khoji parkSpace · Mountain View, California · 2014
Volunteers Contacted a Spacecraft NASA Had Stopped Using
An independent group of engineers and scientists attempts to recover a vintage NASA satellite.
Read in slides1. Launching a Historic Explorer
NASA launched the International Sun-Earth Explorer-3 on August 12, 1978, to study solar-terrestrial physics. The spacecraft became the first artificial object placed in a halo orbit around the Sun-Earth L1 Lagrange point. Following its primary mission, space agencies redirected the probe to intercept comet Giacobini-Zinner. Renamed the International Cometary Explorer, it successfully flew past the cometary nucleus in September 1985.
The spacecraft eventually entered an extended heliocentric orbit.
2. Ending Routine Space Agency Operations
NASA officially terminated routine operations and support for the spacecraft in May 1997, leaving only a carrier signal active. The agency later conducted brief status checks, confirming that many of the original scientific instruments remained functional. Although the probe continued orbiting the Sun, it drifted away from active monitoring. Independent researchers realized the spacecraft would make a close approach to Earth in 2014.
Engineers began studying the feasibility of recapturing the vehicle.
3. Forming the Reboot Project
In early 2014, an unofficial group of scientists, programmers, and engineers formed the ISEE-3 Reboot Project. The team intended to command the spacecraft to fire its engines and return to a stable halo orbit near Earth. Organizers launched a crowdfunding campaign on RocketHub to finance software development and antenna time. The project successfully surpassed its financial goals within weeks.
Volunteers secured partnerships to support communication efforts.
4. Signing an Agreement with NASA
Although NASA was not funding the revival effort, agency officials evaluated the proposal and approved the attempt. On May 21, 2014, NASA signed a non-reimbursable Space Act Agreement with the project organizers. This marked the first time the agency entered such an agreement for a derelict spacecraft. NASA shared historical technical data to assist the team in communicating with the vintage hardware.
The citizen group prepared to transmit commands to the probe.
5. Reestablishing Two-Way Communication
Because original ground station equipment had been decommissioned, project members simulated complex modulators using software-defined radio techniques. They installed this modern equipment on the massive Arecibo Observatory dish antenna in Puerto Rico. On May 29, 2014, the team successfully commanded the spacecraft to switch into engineering mode. The probe began broadcasting telemetry signals back to Earth.
Operators refined orbital parameters using tracking stations.
6. Attempting Propulsion Maneuvers
On July 2, 2014, project operators fired the spacecraft thrusters for the first time in twenty-seven years. The vehicle successfully spun up to its nominal roll rate in preparation for trajectory correction. However, a subsequent longer thruster firing failed on July 8. Investigators determined the failure stemmed from a lack of nitrogen pressure in the fuel tanks.
The team abandoned plans to alter the spacecraft orbit.
7. Transitioning to a Citizen Science Mission
Following the propulsion failure, organizers pivoted to an alternative plan called the ISEE-3 Interplanetary Citizen Science Mission. The spacecraft would gather scientific data as it swung past the Moon and entered a heliocentric orbit. Team members began shutting down propulsion components to maximize electrical power for remaining experiments. Five of the original thirteen scientific instruments remained operational.
Global receiving sites were recruited to collect incoming data streams.
8. Completing the Lunar Flyby
On August 10, 2014, the spacecraft passed approximately 15,600 kilometers above the lunar surface. Following this close approach, the probe continued along its heliocentric path away from Earth. The citizen science team worked to acquire data from across the remaining orbit. Observations focused on monitoring cosmic rays and listening for gamma-ray bursts.
The spacecraft receded further into interplanetary space.
9. Losing Contact with the Probe
On September 25, 2014, the reboot team announced that contact with the spacecraft had been lost on September 16. As the probe moved further from the Sun along its post-lunar orbit, electrical power generated by its aging solar arrays dropped. Without a working battery, the reduced power likely forced the craft into a safe mode. Operators lacked the precise orbital location data required to re-establish transmission links.
Efforts to awaken the dormant spacecraft proved unsuccessful.
10. Reflecting on the Revival Attempt
The volunteers restored communication and received telemetry from ISEE-3, but they did not complete the maneuver needed to bring it back to the intended near-Earth orbit. The spacecraft continued past the Moon in August 2014, and contact was lost the following month. The project’s communication success and its failed orbital-change plan were therefore different outcomes of the same revival attempt.
Contact was restored, but the intended orbit was not.