The FUSE Archival Data Handbook - MAST - STScI

was uploaded to the IDS before each HIST observation. The SIA table was a buffer made up of
512 rectangles. The size of each rectangle was 2048 pixels in X and 16 pixels in Y . Thus, the
512 elements of the SIA table constitute an 8×64 image which spans the 16384×1024 elements
of the detectors. The SIA table specifies which of these rectangles should be saved (mask bit
set “on”), i.e., if the IDS received a photon event from the detector whose (X, Y ) coordinates
map to a location in an active rectangle, then that photon event is stored by incrementing a
counter in a histogram bin at the specified binning. The default histogram binning size was
1×8 (X, Y ) detector pixels. The default SIA table specified storage of a region around the aperture
containing the target, and required ∼20 MB of storage for an orbit’s worth of exposures.
Note that in HIST mode, only data taken through the science aperture were recorded. Because
Doppler compensation was not performed on-board, HIST exposures times were kept short to
avoid losing spectral resolution and minimize smearing from thermal motions. Typical HIST
exposure times were ∼ 400 s. More information can be obtained in the Instrument Handbook
(2009.
2.6 FUSE Mission Short Biography
A series of events impaired optimal use of the FUSE spacecraft and impacted the data acquisition
and processing during those times. A list of the most significant events affecting FUSE
data quality is given in Table 2.3 where Column (1) lists the chronology of these events since
the FUSE launch; Column (2) gives a brief description of the events that took place; and Column
(3) points to Notes to the table. A complete listing of such events can be found in the
Instrument Handbook (2009).
Table 2.3: Significant Events
Date Event Notes
24 June 1999 Launched · · ·
12 December 1999 LiF1 Focus Finalized (1); (3)
16 March 2000 LiF2, SiC1,2 Focus Finalized (1); (3)
25 November 2001 Yaw RWA failed (2)
10 December 2001 Pitch RWA failed (2); Science operations suspended
February 2002 Two-wheel mode begins Observations resumed
03 February 2003 Segment 2A HV confined (4)
31 July 2003 Yaw IRU-B failed (2); Gyroless control mode used
27 December 2004 Roll RWA failed (2); Science operations suspended
March 2005 One-wheel mode begins Observations resumed
12 July 2005 LiF2 made default guiding channel (3)
12 July 2007 Skew RWA failed End of FUSE pointed observations
18 October 2007 Decommissioning End of FUSE mission
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