Missions   ISEE

International Sun-Earth Explorer (ISEE)

ISEE mission poster.

ISEE launch.

The ISEE program consisted of three spacecraft, ISEE-1 and ISEE-3 which were the principal U.S. contributions to the International Magnetospheric Study, and ISEE-2 which was built and managed by the European Space Agency (ESA). ISEE-1 and ISEE-2 launched on October 22, 1977, were in almost coincident orbits around the earth with periods of approximately 57 hours, and their time separation in this orbit could be altered by maneuvering ISEE-2. ISEE-3 was launched on August 12, 1978, and inserted into a "halo orbit" about the libration point situated ~240 earth radii (Re) upstream between the earth and the sun. Plasma passing this point arrives at the earth approximately 1 h later where it may cause changes which can be observed by instruments on ISEE-1 and ISEE-2. These two spacecraft, separated by a variable distance and with similar instrument complements, were able to break the space-time ambiguity inevitably associated with measurements by a single spacecraft on thin boundaries which may be in motion, such as the bow shock and the magnetopause. Apogee of the ISEE-1 and ISEE-2 orbit was 23 Re, so the spacecraft penetrated into the interplanetary medium for up to 3/4 of an orbital period depending upon the time of year. The ISEE-1 and ISEE-2 spacecraft reentered the Earth's atmosphere in September 1987 after 1517 orbits of the Earth. ISEE-3 was taken out of it libration point orbit in the summer of 1983 and after a series of deep passes down the magnetotail, left the gravitational influence of the Earth and passed by comet Giacobini-Zinner in September 1985.

The ISEE program has produced many publications. A bibliography is available. Articles on the instumentation can be found in a special issue of the IEEE Transactions on Geoscience Electronics, GE-16, 1978. A description of the International Magnetospheric Study can be found in the book The IMS Source Book: Guide to the International Magnetospheric Study Data Analysis, edited by C. T. Russell and D. J. Southwood, 304 pages, American Geophysical Union, Washington D. C. 1982.

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Last updated: December 31, 1999