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OSSE - CGRO/OSSE Observations

HEASARC
Archive

Overview

This database table is based on the set of OSSE observation data products available at the HEASARC. The Oriented Scintillation Spectrometer Experiment (OSSE) is one of four experiments on NASA's Compton Gamma Ray Observatory (CGRO) satellite. OSSE was designed to undertake comprehensive gamma-ray observations of astrophysical sources in the 0.05-10 MeV energy range. The instrument also had secondary capabilities for gamma-ray and neutron observations above 10 MeV that are of particular value for solar flare studies.

References

"The Oriented Scintillation Spectrometer Experiment Instrument Description",
W.N. Johnson et al. 1993, ApJ Suppl. 86, 693.

"Initial Results from OSSE on the Compton Observatory", W.N. Johnson et al.
1993, Astron. & Astrophys. Suppl.  97, 21.

Provenance

This database table was last updated in August 2005. The data in this table was supplied by the CGRO Science Support Center.

Data Products

OSSE Spectrum GIF (SPECGIF):
     A GIF image of the spectrum which can be loaded into your browser
     for a quick determination if the observation
     might be of further interest. Not available for all observations.
     This fit is generated on a power-law model.

OSSE XSpec Files (HIXSPEC):
     XSPEC PHA & RMF files (ARF files are not needed) by detector for
     this observation. In some cases, this may also include PHA and RMF
     files generated with the detectors summed. Not available for all
     observations.

OSSE High-Level Quicklook Products (HIQUICKLOOK):
     A more detailed set of products for a given observation. Contains
     details of the detector pointing strategy along with notes as to
     how these high-level data products are generated. A MUST read item
     for any OSSE observation.

OSSE High-Level Summary Spectrum (HISUMMARY):
     Totalled and rebinned background-subtracted count spectra.
     Includes the detector response matrix. Not available for all
     observations. Best used in IGORE.

OSSE High-Level Totaled Spectrum (HITOTAL):
     Total by detector of the background-subtracted count spectra.
     Includes the detector response matrix. Not available
     for all observations. Best used in IGORE.

OSSE 2-Minute Difference Spectra (HI2MINUTE):
     Two-minute, background-subtracted count spectra for the specified
     target. Really only useful for bright sources.  Best used in
     IGORE.

OSSE High-Level Daily Spectra (HIDAILY):
     Background-subtracted count spectra for a given day and detector.
     Best used in IGORE.

OSSE High-Level Processing Products (HIPROCESS):
     Loads of intermediate products (PostScript plots and text files)
     generated by the OSSE high-level data product process.

OSSE Low-Level Targeted Spectra (TARGSPEC):
     Raw count spectra. No background subtraction. Best used in IGORE.
     This would be your starting point for using
     SPECANAL (see the OSSE Guest Investigator Guide).

OSSE Low-Level Non-targeted Spectra (NTARGSPEC):
     Low-level data products generated by the OSSE shields. Best used
     in IGORE.

OSSE Calibration Data (CALIB):
     Low-level calibration files. Really only useful if you have an
     IGORE installation available.

OSSE Low-Level Temporal Data (LOTEMP):
     Pulsar data products. Currently unavailable in FITS. Best used in IGORE.

OSSE Low-Level Support Files (SUPPORT):
     Loads of support data utilized by IGORE.

OSSE Telemetry Scalar Data (TELEM):
     Another OSSE low-level data product. Best used in IGORE.

Caveats

Due to the very wide field-of-view of the OSSE instrument, OSSE database entries may be returned in a Browse archive search for objects that were not actually targets of the given OSSE observation.

Because CGRO viewing periods do not end at 0h GMT, there is often a one day 'carryover' located before and after the real viewing period of the target of interest. Check the start and end times to be sure you are selecting the real observation.

There has been some reorganization of the OSSE Data Products compared to that described in Table 4.3-1 (page 38) of Legacy #7.


Parameters

View_Period
The CGRO viewing period. The first digit is the phase (or cycle) number. The rest of the string is the sequential number of the observation within that phase.

Altvp
Alternate viewing period format. Used internally to locate the OSSE low-level data products.

Target
Most common name of the target.

ObsID
This is the unique observation identifier. For this database table, it is a concatenation of the instrument abbreviation ('O' for OSSE), the viewing period, and target name. It is used by the HEASARC database system to locate the high-level OSSE data products.

Start_Time
Start time of the observation in UTC. For many entries, this is really only accurate to the minute.

End_Time
The end time of the observation in UTC. For many entries, this is really only accurate to the minute.

RA
The Right Ascension of the target in the default equinox.

Dec
The Declination of the target in the default equinox.

LII
The Galactic longitude of the target.

BII
The Galactic latitude of the target.


Contact Person

Questions regarding the OSSE database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 3-Aug-2005