After a few days of waiting for transmission approval from NASA and an earthquake that shook the Arecibo Observatory in Puerto Rico on Wednesday, a private team of space enthusiasts has established two-way communication with the 35-year-old ISEE-3 spacecraft. The probe is now sending back telemetry, team member Keith Cowing says. Over the coming days, the team will analyze the data ISEE-3 is transmitting in order to assess the health of the spacecraft and see if they will be able to fire its thrusters, beginning a process that could bring the spacecraft back to its original orbit near the Earth.
The ISEE-3 reboot team, which raised nearly $160,000 on RocketHub to fund the effort, has been racing to cobble together what they need to communicate with ISEE-3, including transmitters as well as software-defined modulators and demodulators. Everything was in place by last Friday, the team reported, but they had to await clearance from NASA. That put some pressure on the team's already tight schedule: they expect they have until mid-June to command the spacecraft to fire its thrusters for the first time.
I called NASA on Wednesday to ask about the source of the delay. NASA signed an agreement last week that handed over control of the spacecraft to the team, which is led by the California-based firm Skycorp. But that agreement still requires NASA to approve certain steps.
In this case, the main source of the hold-up was getting authorization from the U.S. National Telecommunications and Information Administration to send signals to the spacecraft from Arecibo using the team's 400W transmitter.
"Because NASA still owns the spacecraft, NASA actually has to apply for the license on behalf of Skycorp," David Chenette, the director of the heliophysics division within NASA's Science Mission Directorate, told me. One concern, he says, is damage to other spacecraft. "The power levels are high enough to damage receivers that operate on this frequency should they be going through the beam," Chenette said. That list of potentially vulnerable probes includes NASA's Lunar Reconnaissance Orbiter and Earth Observing-1, JAXA's WINDS spacecraft, and ESA's Cluster and Swarm spacecraft.
Because of this issue, the team only has clearance to transmit to the spacecraft until May 31, Skycorp's CEO Dennis Wingo wrote to me over Skype from Puerto Rico, shortly before today's attempt at communication. "After that we have to say 'mother may I' again," he wrote, adding that going forward his team hopes to automate the communications process so that transmission will not occur if any spacecraft that might be affected are in the area.
In the meantime, the team will be working out how to interpret the data that ISEE-3 is now sending back to Earth. "We will use that data to debug the demodulator software, then we get bits out, then we process for telemetry," Wingo wrote. He hopes that by early next week they'll have some initial idea of how well the spacecraft's systems are faring.
Rachel Courtland, an unabashed astronomy aficionado, is a former senior associate editor at Spectrum. She now works in the editorial department at Nature. At Spectrum, she wrote about a variety of engineering efforts, including the quest for energy-producing fusion at the National Ignition Facility and the hunt for dark matter using an ultraquiet radio receiver. In 2014, she received a Neal Award for her feature on shrinking transistors and how the semiconductor industry talks about the challenge.