The MGS Radio Science Team is currently acquiring new data from the martian atmosphere! This is the Team's first chance to collect martian meteorological data since the middle of April. As of today, MGS is completing one orbit around Mars every four hours and fourteen minutes, and new meteorological data are being acquired twice per orbit. By recording the changing frequency of the MGS radio signal when the spacecraft enters occultation behind Mars, the Team is able to derive an atmospheric profile at a northern martian latititude. Similary, it is possible to observe the atmospheric structure at a southern martian latitude when the spacecraft exits from occultation behind the red planet.
MGS is currently in its second (and final!) aerobraking sequence, and the period of the spacecraft orbit is being reduced by about 30 seconds during the part of the orbit when the spacecraft passes through the upper martian atmosphere. The mapping phase of the MGS mission will begin after the orbit period is reduced to two hours. That is the phase of the mission when most of the scientific data will be collected, and it will continue for one full martian year (687 days).
The latest campaign of atmospheric data acquisition began on November 20 and will continue through the end of December. The Team recently began posting new results from this campaign on the outreach program web site. Classes which have registered for the outreach program may use the tools on the site to access the new results as they are posted. Educators who are interested in registering their classes for the outreach program should contact joe@nova.stanford.edu. Summaries of the latest martian weather observations are available on the site to the general public. These summaries may be checked regularly even by those who have not registered for the program.
The realities of preparing for and executing aerobraking with a short orbit period make it very difficult for the Radio Science Team to adequately perform their radio occultation measurements of the martian atmosphere at this time. It was never intended that any science investigations would be carried out while the spacecraft was aerobraking at Mars, but it was never intended that there would be a one-year delay in the start of mapping either! The Team has been given the go-ahead to collect new data with the understanding that they cannot have any impact on other spacecraft operations. This is not normally how the experiments are conducted!
Results from the current campaign of martian atmospheric observations will continue to be posted as data are acquired and processed by members of the MGS Radio Science Team. It is expected that new results will continue to be posted for the next six to eight weeks, until all of the raw data collected through the end of this month have been analyzed. Once the mapping phase of the mission begins, the Team will not experience the problems which it now faces with aerobraking, and the system for data acquisition and processing will be more routine and timely than it is now.
The early results are already very interesting! It is now late Spring in the northern hemisphere of Mars, and late Fall in the southern hemisphere. The solstice will occur on January 29, 1999. Surface temperatures recorded near 60 degrees south latitude last week were almost 200 degrees below zero Fahrenheit just past the local noon time! Members of the Team have reason to believe that the atmosphere at that temperature may be fully saturated and that it may be snowing frozen carbon dioxide. In the northern hemisphere, early observations indicated surface temperatures in the neighborhood of 70 degrees below zero at 7:30 a.m. local Mars time.
It is now two years since the launch of the Mars Global Surveyor. Another window for launch to Mars has opened, and NASA's Mars Climate Orbiter was lifted off from the Cape Canaveral Air Station last Friday. NASA's Mars Polar Lander will be launched on January 3, 1999. These are exciting times for exploration of the red planet, and the MGS Radio Science Team is thrilled to be a part of it!