ISEE-3 Returns "Home" on Sunday With New Life as Citizen Science Project

NASA’s International Sun/Earth Explorer-3 (ISEE-3) will return to the Earth’s vicinity tomorrow (Sunday, August 10), after more than 30 years of zipping through space.  The ISEE-3 Reboot Project and its partner Google launched a new website yesterday to explain the mission and its future as a “citizen science” project. They and NASA will hold a Google+ Hangout on Sunday to discuss ISEE-3’s new lease on life.

ISEE-3 will loop around the Moon at 2:16 pm Eastern Daylight Time (EDT) on Sunday before continuing its orbit around the Sun.  The Google+ hangout featuring NASA, Google and ISEE-3 Reboot Project representatives begins at 1:30 pm EDT.

As graphically illustrated on the new website, ISEE-3 has followed a complicated orbital trajectory since its launch in 1978.   Originally part of a trio of spacecraft (ISEE-1, -2, and -3) designed to study interactions between Earth and the solar wind, ISEE-3 was initially placed into a position between the Earth and the Sun to alert its two earth-orbiting companions that a solar event occurred.   ISEE-3’s location was the L-1 Sun-Earth Lagrange point where the gravitational forces of the Earth and Sun are in balance.  It was the first spacecraft to be placed into that Sun-Earth L1 location, which since has been used for many spacecraft that study solar-terrestrial interactions.

The first reinvention of ISEE-3’s mission occurred in the early 1980s when a small group of scientists and engineers decided that it should be redirected from Sun-Earth L1 to intercept Comet Giacobini-Zinner.  At the time, the United States had decided it could not afford to build a spacecraft to visit legendary Halley’s Comet as it approached the Sun in 1986 although the Soviet Union, Europe and Japan all were sending probes.

The group, including Bob Farquhar who has written a book that includes the history of the fractious decision-making process involved, did not want the United States to be left out of those early days of comet research and identified Giacobini-Zinner as a target that ISEE-3 could reach before the other probes reached Halley’s Comet.  Indeed, in September 1985, ISEE-3, redesignated the International Cometary Explorer (ICE), flew through the tail of Giacobini-Zinner, winning the title of the first spacecraft to encounter a comet.

Since then, the spacecraft has been travelling through space on its predetermined orbit that, thanks to the laws of physics, brings it back to Earth’s vicinity on August 10, 2014.  Working with Farquhar and others, Keith Cowing of NASAWatch and Dennis Wingo of Skycorp created the ISEE-3 Reboot Project as a “citizen science” effort, raising about $160,000 through a crowdsourcing campaign to build the equipment needed to communicate with the aged spacecraft.  The goal was to reestablish communications and, if all went well, redirect the spacecraft onto a trajectory to begin a new scientific mission.

The group successfully reestablished communications with ISEE-3 and obtained NASA permission to command the spacecraft, but its propulsion system is not functioning.  Physics will keep the spacecraft on its current trajectory and it will return to Earth’s vicinity again in about 15 years.

Meanwhile, though, with communications restored, it can send back data from whatever scientific instruments are still functioning.  Receivers on Earth will be able to pick up the data for about the next year before ISEE-3 once again moves out of range.  The ISEE-3 Reboot Project team’s goal now, in partnership with Google, is to make the data accessible to anyone interested in analyzing it, continuing ISEE-3’s new life as a citizen science project.