UPDATE # 20 - February 7, 1997
PART 1: Next WebChat
PART 2: Mars Pathfinder Mission Status Report
PART 3: Mars Global Surveyor Flight Status
PART 4: Subscribing & Unsubscribing: How to
On Tuesday, February 11, from 10-11 a.m., PST, Mike Mellon from
NASA's Ames Research Center in Mountain View, California, will be
joining us. Water on Mars has attracted a great deal of interest from
scientists, including Mike. His work focuses primarily on studying
martian geology and climate, and as a link between these two,
water. Mike is investigating where water on Mars could be located.
Check out Mike's biography at: http://quest.arc.nasa.gov/mars/team
Please join us! RSVP to Andrea by sending a brief Email note to
firstname.lastname@example.org. This RSVP is very important, as it will
allow us to ensure that the chatroom does not become too crowded.
MARS PATHFINDER MISSION STATUS REPORT
February 4, 1997
The Mars Pathfinder spacecraft is currently 19 million km (11
million miles) from Earth traveling at 30 km/s on its trajectory to
Mars. All spacecraft subsystems continue to operate as expected.
At 5:00 p.m., PST on February 3, we successfully completed our
second Trajectory Correction Maneuver. This maneuver was designed
to correct errors in the first TCM performed on January 9, and move
us closer to our final trajectory. The spacecraft will not be placed
on a Mars atmospheric entry trajectory until after TCM-3
(currently scheduled for May 5) because of planetary quarantine
requirements. The TCM-2 design team, led by Flight Engineer Guy
Beutelschies, developed a two-part approach to perform the
maneuver. In the first part, the spacecraft fired two of its forward-
facing thrusters continuously for five minutes. The change in
velocity for this "axial" component was about 1.5 m/s. The second
part of the maneuver was a smaller velocity correction of 0.1 m/s
performed in the "lateral" mode. In this mode, the spacecraft pulses
all four thrusters on one side of the spacecraft for five seconds.
This pulse causes a small change in the spacecraft velocity in the
direction perpendicular to the spacecraft spin axis. This mode will
be used for all future maneuvers, so TCM-2 was a good proof-of-
concept test. Early analysis of tracking data from NASA's Deep Space
Network indicates that both components were completed
Upon completing the maneuver, the spacecraft's spin axis was turned
15 degrees back toward Earth so that we can perform radio
navigation more effectively. The spacecraft is currently pointed
about 5 degrees from Earth and 2 degrees from the Sun. We will
remain In this attitude until late March.
The spacecraft will remain in a relatively quiescent mode for the
next two to three months. The flight team is currently working hard
to complete planning for Mars entry and surface operations.
For more information, please visit our website at
MARS GLOBAL SURVEYOR FLIGHT STATUS
[Editor's note: This status report on the Mars Global Surveyor
mission was prepared by the Office of the Flight Operations Manager,
Mars Surveyor Operations Project, Jet Propulsion Laboratory.]
Friday, 31 January 1997
Early Monday morning, flight controllers sent several commands to
Surveyor that deactivated the Mars Orbiter Camera's 53-Watt
bakeout heater. This heater was activated on Wednesday, January 22
to remove residual moisture in the camera's graphite epoxy
structure. If the bakeout had not been performed, the moisture in the
camera's tube-like structure would have slowly leaked into space
and caused its length to gradually change. As a consequence, this
tiny, slow-rate change in the structure's length would have resulted
in a gradual shift in the focus of the camera during science
operations. The goal of the bakeout was to remove all of the
moisture at once in order to stabilize the focus of thecamera.
Originally, the bakeout was scheduled to last for 60 days. This
duration was subsequently reduced to 14 days last Wednesday when
data from the camera suggested that the structure contained
significantly less moisture than predicted. Upon request from the
camera team, the flight operations manager made the decision to
terminate the bakeout after only six days. The concern is that baking
the camera for longer than necessary would be detrimental to the
camera's focusing capability.
In several weeks, the camera will image stars over a one-week
period for the purpose of acquiring focus calibration images. These
images will be compared to the star images taken before bakeout in
order to assess the best focus settings for the camera.
Other activities this week included a two-hour radio-science
calibration that occurred Thursday morning, just after midnight.
This test involved using the spacecraft's ultra-stable oscillator to
control the frequency or "tone" of Surveyor's radio transmissions to
Later on Thursday, flight controllers sent a command that activated
a flange heater located near Surveyor's main rocket engine. The
heater will gradually increase the pressure of the nitrogen tetroxide
inside the oxidizer tank. As a consequence, the increase in oxidizer
pressure will improve the efficiency of the propellant during the
second trajectory correction maneuver. This maneuver is currently
scheduled for March 20.
After a mission-elapsed time of 85 days from launch, Surveyor is
19.29 million kilometers from the Earth, 116.49 million kilometers
from Mars, and is moving in an orbit around the Sun with a velocity
of 29.83 kilometers per second. This orbit will intercept Mars on
September 12, 1997. All systems on the spacecraft continue to be in
SUBSCRIBING & UNSUBSCRIBING: HOW TO DO IT!
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