Some good news for solar astronomy.
Walt Williams, 98.10.15
Date: Wed, 14 Oct 1998 17:10:25 -0400 (EDT)
Subject: SOHO IS NEARLY BACK IN BUSINESS
Headquarters, Washington, DC October 14, 1998
Goddard Space Flight Center, Greenbelt, MD
European Space Agency Headquarters, Paris, France
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:
"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
The MDI image can be found at:
The latest SOHO EIT images can be found on the Web at:
Details about the operations and about SOHO in general, can be
Information on the recovery of SOHO can be found at:
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