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#EXPLORERS 1985 EXTENDED UPDATE#
The bit rate then successively dropped to 512 bps (on 9/12/85), 256 bps (on 5/1/87), 128 bps (on 1/24/89) and finally to 64 bps (on 12/27/91).Īn update to the ICE mission was approved by NASA headquarters in 1991. The ISEE-3/ICE bit rate was nominally 2048 bps during the early part of the mission, and 1024 bps during the Giacobini-Zinner comet encounter.
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Tracking and telemetry support have been provided by the DSN (Deep Space Network) since January 1984. ICE data from both cometary encounters are included in the International Halley Watch archive: ICE became the first spacecraft to directly investigate two comets. It also transited between the Sun and Comet Halley in late March 1986, when other spacecraft (Giotto, Planet-A, MS-T5, VEGA) were also in the vicinity of Comet Halley on their early March comet rendezvous missions. As planned, the spacecraft traversed the plasma tail of Comet Giacobini-Zinner on September 11, 1985, and made in situ measurements of particles, fields, and waves. The primary scientific objective of ICE was to study the interaction between the solar wind and a cometary atmosphere. A total of fifteen propulsive maneuvers (four of which were planned) and five lunar flybys were needed to carry out the transfer from the halo orbit to an escape trajectory from the earth-moon system into a heliocentric orbit. At this time, the spacecraft was renamed International Cometary Explorer (ICE). After several passes through the Earth's magnetotail, with gravity assists from lunar flybys in March, April, September and October of 1983, a final close lunar flyby (119.4 km above the moon's surface) on December 22, 1983, ejected the spacecraft out of the Earth-Moon system and into a heliocentric orbit ahead of the Earth, on a trajectory intercepting that of Comet Giacobini-Zinner.
#EXPLORERS 1985 EXTENDED SERIES#
A maneuver was conducted on June 10, 1982, to remove the spacecraft from the halo orbit around the L1 point and place it in a transfer orbit involving a series of passages between Earth and the L2 (magnetotail) Lagrangian libration point. In 1982 ISEE 3 began the magnetotail and comet encounter phases of its mission. ISEE 3 was the first spacecraft to use the halo orbit.įor instrument descriptions written by the investigators, see IEEE Trans. In addition, the heliocentric ISEE 3 spacecraft also provided a near-Earth baseline for making cosmic-ray and other planetary measurements for comparison with corresponding measurements from deep-space probes. In conjunction with the mother and daughter spacecraft, which had eccentric geocentric orbits, this mission explored the coupling and energy transfer processes between the incident solar wind and the Earth's magnetosphere. It was initially placed into an elliptical halo orbit about the Lagrangian libration point (L1) 235 Earth radii on the sunward side of the Earth, where it continuously monitored changes in the near-Earth interplanetary medium. This heliocentric spacecraft had a spin axis normal to the ecliptic plane and a spin rate of about 20 rpm. The launch of three coordinated spacecraft in this mission permitted the separation of spatial and temporal effects. The mission thus extended the investigations of previous IMP spacecraft. The three spacecraft carried a number of complementary instruments for making measurements of plasmas, energetic particles, waves, and fields. The purposes of the mission were: (1) to investigate solar-terrestrial relationships at the outermost boundaries of the Earth's magnetosphere (2) 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 Earth's magnetosphere (3) to investigate motions of and mechanisms operating in the plasma sheets and, (4) to continue the investigation of cosmic rays and solar flare emissions in the interplanetary region near 1 AU. The Explorer-class heliocentric spacecraft, International Sun-Earth Explorer 3, was part of the mother/daughter/heliocentric mission (ISEE 1, 2, and 3).