FUSE Observer's Advisory Committee
Meeting Minutes No. 7
25 October 2002

Present: Dinerstein, Federman, Harper (chair), Holberg (new member), Leighly, Prochaska (new member), Starrfield, St. Louis, Wannier (via conference call)

NASA: Sonneborn, Hayes

JHU: Andersson, Blair, Dixon, Kaiser, Kruk, Moos

Sonneborn opened the meeting by welcoming the new members to the Committee [Holberg, Prochaska, Sembach (absent)] and indicated there was a good response to Cycle 4, with an oversubscription rate close to a factor of 3. He stressed that the role of the Committee is to provide input to NASA and help set priorities for the limited resources available. Moos noted that FUSE was now in the transition phase from the Prime Mission to the Extended Mission where all observing time is for the Guest Investigators (GI), and that a new version of CalFUSE was being developed for Cycle 4.

The main meeting began with highlights of recent science. Dinerstein presented the discovery of Ge III at 1088.46 Angstroms in planetary nebulae and variations in the abundance of Ge from nebula to nebula due to slow neutron-capture nucleosynthesis reactions within the progenitor AGB stars. Federman presented FUSE related results on H2 and CO which are tracers of physical conditions in IS clouds. The CH/H2 ratio shows variations between two different OB associations. He also reported that CO oscillator strengths are now self-consistent in the STIS and FUSE passbands, removing previous discrepancies.

Blair reported on the satellite status. The spacecraft is healthy and using two reaction wheels and magnetic torquer bars for attitude control. The on-source observing efficiency, including Observatory programs, remains good at 33% as compared to the mission average of 28% prior to the Reaction Wheel problems. There have been improvements in predictive software capabilities. Improvements in slewing have been achieved by turning off momentum unloading during slews. Improvement in the antisymmetric (magnetic) axis control has reduced pointing drifts. During Cycle 3 there was an enhancement of calibration programs. He presented the number of Cycle 3 observations scheduled and pending, and those to be carried over to Cycle 4. After March 31 2003 there will be approximately 1300 ksec carried over from previous GI and PI programs, and slightly more than half of this is from Cycle 3 GI programs.

Both the Committee and the Project expressed concern at the large number of unscheduled constrained observations.

Ongoing attempts to improve the scheduling included:

  1. Dividing longer observations into smaller independent observations.

  2. Using partially stable orbits where there may be loss of torque authority during non-viewing periods.

  3. Permitting off-nominal roll pointing, which would have to be assessed on a target-by-target basis, may be useful in specific cases.

  4. Reducing the RAM constraint (the former constraint of +/-20 deg has been reduced to +/- 15 deg and a reduction to +/- 10 deg is planned beginning March 2003, but which will require careful monitoring of the sensitivity).

  5. Lowering the minimum beta-angle from 30 deg to 15 deg. For a steradian near 12 hours on the celestial equator there is poor Torque Authority, and the sky above and below +40 and -40 deg, respectively, remains the main region of good visibility.

Jeff Kruk gave a review of the gyro status and future gyroless operations. The gyro status remains unchanged since the last FOAC meeting (Mar 2002). If a gyro axis on IRU B fails, the attitude control system (ACS) will switch to cross-strapped mode. Kruk then reviewed the operation mode and requirements without three gyros. The implementation of the gyroless mode has required an almost complete rewrite of ACS software. Significant additions were also required to the software in the Instrument Data System (IDS) and Fine Error Sensor (FES). The software has been written, is being tested and is scheduled to be loaded to the spacecraft in Jan 2003. The impact on operations include longer target acquisition times (after gyro control is no longer available for all three axis) and more autonomous error detection and correction.

Sonneborn presented the results of the 2002 Senior Review pertaining to FUSE. They gave FUSE a good ranking for science per dollar for FY03-04 and commended the FUSE team for the rapid recovery after the reaction wheel failures in Dec 2001. The Senior Review recommended an extension of the mission for two additional years (FY05 and FY06).

