground
commands, should hazardous conditions exist. The SIPE interface shall be
as defined in ST-ICD-83.

### Electrical Redundancy

System redundancy shall be provided that is capable of controlling all
WFC3 internal subsystems and of interfacing with the RIU's and the SDF.
The WFC3 shall be capable of operating through either RIU and either SDF
port. The electrical design shall use redundancy where practical and
shall not preclude operational workarounds in the event of different
failures on each of the redundant systems.

## SOFTWARE

The WFC 3 flight software shall be partitioned between the NSSC-1
application processors and the WFC3 processors.

### NSSC-1 Flight Software Interfaces

The WFC3 flight software in the NSSC-1 shall control the following
operations:

#### Monitoring

Monitor WFC3 engineering data for unsafe conditions.

#### Take Data Flag Handling

Retrieve and forward the HST Take-Data-Flag.

#### Requests Response

Receive special engineering data from the WFC3 instrument and respond to
requests embedded in this special engineering data, including: 1)
posting Executive Status Buffer messages; and 2) commanding the WFC3 to
a safe or suspend state.

#### Macro Commands

Send macro commands to the WFC3 instrument flight software.

### WFC3 Internal Flight Software

The flight software in the WFC3 shall perform the following functions,
as a minimum:

#### Command Handling

Receive, decode, and execute commands.

#### Control

Control mechanisms.

#### Science Data Control

Control and acquire science data from the detector.

#### Science Data Management

Format, buffer, and queue science data for output.

#### Engineering Data Management

Collect, format, and process engineering data for output to the NSSC-1.

#### Coordination

Control and coordinate WFC3 activities.

#### Engineering Monitoring

Monitor engineering data for unsafe conditions and report to the NSSC-1
need to safe or suspend.

#### Self Tests

Perform self tests.

#### Error Conditions Reporting

Collect error conditions for output to the NSSC-1.

### Software Design

The WFC3 software design shall be capable of exercising the instrument
in all modes to the performance and functional requirements as defined
by this specification. It shall include all elements required to support
the WFC3, including receipt, decode, and execution of commands received
from the SI C&DH; control of instrument operations; collection,
formatting, processing, and output of engineering and science data to
the NSSC-1 and SDF, respectively; detection of instrument anomalies;
maintenance of the instrument in a safe state; management of instrument
memory, and self-diagnostics.

The WFC3 flight software shall be capable of being modified on-orbit.

Ground test software shall be designed for operation of the WFC3 at
NASA/GSFC, through the HST ground communications system, to produce and
reduce sufficient science and engineering data to optically align and
functionally verify instrument operation, to evaluate performance
characteristics, and to perform calibration.

## OPERATIONS

### Operations Interfaces

Operation of the WFC3 shall occur in the same manner as the Advanced
Camera for Surveys (ACS). Time-tagged command blocks will be transmitted
from the ground to the NSSC-1 on HST. These commands shall be structured
such that observations can begin, terminate, and the data dispositioned
at pre-specified times. For observations, a pre-specified amount of data
at the pre-specified time shall be provided by the WFC3.

The HST will provide the following to the WFC3:

#### RIU discrete commands.

#### Observation and maintenance commands.

#### Spacecraft time.

#### Target lock indicator.

#### Health monitoring.

#### Transmission of engineering and science data to the ground.

#### Error handling.

### Operations Design

The WFC3 design shall support the following operating requirements:

#### Response to loss of lock.

#### South Atlantic Anomaly safe operation.

The WFC3 shall be capable of passing through the SAA with no affect on
any internal systems for at least 5 years other than not being able to
obtain science data during such passages. It is acceptable to require
that WFC3 transition from OBSERVE to OPERATE mode prior to SAA entry.

#### Transfer of science data at commandable times.

#### Hierarchical instrument configuration states and transitions between states.

# PERFORMANCE ASSURANCE

## FLIGHT ASSURANCE

Flight Assurance shall be performed in accordance with an approved
Flight Assurance Program that encompasses all flight hardware and
software per STR-43.

## TEST AND VERIFICATION

### Performance Verification Plan

Test and verification shall be accomplished per STR-43, SCM-1030,
STR-29, and the approved Performance Verification Plan and shall ensure
that the WFC3 hardware and software conform to the design, fabrication,
and performance requirements for a protoflight unit as specified herein.
Test or analysis, as defined in the approved Performance Verification
Plan, shall verify each requirement.

