This story was updated at 5:17 p.m. EST.
While the
unprecedented smashup between a U.S. and Russian satellite earlier this month
sparked a lot of attention, another wayward spacecraft — out-of-whack U.S.
secret satellite DSP-23 — remains a serious concern.
Lofted into
orbit in November 2007, this Defense Support Program (DSP) spacecraft apparently
went belly-up the following year. Making matters worse, DSP-23 died before
it could be nudged into a graveyard orbit, where it would no longer be a collision threat for other satellites.
The
satellite is one of a constellation of Earth-staring spacecraft designed to
spot orbits rocket launches, nuclear blasts, as well as gather other types of
technical intelligence from their 22,300-mile (35,888-km) geosynchronous (GEO).
Last month,
space reporter Craig Covault at Spaceflight Now broke the story that two
Micro-Satellite Technology Experiment (MiTEx) satellites were dispatched to
peek in on the errant satellite. Of course, mum's the word from the U.S.
military on the DSP-23's off-kilter status.
But,
fingers are crossed at SES ASTRA — operator of the ASTRA Satellite System that
provides satellite services in Europe — regarding the meanderings of DSP-23.
The
misbehaving DSP-23 spacecraft has
"visited" ASTRA satellites for the last two months. That SES ASTRA system
is used by a wide range of broadcast and multimedia companies to deliver
revenue generating broadcast and broadband services to 117 million households.
"It will be
of concern for many other positions...for a very long time," said Hugues Laroche
of SES Engineering. "As operators of GEO satellites I guess we are still
exposed to lower
risks of collision probabilities than low Earth orbits, but still this is a
concern," he told SPACE.com.
That's
especially the case, Laroche added, since the GEO ring is such a tiny resource.
When a satellite dies prematurely there, it remains in the vicinity for a long
time...with a longitude swing on one hand and an inclination drift on the other,
he said.
Laroche
said it's time for the actors in the satellite field "to stop acting each one
on their side." Rather, there's need to increase coordination, he concluded.
Spacecraft
drift
Meanwhile,
a loosely knit — but high-tech — group of amateur
satellite detectives has been keeping tabs on the orbital wandering of
DSP-23.
For example, skywatcher Ted Molczan of Toronto, Canada, has used a computer
program developed by fellow hobbyist Mike McCants to predict DSP-23's orbit
through 2051, to chart the spacecraft's drift — a plot that tracks the satellite's oscillation between longitude extremes over a long period of time.
"Currently,
DSP-23's orbit is inclined about 2.8 degrees, which is slowly decreasing, such
that by 2012, it will be inclined just 0.3 deg, whereupon it will begin to
increase," Molczan told SPACE.com. "By 2015, it will have returned to
its present inclination."
Since many,
if not most, operational GEO satellites have similarly small inclinations, this
means that DSP-23 will remain in their immediate vicinity for at least the next
six years, Molczan said. By about 2036, the spysat's inclination will rise to
about 15 degrees, which will reduce the time it spends in close proximity to
operational GEO satellites, he added.
"But
decades later, its inclination will return to its present small value,
increasing the hazard it poses to operational satellites of that time. This
long-term oscillation in inclination will continue for a very long time,"
Molczan said.
Close
encounters
Molczan
spotlights the efforts of his satellite watching colleagues, Greg Roberts of
South Africa and Peter Wakelin of the U.K., since they performed a load of hard
work to track DSP-23 during its time in the eastern hemisphere.
Roberts
used a collection of sophisticated gear to observe DSP-23, though his sightings
suggest that nothing too dramatic is happening to the satellite.
"It has speeded
up its eastward drift... but that's because of natural causes as I don't think
the satellite is under any form of human control," Roberts told SPACE.com.
The two
MiTEx micro-satellites inspectors, Roberts added, are both drifting eastward
and are now too low in his eastern sky to track optically.
"I haven't
heard anything about the results of their inspections in late December 2008 and
early January 2009," Roberts said. "Since then, the two MiTEx satellites have
not changed their orbits so either the operators are happy to leave them in
their current drifting orbits or the satellites are no longer operable —
probably the former.
"Of course
DSP-23 continues on its course and passing close to operational craft quite
frequently...from what I have heard, the closest approach so far has been just
under 12 kilometers (7.5 miles)," Roberts said.
Other than
tracking DSP-23 as a matter of course, Roberts pointed out that the amateur
network is not keeping a look-out for "close encounters" with other spacecraft.
Half of
these occur in the daylight hours in this part of the world so could not be
seen even if there was a possible chance of collision, he said.
"I don't
know if the U.S. Department of Defense is alerting commercial operators of the
possible need to move craft," Roberts said.
But he
would imagine such groups as the International Scientific Optical Network
(ISON), a far flung group of scientific optical facilities for observation of
high altitude geocentric orbit, is busy keeping an eye on all the celestial
action. Network data collecting and crunching is done at the Keldysh Institute
of Applied Mathematics of the Russian Academy of Sciences.
Leonard
David has been reporting on the space industry for more than four decades. He
is past editor-in-chief of the National Space Society's Ad Astra and Space
World magazines and has written for SPACE.com since 1999.
advertisement