Dixon reported on developments of CalFUSE. CalFUSE v2.2.1 was released to the public in September 2002. After minor changes, v2.2.2 is being used for all new data processing and bulk re-processing archival data began in mid-October. The new data products include Quick-Look spectra, and the science data should take six months to process with a further two months for calibration data. New features in v2.2 are a correction for target motion (jitter) within the aperture during TTAG mode exposures; time dependent flux calibrations; improved background fits; count-rate plots for HIST mode to help identify loss of signal for pointing jitter and improved calibrations for Y (cross-dispersion) scale. Dixon described a new calibration pipeline for Cycle 4: CalFUSE v3.0. The data will be kept as a photon list throughout the pipeline, and HIST data will be treated as pseudo-time tagged data. The restructuring of the code and new file format will lead to a significant increase in processing speed. The ability of the user to process the data with different screening parameters after the calibration was seen by the Committee to be a significant advantage over the existing versions of CalFUSE. CalFUSE v3.0 is scheduled to be completed by Dec 2002 for release prior to April 2003. Andersson noted that the details of how the background is treated in CalFUSE v3 remained to be decided.

Dixon then described developments at MAST. A new WEB search form was described, of which only one module was mission specific. The new form contained general improvements over previous search forms, such as improved search and output options. The new search form will be ready within the next couple of months. Lindler has written an interactive IDL routine FUSE_REGISTER which allows combinations of exposures or segments.

Dixon described the response to the Data Analysis Survey which was distributed to the Committee at the end of July 2002.

The morning session ended with discussion followed by the first Executive Session. The Committee was surprised that the Data Analysis Survey had not been distributed to the broader astronomy community. The Committee decided that a broader survey should be undertaken, and charged itself with this task. It will distribute a questionnaire regarding data products, analysis tools, and calibration issues and then forward recommendations to NASA based on the responses.

Harper raised two concerns regarding MAST. First, proprietary FUSE data can only be accessed from MAST by having data moved onto the GI's computer using FTP. This is a security risk, and he suggested that this be highlighted in the next Newsletter. Second, some GI's have experienced incomplete datasets being delivered by MAST.

The afternoon session began with Andersson describing three techniques that are under development and in testing for increasing the brightness limit of targets that can be observed with FUSE. The three methods include observing with only the SiC channels, defocusing the telescope and observing through the HIRS aperture, and pointing off-source and observing the low intensity scattered light. The first two methods present relatively little risk to the detectors, while the scattered light mode suffers the potential risk of the star drifting into an aperture. The last two methods present problems for calibration. These techniques offer a potential reduction in flux incident in active channels by factors of 4-10000. Andersson pointed out that for scattered light, the star would still need to be very close to the edge of the aperture to get a good signal-to-noise ratio.

Andersson then discussed constrained observations, with information for the presentation provided by Martin England. They showed the effect of scheduling of Cycle 3 targets using the new Cycle 4 constraints. Constrained observations require more resources, and lead to a loss of observatory efficiency.

Blair discussed Extended Mission operations (EMO). The Satellite Control Center will be staffed for 16 hours Monday through Friday (currently 24/7), and there will be a reduction of Mission Operation Team staff, which is driving automation of procedures. During the EMO, the goal will be to maintain the present level of schedule efficiency, although a lower achieved efficiency is expected because of increased recovery time from spacecraft and ground based problems. Present levels of data processing, archiving and calibration will be maintained. During the EMO there are no plans for major software development activities, such as new observing capabilities or upgrades to CalFUSE.

