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OSO8RTRAW: Help

OSO8RTRAW - OSO8 GCXSE Raw Rates


Overview

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 raw rates FITS datafile for the A, B and C GCXSE detectors, accumulated every 160 ms in the 2-60 keV energy band.

Data Products

To each database record is associated a file. Each file includes data for one day observation obtained with the CCXSE. The file layout consists of two FITS tables: an housekeeping and a data table. The housekeeping table contains the coordinates of the spin axis and the sun position recorded every spin (about 10 sec). The data table contains counts accumulated every 160 ms 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 1115. Data from 79 days could not be recovered from the original 9 track tapes. The missing data correspond to the following mission days: 453-462 (10), 465-478 (14), 488-499 (12), 509-511 (3), 513-521 (9), 529-530 (2), 533-554 (22), 559-562 (4),565-567 (3).

Note on Database

The CXSE consisted in 3 detectors two aligned with the spin axis in opposite direction (B and C) and a third offset 5 degrees from the spin axis (detector A). The detector A is located on the same side of the B detector. Since the satellite was partially scanning as well as spinning, each data file contains several position in the sky. Each spin period is about 10 sec 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 to each file each database record contains 3 positions (RA and DEC) of the spin axis. The positions were extracted corresponding to the beginning, middle and end of the file. This allows to establish the position variation within a file. Note that the coordinates in the file are in 1975 equinox. The middle and last positions are kept within the database at the 1975 equinox. For each file two database records are available: one containing the position as recorded in the file and a second containing the position opposite at 180 degree. The first set of records are useful to search for position included in the raw data file for the C detector (Parameter SPIN_direction = +) and the second set is useful to search for position included in the B and A detectors, 180 deg from C (Parameter SPIN_direction = -).

Parameters

Filename
Name of the file containing the rate raw data.

Start_Date
File start time given as DD/MM/YY HH:MM:SS

End_Date
File end time given as DD/MM/YY HH:MM:SS

Start_Time
File start time given as SHF (for browse) or MJD for W3browse

End_Time
File start time given as SHF (for browse) or MJD for W3browse

Num_Rows
Number of rows in the file for the data extension (EXTNAME=RATES).

RA
Right ascension of the first point in the housekeeping table contained in the file. (NOTE: if SPIN_DIRECTION is negative the RA value is 180 degree from the value recorded in the file)

Dec
Declination of the first point in the housekeeping table contained in the file.(NOTE: if SPIN_DIRECTION is negative the DEC value is 180 degree from the value recorded in the file)

LII
Galactic Longitude

BII
Galactic Latitude

RA_End
Right ascension of the last point in the housekeeping table contained in the file.(NOTE: if SPIN_DIRECTION is negative the RA_END value is 180 degree from the value recorded in the file). Coordinates at 1975 equinox.

Dec_End
Declination of the last point in the housekeeping table contained in the file.(NOTE: if SPIN_DIRECTION is negative the DEC_END value is 180 degree from the value recorded in the file).Coordinates at 1975 equinox.

RA_Middle
Right ascension of the middle point in the housekeeping table contained in the file.(NOTE: if SPIN_DIRECTION is negative the RA_MIDDLE value is 180 degree from the value recorded in the file). Coordinates at 1975 equinox.

Dec_Middle
Declination of the last point in the housekeeping table contained in the file.(NOTE: if SPIN_DIRECTION is negative the DEC_MIDDLE value is 180 degree from the value recorded in the file). Coordinates at 1975 equinox.

RA_Difference
Right ascension difference in degrees between the first and the last point in the housekeeping table.

Dec_Difference
Declination difference in degrees between the first and the last point in the housekeeping table.

A_Avg_Count
Average number of counts for the A detector. The average corresponds to the sum of all the counts for the detector A divided by the total number of rows.

B_Avg_Count
Average number of counts for the B detector. The average corresponds to the sum of all the counts for the detector B divided by the total number of rows.

C_Avg_Count
Average number of counts for the C detector. The average corresponds to the sum of all the counts for the detector C divided by the total number of rows.

Spin_Direction
Records the spin direction. The '+' is associated to positions seen by the C detector, the '-' to positions seen by B and A detector


Contact Person

Questions regarding the OSO8RTRAW database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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