On Monday of this week, Surveyor's flight team activated the Mars Orbiter Camera in preparation for four days of star imaging. Once per afternoon from Tuesday through Friday, the spacecraft turned to point the camera at a cluster of stars called the Pleiades. Over the course of one hour on each imaging day, the camera observed stars within the cluster in order to perform focus checks.
Communications with the spacecraft during star imaging was not possible because the star-pointed orientation resulted in pointing the high-gain antenna away from the Earth. Consequently, all of the data from the camera was stored on Surveyor's solid-state recorders. This data was transmitted back to Earth approximately three hours after the conclusion of each day's imaging. The daily playback of camera data required 49 minutes. During that time, Surveyor transmitted 250 megabits of data at a downlink rate of 85,333 bits per second.
Next week, the onboard flight computer will activate heaters in the camera that will bake the epoxy structure of the camera to remove residual moisture. A set of four more star images will be taken after the bakeout period ends in late March. The star images taken this week will serve as a reference to assess the focusing capability of the camera after the bakeout.
Other activities this week included a two-hour radio-science calibration that occurred late in the evening on Wednesday. This test involved using the spacecraft's ultra-stable oscillator to control the frequency or "tone" of Surveyor's radio transmissions to the Earth. Normally, the spacecraft listens to a signal transmitted from the Earth as a reference to set the tone of the signal transmitted to Earth. The oscillator functions as an electronic clock that can precisely control the tone of Surveyor's signal without listening to the Earth-based reference signal.
Future tests of the oscillator will occur approximately every other week until the spacecraft reaches Mars. These tests are important because a stable radio signal as controlled by the oscillator will be critical toward the collection of scientific data at Mars.
After a mission elapsed time of 71 days from launch, Surveyor is 16.05 million kilometers from the Earth, 136.00 million kilometers from Mars, and is moving in an orbit around the Sun with a velocity of 30.85 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