ISEE 1 And 2 were launched together on 22 October 1977 and followed the same highly elliptical geocentric orbit (23 RE by 270 km), with a small but variable separation between the two to separate spatial from temporal effects in the observations associated with measurements by a single spacecraft on thin boundaries which may be in motion. Such boundaries include the bow shock and the magnetopause. During the course of the mission, both ISEE 1 and 2 orbit parameters underwent short-term and long-term variations due to solar and lunar perturbations. By maneuvering the 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 rate was nominally 19.8 rpm (19.75 for ISEE-1), so that there was a slow differential rotation between the two spacecraft. The ISEE 2 body-mounted solar array supplied approximately 112 W at launch. The data rate was 2048 bps most of the time and 8192 bps during one orbit out of every five (with some exceptions).
The satellites passed through the magnetosphere and into the magnetosheath during each orbit.
The purposes of the mission were:
Both spacecraft re-entered the Earth's atmosphere during orbit 1518 on 26 September 1987. Seventeen of 21 on-board experiments were operational at the end.
The WIM experiment was designed to identify and to study plasma instabilities responsible for acceleration, source and loss mechanisms, and boundary and interface phenomena throughout the orbital range of the mother/daughter satellites. A proton telescope and an electron spectrometer were flown on each spacecraft to measure detailed energy spectra and angular distributions.
These detectors used silicon surface-barrier, totally depleted solid-state devices of various thicknesses, areas, and configurations. Protons in 8 or 16 channels between 20 keV and 1.2 MeV, and electrons in 8 or 16 channels between 20 keV and 1 MeV, were measured. A separate solid-state detector system measured the energy spectra and pitch-angle distributions of alpha particles and heavy ions in the energy range above 125 keV per nucleon.
BLXTRA
Last update: Mon, 12 Mar 2018