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1993-06-04
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MAGELLAN STATUS REPORT May 25, 1993 8:30 PM PDT
The Magellan spacecraft started its Transition Experiment this
morning at 10:31 AM PDT with an Orbit Trim Maneuver which lowered its
periapsis (closest approach to Venus) to 149.4 km. Telemetry indicated
that the 11.3 minute burn of the thrusters was normal, and the resulting
periapsis altitude was 149.7 km. Following the first atmospheric drag
pass, all subsystems were reported to be nominal. Temperatures of the
solar panels increased by about 7 to 9 degrees C as a result of
atmospheric friction. This is about half the expected value. The
attitude control system generated about 2800 thruster pulses as the
control shifted from reaction wheel control to thrusters and back during
the pass. Much of this activity is caused by the residual momentum from
the wheels being transferred to the body of the craft. Power and Telecom
were nominal. Nearly identical telemetry measurements were received
following the next two drag passes (Orbits 7628, 7629). During the next
four days a series of walk-in trim maneuvers will further lower the
periapsis until the spacecraft is in the desired corridor. Based on the
present navigation and spacecraft data, the next two OTMs (Orbit Trim
Maneuvers) will be the "double down" magnitude. The first of the corridor
-adjustment OTMs is scheduled for 5:46 AM PDT tomorrow.
Ron Baalke Jet Propulsion Lab Pasadena, CA 91109
MAGELLAN STATUS REPORT May 27, 1993 3:00 PM PDT
The Magellan Transition Experimet continues as the flight team carefully
maneuvers the spacecraft toward the desired aerobraking corridor. The
second "double down" trim maneuver was performed at 2:07 PM PDT today to
lower the periapsis to 143 km. At the Mission Director meeting early this
afternoon, a "single down" OTM was approved for execution on Saturday.
This will lower the periapsis by 1.6 km. All spacecraft subsystems
continue to report nominal performance. There have been some difficulties
with transfer of 1200 bps telemetry between JPL and Denver. On the incident
of orbit 7638 last night, Attitude Control estimates that the spacecraft
performed the drag pass about 120 deg.off the proper attitude. Spacecraft
systems responded as designed and there was no damage to the craft. The
solar panels were facing the sun and stayed near 85 degrees C.(instead of
cooling to 25 and then warming to 39 during the drag pass). Attitude
control stayed in phase plane D, and used about 0.046 kg of fuel during
the pass. From orbit 7639 on the spacecraft performance has been normal.
Ron Baalke Jet Propulsion Lab Pasadena, CA 91109
MAGELLAN STATUS REPORT May 27, 1993 10:00 AM PDT
The Magellan Transition Experiment continues as the flight team
carefully maneuvers the spacecraft toward the desired aerobraking corridor.
The spacecraft has now made fifteen atmospheric drag passes with periapsis
below 150 km and all subsystems were reported to be nominal. As the
spacecraft approaches the low part of the orbit, the attitude control
system switches from reaction wheel control to the thrusters. Depending
on the amount of attitude error when this switch occurs, the thrusters
have used from 0.013 to 0.023 kg of fuel to maintain the position within
10! of the velocity vector. The expected fuel consumption is 0 to 0.3 kg
per orbit. Shortly before orbit 7638 last night, an update to the
periapsis time table was sent to Magellan. An error in the coded data was
rejected by the on-board computer, and the spacecraft apparently went
through the atmospheric drag pass in the wrong attitude. Spacecraft
systems responded as designed and there was no damage to the craft. The
solar panels were facing the sun and stayed near 60 degrees C.(instead of
cooling to 25 and then warming to 39 during the drag pass). Attitude
control stayed in phase plane D, and used about 0.046 kg of fuel during
the pass. From orbit 7639 on the spacecraft performance has been normal.
Based on the present navigation and spacecraft data, the next OTM (Orbit
Trim Maneuver) will be the "double down" magnitude. The second of the
corridor-adjustment OTMs is scheduled for 2:07 PM PDT today.
