The X-ray Astronomical Satellite “TENMA” aims to realize high-resolution spectroscopy of X-ray stars and observe gamma-ray bursts using three scientific instruments.


TENMA measured energy spectra of various X-ray stars accurately using the high-energy resolution of gas-scintillation proportional counters. The figure shows an example of the energy spectra obtained from the X-ray pulsar Vela X-1. An emission line from cold iron is clearly detected at 6.4 keV.

Name (pre-launch in parentheses) TENMA (ASTRO-B)
International Designation code 1983-011A
Objectives High-resolution spectroscopy of X-ray stars and observations of gamma-ray bursts
Launch Date February 20, 1983
Launch Location Kagoshima Space Center (Uchinoura)
Launch Vehicle M-3S-3
Weight 216kg
Shape Square pillar, 94cm diameter, 89.5cm high
Four solar paddles
Orbital Altitude Perigee 497km, Apogee 503km
Orbital Inclination 32°
Type of orbit Near circular
Orbital Period 94 min.
Scientific Instruments Gas Scintillation Proportional Counter
X-ray Focusing Collector
Hadamard X-ray Telescope
End of Operation December 17, 1988
Reentered Date January 19, 1989
Operation After launch, the solar paddles were deployed, and initial checks, attitude control with magnetic torquers and spin control were conducted smoothly. Later, attitude control was changed to free-spin mode because trouble with the momentum wheel increased satellite rotation. A problem was found in the power system in July 1984, but observations of X-ray stars continued because the mission instruments remained normal.
Results 1.Discovered hot plasma of several tens of millions of degrees located along the Galactic plane.
2.Discovered the iron absorption line in the energy spectra of X-ray bursts, which was red-shifted in the strong gravitational field of the neutron star.
3.Identified X-ray emission regions in low-mass X-ray binaries as the surface of the neutron star and the accretion disk.
4.Discovered that the cold, i.e., neutral iron is responsible for the emission line from X-ray pulsars.