The Tenma Satellite [Astro B]

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The Tenma [Astro B] Satellite

Astro B was the second Japanese X-ray astronomy satellite. After launch on February 20, 1983, it was renamed Tenma (Japanese for “Heavenly Horse” or “Pegasus”). Tenma carried GSFC detectors which had an improved energy resolution (by a factor of 2) compared to proportional counters and performed the first sensitive measurements of the iron spectral region for many astronomical objects.

Mission Characteristics

Lifetime	20 Feb 1983–22 Nov 1985
Special Features	Suite of instruments covering a wide energy range for simultaneous observations at soft and hard X-ray wavelengths while primarily a Japanese mission, it included contributions from U.S. and European researchers. It established Japan as a major contributor to X-ray astronomy.

Lifetime

20 Feb 1983–22 Nov 1985

Special Features

Suite of instruments covering a wide energy range for simultaneous observations at soft and hard X-ray wavelengths
while primarily a Japanese mission, it included contributions from U.S. and European researchers. It established Japan as a major contributor to X-ray astronomy.

Payload

Instrument	Characteristic	Details
Gas Scintllator Proportional Counter	Energy Range	2–60 keV
	Effective Area	80 cm² each
	Field of View	3.1° FWHM (SPC-A) 2.5° FWHM (SPC-B) 3.8° FWHM (SPC-C)
	Energy Resolution	9.5% at 6 keV
	This was the primary instrument on the satellite. Its main objective was the spectral and temporal study of cosmic X-ray sources. It consisted of 10 gas scintillation proportional counters (GSPC). The ten counters were divided into three groups SPC-A, B and C, with slightly different fields of view through honeycomb collimators. The A and B consisted of 4 counters each, the C instead consisted of 2 counters.
X-ray Focusing Collimator	Energy Range	0.1–2 keV
	Effective Area	7 cm² each at 0.7 keV
	Field of View	5° × 0.2° (FWHM), divided into 7 resolution elements
	The system consisted of 2 identical co-aligned subsystems, each with a position sensitive proportional counter.
Transient Source Monitor	Energy Range	2–10 keV
	Field of View	45° radius
	This instrument carried out continuous monitoring of a wide field of the sky. It consisted of 2 detector groups: (1) a Hadamard X-ray telescope and (2) a scanning counter.
Radiation Belt Monitor/Gamma Ray Burst Detector	Energy Range	10–100 keV
	Effective Area	7 cm² each
	Sensitivity	∼10^-5 erg/cm² detection limit at 1/8 s time resolution
	Time Resolution	1/8 s
	2 sets of scintillation counters. Their primary purpose was to monitor the background variations. They were also used as alarms for satellite entry into the radiation belts, and detect gamma-ray bursts.

Energy Range

2–60 keV

Effective Area

80 cm² each

Field of View

3.1° FWHM (SPC-A)
2.5° FWHM (SPC-B)
3.8° FWHM (SPC-C)

Energy Resolution

9.5% at 6 keV

This was the primary instrument on the satellite. Its main objective was the spectral and temporal study of cosmic X-ray sources. It consisted of 10 gas scintillation proportional counters (GSPC). The ten counters were divided into three groups SPC-A, B and C, with slightly different fields of view through honeycomb collimators. The A and B consisted of 4 counters each, the C instead consisted of 2 counters.

Energy Range

0.1–2 keV

Effective Area

7 cm² each at 0.7 keV

Field of View

5° × 0.2° (FWHM), divided into 7 resolution elements

The system consisted of 2 identical co-aligned subsystems, each with a position sensitive proportional counter.

Energy Range

2–10 keV

Field of View

45° radius

This instrument carried out continuous monitoring of a wide field of the sky. It consisted of 2 detector groups: (1) a Hadamard X-ray telescope and (2) a scanning counter.

Energy Range

10–100 keV

Effective Area

7 cm² each

Sensitivity

∼10^-5 erg/cm² detection limit at 1/8 s time resolution

Time Resolution

1/8 s

2 sets of scintillation counters. Their primary purpose was to monitor the background variations. They were also used as alarms for satellite entry into the radiation belts, and detect gamma-ray bursts.

Science Highlights

Discovery of the Iron helium-like emission from the galactic ridge
Iron line discovery and/or study in many low- and high-mass x-ray binaries and active galactic nuclei
Discovery of an absorption line at 4 keV in the X1636-536 burst spectra

NASA | GSFC | Sciences and Exploration

HEASARC

High Energy Astrophysics Science Archive Research Center

The Tenma [Astro B] Satellite

Mission Characteristics

Payload

Gas Scintllator Proportional Counter

X-ray Focusing Collimator

Transient Source Monitor

Radiation Belt Monitor/Gamma Ray Burst Detector

Science Highlights

Archive

Active Missions

Past Missions

The Tenma [Astro B] Satellite

Mission Characteristics

Payload

Gas Scintllator Proportional Counter

X-ray Focusing Collimator

Transient Source Monitor

Radiation Belt Monitor/Gamma Ray Burst Detector

Science Highlights

Archive