Contents: 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 1999. 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 orientation. * 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 throughput. * 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 procedures. 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 operations. 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 Kbps. 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; email@example.com
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