XTE Will Study Time Variability and Broad-Band Spectral Phenomena

Volume 11, Number 4, December 1995
By Kirk Borne, Vince Kargatis, and William Lawson

Scheduled for launch in December 1995, the X-Ray Timing Explorer (XTE) has the primary objective of studying time variability and broad-band spectral phenomena in the X-ray emission from astronomical sources. Time scales from microseconds to months are covered in an instantaneous spectral range from 2 to 250 keV. XTE is designed for a required lifetime of two years with a goal of five years and will be inserted into a low-Earth circular orbit at an altitude of 600 km.

Operations are managed at the Goddard Space Flight Center (GSFC) with the scientific planning and data processing taking place at the XTE Science Operations Center (SOC) composed of the Science Operations Facility (SOF, which runs the satellite observatory), the Guest Observer Facility (GOF, which provides scientific services to astronomers who use XTE), and the XTE Science Data Center (XSDC, which processes, distributes, and archives the data).

XTE data will consist of both proprietary and non-proprietary data. Data obtained from observations within granted Guest Observer (GO) proposals will remain proprietary for one year after the delivery date after which those data will become publicly accessible. Some data will be immediately public with no proprietary period. These include data from the All-Sky Monitor (ASM), data from the In-Orbit Checkout (IOC) period, spacecraft slew data, and Targets Of Opportunity (TOOs) not specified in GO proposals. High-level ASM data products useful to the general user will be made available on the order of a week after observation. All of these data will be initially accessible from the High Energy Astrophysics Archive Research Center (HEASARC) at Goddard after the 30-day IOC period. Proprietary data, including associated high-level data products, will be made accessible one year after observation through HEASARC and NSSDC.

Data will be sent to the XTE GOF from the XSDC on DAT tape. The data will be converted from the original telemetry stream using the XTE Fits Formatter software (XFF) in the XSDC. The XSDC is responsible for processing low-level XTE data into standard formatted products, distributing XTE data to American and European primary (PI) and guest (GI) investigators, and populating the final XTE public data archive. The XSDC also provides general user remote access capabilities for non-proprietary data. These activities will be facilitated through the use of NSSDC's new Mission Data Staging Service (MDSS), which includes a Digital Linear Tape (DLT) jukebox (capable of holding 5 TB of compressed data) and a front-end SGI Challenge computer engine. The XSDC does not distribute data directly to the public. The NSSDC's MDSS provides the necessary public archive access services to the HEASARC, which will maintain the XTE mission archive and provide public access to the data.

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Author:Miranda Beall
Curators: Erin Gardner and Miranda Beall
Responsible Official: Dr. Joseph H. King, Code 633
Last Revised: 21 Nov 1996 [EDG]