Number 9, November 1999


1) FUSE Mission Status
2) Second FUSE Observers Advisory Committee meeting, on November 15
3) NRA for Cycle 2 of FUSE GI Program

1) FUSE Mission Status

After four months in orbit FUSE has started initial science
observations as In-Orbit Checkout (IOC) activities near completion.
Regular science observations for PI Team and GI programs will begin in
December 1999.

We are happy to report that initial observations of two white dwarf
calibration standards indicate that FUSE's sensitivity in orbit is
excellent. The effective area of all four channels is consistent with the 
pre-launch predictions. The detector
background level is low, at, or slightly below, the pre-launch
estimate. The grating scattered light level is extremely low. This
coupled with the low detector background means that zero (or
non-detectable) flux corresponds to zero counts. The spacecraft
pointing stability is better than the mission requirement. Even though
the telescopes and spectrograph have not yet been focused, the spectra
already have a resolution of about 20 km/sec, which is within 60% of
what we eventually expect to achieve.

Observations of scientific targets began in late September. Both
galactic and extragalactic sources have been observed, primarily for
Early Release Observation (ERO) programs and some from PI Team
programs. A number of interesting scientific results have already
emerged and will be reported in a FUSE poster session at the AAS
meeting in January 2000. More detailed discussions of the early FUSE
results, including instrument performance, will be submitted for
publication in a special issue of Astrophysical Journal Letters, which
we hope will appear shortly before the FUSE Cycle 2 observing proposal
deadline (i.e., spring of 2000).

IOC and Science Verification (SV) activities have taken significantly
longer than the two months planned prior to launch. The main reasons
for the delays are: 1) the spectrograph outgassing was slower than
anticipated, which delayed detector high voltage turn-on by about 4
weeks; 2) target acquisitions were hampered by a bug in Fine Error
Sensor flight software and by larger than expected roll errors
following target acquisition; 3) memory fragmentation in the Instrument
Data System compromised efficient instrument operations; 4)
intermittent problems with the primary FUSE ground station in Puerto
Rico significantly reduced overall operational efficiency; 5) Single
Event Upsets (SEUs) in detector RAM, correlated with passage through
the South Atlantic Anomaly, result in memory errors and occasionally in
detector shut-downs and subsequent lengthy recoveries. These problems
have either been solved (1-4) or an operational solution will be
implemented in the very near future (5).

The ability to coalign the four telescopes to within 2 arcsec has been
demonstrated. Until very recently the SiC channels were generally
misaligned with respect to the LiF channels. The coalignment appears to
be affected by thermal effects, including changes in solar orientation,
especially at high beta angles. Engineering tests are underway and we
expect to finish characterizing the alignment stability by the end of
November.  To date all observations for science programs have had to use 
the LWRS aperture (30x30 arcsec).

A cyclic motion of the spectra during each orbit has been detected and
is being characterized. This spectral drift in the dispersion direction
is about 5-15 detector pixels (10-30 km/sec peak-to-peak).  The
spectral shifts are larger in the LiF channels than in the SiC
channels. Initial studies indicate that this effect may be thermal in
origin and that it can be modeled and removed from time-tag data as
part of the calibration pipeline processing.

In order to expedite delivery of FUSE science data to FUSE observers
and the archive while instrument characterization and calibration
continues, the FUSE data processing pipeline has been modified to omit
several calibration steps. These steps will be implemented at a later
date once accurate corrections have been determined.  Observers should
be aware that at this time the calibrated data will not include
background subtraction (which is probably negligible in many cases),
flat-field correction, astigmatism correction, nor will there be any
correction for the spectral drifts mentioned above.  The FUSE Project
felt it was better to apply no correction than to apply one that is
inappropriate for flight data. The pipeline processing will evolve
with time as more is learned about instrument performance, and the
users will be kept informed about any significant developments via this

FUSE data is currently being processed, as described above, and will
be delivered to the Multi-Mission Archive at the Space Telescope
Science Institute (MAST) over the next few weeks. Access to proprietary
FUSE data will be established through a MAST password protected account
for the program PI, and any designees of the PI, in the same manner as
is currently done for HST programs. Non-proprietary FUSE data can be
accessed by anyone, after registering for an account with MAST. Both
raw data and extracted spectra are stored in the archive.

In summary, we have encountered several bumps in the road that have
slowed the commissioning process, but we are very excited by the early
scientific results from FUSE and look forward to the next several
months when more and more of you will be able to share in what promises
to be a wealth of new scientific discoveries from FUSE.

George Sonneborn
FUSE Project Scientist

Warren Moos
FUSE Principal Investigator

Those of you interested in the progress of IOC and "Science Verification" (SV) 
process, may follow it through weekly summaries of the  status reports posted 

2) Second FUSE Observers Advisory Committee meeting, on November 15
	The FUSE Observer's Advisory Committee (FOAC) will have its second
meeting at JHU on November 15th. The membership of the FOAC and the
minutes from its first meeting can be found at:

The minutes from the second FOAC meeting will also be posted at the above
site as soon as they are ready.

3) NRA for Cycle 2 of FUSE GI Program

	We would like to give you a "heads-up" about the call for proposals
for cycle 2 of the FUSE GI program.  The NASA Resarch Announcement
(NRA) for FUSE Cycle 2 GI proposals is presently planned for release in
February 2000.  Proposals will be due approximately 90 days after the
NRA release, with the exact date being specified in the NRA.

The Observer's Electronic Newsletter is published by the FUSE project
and is aimed at the FUSE user community.

Editor: B-G Andersson, FUSE Guest Investigator Officer.

The FUSE Project is managed by Johns Hopkins University's Center for 
Astrophysical Sciences in Baltimore, MD, for NASA's Goddard Space Flight 
Center.  The FUSE Principal Investigator is Dr. Warren Moos, the FUSE Project 
Manager at JHU is Mr. Dennis McCarthy, and the NASA Project Scientist for FUSE 
is Dr. George Sonneborn.

Further information about the FUSE Guest Investigator Program can  be
obtained from:  Dr. George Sonneborn; sonneborn@stars.gsfc.nasa.gov

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