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WFC3 Instrument Science Report 2009-15

WFC3 SMOV program 11454: Activation Test
L. Petro November 17, 2009

ABS

TRACT

Post-release from Atlantis, this program provided the first verification that the operability of WFC3 for science was unchanged from the post-launch verification made during SM4. The SMOV Activation Test was comprised of a repeat of the SM4 Functional Test with the exception of tests of the TECs. No significant differences between the results of this Activation Test and the Functional Test were identified, which provided the desired verification.

Introduction
The Functional Test (FT) and its associated pass/fail criteria were designed to demonstrate, within limits, that WFC3 could be operated to achieve certain basic science objectives. Those limits derived from WFC3 being in the payload bay of the Shuttle Atlantis and from the small amount of time available from the astronauts during the servicing mission. Although thus limited, the FT did provide a good benchmark of the condition of WFC3, sufficient to determine that leaving it in place in HST was preferrable to replacing it with WFPC2, from a science perspective. The Activation Test, which is described in this Report, used the benchmark established in the FT to demonstrate that WFC3's detectors and mechanisms remained ready to begin the extensive Servicing Mission Observatory Verification (SMOV). In order to avoid putting unnecessary thermal stress on the Thermoelectric Coolers (TECs), they were not rechecked as part of the Aliveness Test. In addition to deleting that part of the FT, the Activation Test differed from the FT by way of the method of implementing the test. Operation of WFC3 for the SM4 FT was obtained via realtime CCLs, whereas the SMOV Aliveness Test operated WFC3 from stored commands that were specified at a high level in a Phase 2 proposal. Ten exposures obtained by the two methods were functionally the same. One exposure additional was required in the Activation Test in order to demonstrate motion of the IR channel Filter Select Mechanism (FSM). The pass/fail criteria of
Operated by the A ssociation of Univ ersities for Research in A stron omy, Inc., for the National A eron autics and Space Adm inistration.


WFC3 Instrument Science Report 2009-xx both tests were assessed in terms of engineering telemetry that demonstrated the intended operation of mechanisims and other devices, and in terms of the examination and analysis of the science exposures obtained from the warm UVIS CCD detector and the warm IR focal plane array (FPA) detector. The exposures necessary to repeat the FT were implemented in the Phase 2 proposal SM4/WFC3 11454. That proposal was also used for three additional purposes: i) after release from Atlantis, to recover WFC3 from Safe mode to Operate mode with the PROTECT thermal set-points; ii) at the end of the out-gassing epoch, to transition from PROTECT to NORMAL thermal set-points; and iii) after the Activation Test, to cool the UVIS and IR channel detectors to their science operating temperatures. However, this Report does not concern those additional uses of SM4/WFC3 11454 and presents only the Activation Test. The eleven exposures of the Activation Test were obtained in the order presented in Table 1. The first six exposures were obtained with the UVIS channel CCD and the last five with the IR channel FPA. The UVIS exposures were intended to demonstrate nominal signals from the detector, to assess the electronic noise of the amplifiers, and to demonstrate sensitivity to light from the internal calibration system. The IR exposures had the same goals, except the dark current of the uncooled detectors saturate in the shortest exposures preventing an assessment of both nominal dark and light sensitivity. Table 1 · Exposures obtained in the SMOV Activation Test, SM4/WFC3 11454
Ser. No. 1 2 3 4 5 6 7 8 9 10 11 03/04 03/05 iabs03uhq iabs03uiq DARK TUN GSTEN 0.143 0.912 IR IRSUB64 BLAN K F140W 02/ 02/ 02/ 03/ 03/ 0 0 0 0 0 4 6 8 1 2 iabs02u iabs02u iabs02u iabs03u iabs03u 8q aq bq dq eq DARK TUN GSTEN TUN GSTEN DARK DARK DARK 1 1 1 20.526 74.231 0.143 UVIS UVIS UVIS IR IR IR NA F606W F350LP BLAN K BLAN K BLAN K Prop osal Visit /Exp. 02/01 02/02 02/03 Dat aset iabs02soq iabs02u5q iabs02u7q Targ et Na m e BIAS DARK DARK Exp . Time [sec] 0 20 1 Aper. UVIS UVIS UVIS Filters NA NA NA Read out Std. Std. EN G WARM/AD EN G WARM/BC Std. Std. RAPID/ 7 STEP25/7 EN G RESET_ON EN G RESET_ON RAPID/ 15

03/03

iabs03ufq

Analysis
The assessment proceeded in three parts. Firstly, during the operation of WFC3, the engineering telemetry was monitored to verify that instrument performed as commanded. The commanding of the exposures closely followed the real-time commands used during the FT, so the Sequence 64 of the SM4 Command Plan and its telemetry verifiers were used to make this assessment during the
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WFC3 Instrument Science Report 200x-xx Activation Test. All verifiers took on the expected values. In particular, the movement of the Channel Select Mechanism (CSM), the UVIS , the IR Filter Select Mechanism (FSM), and the UVIS shutter were monitored and operated as intended. Secondly, after receipt of the science data via OPUS Fast Track processing, a detailed visual assessment of each exposure was made, including an overall judgement. These assessments are presented in Table 2. All images are nominal. The UVIS signals are as expected and known artifacts are present. In particular: i) cosmic ray trails are present in the exposures and change Table 2 · Visual assessment of exposures in SM4/WFC3 11454
Ser. No. Exp osure Specificat ion Activ ation Test Result

