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HETE2TL - HETE-2 Timeline

HEASARC
Archive

Overview

The HETE2TL database table records the pointing direction of the HETE-2 boresight camera and the roll angle of the HETE-2 spacecraft at each given time, as determined by the aspect camera/optical sub-system aboard HETE-2.

HETE-2 (the High Energy Transient Explorer) is an international mission designed to help unravel the mystery of Gamma-Ray Bursts (GRBs). The primary goal of HETE-2 is to determine the origin and nature of cosmic gamma-ray bursts (GRBs) by simultaneous observation of soft and medium X-rays and gamma-rays to provide precise localization of GRBs and identification of counterparts to these explosions. HETE-2 carries three science instruments: a set of wide-field gamma-ray spectrometers (FREGATE), a wide-field X-ray monitor (WXM, and a set of soft X-ray cameras (SXC) HETE-2 was launched on October 9, 2000, and declared fully operational on February 6, 2001.


References

The contents of this database table are derived from the file located at ftp://legacy.gsfc.nasa.gov/hete2/data/timeline/hete_sc_aspect.txt. The contents of that file are in turn derived from the spacecraft aspect data file supplied by the HETE-2 Team at MIT and located at ftp://legacy.gsfc.nasa.gov/hete2/data/timeline/sc_aspect.dat.

Provenance

This HEASARC database table will be updated on a thrice-per-week basis, dependent upon updates to the timeline file.

Data Products

The following HETE-2 data products associated with each entry in the table are available for download:

HETE-2 Daily Products (DAILY):

  All the data recorded for the date specified.

Parameters

MET
The HETE-2 mission elapsed time of the pointing, in seconds. This is given to a precision of 0.1 seconds in the originating timeline file. Mission elapsed time is a monotonically increasing counter whose origin (MET=0) corresponds to 1999-01-26 21:06:15.0 UTC.

Time
The UTC time of the HETE-2 pointing.

GPS_Time
The Global Positioning System time of the HETE-2 pointing, in seconds. Global Positioning System time is the atomic time scale implemented by the atomic clocks in the GPS ground control stations and the GPS satellites themselves. GPS time was zero at midnight UTC on 6 January 1980. Since it is not perturbed by leap seconds, GPS is now ahead of UTC by an integer number of seconds. This parameter value is determined by HETE-2's GPS sub-system. More information about GPS time can be found at http://tycho.usno.navy.mil/gps.html.

RA
The right ascension of the HETE-2 pointing in the selected equinox. This is given in J2000 equatorial coordinates to a precision of 0.001 degrees in the HETE-2 timeline file. In the HETE-2 coordinate system the boresight camera points along the -Z axis, so this right ascension is RA(-Z), the right ascension of the -Z spacecraft axis. It is derived from the right ascension of the +Z axis as tabulated in HETE-2 spacecraft aspect data file using the expression: RA(-Z) = RA(+Z) + 180 degrees. It should be noted that HETE-2 is sensitive to gamma-ray sources within about 70 degrees and X-ray sources within about 40 degrees of each pointing.

Dec
The declination of the HETE-2 pointing in the selected equinox. This is given in J2000 equatorial coordinates to a precision of 0.001 degrees in the HETE-2 timeline file. In the HETE-2 coordinate system the boresight camera points along the -Z axis, so this declination is Dec(-Z), the declination of the -Z spacecraft axis. It is derived from the declination of the +Z axis as tabulated in HETE-2 spacecraft aspect file using the expression: Dec(-Z) = -Dec(+Z). It should be noted that HETE-2 is sensitive to gamma-ray sources within about 70 degrees and X-ray sources within about 40 degrees of each pointing.

LII
The Galactic Longitude of the HETE-2 pointing. This parameter is derived from the Equatorial position in the HETE-2 timeline file.

BII
The Galactic Latitude of the HETE-2 pointing. This parameter is derived from the Equatorial position in the HETE-2 timeline file.

Roll_Angle
The roll angle of the HETE-2 spacecraft, in degrees. This is given to a precision of 0.001 degrees in the originating timeline file.


Contact Person

Questions regarding the HETE2TL database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 1-Dec-2005