The Space Telescope Users Committee met in open session on 24-25 November 1997, in the Board Room of the Space Telescope Science Institute. Committee members in attendence were: W. van Breugel, J. Clarke, R. Fosbury, L. Kay, P. McCarthy, R. Schulte-Ladbeck, S. Terebey, R. Thompson, F. Walter (Chair), and B. Woodgate. Absent were J. Bally and M. Franx.
Monday 24 November
B. Williams, director of the STScI, welcomed the participants and opened the meeting with the STScI perspective. The observatory continues to operate well.
R. Gilliland presented an overview of the spacecraft status. He concentrated on spacecraft operations; discussion of the science instrument (SI) status followed later. The replacement Fine Guidance Sensor, FGS1R, which was installed in SM2, is working well. It is superior to FGS3 in TRANS mode. There are no current plans to replace FGS3 with FGS1R for scientific use, but decisions on what science modes will be offered will be made prior to the cycle 8 CP. (FGS details are available here.)
Use of FGS2 is being kept to a minimum. There have been some losses of lock during small angle maneuvers, but this has not lead to any significant loss of observations.
J. Biretta discussed WFPC2 status. There is some progress on understanding the CTE problem.
D. Calzetti reported on the current status of NICMOS. Currently, science operations are expected to cease in December 1998, about a month prior to depletion of the cryogen. Camera 3 remains out of focus. Use of the coronograph will be enabled by changes to the FSW expected in late 1997.
M. Urry discussed the NICMOS delta CP and the TAC results. 6473 orbits were requested in 449 proposals; 1041 orbits and 473 SNAP targets in 83 proposals were approved by the TAC. She outlined the responibilities of the panels and the TAC, the conflict-of-interest rules, the criteria for ranking the proposals, and the rationale for the new comments table.
D. Machetto described the plans for the NIC3 observing campaigns and the plans for a southern deep field (HDF-S) observation. The NIC3 campaign will take place during the second half of January 1998. All other SIs will be out of focus. 127 orbits will be devoted to GTO observations of the HDF.
S. Baum discussued the current status of the STIS instrument and commanding software. Concerns include the CCD hot pixel growth rate and the lifetime of the NUV flat field lamps. With the exception of the NUV-MAMA dark count rate, STIS is operating at or above specs.
A number of commanding upgrades are planned and proposed in order to increase STIS efficiency and make more observing modes available to the community (see STIS TIR 97-21).
H. Ford discussed the current status of the Advanced Camera for Surveys (ACS), which is to be installed in servicing mission 3 (SM3) in December 1999. At present there are some developmental problems with the CCDs for the WFC (4000 X 4000). Neither meet spec for parallel charge transfer efficiency, and the QEs are about 20-40% lower than expected (but are far above the QE of WFPC2). Further work is continuing on the optical coatings.The flight filters appear to be in good shape.
P. Stanley discussed the current status of cycle 5 and 6 proposals. All cycle 4 programs are now complete. As of 11/1/97, cycle 5 is 99% complete, cycle 6 is 72% complete, and 19% of the cycle 7 observations have been completed. During the third quarter of 1997, the 51% of the available time is devoted to NICMOS, with 24% to STIS and 25% to WFPC2.
She discussed the STScI policy on over/under allocations. If too few proposals are accepted, scheduling becomes inefficient towards the end of the observing cycle. If too many proposals are accepted, scheduling efficiencies are high, but there will be a backlog of unobserved targets carried over into the next cycle. Unanticipated downtime of course affects this backlog. The STScI is making every effort to reduce the backlog. Cycle 5 and 6 programs have higher scheduling priority than do cycle 7 STIS and WFPC2 programs.
Cycle 8 will start in June 1999. The CP will be released in June 1998, with a mid-September 1998 deadline. About 2400 GO orbits will be available. Cycle 9 is planned for one year later, with proposals due in September 1999 and the cycle beginning in June 2000.
D. Machetto presented the recommendations of the parallel observations working group. During cycle 7 only a few pure parallel observing programs were recommended by the TAC. The working group defined 3 generic parallel programs to utilize time that would otherwise have been wasted. These programs include a galactic program for |b|<20, an extragalactic program for |b|>20, and a special objects program. These data are non-proprietary. Further information is available at the STScI Pure Parallel Archive web page
The success of this program will be reviewed prior to the release of the cycle 8 CP.
