[meteorite-list] Communications Established with ISEE-3 Spacecraft

[Ron Baalke]

http://spectrum.ieee.org/tech-talk/aerospace/satellites/isee3-update

Space Hackers Take Control of ISEE-3 Spacecraft
By Rachel Courtland
IEEE Spectrum
29 May 2014 

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.