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ISEE-3: On Track To Come Home

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Intended trajectory from ICE team in 1986 (blue), 2001 ephemeris of ISEE-3 (white) and current ephemeris (red/green). Click to embiggen.

When last we heard of the progress of commanding the derelict ISEE-3 satellite into stable orbit between the Earth and the sun, the team had just made contact with the probe using the giant dish in Arecibo, sent a few commands, and started gathering data to plot where the spacecraft is and where it will be. A lot has happened in a week, and the team is now happy to report the spacecraft is alive and well, and much, much closer to the intended trajectory than initially believed.

Before last week, the best data on where ISEE-3 was heading was from a 13-year-old data set, leaving the project coordinators to believe a maneuver of about 50-60  m/s was necessary to put the spacecraft into the correct orbit between the Earth and the sun. With new data from Arecibo, that figure has been reduced to about 5.8 m/s, putting it extremely close to where the original ICE navigation team intended it to go, all the way back in 1986. This also gives the team a bit of breathing room; the original planned maneuver to capture the spacecraft required nearly a third of the available fuel on board. The new plan only requires the spacecraft expend about 5% of its fuel stores. This, of course, brings up the idea of continuing the planned mission of the rebooted ISEE-3 beyond the Earth-Sun L1 point, but that is very much putting the cart before the horse.

Of course, getting ranging data of the spacecraft is only a small part of what has happened with the ISEE-3 part this week. Thanks to the ‘away team’ sent to Arecibo to install hardware and attempt to make contact with the satellite, both transceivers are working, telemetry is being downloaded from the probe, and work has begun on refining the exact position of ISEE-3 to compute where and when the spacecraft needs to make its maneuver.

Regular Hackaday feature and software defined radio god [Balint] was on hand with the away team at Arecibo to install his company’s SDR unit on the largest dish on the planet. His happy dance of the first data from ISEE-3 made the blog rounds, but the presentation (PDF) and photo gallery tell the story of working on the largest dish on the planet much better.

There’s still a lot of work to be done by the ISEE-3 team as they figure out how best to capture the spacecraft and prepare for the burn in the following week. They should have the exact orbit of ISEE-3 nailed down early this week, and after that, ISEE-3 could on a path back home in less than two weeks.

Talking To ISEE-3

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ISEE-3, the plucky interplanetary spacecraft fueled by the dreams of thousands of crowdfunding backers and hydrazine is now transmitting data to Earth.

Where all radio contact with ISEE-3 this year has only been a carrier frequency, the folks at the reboot project have successfully commanded ISSE via the huge Arecibo telescope to transmit data back to Earth. Usable data are now being received at 512 bits/second at ground stations in Germany, Kentucky, and California, surely being looked over by the ISEE reboot project engineers.

Simply transmitting the commands to put the data multiplexers into their engineering telemetry mode was no small task; a power amplifier needed to be built, shipped to Arecibo, and installed in the giant dome hanging over the Arecibo dish. The amplifier was only installed in the last day, during an earthquake, no less.

There’s still a lot of work to be done before the project can go any further; the team will need to check the status of the spacecraft from the data received, more systems will be checked out, and eventually the spacecraft will be commanded to perform a 17-hour long burn with its small thrusters, putting it on course to be captured by Earth some time in August.

It’s an amazing achievement to do any sort of communication on this scale, and now events in the ISEE-3 mission timeline will be coming rather quickly. We’re trying to organize a video/blog/cast thing with the team from NASA Ames or Morehead State, but the team is, understandably, a little busy right now.

ISEE-3: Ready To Come Home

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The team working to reboot the ISEE-3 satellite hurtling towards an August encounter with Earth is hard at work. They’ve put up a crowdfunding page, and now that they’re completely funded (don’t stop donating, btw), they’re starting to go deeper into the waters that will allow them to capture a forgotten satellite.

The project put up a status report going over what they’ve accomplished so far, and what work has yet to be done. For a few months now, they knew both transmitters aboard the craft were operational, but they were not sending telemetry. The team has gone through the documentation, came up with a set of commands, and are currently en route to Arecibo to transmit those commands.

Two ground station transmitters are being constructed, one specifically built to be installed at Arecibo for this application. The other is a portable, self-contained 700 watt transmitter that will be used at the official ISEE-3 ground station in Morehead State University in Kentucky.

With transmitters taken care of and receiving handled by an SDR from Ettus Research, a lot of work has focused on the command and telemetry systems.  In 1978, the user interface for commands and telemetry was primitive to say the least. The team is now working on a system built-in Labview that’s much easier on the eyes than the vintage text terminal screens.

So far, signals from ISEE-3 are planned to be received at Arecibo, Morehead State, and Bochum observatory in Germany. This will give the team extremely good coverage for most of a day, and there are other ground stations in California that will extend the time the team is able to communicate with ISSE-3 each day by a few hours.

There’s still a lot of work to be done; the team really doesn’t know what systems are still operating, although most of them did make it 20 years with only one fault. In the next few days, we’ll all get to see if this satellite will be up to the task of coming back home to Earth. If everything goes to plan, ISEE-3 will be on track towards a 17 hour burn to put it on the correct trajectory some time in mid June.