A. Storrs and J. Clarke discussed Moving Target and Planetary Target issues. The STScI has addressed each of the issues that the Planetary Working Group has raised, with many issues now resolved and others nearing completion. While the implementation of STIS/MAMA bright object protections for moving targets is being watched carefully, UV-MAMA observations are being conducted routinely now. Due to lack of sufficiently strong community support to justify the required resources, track 48, moving target snapshots, and STIS 45 degree planetary slit capabilities are not being implemented at this time, and the STUC does not intend to push these capabilities unless strong community support were to materialize.
K. Long suggested that the Planetary Working Group had served its purpose, had addressed all outstanding issues peculiar to the planetary observers, and should be abolished. This point will be addressed in the STUC recommendations.
R. Beaser presented the STScI position on GO funding. The STScI recognizes that there is some hardship, with some observations being delayed by years due to various factors. The amount of preparatory funding routinely available has been increased from 10% to 25%. Additional funding is available for programs facing severe financial impacts due to delays in data-taking, subject to review by the Financial Review Committee and approval by the Director of the STScI.
Effective December 1997, foreign travel does not need prior approval, the definition of permanent equipment is increased to $5000, and cost-sharing is no longer required. These changes will decrease administrative costs. Under consideration, to further reduce administrative efforts, is the possibility of electronic submisssion of budgets, award documents, payment requests, and financial reports.
F. Walter raised the possibility of separating the observing and archival proposal opportunities. Due to the extreme length (21 months) of cycle 7, it will be nearly 2 years between archival research proposal opportunities.
The committee then discussed the possibility of a special parallel observation data analysis research opportunity. The justification is twofold. Not only would this meet provide an interim funding opportunity, but, more importantly, it would focus the community's attention on the availability of the parallel data sets. The response to such a specialized call for proposals would serve to demonstrate the value of these data, and justify the efforts that are being made to obtain these data.
It was noted that a precedent for such a special funding opportunity was set during the HDF opportunity.
S. Tereby told the committee of her experiences as a first time user/visitor to STScI.
P. Greenfield discussed efforts to increase the portability of STSDAS. STSDAS v2.0 required IRAF v2.11, because it requires the FITS kernel in IRAF 2.11. IRAF v2.11 is currently available only for SUN platforms, which is inconvenient for users who use other platforms (e.g., DEC Alpha, HP/UX, PC-IRAF, IBM IRIX, SGI AIX). It is expected that IRAF v2.11 will be ported to these platforms shortly. STSDAS v2.0 will be released for these platforms as IRAF v2.11 becomes available.
The STScI processing pipeline is being rewritten in OpenIRAF, using C instead of SPP. The pipeline will produce multi-extension FITS files rather than GEIS-format files.
F. Walter noted that membership in the STUC is normally 12 persons, 4 appointed each year for 3 year terms. Due to a number of resignations, there will be 7 members whose terms expire after the November 1998 meeting. Since the strengths of committees like this one lie in their institutional knowledge, a committee with only 5 veteran members could be a weak advocate. He proposed that 4 new members be appointed to the STUC to replace the 2 retiring members. The STUC would be augmented to 14 members for 1998, and would decline to normal levels in 1999 with the 7 retirements.
The committee reconvened on Tuesday November 25 at 8:00 AM in executive session. The public session began at 8:30AM.
John Campbell provided the HST project perspective.
Spacecraft power is adequate. There are currently 3 failed relays in the power subsystems, causing a 10% reduction in the available power. This has no impact on operations. There have been no recent SADE upsets. The slow warming of the aft shroud continues. In all, the spacecraft continues in excellent health.
The original Fine Guidance Sensors continue to show signs of slow degradation. FGS3 will be replaced in SM3 in 1999; FGS2 will be replaced in SM4 in 2002.
No further degradation has been seen in Gyro 5; Gyro 4 will be replaced during SM3.
The new computer, to be installed during SM3, draws 22 watts, as compared to the 150 watts drawn at present. The bay may run cooler than desired.
The new solar arrays, to be installed in SM3, are made of off-the-shelf IRIDIUM arrays. They have 2/3 the surface are of the current arrays, and hence have less drag.
During SM4, in 2002, a number of proactive subsystem replacements will be made in order to ensure that HST is operations until 2010. The batteries will be replaced, as will FGS2.
NASA and ESA are negotiating an extension of their memorandum of understanding (MOU) to continue international participation in the HST project. The new MOU may include participation in the NGST project.
The HST budget continues to be healthy. Current funding is about $200 million. This will decline to about $50 million (in 1996 dollars) by 2002, as NGST ramps up. Overall funding for HST+NGST remains approximately constant through 2002.
