SOHO Is Nearly Back In Busines
Ron Baalke
Headquarters, Washington, DC October 14, 1998
(Phone: 202/358-1727)
Bill Steigerwald
Goddard Space Flight Center, Greenbelt, MD
(Phone: 301/286-5017)
Simon Vermeer
European Space Agency Headquarters, Paris, France
(Phone: 33-1-5369-7155)
RELEASE: 98-190
SOHO IS NEARLY BACK IN BUSINESS
High-quality new pictures of the Sun, taken earlier this
week from the Solar and Heliospheric Observatory (SOHO), have
raised hopes that the mission may soon be returned to scientific
operations. Engineers have successfully reactivated nine of the
12 instruments on the European Space Agency (ESA)/NASA SOHO
mission, which has been out of commission for nearly four months
after contact was lost on June 24.
Images from the Michelson Doppler Imager and the Extreme
Ultraviolet Imaging Telescope on SOHO are posted on the Internet
at: http://sohowww.nascom.nasa.gov
"Scientists on both sides of the Atlantic have waited
anxiously for the recovery of SOHO," commented Roger Bonnet, ESA's
director of science. "Thanks to the extraordinary determination
and skill of ESA and NASA personnel, with industrial contractors
and scientific teams also playing their part, the world has
recovered its chief watchdog on the Sun. SOHO is needed more than
ever, because the Sun is rapidly becoming stormier with a mounting
count of sunspots."
"It's very exciting to see these images again after so
many weeks of concern. We hope that all the SOHO scientific
instruments can be returned to the same level of health, so we can
resume normal scientific operations in the near future," said Dr.
Joseph Gurman, the U.S. project scientist for SOHO, and co-
investigator on the Extreme Ultraviolet Imaging Telescope (EIT).
"As of today, nine of the 12 instruments on board SOHO
have been turned on. Four of them are already fully functional;
the other five are still undergoing careful recommissioning
activities. But so far no signs of damage due to thermal stress
during the deep freeze have been detected. I tip my hat to the
engineers who built this spacecraft and these sensitive but robust
instruments," said Dr. Bernhard Fleck, the ESA project scientist
for SOHO. The remaining three instruments will be switched on
over the next few weeks..
The images are the latest success for the team during a
complex, challenging recovery sequence. On July 23, SOHO was
located using radar techniques with the 305-meter Arecibo, Puerto
Rico, radio telescope of the U.S. National Astronomy and
Ionosphere Center as a transmitter and a 70-meter dish of the NASA
Deep Space Network as a receiver. SOHO first responded to radio
transmissions on August 3, and telemetry from SOHO was received
August 8, telling controllers the condition of the spacecraft and
its instruments. The spacecraft's frozen hydrazine fuel was
gradually thawed, and on September 16, SOHO's thrusters were fired
to stop its spin and to place it in the correct orientation
towards the Sun.
Prior to the interruption, instruments on SOHO had taken
about two million images of the Sun, an activity representing over
a terabyte (a trillion bytes) of data. After its launch on Dec.
2, 1995, SOHO revolutionized solar science by its special ability
to observe simultaneously the interior and atmosphere of the Sun,
and particles in the solar wind and the Sun's outer atmosphere.
SOHO observations have been the subject of more than 200
papers submitted to refereed, scientific journals. Apart from
discoveries about flows of gas inside the Sun, giant "tornadoes"
of hot, electrically charged gas, and clashing magnetic field-
lines, SOHO also proved its worth as the chief watchdog for the
Sun, giving early warning of eruptions that could affect the
Earth.
SOHO operates at a special vantage point 1.5 million
kilometers (about one million miles) out in space, on the sunward
side of the Earth. The spacecraft was built in Europe and it
carries both European and American instruments, with international
science teams. SOHO was launched on an Atlas IIAS rocket and is
operated from NASA's Goddard Space Flight Center in Greenbelt,
Maryland.
In April 1998, SOHO's scientists celebrated two years of
successful operations and the decision of ESA and NASA to extend
the mission to 2003. The extension enables SOHO to observe
intense solar activity, expected when the count of sunspots rises
to a maximum around the year 2000.
- end -
The first EIT image taken in the Fe IX/X line at 171 A is
available at:
http://sohowww.estec.esa.nl/operations/Recovery/eit_171_981013.gif
and
http://sohowww.nascom.nasa.gov/operations/Recovery/eit_171_981013.
gif
The MDI image can be found at:
http://soi.stanford.edu
The latest SOHO EIT images can be found on the Web at:
http://umbra.nascom.nasa.gov/eit/eit_full_res.html
Details about the operations and about SOHO in general, can be
found at:
http://sohowww.estec.esa.nl
and
http://sohowww.nascom.nasa.gov
Information on the recovery of SOHO can be found at:
http://sohowww.nascom.nasa.gov/operations/Recovery//operations/Rec
overy/
* * *