|FUSE Observer's Advisory Committee|
|Meeting Minutes No. 8|
|14 May 2003|
Present: Dinerstein, Dupree (new member), Federman, Harper (chair),
Holberg, Prochaska (via conference call), Sembach, Starrfield,
St. Louis, Wannier
NASA: Sonneborn, Hayes
JHU: Andersson, Blair, Dixon, Kaiser, Kruk, Moos
Sigma Space Corporation: Lindler
Sonneborn opened the meeting by welcoming the new committee member, Dupree, and announced that Blair was now a Co-Investigator and the Deputy PI for the FUSE Mission. Blair told the committee that he felt that the committee should now be advocates for FUSE in the extended mission. Sonneborn drew attention to the May 2003 ApJS edition which contained three FUSE O VI survey papers.
Mission Status Report:
* Review of Prime Mission
Blair started with a brief high-level review of the prime mission which concluded on March 31st 2003. The overview is available from the FUSE WEB site.
* Satellite Performance
Operations remained nominal through the end of the prime mission.
The RAM avoidance angle constraint was lowered from 15 degrees to 10 degrees prior to Cycle 4 as expected. However, since the atmospheric density has not decreased significantly since solar maximum a further reduction of the RAM avoidance angle is not currently planned for Cycle 5. Careful monitoring of the sensitivity after low RAM avoidance angle observations, "RAM dipping", has revealed no degradation.
To supplement the target pool, about 0.5 Msec of Cycle 4 time was observed before official start of Cycle 4. About 50% of the Observatory targets, which form a significant fraction of the total science observing time, have now been observed. The remaining Observatory targets are still in the pool, but have a very low priority. There was a reaction wheel anomaly in December 2002 which led to five days where no science observations were performed. Following this anomaly, as a precaution against having the reaction wheels stop spinning, the reaction wheels were initially biased to higher spin rate. After consultation it was determined that the reaction wheels could be safely returned to their default "zero bias" configuration. In February 2003, the reaction wheels resumed operating in their default configuration.
* Transition to the Extended Mission
The transition to the Extended Mission (EM) officially started on April 1st, 2003. Cycle 4 science observation scheduling commenced shortly prior to this date as targets became available on a non-competitive basis with earlier cycles. However, the transition to the EM operations has not yet been fully realized as a result of the loading and testing of zero-gyro (ZG) operations mode. Automation at the Satellite Control Center is nearly complete. Blair discussed the impact of operations that would occur in the EM, including larger down times following detector anomalies which typically occur about twice a month. Because of real-time interaction with the satellite, each event can lead to 1-3 days of down time on the affected detector. The risk of lower efficiency is an accepted part of the EM with its more limited resources. Channel alignment activities may be scheduled on a regular basis during the week when staff are at hand. These alignment activities are currently performed immediately prior to the science observation at the new (significantly different) telescope pointing, regardless of the time of day this activity occurs. Aborted observations are now rare, and when problems do occur the satellite continues with the next scheduled observation in the time-line. Blair then reviewed the staffing changes and informed the committee that the Program Manager, Joyce, will be stepping down in June 2003. The committee expressed their appreciation to Joyce for his many contributions to FUSE.
Cycle 4 Proposal Review:
Sonneborn described the Cycle 4 proposal review process.
There was considerable discussion concerning proposals where the number of targets/time had been reduced from those requested. It was noted that while the over-subscription for observing time was close to 3:1, the ratio of proposed to accepted proposals was much smaller. Sonneborn discussed the various circumstances when target reductions had occurred and told the committee that investigators affected were informed of the reasons for a target reduction. Only very constrained observations in proposals which were close to the acceptance cut-off were purged; Blair indicated the number of accepted constrained proposals would not be an undue burden to the Mission. Sembach showed the over-subscription ratios from HST Cycle 12 and noted that HST encouraged a similar ratio for both time and number of proposals - quite unlike that in FUSE Cycle 4.
Feedback from the Peer Review was that the Survey programs, which were introduced in Cycle 4, contained very good science; the new category was a success. Unobserved Cycle 4 Survey targets will remain in the observing schedule until the beginning of Cycle 5. New proposals will be allowed to include unobserved Cycle 4 Survey and Observatory Program targets.
Sonneborn then reviewed the budget formula, which is based on the amount of time awarded and a proposal grade-level bonus at the 10-15% level. Accepted proposals were quite evenly distributed in the time requested. Sonneborn indicated that in Cycle 5 there would be less data analysis funding available and pointed out that proposers should be aware that small programs will have modest funding. The committee advised him that there was a minimum useful grant size which was of order $20-25K. The committee also recommended that the level of data analysis be a new factor in the formula at a similar level to the grade-level adjustment.