David Leckrone, HST Project Scientist, reported on the long term prognosis for HST, through the year 2010.
The WFPC2 will be supported at least through Cycle 9 for scientific use, providing a full cycle of overlap between the WFPC2 and the ACS. Thereafter continued support of the WFPC2 will be based on "TAC assessment of uniqueness of proposed WFPC2 observations".
The Project and the STScI plan to continue support for scientific use of the FGSs "indefinitely".
Two independent Science Reviews (ISRs) were convened.
The Longair Committee met on May 29-30 to discuss the reduced lifetime of NICMOS. Their recommendations were essentially identical to those of the STUC, and have been implemented.
The Harwit Committee met on September 10-12 to review the proposed NICMOS cryocooler. They recommended development of the cryocooler, and a test flight in 1998. They will reconvene in late 1998 to re-evaluate technical issues and the NICMOS science return. There is some concern that NICMOS science will not be scientifically compelling in the era of the 8-meter IR-optimized telescopes with advanced IR detectors.
The Cosmic Origins Spectrograph (COS) was selected as the 2002 (SM4) instrument. PI is Jim Green (University of Colorado); Ball Aerospace is the prime contractor. This is a high throughput UV spectrograph.
NASA intends to operate HST through 2010. SM4, in 2002, will be the last servicing mission. The HST will be recovered and de-orbited in 2010. Low cost operations are planned after 2005. Strategic planning is underway for the extended mission, and will include community input, but any planning involving SM4 must be completed by early 1998. The goals of the strategic planning are to maximize the likelihood that the HST will function until 2010, will continue to produce excellent science, and that these objectives can be accomplished at low cost. Low cost can be achieved by re-using established technologies and instrument heritages.
To maximize the likelihood of HST survival, a number of options are being considered to provide for backup instruments. The COS capabilities may be extended to provide backup to the STIS in the near-UV. WFPC1 may be refurbished (see below) with spare ACS detectors as a backup imager. The Project is considering adding coronagraphic capability, based on the CODEX design, to the refurbished WFPC1. These issues will be reviewed by the 2002 instrument review panel in January 1998.
Note that there are currently no funds available for thw WFPC1 refurbishment. If no other source of funding can be identified, funds may be taken from UPN459 for this.
Projections for UPN459 funding levels are stable through 2010.
K. Long reported that the FOC will be decommissioned at the end of cycle 7. Demand has been low. User support will be maintained through March 1999 The last programns are on the long term timeline in January 1999.
J. Green presented the Cosmic Origins Spectrograph (COS) to the committee. The COS is to fly in 2002. COS is a high throughput point source spectroscopy instrument operating between 115 and 300nm. It was proposed to operate in the far-UV, but the project has asked that the near-UV capability be added as a backup to STIS.
E. Cheng reported on the status of the proposed cryocooler for NICMOS. The cryocooler is expected to be able to maintain the cold well at 72K and the filter wheel at 160K, both warmer than current temperatures but scientifically acceptable. Development of the cryocooler was endorsed by the Harwit ISR in September 1997. The system will be flight-tested on the Space Shuttle in late 1998. The Harwit ISR will be reconvened to assess the cryocooler after that flight, and to recommend whether or not it be included in the SM3 activities.
E. Cheng also discussed possibilities of refurbishing WFPC1 for flight in 2002 as a spare camera. The concern is that in 2002 the ACS will be 3 years old and WFPC2 will be 9 years old. STIS has a meager complement of filters. If HST is to be a capable telescope through 2010, a backup imaging capability may be prudent.
The project is considering a wide field camera (WF3), possibly incorporating elements from the proposed CODEX coronagraph. The instrument would occupy a radial bay, and would be built from parts from the WFPC1 where possible. A new carrier will need to be constructed, assuming that FGS2 is replaced during SM4. A decision on whether to proceed is due in early 1998.
It was noted that this camera is unbudgeted. Expected costs run $30-$40 million. If development continues, and costs cannot be obtained from within UPN458, then UPN459 funds, which include GO support, may have to be used.
The next meeting of the STUC is scheduled for May 18-19 1998.
The STUC thanked W. van Breugel and M. Franx for their service on the committee.
The STUC entered executive session, and adjourned at 2:30 PM.
DISCLAIMER: All technical details reported above are accurate as of 25 November 1997. Readers should refer to the STScI web site for updated information, and for details not reported here.
This report submitted by Frederick M. Walter
Chair, Space Telescope Users Committee