Дата: 26 марта 1998 (1998-03-26)
От: Alexander Bondugin
Тема: STARDUST Update - March 20, 1998
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STARDUST Status Report
March 20, 1998
Ken Atkins
STARDUST Project Manager
Assembly, Test, and Launch Operations (ATLO) activities: Propulsion testing
was completed. The Pyro Initiator Unit (PIU) also completed testing. As
noted last week, this element of the electric power subsystem triggers the
various releases and deployments during the mission (e.g. Sample Return
Capsule (SRC) separation from the spacecraft.)
Testing of the SRC continued to go very well. The acoustic test , validating
compatibility with the environmental frequencies representative of the
launch vehicle, was successfully completed. The SRC was moved to the thermal
vacuum test facility and the functional tests run.
The flight solar array, the unit that converts sunlight to electricity for
powering the Stardust spacecraft, completed its pre-ship review at
Lockheed-Martin Sunnyvale. Shipment to Denver is set for March 23.
More good news on the Inertial Measurement Unit (IMU ) that helps control
the spacecraft's attitude in space: The leak tests were consistent with
lifetime requirements. The results show good margin for the STARDUST
application.
Opportunity and Outreach: One of our educational outreach partners, the
JASON Foundation, affiliated with Dr. Robert Ballard, the discoverer of the
Titanic, began broadcasting of their annual event this week. The broadcast
will run from March 16th to March 27th, and includes a segment mentioning
STARDUST. The broadcast will be viewed by 1 million children and teachers
from JASON's electronic satellite sites, classroom locations, or Internet
connections. Special viewing for Congress, their staffers and families are
to be held this Saturday, March 28, 10 am, 11:30 am, and 1 PM EST, at the
National Geographic site in Washington D.C.
For more information on the STARDUST mission - the first ever comet sample
return mission - please visit the STARDUST home page:
http://stardust.jpl.nasa.gov/
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Дата: 26 марта 1998 (1998-03-26)
От: Alexander Bondugin
Тема: Galileo Update - March 25, 1998
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MEDIA RELATIONS OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
http://www.jpl.nasa.gov
Galileo Europa Mission Status
March 25, 1998
NASA's Galileo spacecraft is sending to Earth the final
pictures and science information stored on its onboard tape
recorder during the December 1997 flyby of Jupiter's moon Europa.
These data include an observation of a region on Europa with
wedge-like features, which may indicate that a liquid ocean lies
under the surface, and another observation of volcanic activity
on Jupiter's moon Io. An observation by the photopolarimeter
radiometer is part of a series designed to look for hot spots
which might offer evidence that a heat source on Europa led to
the creation of a liquid ocean or slush.
The flight team is preparing for Galileo's next Europa
flyby, scheduled for Sunday, March 29, at an altitude of about
1,645 kilometers (1,022 miles). A flight path correction was
performed on Friday, March 13, and an attitude update was
performed Thursday, March 19. Both events went well, even though
they used the gyroscopes, the known cause of recent anomalous
behavior of the attitude control system. Precautions were taken
to prevent the gyroscope anomaly from affecting activities. The
flight team has decided the upcoming Europa flyby will be
performed without the gyros. This means there will be no way to
compensate for any wobble that may be present in the spacecraft's
spin axis, and instrument pointing and stability are likely to be
degraded somewhat. Only very minimal effects on images taken by
the spacecraft's camera are expected, with a somewhat greater
impact anticipated for another instrument, the near infrared
mapping spectrometer.
On Thursday, March 26, Galileo will perform its final flight
path correction before Sunday's Europa flyby, and the flight team
will send computer commands to control all spacecraft activity
during the encounter period. Regular maintenance of Galileo's
onboard tape recorder will be performed Friday.
Galileo's flight team is nearing completion of modifications
to the attitude control system flight software that would allow
the spacecraft to operate with only one gyro. Although this
won't be a complete "fix," it will eliminate the need for
workarounds currently being used for maneuvers and attitude
updates.
The recent anomalies may be caused by Galileo's long-term
exposure to Jupiter's intense radiation. The spacecraft
successfully completed its primary mission in December 1997 and
is now in its two-year extension, the Galileo Europa Mission.
The flight team will continue to monitor the radiation's impact,
but current plans include five more Europa flybys, four Callisto
encounters, and one or two of Io, depending on spacecraft health.
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