Sonneborn discussed the requested and recommended funding levels from the 2002 Senior Review and statistics for the response to Cycle 4. He noted that in the Extended Mission costs associated with future gyro failures would come from the Data Analysis budget. FUSE will now be included in Research Opportunities in Space Science (ROSS) which will increase flexibility for the FUSE NRA. The amount of observing time to be allocated by the forthcoming Time Allocation Committee (TAC) was not known because of uncertainties in the number of constrained observations being carried over to Cycle 4 from previous Cycles. Wannier and Prochaska suggested that plots of time requested, and of over-subscription be plotted as a function of position in the sky. The Committee felt that this would be an invaluable tool to help understand problems associated with constrained observations, and to determine whether parts of the sky with low visibility will become oversubscribed.

Sonneborn briefly summarized the Education and Public Outreach (E/PO) for Cycle 3. He had recently been informed that three proposals had been accepted and the funding for these was not taken from the Data Analysis budget. Blair reported on the E/PO efforts at the Project. During the Prime Mission the Project had contributed to an exhibit at the Maryland Science Center by raising significant donations, and also maintained a Web-page. Individuals from the Project also performed volunteer work. The funded staffing was at less than one half FTE. In the Extended Mission there was one half FTE which represents a small increase in funded E/PO. Hayes said that NASA's E/PO was being reorganized and will be called Code-M.

After the formal presentations there was general discussion: Andersson indicated that there had been no major problems in the proposal submission process submitted by proposers to FUSE Support in the weeks prior to the Cycle 4 deadline; however, Sembach (in absentia) reported some users found it difficult to locate information on the FUSE GI Web page. There was discussion on ways to improve the ease of accessibility of on-line information contained in the numerous documents which are currently linked to the FUSE GI site. To alleviate future problems of this kind, Harper proposed that for Cycle 5 an on-line cross-linked "proposal check-list" be added to the GI site. (A check-list does exist in the Latex proposal template). The large number of constrained targets carried over from previous Cycles was a concern for the Committee. More information was needed before any decisions could be made.

The meeting ended in a final executive session. The Committee recognized the importance of dividing long exposures into smaller ones to aid the scheduling process. If implemented soon this will also help reduce the number of observations carried over from previous cycles. The Committee discussed the recommendations of the 2002 Senior Review. Existing and potential observing programs were identified which may constitute Legacy-type proposals. It was decided that the Committee would consider Legacy proposals and discuss the matter in detail at the next meeting in preparation for Cycle 5.

The Committee was very concerned by the lack of Quick-Look spectra (GIF files) at MAST. These were endorsed at the Committee at meeting No. 4 (3 Nov 2000). Quick-Look spectra provide an important tool for prospective users and researchers considering using NASA Archives. Images from reprocessing of the Archive with CalFUSE v2.2 are not expected to be completed for another 6 months. It was noted that this would be so late as to be of minimal use for proposers of NASA cross mission ADP and LTSA programs, and provide little lead time for FUSE Cycle 5 proposers.

Sonneborn informed the Committee that there will be a FUSE Science Conference, which is currently scheduled for Summer 2004 in Victoria, Canada. Sonneborn is coordinating the Conference and will be establishing a Scientific Organizing Committee. In April 2003 there will be a FUSE workshop at JHU which will combine both data analysis and scientific results. The opportunities for presenting a broad range of FUSE science at the Symposia and Joint Discussions at the IAU General Assembly (Sydney, Australia: 13th-26th July 2003) were highlighted. The Committee decided to rotate off one member at the end of the next meeting.

The Committee Recommends:

  1. As a matter of the highest priority, GIF images of Quick-Look spectra of non-proprietary data should be linked to MAST. All such observations should be made available by the end of December 2002.

  2. That, if requested, proprietary data be written to data tape and sent to the PI (or designate). Sonneborn should investigate the concerns raised about the use and problems of FTP at MAST and establish procedures for production of data tapes, and report his findings to the Committee.

  3. That sky maps showing requested, and ratio of requested to available observing time in suitably averaged angular bins, be prepared and made available to the Committee and TAC of Cycle 4. Clear guidance should be given to the TAC about scheduling of constrained observations.

  4. That the MAST FTP security issue be described in a FUSE Newsletter.

Go to the top of this webpage