@ Since the arrival of MGS at quite an elliptical orbit around the planet on 11 Sept, the flight team tried to lower the lowest point of 262km into the upper parts of the Martian atmosphere to slow down by use of air resistance, and make the high point of the orbit begin to drop. The original plan was to use this "aerobraking" scheme to lower the high point of the orbit from 56,026 km down to 450 km by repeatedly flying through the atmosphere for four months.
@ However on 11 Oct the flight team decided to raise the low point because the aerobraking was too much performed, and MGS's two solar panels were bent back; It was possible the panel was already damaged shortly after launch in Nov 1996.
@ With the new mission plan, aerobraking shall occur with the low point of the orbit at an average altitude of 120 km, instead of the original altitude of 110 km. This slightly higher altitude results in a decrease of 66% in terms of air resistance pressure by May 1998.
@ During the six months, aerobraking will reduce the orbit period 45 hrs down to between 12 to 6 hrs. From May to November, aerobraking will be temporarily suspended to al low the orbit to drift into the proper position with respect to the Sun. Without this hiatus, MGS would complete aerobraking with its orbit in the wrong solar orientation. During next six months from Nov 1998 to Mar 1999, aerobraking will continue and will shrink the high point of the orbit down to 450 km. At this altitude, MGS will circle Mars once every two hours.
@ In March 1999, aerobraking will terminate and at the same time the orbit will settle into its correct alignment with the Sun. MGS will make its observations in a south to north direction in the sunlight. The new mapping orbit will cross the Martian equator at 2:00am (local Martian time) during each orbit. This plan is very opposite to the original one and thus to achieve they needed another Earth year.
@ At the beginning of May 1999, Mars will be close to the Earth with
the apparent diameter of 16 arcsecs. In March 1999 the spacecraft will
begin to take pictures of the northern summer of the planet. On 15 March
1999, the apparent diameter from the Earth will attain 12 arcsecs and the
season will be 110°Ls.