Imagine the Universe!

Satellite Showcase


Credit: NASA

The Mission

Astro-C, renamed Ginga (Japanese for 'galaxy') on orbit, was launched from the Kagoshima Space Center on 5 February 1987. It was put into an orbit with an orbital period of ~96 minutes. Ginga was the third Japanese X-ray astronomy mission, following Hakucho and Tenma. It had two main science objectives:
  1. study time variabilities from milliseconds to years for all types of X-ray sources, and
  2. study the spectra of sources. After a highly successful mission, the Ginga satellite reentered the Earth's atmosphere on 1 November 1991.

The Instrumentation

Ginga was approximately 1000 x 1000 x 1550 mm in size. It weighed about 420 kg. There were 3 science instruments on board: a large area proportional counter (LAC), an all-sky monitor (ASM), and a gamma-ray burst detector (GBD).

The LAC was the main scientific instrument aboard Ginga. It was designed and built under a Japan-United Kingdom collaboration (ISAS, U. Tokyo, Nagoya U., U. Leicester, Rutherford Appleton Lab). The LAC consisted of 8 identical proportional counters, with a total effective area of ~ 4000 sq-cm. The instrument was sensitive to ~1-37 keV X-ray photons.

The ASM consisted of 2 identical gas proportional counters, and was sensitive to 1-20 keV X-rays. The aim of the ASM was to create an all-sky survey every 1-2 days to look for transient events (for alarm to the LAC) and to collect a long-term record for X-ray sources.

The purpose of the GBD was to detect gamma-ray bursts in the energy range 1 - 400 keV with a high energy resolution. The GBD could also operate as a radiation belt monitor for high particle backgrounds which could harm the other 2 experiments.

The Science Results

Ginga performed approximately 1000 observations of about 350 different objects. The observing program included all known classes of X-ray sources and produced many significant results. Some highlights are:
  • The ASM discovered 2 very bright transients GS2023+338 and GS2000+25.
  • The LAC found cyclotron features in several X-ray pulsars, such as 4U1538-522, V0332+53, and Cep X-4.
  • A large number of pulsar transients in the galactic ridge were observed.

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
Acting Project Leader: Dr. Barbara Mattson
All material on this site has been created and updated between 1997-2012.

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