The A2 experiment was flown on the HEAO-1 satellite, between August, 1977
until January 1979. The experiment consisted of six multi-layer multi-anode
collimated gas proportional counters. These were two LEDs (Low Energy
Detectors), a MED (Medium Energy Detector), and three HEDs (High Energy
Detectors). The first 6-months of mission were dedicated to an all-sky scan
after which a pointing phase started. This database accesses the raw rate data
obtained from the A2 MED (small and large field of view, FOV) and HEDs (1,2
and 3 small and large filed of view) detectors during the scanning and pointed
Note: This database does not contain coordinates. Since the satellite was
mostly scanning, the XRATE database, from which the FITS files are generated,
was organized in time.
The raw rate FITS files were created from the XRATE database which contains
the rates for the MED and HED data only. Each FITS file consists of only one
extension containing housekeeping parameters and data. Data from the HED
detectors 1, 2, and 3 large and small FOV are all included in a file. A
separate file contains the MED (large and small FOV) data. Each FITS file
contains up to twelve hours of data and represents a single tape file from the
original XRATES database. For each 12 hours per instrument (HED or MED) two
sets of files are available with integration time of 5.12 and 1.28 seconds.
Root of the filename containing the raw data. The naming convention for the A2
raw rate datafile is the following: a2_xrateXXXXIIII_KKK.raw where XXXX is a
sequential number ranging from 0001 to 1009, IIII identifies the instrument
(either med or hed), KKK is the integration time either 128 or 512 sec.
Data integration time. The values are 1.28 and 5.12 seconds.
Detector name. The values are MED and HED. The HED file include data
for the HED1, HED2,HED3 detectors.
Date and Time of first data record, character string representation:
Date and Time of last data record, character string representation:
Date and Time of first data record.
Date and Time of last data record.
Questions regarding the A2RTRAW database table can be addressed to the
HEASARC User Hotline.
Page Author: Browse Software Development Team
Last Modified: Tuesday, 09-Nov-2004 22:01:57 EST