Imagine the Universe!
Imagine Home | Satellites and Data |

Radsat

* Mission Overview

The spin stabilized satellite Radsat was launched by the US Air Force on 2 October 1972 into a noon-midnight, Sun-synchronous orbit. The satellite is sometimes referred to as 1972-076B (its international launch number) or P72-1. The inclination was 98.4 degrees; the apogee and perigee were 761 and 736 km, respectively. The cylindrical spacecraft was 2.13 m long and 1.37 m in diameter. Antenna booms extended 2.74 m from each end, coincident with the spin axis. The orbital period was 99.5 minutes, and the spin period was 5 s. The satellite carried 5 instruments: a gamma-ray spectrometer, an extreme ultraviolet detector, 2 low-altitude particle detectors, and a thermocontrol coating test instrument. The satellite is not expected to decay into the atmosphere until the year 2012. The gamma-ray instrument, however, ceased function after ~7 months.

* Instrumentation

The gamma-ray detector was a 50 cubic-cm Ge(Li) spectrometer with an active area of 15 sq-cm. It was cooled by solid CO2. The detector was surrounded by a W collimator and a stainless steel tungsten rear shield, which was in turn surrounded by a 4-pi anticoincidence plastic scintillator. The detector covered the energy range 40 keV - 2.8 MeV, with 4096 channels. The maximum resolution was ~ 4 keV (FWHM) at all energies. However, this resolution was short-lived, and during most of the lifetime of the experiment the resolution was between 10 - 50 keV. Data were accumulated in 1-ms time bins during a burst. This instrument represented the first high-resolution germanium spectrometer flown on a satellite.

diagram of Radsat's instrument

* Science

Several gamma-ray bursts which were also seen by the Vela satellites were seen by Radsat. A ~60-ms microburst was seen prior to the Vela trigger time for the 18 December 1972 event. Furthermore, the spectrum was seen to soften in this event at later times.

*Other information

  • Imhof et al, 1974, Ap J Lett, 191, L7-L10.
  • Imhof et al., 1975, Ap J, 198, pp. 717-725.
  • E.L. Chupp, Gamma-Ray Astronomy, pp. 238-242.
  • The RAE Table of Earth Satellites 1957-1982.

If words seem to be missing from the articles, please read this.

Imagine the Universe! is a service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Alan Smale (Director), within the Astrophysics Science Division (ASD) at NASA's Goddard Space Flight Center.

The Imagine Team
Project Leader: Dr. Barbara Mattson
Curator: Meredith Gibb
Responsible NASA Official: Phil Newman
All material on this site has been created and updated between 1997-2014.
This page last updated: Monday, 15-Oct-2007 11:40:58 EDT