Fact Sheet
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Cos-B was ESA's first satellite dedicated to a single experiment. Its scientific mission was to study in detail the sources of extra-terrestrial gamma radiation at energies above about 30 MeV. The originally foreseen duration of the mission was two years, but in fact Cos-B functioned successfully for 6 years and 8 months. During this time an extensive survey of the Galaxy was made in the energy range 50 MeV to 5 GeV.
Mission Objectives
Cos-B's scientific mission was to study in detail the sources of extra-terrestrial gamma radiation at energies above about 30 MeV. The principal objectives were:
- Study spectrum and distribution of galactic gamma-rays
- Flux and distribution of extragalactic gamma-ray emission
- Study known point sources
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Search for new point sources
Spacecraft
Cos-B was configured as a cylinder 1.40 m in diameter and 1.13 m long, with the main experiment package occupying the central region.
Instruments
The Gamma-Ray Telescope
Orbit
The orbit of Cos-B was roughly 100 000 km with a period of 37 hours. This eccentric orbit was chosen to ensure that for most of the time the satellite was outside the Earth's radiation belts. This led to an efficient viewing programme at the price of high cosmic-ray background.
Vital Statistics
| Overall weight | 280 kg |
| Weight of payload | 120 kg |
| Height of satellite cylinder | 1.20 m |
| Diameter | 1.40 m |
| Number of solar cells | 9480 |
| Initial power | 109 w |
| Power after two years | 82 w |
| Average Power | 59 w |
| Battery capacity | 6 Ah |
| Attitude measurement accuracy | 1 degree |
| Transmission frequency | 136.95 MHz |
| Transmission power | 6.5 w |
| Information rate (real time) | 80/160/320 kbit/s |
| Modulation | PCM in up-link and down-link |
| Stability of onboard clock | 0.25 msec/3h |