A
student-built satellite experiment shattered records by deploying the longest
space tether ever flown in space, but the missing return capsule remains a
mystery to unravel months later.
On Sept.
25, hundreds of students worldwide watched remotely as a Russian-built Foton-M3
spacecraft began unwinding a 19.7-mile-long (31.7 km) super-strong space tether
no thicker than a string. The experiment's small Fotino capsule dropped from it
toward Earth, preparing to release at the right moment for re-entry into the
atmosphere.
The goal
was to demonstrate a
"space mail" system of delivering packages to Earth using
just a tether.
But the
experiment hit
a snag when critical telemetry sensors on the tether deployment mechanism
shut down. That left the onboard computer unable to control how quickly the
space tether unwound from its spool. Early data suggested the tether reached a
length of just 5.3 miles (8.5 km) before cutting the Fotino capsule loose.
"We
were kind of disappointed by the fact," said Marco Stelzer, a mission
analyst and ground support engineer with the European Space Agency (ESA).
Steizer
joined the Young Engineers Satellite (YES2) experiment – sponsored by the ESA
Education Office – as a university student when he saw the tether idea promoted
by Delta Utec SRC, a private space consultancy company that contracted with
ESA. Almost 500 students from Europe, the United
States, Russia, Japan, and Australia worked on YES2.
Hope
revived
New telemetry
data from the Foton spacecraft saved students from a mission cliffhanger,
revealing that the space tether deployment had accelerated rather than slowing
down as first thought.
"Later
on, we found out that the tether deployed to its full length, even more than
originally planned," Stelzer told SPACE.com.
Additional
data from the U.S. Space Surveillance Network showed that the Foton spacecraft
moved close to a mile higher in orbit when the capsule cut free – as expected
when a 19.7-mile-long tether's swinging momentum that launched the capsule also
transfers to the much heavier spacecraft.
Where's
the capsule?
Having
smashed the world record for the longest man-made object flown in space, the
YES2 team turned its attention to what happened with the Fotino capsule. The
onboard beacon had failed to activate and signal the capsule's final location.
"We
have some confidence that the capsule actually came down," said Stelzer,
pointing out that a full-length tether deployment would have released the
capsule back into Earth's atmosphere. A U.S.
ground station in Alaska did not detect Fotino flying
overhead after the tether release, also suggesting the capsule re-entered
instead of continuing in a low-Earth-orbit with the Foton spacecraft.
"It may
have burnt up on re-entry, it may have crash-landed, it may have touched down
in difficult terrain somewhere in Turkmenistan, Kazakhstan or Siberia, or its radio beacon did not transmit," said Roger
Walker, YES2 project manager for ESA's Education Office, in a public statement.
More information will come in the next several weeks from other experiments and
sensors onboard Foton.
Whatever Fotino's
fate, the YES2 team cheered the test of the "space mail" delivery
system using the space tether – even if the package was lost along the way.
"We
proved that tether technology actually works," Stelzer said.
Future
space tethers might not only deliver parcels to Earth, but also swing
spacecraft or satellites into different orbits or towards other planets.
The ESA
Education Office has additional satellite projects in development, including
the European Student Earth Orbiter (ESEO) planned for 2010 and the European
Student Moon Orbiter (ESMO) planned for 2011.
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