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A2SPECBACK: Help

A2SPECBACK - HEAO 1 A2 Spectra Background


Overview

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 table accesses all the background files available at HEASARC obtained from the A2 MED (small and large field of view) and HEDs (1 and 3 small and large filed of view) detectors during the pointed phase.


Data Products

The MED and HEDs have two different field of views a small and a large, which sizes are from various combination of 3.0 X 1.5 degrees 3.0 x 3.0 degrees, 3.0 x 6.0 degrees (FWHM). The collimators were aligned so the 3.0 degree response was aligned with the spin axis.

Several background files were derived from the a2 pointing observations. Each entry in this database has associated one background file obtained with one of the detectors, MED or HD1 or HD3, either with the small or large field of view.

Most the these background files were derived when the A1 was the primary pointing experiment. The A2 instrument was mounted on the opposite side of the HEAO-1 satellite from most of the detectors in the A1 instrument. Thus when A1 performed a pointed observation, A2 made a pointed observation of the opposite direction in the sky. From the black sky A2 observations background spectral file were derived.


Parameters

Name
The parameter 'name' contains the value stored in the OBJECT keyword of the FITS file.

RA
The RA is the Right Ascension of the pointing.

Dec
The Dec is the Declination of the pointing.

LII
The galactic longitude of the pointing.

BII
The galactic latitude of the pointing.

Count_Rate
Count rate from the spectrum obtained in the following energy range for the different detectors : MED between 2-10 kev and HED3 and HED1 between 8-15 keV. The count rate are not background subtracted.

Count_Rate_Error
Error on count rate from the MED-S detector.

Exposure
Exposure given in seconds.

Start_Date
Date of Observation Start given as DD/MM/YY hh:mm:ss (string).

Stop_Date
Date of Observation Stop given as DD/MM/YY hh:mm:ss (string).

Start_Time
Start time of the observation stored as a short history file key (SHF). SHF is the number of seconds before or after 1 January 1980 at 00:00 hrs UT.

Stop_Time
Stop time of the observation stored as a short history file key (SHF). SHF is the number of seconds before or after 1 January 1980 at 00:00 hrs UT.

Rspfile
Response Matrix File Name

Filename
Name for the background spectral file. This product is in FITS format.


Contact Person

Questions regarding the A2SPECBACK 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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