The Orbiting Solar Observatory-I (OSO-8) was launched on 21 June 1975 into a
550 km circular orbit at 33 degrees inclination. Data were obtained from the
mission until late September 1978. The spacecraft structure consisted of a
rotating cylindrical base section called the "wheel" and a non-spinning upper
section called the "sail". While the primary objectives of the mission were
solar in nature, there were 3 detectors, the GSFC Cosmic X-ray Spectroscopy
experiments (GCXSE detectors A, B, and C), mounted in the rotating wheel which
had exclusively non-solar objectives. Their fields-of-view were either aligned
to the spin axis or at small angles to it, hence they always view the portion
of the sky at right angles to the earth-sun line. This database accesses the
pha FITS datafiles for the A, B, and C GCXSE detectors. Data was accumulated
every quarter of a rotation period (~2.56 s) for the A detector and every 40.96
s for the B and C detectors in the 2-60 keV energy band.
To each database record is associated a file. Each file includes pha data for
~two weeks of observations with the A detector and 200 days of observations
with the B and C detectors. The file layout consists of two FITS tables: a
data table and a Good Time Interval (GTI) table. The data table contains the
coordinates of the spin axis and the sun position recorded every spin (about 10
s). The data table also contains counts accumulated at the appropriate time
interval for the A, B, and C detectors. The total number of mission days are
1194 but the number of files available in the archive are 94, 82 for the A
detector and 6 each for the B and C detectors. Data from 59 days could not be
recovered from the original 9 track tapes. The missing data correspond to the
following mission days: 176 (1 detector A only), 179 (1), 201-202 (2), 244-245
(2), 330 (1), 438 (1), 508 (1), 783-788 (6), 854-857 (4), 974-987 (14), 1032-
1034 (3), 1036-1045 (10), 1288-1290 (3), 1294-1303 (10).
The GCXSE consisted of 3 detectors, two aligned with the spin axis in opposite
directions (B and C) and a third offset 5 degrees from the spin axis (detector
A). The A detector is located on the same side of OSO-8 as the B detector.
Since the satellite was partially scanning as well as spinning, each data file
contains several positions in the sky. Each spin period was about 10 s and
within one file typically the spin axis changes by a few degrees. Since there
is not a unique pointing position in the sky associated with each file, each
database 2 positions (RA and DEC) of the spin axis. The positions were
extracted corresponding to the beginning and end of each file. This allows
one to establish the position variation within a file. Note that the
coordinates in the file use the 1975 equinox. Note also that the position
coordinates for the C detector are 180 degrees from those for the A and B
Name of the file containing the PHA data.
Name of the detector used.
Start date/time of the observation as DD/MM/YY HH:MM:SS.
Start date/time of the observation.
End date/time of the observation as DD/MM/YY HH:MM:SS.
End date/time of the observation.
Number of rows in the FITS file's data extension.
Questions regarding the OSO8PHARAW database table can be addressed to the
HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Tuesday, 09-Nov-2004 23:34:00 EST