|FUSE Observer's Advisory Committee|
|Meeting Minutes No. 3|
|5 May 2000|
Present: Bregman, Chu, Federman, Guinan, Harper, Koratkar, Raymond,
Robert (replaces Hutchings), Wannier
JHU: Blair, Friedman, Massa, Moos, Murphy, Oegerle, Weaver
Sonneborn opened the meeting by giving the current status of the Mission. The observing efficiency (defined as the ratio of on-target exposure time to clock time) is typically 20-25%. Many of the difficulties/problems reported earlier are no longer issues. Detector software corrupted by Single Event Upsets (SEUs) is reloaded on the fly. SEUs have been much less frequent lately, probably the result of more stringent beta angle constraints. Channel coalignment is maintained for most LWRS observations. The instrument is now focussed, with resolving powers of 15,000 to 25,000 in the LWRS aperture.
The FUSE Project submitted a proposal to NASA HQ for the June 2000 Senior Review. The proposal includes a request for funds in FY 2002 to complete the nominal three-year mission and for funds for an extended mission (2003-2004).
Friedman presented a science update, much of which will appear in an upcoming special issue of The Astrophysical Journal Letters. Highlights included the detection of H2 in the Magellanic Stream, O VI in the intergalactic medium (Ly-alpha absorbers), and H2/HD in a translucent cloud.
Oegerle gave an update on science operations and instrument performance. Scheduling now takes place 7-10 days in advance. Long, accurate slews are now possible, thereby simplifying acquisitions. There is no evidence for any sensitivity degradation, at least to the measurement accuracy level of ~5%. The shifting of spectra on the detector due to thermally-induced motions has the positive effect of washing out fixed pattern noise when spectra are coadded after using features in the spectra to coalign them. A new wavelength solution is available for the pipeline (but calibration will continue throughout the mission). Available flats are not useful; white dwarf spectra collapsed to one dimension will be tried. Work on the asigmatism correction is in progress. A significant amount of discussion centered on a recent gyro problem: the laser output is low in one of the two units. The second unit will be turned on if necessary.
Blair presented the current planning and scheduling constraints. The LWRS aperture is currently the default, but some programs (e.g., D/H) require the MDRS aperture. Frequent peakups are required when using the MDRS aperture in order to maintain channel alignment, and this degrades the observing efficiency from ~30% to ~20%. Ever changing guidelines (e.g., beta angle constraints) inhibit smooth long-range planning. Sky visibility plots are now available to aid in planning. Observations of a time critical nature, with specific roll angle/aperture orientations, coordinated with others, and of moving targets continue to be an issue.
Murphy summarized the status of the calibration software. Much progress was noted. Once the flats become available, all data will be passed through the current version of the pipeline. The calibration pipeline (occupying 1-2 GB) will be made available to others. It requires machines running Solaris 2.6 or later, with a minimum of 256 MB RAM (but 512 MB preferred), and 3 GB per exposure for intermediate products.
Massa presented results of analyzing FUSE data with IDL code developed by him. One of the main reasons for this effort was to develop a package that could be used on any platform and that runs on a PC with 64 MB of RAM. Results are essentially indistinguishable from data reduced via the pipeline, but some of the techniques employed are specific to the case of TIME-TAG data for objects having relatively strong continua.
Sonneborn described aspects of the upcoming Cycle 2. There will be about 3600 ksec available to GIs, with about 75% of the time given to programs of 100 ksec or longer. Observations with the MDRS aperture must be justified and the relative priorities for the LiF and SiC channels must be given. The funding for individual investigators will be similar to that for Cycle 1.
The meeting ended with an executive session. Federman was elected Chair for the coming year. One issue involved how best to get the results to final product, in light of the complex data products. The FOAC felt that occasional short (2 - 3 day) visits to JHU by GIs for help in data reduction appears necessary. This can take place once the second GI support person is hired at JHU. A key problem identified during the session was the lack of an operational long-range planning tool. This severely limits the types of observations that can be accomplished. The FUSE Project should give the development of a long-range tool the highest priority.