The International Sun-Earth Explorer (ISEE-3) satellite, launched 36 years ago, has been resurrected by amateur researchers, in the first operation of its time in history. Thrusters were fired on the spacecraft for the first time in decades.
The ISEE-3 Reboot Project, a crowd-funded organization based in Virginia, took command of the vessel in May. The team is composed of three groups - Space College, Skycorp and SpaceRef.
Thrusters were fired on the vehicle to increase the spin rate of the craft. The vehicle was designed to rotate 19.75 times every minute. When the Reboot Project took over control, that rate had slowed to 19.16 rpm. The hydrazine thrusters were fired 11 times, bringing the rotational rate up to 19.76 rotations each minute, well within design specifications. This maneuver also tested that the engines were still functional, and that the team could control the craft.
"If all goes according to plan on Tuesday, 8 July, we will conduct the Trajectory Correction Maneuver (TCM). This will require a much longer firing of the spacecraft's thrusters. If the burn is a success we will follow up with another ranging session using the DSN to get an exact measure of the spacecraft's position, trajectory, and speed," team members reported on their website.
After the second firing, predicted to consist of between 432 and 435 pulses, the craft should be ready to for its next mission. The ISEE-3 will be moved to a trajectory that will bring it past the moon on 10 August. After that flyby, mission controllers will direct the craft into orbit between the Earth and Sun.
The vehicle was launched on 12 August 1978, originally intended to study interactions between solar wind and the Earth's magnetic field. It was one of three craft launched on the mission into an orbit around the Sun. it was later re-branded to explore a comet.
The national space agency last made contact with ISEE-3 late in the 1990's. In May, the vehicle approached the Earth, allowing researchers an opportunity to resurrect the craft. Without funding to manage the mission, command was turned over to amateur space enthusiasts.
Communication hardware to control the vehicle was destroyed in 1999. The cost of replacing the machines was deemed too high to be practical, so the reboot team designed a virtual simulator, allowing them to maintain two-way communication with ISEE-3. Once the craft is back in a viable heliocentric orbit, the new team plans to restart the original mission of exploring the solar wind and the Earth's magnetic field.
This is an early success for the first NASA spacecraft ever given away to amateurs.
