Satellite Status

Report #10
Star Date: Feb. 3, 1999

A major milestone was passed last week when the FUSE satellite was removed from the thermal-vacuum chamber and returned to the large cleanroom at NASA/Goddard. Prior to exiting the vacuum chamber we completed verification that the mechanical design problem, described in Status Reports #7 and #9, 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 Fine Error Sensor (FES), and the satellite is automatically commanded to slew to the proper orientation.
  • An FUV peakup alignment, whereby the four channels in the FUSE instrument are finely aligned by making a series of tiny slews and measuring when the light from the simulated star properly goes down each spectrograph aperture. After the measurements are made the apertures are realigned 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 Hubble's 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 procedures.

With these tasks completed, we felt comfortable that FUSE had been adequately tested in vacuum.

Once in the clean room, the second inertial reference unit (IRU), each of which contains three gyroscopes, was removed from the satellite and returned to the vendor for repair. One repaired IRU is due back in mid-February and the one just sent will return in early March. In the meantime, 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 on May 28, 1999.

Reported by: Scott Friedman, JHU Project Scientist

Photo: FUSE being removed from the thermal vac tank at NASA/GSFC, January 28, 1999. [Digital camera photo courtesy Jann Smith, ICS.] (Click on photo to see enlarged version.)


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