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SOHO: On The Road To Recovery

European Space Agency
Press Release No 30-98
Paris, France				11 August 1998

SOHO: on the road to recovery

Six days after receiving the first signal from the dormant SOHO Spacecraft,
several blocks of telemetry data giving the spacecraft's on-board status
were acquired late Saturday night, 8 August, at 23:15 hrs GMT. Further data
acquisitions took place on Sunday 9 August and will continued in the
following days.

"This is the best news I've heard since we lost contact with SOHO on 25
June" said Roger Bonnet, ESA's Director of Science. "I never gave up hope of
some recovery of this fantastic mission. We should just hope that the damage
sustained by SOHO's enforced period of deep freeze does not affect the
scientific payload too much."

Following analysis of the expected on-board conditions by engineers from the
European Space Agency and Matra Marconi Space (builders of the SOHO
spacecraft) a series of command sequences was up-linked through the NASA
Deep Space Network (DSN) station at Goldstone,CA. These sequences were
designed to divert the available solar array power into a partial charging
of one of the on-board batteries.

After 10 hours of battery charging, the telemetry was commanded on and seven
full sets of data of the on-board status were received. After one minute
telemetry was switched off from ground controllers in order to preserve
on-board resources. Further details on the on-board conditions were obtained
the following day (Sunday 9 August) in two subsequent telemetry acquisitions
lasting four and five minutes respectively. Data gathered included
information on temperature and voltages for payload instruments, which are
currently being analysed.

With the battery charging technique proven successful, the team has
requested a full 24-hour coverage of SOHO to attempt a more complete
charging. The NASA DSN has accepted this request as a "Spacecraft Emergency"
giving it priority over other DSN scheduled activities. The procedure is
currently on-going.

ESA's Francis Vanderbussche, in charge of the SOHO Recovery Team at GSFC,
said "I am truly satisfied with the information the data we acquired gives
us. Conditions on-board are as good as we expected them to be". At the
moment the team is working on the next series of procedures which will be
aimed at thawing the on-board hydrazine fuel, currently at 0 C, to enable
attitude control of the spacecraft to be re-established. This will be
attempted once full charge can be established in both on-board batteries
later this week.

Radio contact with SOHO, a joint mission of ESA and NASA, was interrupted on
25 June 1998. The delicate recovery activities are being directed by the ESA
SOHO project team from the NASA Operation Centre at GFSC.

SOHO had completed its nominal two-year mission in April 1998. The
spacecraft has already achieved spectacular results concerning the dynamics
of the solar interior and has given a comprehensive view of the solar
corona. Its mission had recently been extended to 2003 to cover the upcoming
period of maximum solar activity expected to peak in 2001.

More information on SOHO, including mission status reports, is available on
the Internet at http://sohowww.estec.esa.nl or via the new ESA science
website: http://sci.esa.int

For further information please contact:

Franco Bonacina, ESA Headquarters
Paris, France
Tel. + 33 (0)1 5369 7713

Don Savage, NASA Headquarters
Washington, D.C.
Tel. + 1 202 358 1727 Bill

Steigerwald, NASA Goddard Spaceflight Center
Greenbelt, MD
Tel. + 1 301 286 5017

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