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The Explorer-class daughter spacecraft, ISEE 2 (International Sun-Earth Explorer 2), was part of the mother / daughter / heliocentric mission (ISEE 1, ISEE 2, ISEE 3).

The purposes of the mission were:

  • to investigate solar-terrestrial relationships at the outermost boundaries of the Earth's magnetosphere,
  • to examine in detail the structure of the solar wind near the Earth and the shock wave that forms the interface between the solar wind and the Earth's magnetosphere,
  • to investigate motions of and mechanisms operating in the plasma sheets, and
  • to continue the investigation of cosmic rays and solar flare effects in the interplanetary region near 1 AU.

The three spacecraft carried a number of complementary instruments for making measurements of plasmas, energetic particles, waves, and fields. The mission thus extended the investigations of previous IMP spacecraft. The mother/daughter portion of the mission consisted of two spacecraft (ISEE 1 and ISEE 2) with station-keeping capability in the same highly eccentric geocentric orbit with an apogee of 23 Earth radii. During the course of the mission, the ISEE 1 and ISEE 2 orbit parameters underwent short-term and long-term variations due to solar and lunar perturbations. These two spacecraft maintained a small separation distance, and made simultaneous coordinated measurements to permit separation of spatial from temporal irregularities in the near-Earth solar wind, the bow shock, and inside the magnetosphere. By maneuvering ISEE 2, the inter-spacecraft separation as measured near the Earth's bow shock was allowed to vary between 10 km and 5000 km; its value is accurately known as a function of time and orbital position.

The spacecraft were spin stabilized, with the spin vectors maintained nominally within 1 degree of perpendicular to the ecliptic plane, pointing north. The spin rates were nominally 19.75 rpm for ISEE 1 and 19.8 rpm for ISEE 2, so that there was a slow differential rotation between the two spacecraft. The ISEE 2 body-mounted solar array supplied approximately 112 Watts at launch. The ISEE 2 data rate was 2048 bps most of the time and 8192 bps during one orbit out of every five (with some exceptions).

Both ISEE 1 and ISEE 2 re-entered the Earth's atmosphere during orbit 1518 on 26 September 1987. Seventeen of 21 on-board experiments were operational at the end.

ISEE 2 was not considered part of the Explorer program as it was provided by ESA.

Nation: Europe
Type / Application: Research
Operator: ESA
Contractors: Dornier-System GmbH
Propulsion: ?
Power: Solar cells, batteries
Mass: 166 kg
Orbit: 779 km × 137511 km, 30.41
Satellite COSPAR Date LS Launch Vehicle Remarks
ISEE 2 1977-102B 22.10.1977 CC LC-17B Delta-2914 with ISEE 1


  • NSSDC Master Catalog: ISEE 2

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