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ISS a, b (Ume 1, 2)


The ISS (Ionosphere Sounding Satellite) series of satellites was Japan's first ionosphere sounding satellite project. After reaching orbit, they were named Ume.

ISS a or Ume 1 was used to monitor radio waves in the ionosphere and forecast conditions for optimal use of shortwave communications. A power supply system failure caused Ume to malfunction one month after launching.

ISS b or Ume 2 was put into orbit two years later as a replacement. Ume-2 kept gathering observation data even after its 1.5 year mission term. It finished its operation on 23 February 1983, because of deterioration of power generation.

Nation: Japan
Type / Application: Research, Ionosphere
Operator: NASDA
Contractors: Mitsubishi Electric (MELCO)
Power: Solar cells, batteries
Mass: 139 kg (#a), 141 kg (#b)
Orbit: 991 km × 1005 km, 69.67 (#a); 974 km × 1220 km, 69.36 (#b)
Satellite COSPAR Date LS Launch Vehicle Remarks
ISS a (Ume 1) 1976-019A 29.02.1976 Ta LP-N N-1
ISS b (Ume 2) 1978-018A 16.02.1978 Ta LP-N N-1