G. E. Cunningham
27-MAR-98 2:00 PM PST
Early in the morning of March 27th, Mars Global Surveyor executed a 4.43 m/s bi-propellant main engine burn at the apoapsis of its 201th orbit of Mars to raise its orbit’s periapsis from 123 km to 170 km and effectively terminate the first phase of aerobraking.
MGS will remain in this 11.6-hour duration orbit until early September 1998, when aerobraking operations will be undertaken again, further reducing the orbit period to the 2-hour, circular, sun synchronous mapping configuration.
The spacecraft was configured for this science phasing orbit period and the science instruments were turned on again later Friday morning.
During the five month period without aerobraking, MGS will return to taking science data with all its instruments. At each periapsis passage, Mars Orbiter Camera images and Mars Orbiter Laser Altimeter measurements will be taken. Magnetometer/Electron Reflectometer and Thermal Emission Spectrometer data will be taken all through the orbit period. Radio science data will be taken at every opportunity. X and Ka-Band propagation data will be acquired as the spacecraft approaches solar conjunction during May.
During April, MGS will have the opportunity to perform some "targeted" imaging of the Mars Pathfinder and Viking landing sites, as well as the Cydonia region. There will be three opportunities on eight day centers to image each of the sites during April. According to our previously announced process for imaging Cydonia, the Project has announced the opportunities (press release on March 26th), and will announce the detailed times of image acquisition and release early next week when updated orbit data is available.
The MGS spacecraft continues in excellent health.