A.I. 1 Assess the risk to STIS during the NCS cool down. Evaluate if the schedule should be adjusted to help mitigate the risk. Response provided by Teri Gregory, Colleen Townsley, and Jeff Valenti. It is recommended not to turn on the STIS MAMAs until after 100 hours after the NCS initial turn-on, assuming that the valve heaters are shown to be cycling properly and controlling the value temperatures above their leak level. This recommendation may change depending on the final assessment from the CHAMPS Thermal group of the following risk periods. This final assessment is dependent upon the NCC portion of the model finalized. The Thermal group expects this work to be completed by the end of May01. [Emphasis added by C. Biagetti] There are three times of high risk times for turning on the high voltage on the MAMAs due to potential leaks from the NCS during initial turn-on and cool down: Risk #1: There is a risk of a potential leak during the initial fill of the NCC. The initial fill will be done prior to the first maximum cool-down. a. The initial fill will be done via the command plan, and the instruments will be safed during this time. Since STIS will be safed during this time period this is a non-issue for managing the MAMA high voltage. Risk #2: Preliminary thermal assessment shows the first 10 hours of NCC operation as the greatest rate of temperature change for the cool down of the values and bayonets. a. Recommendation is to wait until approximately 48 hours after the inlet valve and bayonet have stabilized (~10 hours after initial cool down). During the first 48 hours, the system is reaching equilibrium and a possible leak could occur. Risk #3: Another risk period for a potential leak could occur as the NCC begins its cool down before the valve heaters are shown to be cycling properly and controlling the valve temperature above their leak level. Preliminary thermal assessment show that the valves settle into their cycling in approximately 100 hours. [Note: The 100 hours in question occurs between the start of SMOV day 7 and SMOV day 11 thereby forcing the final STIS End-of-BEA Test, which uses a MAMA, to occur no earlier than ~ day 11.5, a couple of days later than originally planned. Therefore, adding some analysis time for the decision to end the BEA and allowing some time for scheduling of uplink opportunities means that the BEA period may need to extend by a day or two. We will have a better estimate as detailed proprosal processing proceeds. Note also that, according to the italicized statements in the first paragraph, the constraint period may increase to something greater than 100 hours, thereby further extending the BEA period. Depending on the magnitude of this 1 extension, we may wish to revisit the plan for starting NICMOS cooldown on SMOV day 7.-- C. Biagetti]. A.I. 2 Determine the first opportunity to take ERO pictures for ACS and NICMOS. A.I. 2a ACS EROs – Response provided by Guido De Marchi. Early release observations not requiring accurate pointing (thus excluding, for instance, all coronographic observations) could be scheduled right after the end of the coarse and fine alignment programmes (ACS13 and ACS14, respectively). Observations carried out as part of the fine alignment proposal will allow the IDT to verify the quality of the PSF over various regions of the FOV of the cameras. As suggested by A. Fruchter, a series of three exposures of a moderately crowded stellar field of about 15 min duration each will be scheduled at the end of the fine alignment tests. These data will be used to verify that the PSF is indeed stable over time spans typical of ERO images and over a wide spectral range. Assuming a launch date on Jan. 17, 2002, the first ERO frames could be collected on approximately Feb. 25, 2002, i.e. during the fifth week of SMOV. We estimate that about three weeks will be necessary to the ACS team to process the ERO data, in light of the complexity of the latter and of the novelty of the instrumentation. OPO have estimated that they will need an additional 10 days to prepare the ERO data for final release (including all the printed products). Because no flight calibration data will be available prior to the execution of the first ERO programmes, calibration data collected on the ground will be used to process the ERO frames. We do expect, however, the geometric distortion programme (ACS28) to begin execution in parallel to ERO. Depending on the complexity of the data analysis, it might be, thus, possible to use the new geometric distortion calibration obtained in this way to process the ERO data. We should like to note here in passing that the short PSF stability test run at the end of fine alignment cannot replace programme ACS17 (pointing stability). The latter will still have to be executed to prove that the PSF is stable over time also for longer exposures and, more importantly, in different thermal environments. Some of the ERO programmes require accurate pointing, which in turn need the ACS to be properly aligned with the reference frame of the 2 FGS. These observations can only take place after the ACS to FGS alignment proposal (ACS11) has been executed and after having updated the appropriate calibration tables (apertures location) in the flight software. We expect all keywords to be in place by the end of week 8 of SMOV (Mar. 21, 2002). A.I. 2b. NICMOS EROs – Response provided by Carl Biagetti with STScI NICMOS Team concurrence. NICMOS EROs were originally scheduled for execution at launch plus 9 weeks (~ Jan. 30 based on a 29Nov01 launch) following instrument recooling (week 2) during the BEA period, a 2-week monitoring and analysis period for temperature set-point determination, and a 2-week PAM alignment operation for all 3 cameras. The remaining 3 weeks were a conservative allotment for NICMOS for parameter updates occasioned by the PAM alignment. In response this action item, the team believes that, since PAM focussing is relatively insensitive to temperature changes, it will be possible to commence the PAM alignment process very soon after SI cooldown rather than waiting the additional 2 weeks for temperature set-point determination. In addition, the resulting parameter updates can probably be accomplished in two weeks instead of three, as long as we assume the NICMOS-to-FGS frame alignment is not required for at least the initial EROs. In this case, the initial NICMOS EROs can be accomplished at approximately 6 weeks following launch (~ Mar. 3 for a 17Jan02 launch). Note that, in the event of observations requiring optimized pointing accuracies, e.g., a coronographic observation, such EROs would not be achievable before early May02. A.I. 3. Supply the Project plan for implementing dual SSR capability. SM/Pilkington Response TBS A.I. 4. Present to Project management the assessment for using the second transmitter during SMOV. Response provided by Carl Biagetti. Prior the SPR, Alan Patterson, STScI Planning & Scheduling, issued a white paper on projected SMOV data volumes. While the paper's principle recommendation was to use both Solid State Recorders (SSR) in SMOV3b, it also assessed the effect of using both high-rate transmitters for the same time period. This assessment appears in section 3.1.2 (2-SSR/1-transmitter operations) and 3.1.4.