Number 5, February 1999


1) Message from the Project Scientist 
2) Launch date update 
3) Satellite gyros
4) FUSE satellite testing 
5) Ground systems/Communications network 
6) FUSE paraphernalia!

1) Message from the FUSE Project Scientist

	The FUSE Project at Johns Hopkins University has successfully passed its
penultimate major milestone in the FUSE mission development with flying colors -
completion of thermal-vacuum testing of the FUSE satellite.  (The final
milestone is the FUSE launch!)  FUSE is now on schedule for launch in early June

	The satellite was under vacuum from mid-November 1998 to 25 January 1999
(with a two-week break over the Christmas and New Years holidays).  During this
period the FUSE Team worked around the clock to test all spacecraft and
instrument functions at a range of temperatures closely simulating on-orbit
conditions, verified the thermal control system performance, demonstrated that
automated target acquisition flight software functions as intended, and
performed FUV end-to-end tests of the FUSE optical system.  Thanks to the
end-to-end tests, a serious problem with the design of the instrument structure
affecting the alignment of the spectrograph was discovered and corrected.

	There is more good news.  The problem with the shortened lifetime of the
gyros to be used by FUSE has been solved to the satisfaction of Project
engineers and outside experts.  Further details on these and other recent events
are provided in this issue of the FUSE Newsletter.

	FUSE emerged from the vacuum chamber on 28 Jan 1999 and now is in a
clean room at Goddard Space Flight Center.  We are all indebted to the
scientists and engineers (~100 in all) who worked such long hours to bring FUSE
to a state of launch readiness.

	For those U.S.  astronomers with FUSE Cycle 1 Guest Investigator
observing programs, NASA is reviewing the FUSE data analysis budget in order to
make funding allocations and to request budgets from you.  You can expect to
receive further information on Cycle 1 GI funding early this spring.

	George Sonneborn 
	FUSE Project Scientist 
	NASA/Goddard Space Flight Center

2) Launch date update

	As most of you no doubt know, the FUSE project late last year requested
and was granted a change in the launch date.  This was mainly due to the IRU 
situation.  As our project manager, Dennis McCarthy, put it:  
	"It was our position that the practical, prudent, and realistic approach
to mitigate on-orbit operational risk was to provide more test opportunity, as 
well as reworking the current IRU's."
We now have a slot in the Delta II launch manifest on June 11.  The exact date 
is under the control of the launch pad managers.  As you can see from the next 
two sections, we are confident that we have found and fixed a number of 
important problems.

3) Satellite Gyros

	As we reported in the December newsletter, the vendor for the inertial
reference units (IRUs), which contain three gyroscopes each, have identified the
problem that limited their expected lifetimes as well as a way to correct and 
test it.  A team of engineers and scientists from JHU and GSFC reviewed their 
findings and found them to be convincing.  Reworking of the IRU units are under 
way.  The second IRU was removed from the satellite and returned to the vendor 
for repair at the end of thermal vacuum testing (see below).  Both repaired IRUs
are due back to GSFC in early March when they will be reinstalled and tested.
A third IRU, of a different design and from a different vendor, will be added to
the spacecraft for extra redundancy.

4) FUSE satellite testing

	A major milestone was passed at the end of January when the FUSE
satellite was removed from the thermal-vacuum chamber and returned to the large
clean room at GSFC.  Prior to exiting the vacuum chamber we completed
verification that a mechanical design problem, causing unacceptably large
thermal distortions to the optical bench, had indeed been fixed.  Also, the
Satellite Control Center (SCC), on the JHU campus, successfully ran a variety of
important tests including:

* A simulated target acquisition in which the position of the target is measured
with the FES, and the satellite is automatically commanded to slew to the proper

* A FUV peakup, in which the four channels in the FUSE instrument are finely
aligned, or peaked up, by making a series of tiny slews and measuring when the
light from the simulated star properly goes down each slit.  After the
measurement is made the slit are slightly moved to maximize instrument

* A focal-plane split, in which 4 exposures of the same simulated star are taken
with the spectra falling on different parts of the detector.  This technique,
used successfully on GHRS and elsewhere, is used to improve the S/N ratio of
data taken with detectors having pixel-to-pixel response variations.

* A couple of target acquisitions followed by time-tagged and histogram
exposures, demonstrating successful execution of flight-like data acquisition

With these tasks completed, we feel comfortable that FUSE had been adequately
tested in vacuum.  The SCC continues to run tests to prepare for flight

FUSE is scheduled to be shipped to Cape Canaveral on March 31, and be launched
in early June.

	As usual, status reports (more frequent and somewhat more detailed than
the ones you see in this newsletter) can be found at:

5) Ground Systems/Communications Network

	The repairs of the ground station at the University of Puerto Rico,
Mayaguez, are on track to get the station back to operational status by March
31, 1999.  The new radome and steel platform have been shipped to Mayaguez.

	For launch operations and emergencies FUSE will now be able to use the 
TDRSS communications system.  Tests with the Space Network have been mostly
successful.  We have established the ability of FUSE both to downlink and
receive commands via the TDRSS satellites.  (During the tests FUSE "talked" to
TDRSS via a fiber-fed antenna at GSFC.) Commands were received at the satellite
and downlink via TDRSS was successfully recharacterized at both 1Mbps and 16

6) FUSE paraphernalia!

	FUSE, as any self-respecting project, does have a number of souvenirs
available for purchase.  T- and polo-shirts with the FUSE logo embroidered on
the front ($15 & $29/32, respectively).  Embroidered FUSE-logo patches (no
prescription needed!) in two sizes ($3.50 & $38) and FUSE-logo stickers ($1).
Also available are clear glass coffee mugs (10oz) with the FUSE logo in color 
($9) and plastic travel mugs (B/W; $4).

-- Your old tie-dyed T's are worn out anyway, it's time for some new stuff!!

Please see our web site for further details and ordering information:

The Observer's Electronic Newsletter is published Monthly 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

Return to the List of FUSE Newsletters