For the Cycle 5 AO, Sonneborn indicated that the text for FP-SPLIT observations needed revision to clarify the calculation of the time overhead. The Cycle 5 AO will also emphasize the need for detailed selection criteria for Survey targets.
It was felt there was no need to change the Cycle 4 definition of a constrained observation, i.e., an observation with less than 21 days of visibility per year. However, it was requested that more information be provided in the Cycle 5 AO regarding the impact of numerous short visibility windows on long observations.
The afternoon session began with Kruk presenting a review of Gyroless Operations Developments. Since the last FOAC meeting, the ZG development and testing have had a significant impact on operations personnel and resources.
All existing science modes are still supported. Remaining issues are: the attitude control system is too susceptible to noise in the FES data, with software improvement being considered; and the reaction wheel management has not been optimized with respect to the balance between control and momentum unloading. Since the last FOAC meeting the IRU B Z axis triggered the laser intensity warning. If a gyro fails in IRU B, FUSE will begin 2-gyro operations with IRU A turned off until 2 gyros are lost in IRU B when IRU A will be used.
Dixon provided an update of CalFUSE. He reviewed corrections to the calculation of error bars (v2.3) and a bug fix to avoid extrapolation of time dependent flux calibration files (v2.4). The latter affects all observations that were obtained after 06/19/2002 and processed with a version of CalFUSE numbered v2.2.1 through 2.3.1. Any FUSE data that entered MAST between August of 2002 and May of 2003 may be affected.
CalFUSE v3.0, the next generation pipeline, is not yet complete. The geometric correction is in progress and the other calibration files depend on this development. Dixon gave a detailed description of the new intermediate data file (IDF) which contains the photon list. A new feature of CalFUSE v3.0 is that no photons are discarded in the pipeline. Instead, photons which do not meet the default screening parameters are simply flagged. This permits fast, efficient, post-calibration screening with user defined parameters. V3.0 is expected to be completed this June and tested by August, with a general release in November 2003. Dixon will prepare a PASP article describing the new pipeline. To make the data more accessible to non-IDL users, there are plans to develop a program to convert the IDF file into an QPOE file for use in IRAF. Lindler gave a demonstration of a new post calibration analysis tool written in IDL which combined calibrated datasets. The WIDGET format is similar to FUSE_SCAN. Currently cross-correlation is not supported within this tool but a WIDGET exists to do this as a separate task. Model spectra can be included as a dataset if supplied in a FITS format. The committee expressed their appreciation.
Federman brought to the attention of the Committee two items of atomic data which are relevant to FUSE data analysis: a revised line list by Morton which contains transitions longward of the Lyman limit, and the IAU Commission 14 report on the recent atomic and molecular data. It was suggested that these resources be linked to the FUSE WEB site (see Data Analysis link or FUSE Documentation link).
Cycle 5 NRA and Legacy Program
A Legacy program had been recommended at the 2002 Senior Review. The morning session ended with a lengthy discussion on the scope, size, level of data analysis, acceptability of constrained observations, proprietary period, and funding available for a potential Legacy category in Cycle 5. Kaiser noted that FUSE already had PI, Observatory and Survey programs - and that a Legacy category would need to provide a new component to the AO (albeit, this new component may mirror some of the goals and motivation of PI programs such as the D/H program).
The committee continued its morning discussion of a potential Cycle 5 Legacy program. A consensus was reached on the following points:
Further discussions were scheduled to occur via email in the week following the meeting.
2004 Senior Review:
The committee discussed issues pertaining to the next Senior review. It was felt that FUSE needed to increase its visibility within the community. As there are no planned new FUV missions, FUSE's key strengths are still its unique spectral coverage and sensitivity. It was felt that FUSE could be a valuable observatory for follow-up observations from newly discovered objects in the GALEX UV survey. Dupree recommended that a FUSE clinic be held at the AAS meetings; this was endorsed by the committee. It was agreed that the senior review should be coordinated by someone at JHU with scientific input provided by members of the FOAC.
FUSE Science Conference in August 2004:
The initial announcement of the FUSE science conference in Victoria, B.C. (August 2-6 2004) has been posted on the FUSE web pages. The Science Organizing Committee will be chaired jointly by Sonneborn and Moos, and the Local Organizing Committee by John Hutchings at the host institution.
The meeting concluded with a discussion of Action Items from last meeting.
New action items include
The Committee Recommends: