There is now a mailing list for the MGS Radio Science Team Education Outreach Program. Any person with an interest in this program is welcome and encouraged to subscribe!
The status of the MGS spacecraft has not changed since the last news report. The spacecraft continues to be "parked" in an elliptical orbit around Mars with a period of 11 hours and 38 minutes. The altitude of the closest approach to Mars (periapse) on each orbit is 110 miles. The altitude of the apoapse on each orbit is approximately 11,160 miles. Since arrival at Mars, MGS has completed nearly 500 orbits!
Aerobraking is scheduled to begin once again in September, and MGS is expected to reach its final mapping orbit in March, 1999. The start date of the mapping phase of the MGS mission has not yet been determined, but it should be some time in March. This next aerobraking sequence is being called Aerobraking-2 (AB2) by people involved with the mission. At the end of AB2, the orbit of the MGS spacecraft should be nearly circular with a period of two hours and an altitude of approximately 250 miles. The tight, nearly circular orbit around the poles of Mars is well suited to mapping the red planet with a number of different instruments.
Our Team has not acquired any new meteorological data from Mars since April. We are preparing a Mission Change Request (MCR) for submission to MGS management which will allow us to acquire new data between late November and January. During that time period it will be late spring on Mars in the northern hemisphere where we will acquire data during the entry occultations of the MGS spacecraft, and late fall in the southern hemisphere where we will acquire data during the exit occultations of MGS. The data will be made available to participants in the outreach program as soon as we have the necessary spacecraft trajectory information and the data have been processed.
The first measurements in the northern hemisphere are expected to occur near the martian equator at approximately 8:30 am local Mars time, and the final measurements are expected to be near 65 degrees north latitude at approximately 4 am local time on Mars. The first measurements in the southern hemisphere are expected to occur near 25 degrees south latitude at 9:15 am local Mars time, and the final measurements near 68 degrees south latitude at 3 pm. As with our last observations, the latitudes and local times will vary smoothly from one orbit to the next. In late November the distance between Earth and Mars will be over 1.8 astronomical units (where 1 AU is the average distance between Earth and the Sun), and in January when we acquire our last data the distance will be about 1.5 astronomical units.
Unfortunately, details of the MGS mapping mission are still up in the air. The mission plan calls for the MGS high-gain (dish) antenna to be fully deployed once the aerobraking phase of the mission is complete and MGS is in its final mapping orbit. When the antenna is fully deployed on its boom, azimuth and elevation gimbals will allow the antenna to constantly track the Earth even while the MGS instruments are directed toward Mars. This, of course, allows data and commands to be communicated between MGS and Earth-based stations while the instruments perform their mapping data acquisition.
Currently, the high gain antenna is fixed to the side of the MGS spacecraft and is not capable of independently tracking the Earth. The spacecraft itself must be pointed to Earth in order to communicate by radio, and scientific data cannot typically be acquired in this configuration.
NASA is concerned that the high gain antenna system (and possibly the MGS spacecraft) might be irreparably damaged when and if the antenna is fully deployed because the deployment mechanism utilizes a damper whose performance is suspect. The MGS mission has already been delayed for one year because a similar damper failed when the MGS solar panels were deployed and one panel and its hinge were damaged. NASA management is evaluating whether to sacrifice some of the potential science return from Mars by delaying the deployment of the high gain antenna. Such a delay would increase the likelihood that at least some useful data are returned during mapping.
The situation is very complicated! NASA issued a press release regarding the antenna deployment this week. Suffice it to say that the plans of the Radio Science Team for the mapping phase of the MGS mission are very much linked to the deployment (or non-deployment) of the antenna. The final decision on when to deploy the antenna will not likely be made until next year. The MGS Radio Science Team is meeting at Stanford next month to discuss options and strategies. Hopefully, we will come up with some creative means to ensure that we can continue our atmospheric investigation in the spirit of the initial MGS mission plan even if the deployment of the high gain antenna is substantially delayed.