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 22nd 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 the camera.
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 20th.
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 12th, 1997. All systems on the spacecraft continue to be in excellent condition.
Status report prepared by:
Office of the Flight Operations Manager
Mars Surveyor Operations Project
NASA Jet Propulsion Laboratory
California Institute of Technology
Pasadena, CA 91109