FOAC Meeting Notes

FUSE Observer's Advisory Committee

Minutes for Meeting No. 12

June 9, 2004

Johns Hopkins University





Ed Fitzpatrick, Michael Crenshaw, Andrea Dupree, Cynthia Froning,  Jay Holberg, Alain Lecavelier des Estangs, Evan Skillman, Nicole St-Louis, Ken Sembach, Sumner Starrfield

Via Telecon; Jason Prochaska

Warren Moos, William Blair, Mary Beth Kaiser, B-G Anderson

George Sonneborn, Jeffery Hayes



Observatory Status – Blair (JHU)

The chronology of the events following the Dec. 27 2004 loss of the Roll Reaction Wheel was reviewed.   On Jan. 20, 2005 a stable nadir pointing safe mode for the spacecraft was established and on Feb. 8 this was revised to allow for “yaw steering”.  During the remainder of Feb. and March, 1-wheel control software was developed and tested and uplinked on March 22.  On March 28, the doors were opened and limited science operations were resumed near the pole.  No loss of instrumentally sensitivity was observed and sub-arcsec pointing control was demonstrated.  


On April 17, 2005 the redundant roll axis gyro failed and the spacecraft was returned to a nadir pointing mode with the doors closed.   After that time, three attitude control software patches were developed and tested to allow for < 3-gyro (pitch and yaw, but not roll) control of fine pointing together with tweaks to allow for improved performance. A decision was made to produce a new control software code incorporating these and other changes reflecting the new state of the spacecraft.   Testing of the spacecraft continued to assess the areas of probable sky coverage and to determine ways to predict stable regions as a function of time.  Practical schemes for slewing the spacecraft will require the study and analysis of deviations between predictions and actual spacecraft performance.   Training of mission planning and science operations staff will be required for the use of the new tools that are being developed.   On June 2, the doors were reopened and tracking and fine pointing tests were resumed.  Conservative operations near the celestial south pole were resumed on June 6 and will continue until new ACS code is tested and loaded.


FUSE GI Progam Status: Sonneborn  (Goddard)

Cycle 6 produced the largest demand yet for FUSE observing time; 28.6 Msec requested by 183 proposals.  As a result only (57) Excellent and Excellent/Very Good proposals were accepted.  Following the Dec. 27 reaction wheel failure the approved Cycle 6 proposals were subjected to the following additional technical selection criteria:, including a target exclusion zone (06 hrs to 18 hrs and |dec| < 30 degrees), no moving targets, and a 35% reduction in available observing time.   These selection criteria were implemented prior to the announcement of Cycle 6 results.  Current plans call for a four-level prioritization of the observational scheduling based on science objectives. In addition a detailed examination of the feasibility of all pending observations will be conducted.  PI’s will be contacted regarding the outcome of this review.   The Project Scientist also outlined possible options for Cycle 7 and reviewed project budget status and budget projections.   The Project Scientist noted NASA’s continued support and encouragement of the FUSE recovery effort.


FUSE Data Calibration, Reduction and Archiving: Van Dixon (JHU)

Van Dixon reported the CalFUSE v3.1 pipeline is complete and that the documentation and calibration efforts are ongoing.  Final processing of the FUSE archive with CalFUSE v3.1 will begin this summer.   CalFUSE v3.1 will include a number of significant improvements, including a more robust jitter algorithm, new limits on detector high voltage, wider HIST extraction windows and walk corrections, and a revised background-scaling routine.  A new format for extracted spectral files is provided along with new time-dependent calibration files and a new algorithm for locating spectra on the detector.


CalFUSE v3.1 is intended to be the final revision to the FUSE data reduction software package and to be the processing benchmark for the final FUSE data archive.  A PASP article will be written to document and explain CalFUSE v3.1 and augmented by on-line CalFUSE v3.1 documentation.


Nearly all FUSE data has now been processed by CalFUSE v3.0 and archived at MAST.  Beginning this summer, all FUSE data will be re-processed by CalFUSE v3.1.  This effort will be concluded by Sept. 2006.


FOAC Discussions:

The FOAC spent considerable time discussing the impact of the attitude control system problems on the mission’s science capabilities and the steps which could be taken to maximize these capabilities.   A discussion of options for Cycle 7 quickly converged on retaining the planned proposal deadline and planning for a full year of observing.  The need for various restrictions in Cycle 7 was also discussed and recommendations (see below) were adopted.   One over riding observational constraint is likely to be targets restricted to high declinations (|dec| >~50 degrees).  The need to maximize the science which could be achieved by FUSE in the coming months was also discussed.   There was widespread agreement that a prioritization of programs and observations and was desirable and should be in place to augment the normal mission planning procedures, when high value targets become observable.  Other items briefly discussed include, a special FUSE session scheduled for the winter AAS meeting and plans for the 2006 Senior Review.


FOAC Recommendations:


The FOAC recognizes the extraordinary effort being made by the FUSE project in reacting to the spacecraft attitude problems that have occurred during the last six months. We wish to commend all who have worked so hard to regain control of the spacecraft and to re-establish a viable scientific observing program.


We recommend that:


1.  Cycle 7 proceeds on schedule with the goal of a full year of planned observations.


2.  To assist proposers,  observational planning aids such as newly defined target visibility zones and availability be made available in a timely manner prior to the proposal deadline.


3.  Observing restrictions including no moving targets and no coordinated observations, be accepted in Cycle 7.


4. Programmatically Cycle 7 should not include Legacy Programs or Multi-Year Programs.  Survey Program Proposals should be encouraged.





Action Items:

  • The Project Scientist will issue a community newsletter indicating the need for a “triage” of existing targets and programs which no longer appear feasible and he will provide examples of how this may operate.


  • The Project Scientist will call community attention to the results of Cycle 6 and its high oversubscription rate, particularly after the changes necessitated by the Dec. 27, reaction wheel failure.  Plans and objectives for Cycle 7 will be mentioned.


  • The Project Scientist, with the assistance of the FUSE Mission personnel, will create a prioritized a short list of high priority must-do-targets to ensure that the maximum scientific use is made of current science resources.


  • The Project Scientist will search for at least two new FOAC members.


  • Van Dixon will circulate a draft of his planned CalFUSE paper to a range of users/readers in order to ensure that it will be a valuable resource for potential FUSE users of all skill levels.


  • The FUSE project should make sure that Van has the time and resources available for the above task.


  • Ken Sembach will identify a minimum “tool box” of useful FUSE data reduction and analysis tools.