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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 do it!


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
andream@quest.arc.nasa.gov. This RSVP is very important, as it will
allow us to ensure that the chatroom does not become too crowded.

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 successfully. 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 http://mpfwww.jpl.nasa.gov

[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 the Earth. 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 excellent condition.

SUBSCRIBING & UNSUBSCRIBING: HOW TO DO IT! If this is your first message from the updates-lfm list, welcome! To catch up on back issues, please visit the following Internet URL: http://quest.arc.nasa.gov/mars/updates To subscribe to the updates-lfm mailing list (where this message came from), send a message to: listmanager@quest.arc.nasa.gov In the message body, write these words: subscribe updates-lfm CONVERSELY... To remove your name from the updates-lfm mailing list, send a message to: listmanager@quest.arc.nasa.gov In the message body, write these words: unsubscribe updates-lfm If you have Web access, please visit our "continuous construction" site at http://quest.arc.nasa.gov/mars


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