Assessment of Science Imag e Cosmic Ra ys visible. Scratches in Amp B quad not visible. Shading from da rk accumula tion d uring read out appa rent. Different Cosmic Ra ys visib le. 2 Scratches in Amp B q uad visib le. Dark shading visib le. Bea ch ball a nd elep hant's trunk visib le. Snowba lls visible. Amp s AD readout. Nomina l app ea rance. Std. D ev. = 1.97 DN Amp A. Amp s BC readout. Nomina l appea rance. Std. D ev. = 2.12 DN Amp B. Lamp 1. N ominal app ea rance. Baffle a rcs in corners. D roplet features. Light sig nal ~7,500 DN. Lamp 3. All features simila r to F606W . Lig ht signa l ~ 28,000DN. Saturated. Q1 amp lifier corner is round ed, which is nomina l. Single fra me shows D eath Sta r. Saturated. Simila r app ea rance to RAP ID. Nominal. Vertica l b locks in single fra me. Std. D ev. of d ifference of 2 fra mes = 2.4 DN. Same as p revious. Std. D ev. = 2.4 DN. Lamp 2. 64x64 subarra y with 5- reference pixel bord er. Exp osure not in SM4 FT. Demonstrates FSM op eration. Also demonstrates subarra y a nd Tungsten Lamp 2.

1

UVIS Bias

N o m i na l

2 3 4

UVIS 20-sec D ark UVIS Noise UVIS Noise UVIS 1- sec F606W , Tung sten Lamp UVIS 1- sec F350LP, Tung sten Lamp IR Da IR Da R APID , N SAM P 7, rk STEP25, NSAMP 7, rk

N o m i na l N o m i na l N o m i na l

5 6

N o m i na l N o m i na l

7 8

N o m i na l N o m i na l

9 10

IR N oise IR N oise

N o m i na l N o m i na l

11

IR F 140W, SQ64 suba rray, N SAMP 15, Tung sten Lamp

N o m i na l

from exposure to exposure, as appropriate to the space environment; ii) the diffuse background signal shades away from the side with the serial readout registers as expected for a warm dark signal that accumulates while the parallel transfer is made; iii) two regions of anomalous sensitivity (named the "beach ball" and the "elephant's trunk"), known from operations during ground testing, are apparent as expected (see Fig. 1); iv) in the amplifier B quadrant, scratches
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WFC3 Instrument Science Report 2009-xx known from cryogenic, ground operations of this detector are visible in the DARK exposure, but not in the BIAS exposure, as expected from ground operations at non-cryogenic temperatures (see Fig. 1); v) the images with illumination from the internal calibration lamps show the expected artifacts ­ "droplets" and baffle stray light arcs (see Fig. 1); and vi) the light signal in the long pass F350LP filter is approximately 4в greater than in the narrower F606W filter, as expected. The similarities of the Activation Test and FT can be seen in Figure 1, which compares the key DARK and internal calibration lamp exposures.

Figure 1 · Comparison of warm UVIS dark and flat field exposures from the SMOV Activation Test and SM4 Functional Test. The IR exposures are similar to the matching exposures from the FT and to exposures taken during ground operations. In particular: i) the regions of off-nominal response are distinguisable from the remainder of the FPA ­ the "death star" in the Amplifier 2 quadrant and the "rounded" corners of the FPA; and ii) the rectangles in the RESET_ON, warm engineering test readout sequences. Thirdly, a quantitative comparison of matching exposures taken during the SM4 FT and the SMOV Activation Test were made. The UVIS and IR exposures are compared in Table 3. The temperature of the UVIS CCD is similar during the two tests, but the IR FPA is 10° C colder
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WFC3 Instrument Science Report 200x-xx during the Activation Test. The signals from the internal lamp through each UVIS filter, F606W and F350LP, during each test do not differ significantly. No significant change between the two tests of the read noise of the UVIS CCD, or the IR FPA occurred. Table 3 · Comparison of signals and noise of Functional Test and Activation Test
UV IR UV UV UV IR Quantity IS CCD Tempera ture FP A Temp erature IS Lamp F606W, lig ht IS Lamp F350LP, lig ht IS Elec. R ead N oise Elec. R ead Noise SM4 FT DOY 135 2° C -18° C 4,530 DN 24,600 DN 2.1 DN 2.4 DN AT DOY 149 0° C -28° C 4,250 DN 23,700 DN 2.0 DN 2.4 DN

Conclusions
Post-release from Atlantis, the WFC3 detectors and mechanisms continued to operate nominally and as expected. This conclusion is based upon monitoring of engineering telemetry during the execution of the exposures comprising the Activation Test, visual examination of the eleven UVIS and IR science images, and measurement of signals and characteristic electronic noise. No significant difference between these SMOV Activation Test exposures and the matching SM4 FT exposures was found.

Acknowledgments
Several indivi developed the developed the developed by duals contributed to the developments that made this test a success. Bryan Hilbert analysis script for the SM4 Functional Test; Alan Welty and Ilana Dashevsky special commanding for the Activation Test; and the SM4 Functional Test was Randy Kimble, John MacKenty, Olivia Lupie, and Dave Hickey.

References
HST Servicing Mission 4 Command Plan, Launch Update #4.1, April 28, 2009 [NASA GSFC].

Revision History
2009-10-06 ­ Original publication.

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