### Subsystem Testing

All subsystems shall be qualified prior to integration to the next
highest level.

### Life Testing

Life testing shall be performed, as required, to verify that the WFC3
will meet the life requirements specified herein. Lifetime requirements
shall be derived from estimates of nominal use during ground testing and
calibration, and over the course of a five-year flight mission, plus
contingency, that includes science observations and calibration, as a
minimum.

### Minimum Test Suite

As a minimum, the following tests shall be performed in the completed
WFC3 protoflight unit.

#### Functional Test

Operational tests of WFC3 shall be performed wherein all functions are
checked for compliance with the applicable specifications. Functional
tests shall be run periodically throughout the test program, including
before and after environmental tests.

#### Vibration/Acoustics

Vibration/acoustics tests shall be performed at protoflight levels in
accordance with GEVS-SE as reflected in STR-43.

#### Acceleration

Acceleration requirements will be verified by analysis and a combination
of random and quasi-static load tests performed at proto-flight levels
in accordance with the guidelines of GEVS-SE as reflected in STR-43.

#### Thermal Balance

A thermal balance test shall be performed for two cases (hot operate and
cold hold) to verify the WFC3 thermal design. Transitions between
conditions shall be controlled to obtain sufficient data for transient
thermal math model correlation. A light stimulus shall be applied during
the hot operate case to verify alignment of WFC3.

#### Thermal Vacuum

Functional operations and performance testing shall be conducted in
thermal vacuum, as applicable, for verification and calibration per
GEVS-SE as reflected in STR-43. A minimum of 2 cycles shall be used for
thermal vacuum verification.

#### Electromagnetic Compatibility (EMC)

The WFC3 shall be designed for electromagnetic self-compatibility with
HST for all phases of the mission and for EMC with the shuttle for those
phases of the mission in which HST is active and in proximity with the
shuttle. The WFC3 shall be designed and tested per ST-ICD-03.

#### Magnetics

The WFC3 shall be tested for magnetic field intensity and susceptibility
to demonstrate compliance with ST-ICD-03.

#### Envelope

The physical envelope dimensions of the WFC3 shall be verified to
demonstrate compliance with ST-ICD-03.

#### Mass Properties

Mass properties measurements, including center of gravity and moments of
inertia of the complete end item SI, shall be performed to demonstrate
compliance with ST-ICD-03.

## Calibration

The WFC3 shall be operated in facilities that allow production of
characteristic WFC3 images. These images shall be analyzed to determine
system performance, to define operation and calibration parameters, and
to verify that the performance requirements of this specification are
met.

## CONTAMINATION CONTROL

Contamination control shall comply with STR-29 and the approved WFC3
Contamination Control Plan. Contamination control within the WFC3 shall
ensure that the instrument will meet the performance requirements
specified herein over the life of the instrument.

## MAINTAINABILITY

Maintainability shall be in accordance with the approved Performance
Assurance Program. WFC3 components subject to maintenance shall be
designed, selected, and installed to facilitate the performance of such
tasks with minimum hazards to equipment and personnel and to provide for
maximum use of standard tools and test equipment. The WFC3 design shall
provide for easy removal and replacement, and re-alignment if necessary,
of subsystems such as detectors, electronics, and major mechanisms.

## CREW SYSTEMS

The WFC3 shall be designed in accordance with NSTS 07700, Vol. XIV,
Appendix 7. It shall be designed to preclude damage through handling and
inadvertent contact by pressure-suited crew. Shields or covers shall be
provided for non-ruggedized equipment to protect against damage. The WFC
3 will be designed to meet the minimum EVA crew safety and design
requirements specified in NSTS-07700, Vol. XIV, Appendix 7, and safety
policy of NSTS-1700.7B.

## DESIGN AND CONTRUCTION STANDARDS

The WFC3 shall be designed to minimize damage through handling and
inadvertent contact by the pressure suited astronaut crew. Design and
construction standards shall be in accordance with the approved WFC3
Performance Assurance Plan and STR-43. Specifications and standards
necessary for the design and development of the WFC3, in addition to
those specified in this document, shall be selected in the following
order of preference except as otherwise specified in this document:

NASA Specifications and Standards

GSFC Specifications and Standards

Other NASA Center Specifications

Federal Specifications and Standards

Military Specifications and Standards (MIL, JAN, or MS)

Other Government Specifications

Specifications released by nationally recognized associations,
committees, and technical societies

Vendor Specifications

### Electrical

#### Electrical Design Standards 

Electrical design standards shall be in accordance with the approved
WFC3 Performance Assurance Program to ensure equivalence with NASA
standards and STR-43. Electrical interfaces will be in accordance with
requirements of the SI to OTA/SSM IRD STR-02D, sections 3.1.6 and 3.2.3,
and the requirements of the SI to SI C&DH IRD STR-10.

