[meteorite-list] Phobos-Grunt Mars Probe Remains Silent in Earth Orbit

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sun, 13 Nov 2011 20:00:13 -0800 (PST)
Message-ID: <201111140400.pAE40DZ8008040_at_zagami.jpl.nasa.gov>

http://www.spaceflightnow.com/news/n1111/11phobosgrunt/

Phobos-Grunt Mars probe remains silent in Earth orbit
BY STEPHEN CLARK
SPACEFLIGHT NOW
November 11, 2011

Russia officially remained silent on the status of its beleaguered
Phobos-Grunt Mars probe Friday as concerns grew that the toxic
fuel-laden spacecraft could crash back to Earth by December.

Efforts to salvage the Phobos-Grunt mission Wednesday and Thursday were
unsuccessful, but the Russian space agency issued no updates on the
recovery following an initial statement after launch.

Phobos-Grunt is still circling Earth at an altitude between 128 miles
and 210 miles after launching Tuesday from the Baikonur Cosmodrome in
Kazakhstan.

After being shot into orbit by a Zenit rocket, the 29,000-pound
spacecraft was supposed to fire its engines twice to accelerate to
escape velocity, the speed required to overcome Earth's gravity and head
for Mars.

But neither rocket burn occurred, and Russian engineers don't know why.
Phobos-Grunt's rocket pack was scheduled to fire over South America, out
of range of Russian ground tracking sites.

Russia did not request support from European and U.S. communications
stations in the Americas before the mission, but ESA ground sites in
South America and Australia have been listening for radio signals from
Phobos-Grunt.

Phobos-Grunt was heading to the Martian moon Phobos, where it would
touch down, gather a half-pound of samples and return them to Earth in a
shielded re-entry capsule.

With no success so far in reviving the $163 million mission, experts are
more convinced Phobos-Grunt will crash somewhere on Earth in the next
few weeks. For now, Russia plans to keep trying.

Major General Vladimir Uvarov, a former space expert in the Russian
military, told the Rossiiskaya Gazeta newspaper he has lost optimism in
Phobos-Grunt's chances for recovery.

"In my opinion, the Phobos-Grunt probe has been lost. This probability
is very high. At any rate, it is much higher than the chances for
reactivating the probe," Uvarov told the newspaper.

Quoting an unnamed source in the Russian space industry, the RIA Novosti
news agency reported Friday engineers were unable to contact the probe
Wednesday or Thursday. A report by Anatoly Zak, a Russian space expert,
says Phobos-Grunt's low-gain antenna may be blocked by fuel tanks on the
craft's rocket pack. The tanks were supposed to be jettisoned after one
of the engine firings.

The two rocket burns that failed were scheduled to occur within five
hours after liftoff without input from the ground. The automated firing
sequence ran into a problem, and officials aren't able to diagnose it or
uplink any commands to recover.

Phobos-Grunt carries a main propulsion unit based on the Fregat upper
stage, a space tug that has amassed a successful track record delivering
satellites into high-altitude orbits above Earth. Designers added
auxiliary propellant tanks, extra insulation and made other
modifications for the long-distance journey to Mars.

It's also unclear whether Phobos-Grunt is alive and under its own
control. Observations from experienced satellite trackers indicate the
spacecraft has a steady brightness, meaning it could be stable and not
tumbling.

Ted Molczan, a respected Canadian satellite observing hobbyist, said
Friday that U.S. military tracking data showed Phobos-Grunt in a
slightly higher orbit, which could be the result of an intentional
maneuver. It's also possible the orbit change could be caused by venting
propellant.

If Russia not able to save the mission, it will succumb to atmospheric
drag and fall back to Earth by the end of the year.

With 11 tons of toxic hydrazine and nitrogen tetroxide propellant still
in its fuel tanks, Phobos-Grunt's potential re-entry is stirring
concerns of space experts after two high-profile returns of large
satellites in September and October.

NASA's Upper Atmospheric Research Satellite and Germany's ROSAT
spacecraft plummeted back to Earth in the last two months. Both
satellites fell harmlessly.

Phobos-Grunt is more than twice as massive as UARS and five times as
heavy as ROSAT, but like all satellites, it's more likely the probe will
fall in an ocean of unpopulated area.

Nicholas Johnson, an orbital debris expert at NASA, said it is difficult
to compare Phobos-Grunt's potential re-entry with UARS or ROSAT.

"NASA predicts that in its current condition Phobos-Grunt will not
re-enter until next month, possibly even late December," Johnson told
Spaceflight Now in an email. "This is dependent upon solar activity and
the attitude/stability of the spacecraft. As the re-entry gets closer,
the uncertainty in the re-entry prediction will likewise become smaller."

The fate of Phobos-Grunt's toxic propellant is also an issue. It could
add to the risk of the re-entry if it fell in a populated area.

"If the Phobos-Grunt propellant tanks are aluminum, they will probably
burn up and dissipate the propellants, whether they are liquid or
frozen," Johnson said.

Phobos-Grunt also has a capsule with a heat shield designed to return
rock samples from Phobos, which could survive re-entry.
Received on Sun 13 Nov 2011 11:00:13 PM PST