Launch Date: December 02, 1997
Mission Project Home Page - http://www.mpe-garching.mpg.de/EQS/eqs_home.html
EQUATOR-S was a low-cost mission designed to study the Earth's equatorial magnetosphere out to distances of 67000 km. It formed an element of the closely-coordinated fleet of satellites that compose the IASTP program. Based on a simple spacecraft design, it carries a science payload comprising advanced instruments that were developed for other IASTP missions.
Unique features of EQUATOR-S were its nearly equatorial orbit and its high spin rate. It was launched as an auxiliary payload on an Ariane-4, December 2nd, 1997. The mission was intended for a two-year lifetime but stopped transmitting data on May 1, 1998.
The idea of an equatorial satellite dates back to NASA's GGS (Global Geospace Science) program, originally conceived in 1980. The equatorial element of the program was abandoned in 1986 and several subsequent attempts to rescue the mission failed, leaving a significant gap in both NASA's GSS and the international IASTP programs.
The Max-Planck-Institut für Extraterrestrische Physik (MPE) decided to fill this gap because of its interest in GSS and the opportunity for a test of an advanced instrument to measure electric fields with dual electron beams. In addition to MPE-internal funds and personnel, the realization of EQUATOR-S was possible through a 1994 grant from the German Space Agency DARA (meanwhile part of DLR).