This week, the Mars Global Surveyor science team received an unexpected bonus from the Sun due to a solar flare eruption that took place on Monday. Eruptions of solar flares occur when disturbances deep within the Sun's interior cause streams of electrically charged atomic particles to be ejected from the solar surface. These charged particles move through the solar system at speeds in excess of 1,000,000 kilometers per hour.
In order to allow the science team to study this event, the flight team sent commands to Surveyor that enabled the spacecraft to record solar flare data gathered from the Magnetometer science instrument. These commands activated the spacecraft's data recorders late Wednesday afternoon, about half a day before the stream of charged particles from Monday's eruption reached Surveyor. Although past occurrences of solar flares have both disrupted space communications and damaged spacecraft, Monday's eruption was relatively mild in comparison. The Mars-bound Surveyor spacecraft sustained no damage from the solar flare.
Late Thursday afternoon, the navigators on the project canceled the trajectory correction maneuver that was planned for later this month. This maneuver would have refined the flight path to Mars by slightly altering the spacecraft's speed and velocity. However, analysis showed that this month's maneuver involves a velocity change of only 40 millimeters per second (less than one-tenth of a mile per hour). The maneuver was canceled because with such a small velocity change, the errors in executing the maneuver are comparable to the size of the maneuver.
This canceled maneuver would have been the third of four planned maneuvers during the journey to Mars. The first two occurred in November 1996 and March 1997. The fourth trajectory correction maneuver will take place on August 25th, 1997.
Yesterday marked the halfway point in the journey to Mars with respect to time of flight. As of April 10th, Surveyor has completed 154 of the 308 days required to reach the red planet. The halfway point in terms of distance between the Earth and Mars occurred last week on Monday, March 31st. This difference in halfway dates arises from the fact that the positions of the two planets constantly change during the spacecraft's journey to Mars.
After a mission elapsed time of 155 days from launch, Surveyor is 68.43 million kilometers from the Earth, 48.55 million kilometers from Mars, and is moving in an orbit around the Sun with a velocity of 24.98 kilometers per second. This orbit will intercept Mars 153 days from now, slightly after 6:00 p.m. PDT on September 11th (01:00 UTC, September 12th). The spacecraft is currently executing the C6 command sequence, and all systems 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