Ron Baalke Jet Propulsion Lab Pasadena, CA 91109
PUBLIC INFORMATION OFFICE JET PROPULSION LABORATORY CALIFORNIA
INSTITUTE OF TECHNOLOGY NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
PLANETARY MISSION STATUS May 27, 1993
GALILEO: The spacecraft is now en route to Jupiter, scheduled to
enter orbit December 7, 1995. Spacecraft performance and condition are
excellent except that the high-gain antenna is only partly deployed;
science and engineering data are being transmitted via the low-gain
antenna. The mission team is planning to use the low-gain antenna for
the Jupiter mission and for the encounter August 28, 1993 with asteroid Ida.
Galileo was launched October 18, 1989, flew by Venus in 1990 and Earth in
1990 and 1992 for gravity assists, and flew by asteroid Gaspra in October
1991 for scientific observation. Contact: Jim Wilson, (818) 354-5011.
MAGELLAN: The Magellan spacecraft has concluded its eight-month
survey of the gravitational field of Venus from its elliptical orbit.
On May 25, flight controllers began an 80-day program to lower and
circularize the spacecraft's orbit by aerobraking, dipping into Venus's
upper atmosphere each orbit. Magellan was launched May 4, 1989 and
radar-mapped more than 98 percent of Venus's surface from September 1990
to September 1992. Contact: Jim Doyle, (818) 354-5011.
MARS OBSERVER: Spacecraft health and performance are normal, after
several episodes in which it entered contingency mode, a safe state
triggered by the spacecraft computer because of attitude-reference
anomalies. A software fix has solved the problem. Mars Observer is
scheduled to enter Mars orbit August 24, 1993; it will be moved into a
mapping orbit by November 8 and science operations are planned to start
November 22. Mars Observer was launched September 25, 1992.
Contact: Diane Ainsworth, (818) 354-5011.
TOPEX/POSEIDON: The satellite is healthy, and all scientific instruments
are performing normally, typically providing three playbacks per day. The
mission is mapping ocean circulation. TOPEX/Poseidon was launched August
10, 1992. Contact: Mary Hardin, (818) 354-5011.
ULYSSES: The spacecraft is in a highly inclined solar orbit now 31.7
degrees south relative to the Sun's equator, in transit from its Jupiter
gravity assist in February 1992 toward its solar polar passages (about 80
degrees south and north) in 1994 and 1995. Spacecraft condition and
performance are excellent, with Ulysses gathering data on the heliosphere
-- the realm dominated by the solar wind, a stream of charged particles
flowing from the Sun. The Ulysses spacecraft was built by the European
Space Agency and launched October 6, 1990.
Contact: Diane Ainsworth, (818) 354-5011.
VOYAGER 1 and 2: The two Voyager spacecraft have detected low-frequency
radio emissions believed to originate at the boundary between the solar
wind and the interstellar medium, called the heliopause. Detection and
measurement of this boundary is the principal goal of the Voyager
Interstellar Mission. Voyager 1, launched September 5, 1977, is currently
7.8 billion kilometers (4.8 billion miles) from the Sun after flying by
Jupiter and Saturn in 1979 and 1980; Voyager 2, launched August 20, 1977,
to fly by Jupiter (1979), Saturn (1981), Uranus (1986) and Neptune (1989),
is now 6 billion kilometers (3.7 billion miles) from the Sun.
Contact: Mary Hardin, (818) 354-5011.
Ron Baalke Jet Propulsion Lab Pasadena, CA 91109
VOYAGER HELIOPAUSE DIAGRAM May 28, 1993
A GIF image of the Voyager heliopause diagram is now available at the JPL
Info public access site. Note that the image is in GIF89a format, so make
sure your display software supports this format (as opposed to the older
GIF87a format). The image is available by dialup modem at
+1 (818) 354-1333, up to 9600 bps, parameters N-8-1 (will be moved to
the images directory in 30 days) file: vgrhelio.gif
Ron Baalke Jet Propulsion Lab Pasadena, CA 91109