OSO-8 Software:
Example 1 - Extract a lightcurve from raw rates data

artist concept of OSO-8

To extract a lightcurve from the raw rates data, use the task osofindfast (step 1) and osorat (step 2).

Osofindfast, for a given sky position determines times when that position was viewed by the A, B or C detector. This routine generates two output files, one for the A and B and one for the C detector. The file names listed are of the form oso8_csxabc_XXXX.fits where XXXX is the mission day number since January 1975 and ranges from 176 to 1369. Osorat operates on the raw rates data and extracts a 160 ms lightcurve.

* Using osofindfast (step 1) Run the perl script OSOFINDFAST. This script determines the days of the mission when the source is MOST likely to be in the detector FOV (the `good' observing days). For example, consider the source A0620 (coordinates R.A.(1950)=95.046, Dec (1950)=-0.32)

% osofindfast
Equinox [ 1950 ]: 
Source RA [ 0 ]: 95.046
Source Dec. [ 0 ]: -0.32
Output listing filename: a0620
Output orbit file lists ? (y/n): n
Precessed RA and DEC values to 1975 epoch : 
               95.3653672590687 -0.332627716087411 
Opening output list for C detector : a0620_c 
Opening output list for A detector : a0620_a 
 ** OSOFINDFAST.PL 1.0.0 finished **

% cat a0620_c
To check the stability of the pointing there are plots available in the OSO-8 FTP area in the HEASARC archive. For this observation the relevant plot is oso8_237_294_neg(pos).ps
* Using osorat (step 2) Run the ftool OSORAT. This tool will produce a background subtracted and collimator-corrected light-curve only (integration time of each data bin is 160 millisecs).

% osorat
Equinox (d/f 1950)[1950] 
RA in hh mm ss.s or degrees[95.046] 
DEC in dd mm ss.s or degrees[-0.32] 
Detector: 1, 2, or 3, for A, B, or C[3] 
File containing list of input OSO-8 rates files[a0620_c]
Name of output file[a0620]
 Open output file a0620_1
 Detector  DET-C

 Calculating srce count corrns for lightcurve : a0620_1
 **** OSORAT 1.3.0   finished *********

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Last modified: Tuesday, 21-Apr-2020 15:46:22 EDT