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Space station glitch possibly caused by solar flare
By Tariq Malik
HOUSTON -- A glitch in the International Space Station’s (ISS)
U.S.-built attitude control system may have its root in a massive solar
flare that erupted from the Sun this week, a NASA flight director said
Friday.
“The leading theory right now is that the additional solar activity
has taken the normal density of the [Earth’s] atmosphere and it's
about two and a half times more than it normally is,” ISS flight
director Joel Montalbano said during a morning update here at the Johnson
Space Center. “So we’re seeing some problems with our software
converging on a nice stable attitude for attitude control.”
The space station typically relies on four large gyroscopes —
one of which is currently offline—that spin to maintain attitude
control without consuming precious propellant.
Only two gyroscopes are required to maintain ISS orientation with the
system. The station is also equipped with Russian thrusters and can be
oriented by docked spacecraft, such as Russian Soyuz and Progress vehicles,
as well as NASA shuttles.
NASA flight controllers opted to use the space shuttle Discovery’s
thrusters to orient the ISS on Thursday until the non-propellant mode
is reactivated, Montalbano said.
“So what we’ll do is that solar activity is dying down and
were going to try again to go to a non-propulsion mode later today,”
Montalbano said, adding that Discovery is well stocked with propellant
to help control ISS attitudes through the two spacecraft’s docked
STS-116 mission operations. “We think we understand the problem.”
To date, solar activity has not endangered the astronauts and their
ISS counterparts in any way, though they did take precautions earlier
this week to be safe. Spacewalking astronauts mentioned the solar flare
may have led to some stunning auroras they spotted while working outside
the ISS on Thursday.
Flight controllers mentioned the solar flare’s effects in the
morning mail to Discovery’s STS-116 crew.
“Isn’t it interesting that solar winds appear to be affecting
your flight!” flight controllers relayed up to the shuttle astronauts.
“We hope that all of you take a little time today to catch your
breath and to look out the window in order to store future memories.”
While NASA might not seem overly concerned about the recent solar activity,
European Space Agency (ESA) mission controllers have taken steps to avoid
damage to spacecraft after several of them began acting strangely shortly
after the flares.
"We saw three anomolies on December 13," said Juergen Volpp,
Spacecraft Operations Manager for ESA's Cluster mission, which uses four
identical spacecraft to study the Earth's magnetosphere.
"Cluster 1 had a minor instrument anomoly, while Cluster 2 and
4 had on-board systems affected," Volpp said.
Other ESA missions, including Envisat and Integral, also appeared to
be affected. In all three cases, steps were taken to protect the spacecrafts'
sensors.
http://www.space.com/missionlaunches/
061215_sts115_issflare.html
Our thanks to Mike Terry for
directing us to this article
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