Rebooting a Mothballed Mission – ISEE-3
Keith Cowing is no stranger to old space hardware. Since 2007, Cowing and his colleague Dennis Wingo have been at the head of the Lunar Orbiter Image Recovery Project (LOIRP), which has successfully rescued and restored thousands of images stored on magnetic tapes dating back to the mid-60s. Now Cowing has a new project in mind: returning the International Sun Earth Explorer 3 (ISEE-3) probe to service.
ISEE-3 has a long and storied history. Launched in 1978 to study to solar wind’s effect on Earth’s magnetosphere, or “space weather before it was called space weather” as Cowing puts it, ISEE-3 was the first mission to make use of the Earth-Sun L1 point. There, a spacecraft could remained stationed between the Sun and Earth with a minimum amount of energy.
The man who got it there, Robert Farquhar, was one of NASA’s best trajectory men. His dream was to make NASA the first space agency to visit a comet. But by the early 80s, NASA was a cash-strapped agency. Between the development of the space shuttle and large cuts to the agency’s budget following the Apollo program, NASA didn’t have the money to build and support a dedicated comet mission. With the Soviet Union, European Space Agency, and Japan all set to send their own missions to Halley’s comet in early 1986, it seemed like Farquhar’s dream was dead in the water.
So Farquhar hatched a scheme. If NASA couldn’t build a dedicated comet mission, he would use existing hardware. ISEE-3 was ideally suited for the task. Perched at the edge of Earth’s gravitational well, it only needed a little kick to fly towards a comet. Farquhar designed a comet rendezvous mission for ISEE-3 and lobbied NASA to approve the plan. He succeeded. At the end of ISEE-3’s main mission in 1982, it fired its engine and set course for Comet Giacobini-Zinner. Now named the International Cometary Explorer (ICE), it flew by the comet in September 1985, laying claim to the first probe to visit a comet.
The heliophysicists who had operated the probe howled that Farquhar had “stolen” it from them. But Farquhar claimed he had only borrowed it – his trajectory brought it back to Earth in 2014. After it flew by Giacobini-Zinner, ICE also visited Halley’s Comet in 1986 before being returned to service to study the solar wind in 1991. In 1997, NASA pulled the plug on the mission, commanding it to turn off everything but its carrier signal. That would be the end of things, had it not been for a JPL engineer’s mistake.
Removing the Mothballs
In 2008, the Deep Sky Network turned its radio dishes towards ICE’s predicted location to check its location. To their surprise, they found that its radio transmitters hadn’t been turned off like they were supposed to. That meant that the probe was still capable of receiving commands from Earth. They also discovered that many of probe’s sensors were still functional. Farquhar, who had recently retired from NASA, worked to get the probe returned to service in its original L1 halo orbit.
“It’s the most cost-effective spacecraft we ever had and I’d like to make it even more cost-effective. It can do more missions,” Farquhar told NPR in March. Unfortunately, the NASA of 2014 is struggling to make ends meet. Already struggling to maintain full funding for their large fleet of existing spacecraft, there was nowhere in the budget to add a retired probe. Despite the additional data ISEE-3 could provide for space weather research, NASA denied the mission extention. Enter Keith Cowing and Dennis Wingo.
The two men have worked together on the Lunar Orbiter Image Recovery Project (LOIRP) since 2007. Today, Cowing heads Space College, a non-profit group dedicated to fostering professional-amateur collaborations on space science. Space College opened its doors in January of this year, and Cowing saw the ideal project for it in returning ISEE-3 to service. He told me he remembered ISEE-3’s original mission redirect, but it wasn’t until he was looking through old files months ago that he realized that ISEE-3 would return to Earth’s neighborhood in 2014.
Since then, there’s been a scamble to get together the equipment needed to send new commands to ISEE-3. To return ISEE-3 to its original orbit, the probe will need to fly by the Moon only 117km (73 miles) from its surface. If it misses that narrow corridor, it will fly off back into space. To get on the right trajectory, ISEE-3 will need to fire its engine sometime in May or June. “The sooner we contact it, the better,” Cowing said. “The probe only has about 150 m/s of delta-v [a measure of how much the probe can change its velocity] and the longer we wait the more of that we’ll have to use.”
Communicating with ISEE-3 by June will be the group’s only chance at recapturing the spacecraft. “It follows an orbit very similar to Earth’s orbit, so it takes a long time to catch back up to Earth. It’ll be another 30 or 40 years when we see it again,” Cowing said. Although ISEE-3 has been active since 1978, it’s unlikely to soldier on long enough to make another pass.
ISEE-3’s Third Life
Turning on a cold engine after 30 years has its risks. There’s always the possibility that the spacecraft’s engine bell could disintegrate. However, Cowing sees a lot of value in taking that risk. 12 of its 13 instruments are still partly or fully functioning. These instruments collect data on critical values in forecasting space weather around Earth: magnetic field strength, plasma waves, energetic particle count and more. Although NASA has satellites that measure these values close to Earth, only one, the Solar and Heliospheric Observatory (SOHO), measures them from L1. The redundancy that ISEE-3 provides is important, because an antenna problem on SOHO leaves it out of communication with Earth for a couple of weeks four times a year.
A successful burn doesn’t mean that ISEE-3 is out of the woods, though. Another problem is that the probe has no battery power – they died more than 20 years ago. As it makes its flyby of the Moon, it will pass through its shadow for 20 minutes. The effect of passing through the Moon’s shadow is completely unknown. ISEE-3 has been bathed in constant sunlight since 1978. With no battery to power its heaters, ISEE-3’s equipment could become dangerously cold. Cowing says that the Reboot Project has been developing a workaround to the problem. “So far the plan is to warm up the spacecraft as long as possible with the heaters before the eclipse and hope it’s enough.”
If the capture is successful, Cowing plans to turn the probe over to citizen scientists. NASA has said it could also make use of the data if it is made available. Even if ISEE-3’s sensors fail when it passes behind the Moon, the accomplished probe could be put to yet another use. Cowing says that astronomers could still make use of the probe’s radio beacon. “It becomes a high-precision beacon. It’s at a known location in cis-lunar space – making it a good way to calibrate radio telescopes.”
How to Help
The ISEE-3 Reboot Project is attempting to crowdfund the rescue attempt at Rockethub. The project is seeking $125,000 and Cowing says “we need every penny of it.” The money will fund a search for the spacecraft’s original documentation, if it still exists, as well as recreate the equipment needed to communicate with ISEE-3. After its mission ended in 1997, the Deep Space Network removed the computers that sent commands to the probe. Instead, the ISEE-3 Reboot Project intends to construct software emulations of the original hardware.
And although the project has been soliciting donations for equipment, “we still have to pay to get it shipped,” Cowing said. Cowing said that the group had several donations in the pipeline, and the crowdfunding campaign would help get the equipment where it needs to go. When asked if he thought that the crowdfunding campaign would be successful, he said “From prior experience it looks like it. But we need every donation. Even ten dollars is helpful. It may not seem like a lot, but if a lot of people contribute, it really helps.”
Image Credit: NASA Goddard Spaceflight Center
Special thanks to Keith Cowing for the phone interview.