Дата: 02 февраля 1998 (1998-02-02)
От: Alexander Bondugin
Тема: Lunar Prospector Update - January 29, 1998
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Lunar Prospector Mission Status Report #16
January 29, 1998
7 p.m. EST (4:00 p.m. PST)
The Lunar Prospector spacecraft continues to
operate well according to Mission Control at NASA_s
Ames Research Center. The current state of the
vehicle (as of 0000 GMT [Zulu] on Jan. 30),
according to Mission Operations Manager Marcie
Smith, is as follows:
Spacecraft Orbit Number: 211
Data Downlink Rate: 3600 bps
Spin Rate: 11.94 rpm
Spin Axis Attitude:
Longitude 250.7 degrees
Latitude 89.2 degrees
Trajectory:
Periselene: 86 km
Aposelene: 114 km
Period: 118 minutes
Occultations: 43 minutes duration
Eclipses: 30 minutes duration
On Wed. Jan. 28 at 23:48 GMT, five (5)
configuration commands were sent to the
Magnetometer/Electron Reflectometer instrument box.
Lunar Prospector is in its second week of mapping
orbit operations and has transitioned into a
production mode. Now, telemetry and orbit ephemeris
products are routinely generated in support of
science data processing. While Lunar Prospector has
no onboard tape recorders, it stores up to 53
minutes of data in solid state memory and
continuously replays that delayed stream of data,
along with the real-time stream. This provides
access (that would otherwise be unavailable) to
data collected during ground station occultations
-- when the spacecraft passes behind the moon as
viewed from Earth.
LP telemetry contains measurements made by each
science instrument at regular intervals. Knowing
the time of the measurements and having an orbit
ephemeris indicating where the spacecraft was at
those times, allows scientists to compile a history
of measurements over each region of the moon. A
very large number of measurements is required since
the various data signals being measured by each
instrument are low in power and high in noise
level. It is only by taking a large number of such
measurements that the noise on the signal can be
"averaged out" (since, typically, such noise is
random in nature), leaving only the true
measurement behind.
Having successfully placed Lunar Prospector into
the required mapping orbit and having checked out
the spacecraft, scientists and engineers are now
focusing the bulk of their attention on the
important task of science data collection and
processing (while, of course, continuing to monitor
spacecraft health and other relevant vehicle and
mission parameters).
David Morse
Ames Research Center
Moffett Field, CA 94035
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