#### Electrical, Electronic, and Electromechanical (EEE)

Parts EEE parts shall be selected in accordance with the approved WFC3
Performance Assurance Program to ensure equivalence with NASA standards
and STR-43.

#### Electronic Component Design

All designs shall be based on conservative derating factors for
components per PPL-13, Appendix B and STR-43.

#### Electronic Grounding

Electrical grounding shall be in accordance with ST-ICD-03. Primary DC
power shall be isolated from all structure.

#### Redundancy

Where electronic redundancy is employed per the requirements of this
specification, the WFC3 shall include the capability to verify redundant
items as part of the normal ground checkout sequence. In addition, one
fault shall not cause the loss of both the primary and redundant
capability. Redundant critical components shall be isolated to the
maximum extent possible.

### Structural

The design shall accommodate the mechanical loads due to acceleration,
thermal, vibration, and acoustic excitation as defined is ST-ICD-03.
Except under emergency and crash loads, the design shall not experience
plastic deformation. The structure may yield but not fracture under
emergency landing. Safety factors shall be applied in accordance with
GEVS-SE as reflected in STR-43.

### Materials

The design shall use materials in accordance with STR-43. The value of
thermal properties for surface finishes and insulation materials shall
be verified by established references or by measurements that are
submitted to GSFC for final approval per STR-43 and SCM-1030. In
addition, the procedures used for fabrication and installation of
thermal insulation shall be approved by GSFC. Metal parts shall be
protected from corrosion by stress relieving, plating, anodizing,
chemical coating, organic finish, or combinations thereof provided that
such protection is compatible with the operating and environmental
requirements.

### Coordinate System

The WFC3 coordinate system shall be in accordance with ST-ICD-03.

### Identification and Marking

Identification and marking shall be in accordance with the requirements
of the approved Performance Assurance Program and Contamination Control
Plan.

## Radiation Properties

The radiation environment, as defined by the HST orbit and ST-ICD-03,
shall be accounted for in the WFC3 design. Component selection and
shielding shall be accomplished in a manner that ensures required life
as well as the ability to meet the functional and performance
requirements in the radiation environment.

Sensitive instrument components shall be adequately shielded from
particle radiation to preclude radiation effects damage that would
impair intended function for at least 5 years, and to 15 years as a
design goal. No component shall be designed for early replacement (less
that 5 years) due to radiation effects.

All on-board computer, memory, and control circuits shall be immune to
single event upsets

## MAGNETIC PROPERTIES

The WFC3 shall be capable of meeting performance requirements within the
magnetic fields defined in ST-ICD-03 for other HST systems and also
within the magnetic field of the defined HST orbit. Fields generated by
the WFC3 shall conform to ST-ICD-03. In addition, magnetic interaction
of various subsystems within the WFC3 shall not adversely affect
operations or performance.

## TRANSPORTABILITY

The WFC3 shall be prepared for shipment in accordance with STR-43 and
shall be shipped in a container specifically designed for its protection
during highway and air transportation. Vibration, shock, pressure,
temperature, humidity, and contamination shall be controlled by the
container to within the limits specified in ST-ICD-03 and STR-29.
Provisions shall be made in the structure for suitable tie-down, lift,
and attachment points. All handling and transportation equipment shall
be compatible with the ST-ICD-03 structural and environmental limits.
The WFC3 shall be designed to be transported in either the horizontal or
vertical position.

All containers proved for the purpose of shipping WFC3 components, such
as optics, shall be specifically designed to protect those components
during highway and air transportation. Containers required to
hermetically isolate their contents from the exterior environment shall
be capable of purging with bottled gas; e.g., dry nitrogen. Vibration,
shock, pressure, temperature, and contamination shall be controlled to
the limits specified in ST-ICD-03, STR-29 Contamination Control Plan.

## SYSTEM SAFETY

The design shall be in compliance with the system safety requirements of
STR-43.