[Laser] Ham 'can do' triumphs in space ;-)
John McNulty
[email protected]
Wed, 03 Mar 2004 10:32:58 +0100
OK OK it's not lasers but, as they say here in Paris - 'chapeau' (hats-off)
to these enthusiasts ;-)
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A spacecraft built in six months by amateur radio operators is celebrating
its 20th birthday in orbit this week.
Story location: http://www.wired.com/news/technology/0,1282,62471,00.html
02:00 AM Mar. 02, 2004 PT
The AMSAT-UK group proudly announced "UoSAT-Oscar-11, (also known as UOSAT-2
and UO-11) was launched on 1 Mar 1984, and has been performing well in orbit
for 20 years," even though the satellite had a planned lifetime of about a
year in space. Amateur radio operator Roger Smith quipped, "I wish I had a
car which outlasted its warranty by that much."
UO-11 blasted into space by piggybacking on the launch of NASA's Landsat 5,
an Earth ecology-monitoring satellite.
Landsat 4, Landsat 5's predecessor, was launched in 1981 with the UoSAT-1
satellite for the University of Surrey in England, but because it had
problems in orbit NASA decided to launch Landsat 5 as a backup. Again the
offer to fly a secondary payload was extended, but the launch was less than
a year away. Could Surrey produce a satellite in time? The answer was yes,
and Landsat 5 and UO-11 were launched on March 1, 1984.
About the name: The satellite carried the UoSAT-2 tag while on the ground,
but once it established orbit, the small satellite was tagged University of
Surrey Orbiting Satellite Carrying Amateur Radio 11, or more simply UoSat
OSCAR 11, or just UO-11. UO-11's path takes it over the Earth's poles with
an orbit every 99 minutes. That works out to more than 106,000 orbits over
the past two decades.
From an engineer's perspective, that's 106,000 trips in and out of
sunlight, or 106,000 charge-discharge cycles for its solar-powered cells.
During an orbit, half the time the satellite is in sunlight, and the other
half it's in the dark. When the spacecraft is in sunlight, solar panels on
the orbit charge the batteries. Battery guru Larry Kayser said the trick to
efficiently assembling a battery is to use battery cells with identical
performance.
"If you have done a careful matching job of the cells that make up your
battery, there should be almost no chance of cell shorting or reversing
early in life," Kayser said. "The battery in UO-11 has had, on occasion,
terrible treatment; it was out of control from several months early in its
life and was subjected to brutal discharge levels."
UO-11's primary purpose was to showcase current technology, and for the
mid-1980s it was impressive. The satellite even had digital speech hardware
with a vocabulary of 500 words.
UO-11 has only 36K of RAM, and its processor is a 1-Mhz, 8-bit RCA COSMAC
1802. For its time, that was the state of the art for any spacecraft.
One of UO-11's more unusual feats took place during a 1988 Canadian-Soviet
trans-Arctic expedition. Michael Meerman, one of the amateur radio operators
at the ground station, said "UoSAT-OSCAR-11 was used to relay the group's
position, using the Digitalker on board the satellite." The satellite served
as a backup to more conventional navigation techniques, such as observing
the sun's position over time.
The expedition carried an off-the-shelf location transmitter that was
monitored by Soviet navigation satellites. Ground stations used those
signals sent by the transmitter, in conjunction with UO-11, to determine the
expedition's location and its progress across the Arctic wilderness.
Each morning the team would listen to UO-11 on their radios, hearing the
digital voice tell them their location. Meerman said a typical message would
include "Time 12 hours and 52 minutes GMT. You are at 84 degrees 25.6
minutes N and 95 degrees 58.2 minutes E." Thousands of schools and amateur
radio operators also followed the expedition's progress by listening to
UO-11.
In the mid-'80s, a fairly sophisticated setup was required to communicate
with UO-11, primarily a specialized "radio modem" that would hook up the ham
radio receiver to the computer. But now the modem can be replaced by a sound
card with a freeware program. Software can be used to listen to the tones
from the satellite and translate them back into information about battery
voltages, temperature and other data.
Anybody with a VHF radio and a computer with a sound card can monitor
UO-11's communications on 145.825 MHz -- no amateur radio license or special
permissions are required.
To commemorate UO-11's anniversary, the AMSAT-UK club is staging a contest.
If you hear UO-11's signal in March 2004, you're eligible to receive a
commemorative card. The reward may be an e-card, but the group has indicated
they're thinking about printing an actual postcard if there's enough
interest.
And Landsat 5, the main payload that was launched with UO-11? It's also
still running, but one of its scientific instruments has failed and the
other is somewhat degraded. But control operators are hopeful they can keep
it running for another couple of years.