[amsat-bb] Space Hackers Prepare to Reboot 35-Year-Old Spacecraft (Long)

Eric Rosenberg ericrosenberg.dc at gmail.com
Wed May 21 10:03:58 UTC 2014

This long piece comes from IEEE Spectrum

AMSAT-DL is mentioned throughout this piece. Dennis Wingo is KD4ETA. He has
a blog http://denniswingo.wordpress.com/


Eric W3DQ

Space Hackers Prepare to Reboot 35-Year-Old Spacecraft

By Rachel Courtland

Posted 15 May 2014 | 17:00 GMT

Early next week, a team of volunteers will use the Arecibo Observatory in
Puerto Rico to see if they can make contact with a spacecraft that hasn't
fired its thrusters since 1987. If all goes well, the effort could bring
the 35-year-old spacecraft, the International Sun-Earth Explorer
back into position near the Earth, where it could once again study the
effect of solar weather on Earth's magnetosphere.

It will be a race against time. ISEE-3, which is transmitting two carrier
signals, only came into hearing range a couple of months
Dennis Wingo, CEO of California-based Skycorp
Incorporated<http://www.skycorpinc.com/Skycorp/Home.html>, and
his colleagues reckon ISEE-3 still has enough fuel to make it back to its
original orbit at the Lagrangian point
at a spot between the sun and the Earth where a spacecraft can stay in sync
with Earth's orbit. But to make it, Wingo says, the spacecraft must
be commanded to fire its thrusters by mid-June.

And that's far easier said than done. NASA no longer has the hardware to
communicate with the ISEE-3. So in April, Wingo and Keith Cowing, a former
NASA employee and editor of the websites NASAWatch <http://nasawatch.com/>and
SpaceRef <http://www.spaceref.com/>, started a (still-running) crowdfunding
campaign <http://www.rockethub.com/42228> on RocketHub to develop what they
need to communicate and control the spacecraft: signal modulators and
demodulators, transmitters, and a software-based mission control console to
monitor the spacecraft's propulsion and attitude control systems.

Building all of this even 10 years ago "would have been impossible," Wingo
says. But with the advance of embedded systems technology, the team can
construct radio components in software and debug them on aggressive
timescales without breaking the bank.

With no time to wait, the team has already purchased software-defined radio
peripherals <https://www.ettus.com/product/details/UN210-KIT> built by
Ettus Research, which can be used to implement modulator and demodulator
programs that would once have had to be built in hardware.

Ettus has volunteered to help with the programming, and one member of the
company will join Wingo in Arecibo. They'll set to work there on 19 May,
using a 400-watt transmitter shipped in from Germany to try to make contact
with the spacecraft. One of the first things they'll do is command the
spacecraft into engineering telemetry mode, where it's hoped it will send
signals that will give the team a better sense of the condition of the

Assuming ISEE-3 is in good health, Wingo says, the next big challenge will
be to assess its trajectory for a proper thruster firing. The team will use
transmitters and antennas at Arecibo, Morehead State University in
Kentucky, the Bochum Observatory in Germany, and, potentially, the Allen
Telescope Array in California, to ping the spacecraft. The hope is that the
team will not only be able to measure Doppler shifts in frequency to get a
fix on the spacecraft's velocity, but also signal time of flight to
triangulate its position. This will be difficult, so even though the
project met its fundraising goal on Wednesday, Wingo says the team is still
seeking funds in case they must pay NASA to do the ranging for them.

The reboot project schedule is aggressive. "We're in panic mode every day,"
Wingo says. "But I think we have a reasonable chance of making this work if
the spacecraft is healthy."

 If the effort succeeds, it won't be the first time that ISEE-3 has had a
change of course. After its launch in 1978, the spacecraft was repurposed
(and renamed the International Cometary Explorer) in the early 1980s to
chase Halley's Comet, then tasked again with performing solar observations
in 1991 before mission cancellation in 1997.

Although more capable spacecraft have since launched, recapturing ISEE-3
could give researchers access to a consistent set of instruments with which
to compare old measurements of the Earth environment, Wingo says. The peak
of this solar cycle is about half as
the peak of solar cycle 21, which ISEE-3 observed.

"[We can use the] same set of instruments to look and see what the
differences are in Earth's magnetosphere," Wingo says. Most of ISEE-3's
science instruments could still be in good working order, Wingo says, as
well as the core command components of the spacecraft, which has no
microprocessor and hence no memory to corrupt.

If the team can get ISEE-3 to fire its thrusters by mid-June, the
spacecraft will swing past the moon at an altitude of less than 50
kilometers on August 10. A few more engine firings could place it back at
L1, where the spacecraft could potentially start collecting data by
mid-September. If the plan works, Wingo says, the team hopes to have a
website up where people can see the spacecraft's engineering telemetry and
science data for themselves.

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