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ASCA Guest Observer Facility


Prepared by: Alex Brown, Chair

Members Present: Alex Brown, David Burrows, Jules Halpern, Mark Henricksen, Jack Hughes, Christine Jones, Greg Madejski, Chris Mauche
Members Absent: Paul Plucinsky, Craig Sarazin, and Kim Weaver
Others: Keith Arnaud, Ken Ebisawa, Eric Gotthelf, F. Rick Harnden, Lou Kaluzienski, Rob Petre, Nick White

Headquarters Situation - Lou Kaluzienski

Lou reported that he is now the Program Manager for ASCA, due to Alan Bunner becoming director of ``Structure and Evolution of the Universe'' at NASA HQ. He outlined the difficulties that HQ faces managing a large number of missions with seriously declining manpower.

ASCA Mission Status Report - Nick White

Nick described the mission status at roughly the mid-point of AO4. Serious pointing problems occurred during the period April 23 - May 11 due to a bad gyro. This gyro was switched out and was showing signs of recovery.

The AO5 proposal announcement will be released on May 28 with proposals being due on August 6. AO5 will cover the one year period starting 1996 December 15.

The AUG were asked by Nick to help prepare the ASCA Senior Review proposal that is due on June 21. The Senior Review will take place on July 29-31. This mission evaluation and funding review will apply to FY97-8 and provide guidelines for 1999/2000. This Review is critical for the ASCA mission, which does not have funding beyond 1997, but has significant unfulfilled science goals and an observing capability extending to at least 2002.

The AUG raised questions concerning the ASCA mirror performance and uncertainties in the off-axis point spread function and ghost images.

GIS status report - Ken Ebisawa (see handout)

Ken discussed the GIS instrumental and calibration status. Observations of the supernova remnant Cas A show that the calibration of the GIS is in reasonable shape. No energy resolution degradation is evident compared to earlier observations. The positional gain correction appears good to tex2html_wrap_inline27 1% within 15 tex2html_wrap_inline29 of the center of the field of view. The temporal gain is good to tex2html_wrap_inline27 0.2% . The Redistribution Matrix File (RMF) released in March 1995 will probably be the final version. The current Ancillary Response File (ARF), which describes the XRT effective area and GIS efficiency, shows residuals at the 5% level and produces slightly harder spectra than the original ARF. A new ARF is in preparation that provides a good fit to GIS spectra of the Crab Nebula. The remaining discrepancies between GIS and SIS spectra are being controlled using ``ARF filters'' that normalize the effective areas of the individual GIS and SIS detectors. The primary effect is to lower the GIS effective areas by tex2html_wrap_inline33 10 % and raise the SIS effective areas by tex2html_wrap_inline33 5 % . Some other problems remain including apparent motion of the GIS3 calibration source, PHA - PI conversion problems due to degradation of the quartz windows, and a count rate dependence for the gains when observing the very brightest sources.

SIS status report - Keith Arnaud (see handout)

Keith gave a presentation on the status, calibration, and performance of the SIS. The main concerns related to hot and flickering pixels, the Data Frame Error (DFE) problem, and the low energy calibration. The flickering pixel problem has been addressed by raising the event thresholds from 100 ADU to 120 ADU (i.e. from tex2html_wrap_inline33 0.36 keV to tex2html_wrap_inline33 0.4 keV). Operation in 1-CCD mode should be fine for the foreseeable future. New DFE correction methods have been implemented (See page 4 of the May 1996 (Number 4) issue of ASCANews). Errors in the current low energy calibration result in a spurious offset of 2 10^20 cm^-2 in estimated interstellar column and 10% systematic residuals below 0.6 keV. A recalibration of the low energy response of the XRT is planned.

The ASCA Archive - Eric Gotthelf

Eric presented the status of the ASCA archive which opened on November 15 1994. The archive is currently up-to-date with data being entered as processed, then protected, and eventually verified and released. Data is starting to be supplied on CDROM. So far there have been no user complaints and no significant downtime. Currently 1,337 observation sequences are archived, of which 883 are public. Current projects include an SIS source catalog, a possible GIS source catalog, and SIS image catalog, and work on calibrating the aspect solution. Rev. 2 processing will produce the ``Final Archive'', probably starting in early 1997.

AO-4 Proposal Review and Merging; AO-5 Plans - Rob Petre

Rob summarized the AO4 review process. Of 185 submitted proposals, 102 were accepted and 122 targets awarded. Some problems arose from ``Contingent'' acceptances where time was awarded conditional on success in acquiring time on other satellites or telescopes. There were two protests to NASA HQ regarding AO-4 proposals. The budget review awarded $ 2M after three iterations among the panel members.

Stability is being sought in the US Merging Committee membership. No A or B targets were dropped due to oversubscription during the merging process, although 5 B targets became scheduled C targets and there was substantial shuffling of A and B targets. The US delegation placed higher premium on US-only B time than USJ A time. 19 mergers took place, including two mergers of US/ESA targets. The merging process results in low ranking US C targets being preserved by merging with higher ranked Japanese proposals for the same target.

The AUG expressed concern about JUS proposals that did not go through NASA peer review but appeared as budgetary requests during the Phase 2 propsal process. Rob indicated that this concern would be addressed for AO-5. The AO-5 review should occur in mid-October 1996 with at least $ 1.2M available.

Discussion and Policy Issues

Much of the remainder of the meeting was spent discussing strategy for the Senior Review proposal. Assigments were made among the AUG members and GOF staff for preparation of text within specific subject areas. It was decided that the presentation to the Senior Review would be made by the current and past AUG chairs, Alex Brown and Jack Hughes, and the Project Scientist, Nick White.

Jack Hughes asked if more information on the status of the XRT calibration could be made available to the user community. The project has made such information available at

Next Meeting

The next AUG meeting is expected to be held in May 1997. The committee were in favor of a meeting that would be earlier in May than the case this year.

Alex Brown
Wed Dec 11 13:02:40 MST 1996
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