(2-SSR/2-transmitter operations). The recommendations (Sec. 4.0) are reproduced below. 3 =============================================================== High Data Volume SMOV Requirements and TDRS downlink capability Alan Patterson, 17Jan01 Excerpt: "4.0 Recommendations It is recommended that both SSRs be in use at the same time during SMOV. This will avoid a forced extension in SMOV activities. If there are very few SMOV activities that require rapid access and these do not include any high data volume ACS programs then the careful placement of the known visits can be handled with single transmitter operation. If there are more than a handful of high data rate and volume ACS visits requiring rapid access it is recommended that both transmitters be in operation during the first few, critical weeks of SMOV. If part 2 of ACS program 9005 must be executed contiguously then 2 transmitter operation is necessary. It is recommended high data rate high data volume SMOV visits that do not require rapid access be split into pieces and scheduled separately." Note: Except for Part 2 (CTE measurement), the ACS CCD functional (9005) will be scheduled during the first week of SMOV. Part 2 will go later in SMOV at a time convenient for handling the data volume. The other high-volume ACS activities will not require scheduling in contiguous orbits. Therefore, two-transmitter operation is not required by ACS. The only SMOV3b activities that require rapid downlink (rapid enough to require a second transmitter) are the initial WFPC2 Cooldown & UV monitors (WFPC2-03) which occur shortly after the Bright Earth Avoidance (BEA) period. These are relatively lowvolume (compared to ACS) but they occur during the high-volume NICMOS internals, requiring some judicious scheduling but not a second transmitter. Conclusion: While two-transmitter operation during SMOV3b would be handy in 2 or 3 specific instances, it is not required for planned SMOV execution. A.I. 5 EPS personnel should add to their analysis plan, tracking of the SADM Performance. Data should be compared to SA2 SADM performance. Response provided by S. Krol and N. Seftas. Data extraction of SA-2 Command Profile Error has started. Following SM-3B, Command Profile Error data for SA-3 will be compared to that of SA-2. 4 A.I. 6 Investigate solar array position optimization during -V1 pointing during the VDT. Response provided by S. Krol, N. Seftas. HST will need to be at the Anti-Sun Attitude (sun vector is within +/- 10 degrees of the -V1, SA incidence angle less than 5 degrees) to support power measurement calculations. For SMOV3B, it would be good to more formalize the normal scheduling procedure as follows (per activity summary EPS-2): From the end of BEA through the end of SMOV, when the vehicle pointing is within 10 degrees of the antisun for longer than one orbit, ensure that the solar arrays are set to within 5 degrees of normal. There are two obvious opportunities currently during SMOV3B that may provide good data for solar array power determination. 1) Soon after the end of BEA, there will be a 5 orbit Vehicle Disturbance Test that required an antisun pointing (PN format engineering data). 2) About 6-7 weeks after the end of BEA, there is a ~8 orbit ACS test that requires an antisun pointing. 3) Any other serendipitous opportunities that occur in the schedule will be set up to allow them to be utilized. A.I. 7. Add spacecraft tests to the SMOV timeline chart. Response provided by Carl Biagetti. The tests will be added to the network chart as they become known. A.I. 8 Assess the impact of OTA focus changes on the ACS Pointing Stability Test. Response provided by Chris O’Dea and George Hartig. As currently planned, the pointing stability test (ACS16) is intended to measure the combined OTA plus internal ACS image position drift, as it is this cumulative effect that will, in practice, reflect onto the science observations. Although the response of the OTA to thermal variations may change both image focus and position, we expect that focus changes will not significantly affect our ability to measure positional changes. Furthermore, the observational approach has been devised in such a way that we can separate the two components: OTA changes will be manifest as image movements in the same direction and magnitude (projected on sky) for both HRC and WFC detectors, whereas various instability mechanisms internal to the ACS will likely result in different behavior for the two channels. During the review, M. Reinhart suggested that the order of the observations could be reversed and that the spacecraft should drift 5 from a cold to a warm attitude during the test (instead of moving from warm to cold). The advantage of this approach would be to leave the spacecraft, at the end of the test, in a more nominal condition for the observations to follow. Since the order of the temperature changes will have no significant effect on the pointing stability test, we fully agree with M. Reinhart's suggestion. A.I. 9 Assess requirement J.10.4.4.5.3. In particular, determine if one month is the proper length of time for the +/- 0.5 deg K stability requirement. Response provided by Carl Biagetti and Bahram Mobasher. The requirement stands as is. The one month timeframe is proper for a SMOV requirement, though it is understood the CEI spec requirement spanning a year-long interval is the more scientifically meaningful one. A.I. 10 Add to the SMOV timeline chart a Project technical review date to determine the NCC set point. Response provided by Carl Biagetti. A NICMOS temperature set point FRR has been added to the network chart at a point two weeks after completion of the NICMOS cooldown. Thus, the FRR would be expected to occur at about Release + 26 days (~20Feb02 for 17Jan02 launch). 6