Tim Furniss/LONDON
NASA has revealed a year's delay - to March 1999 - of the mapping mission to be undertaken by the $250 million Mars Global Surveyor (MGS).
The announcement came almost simultaneously with the news that the Agency's successful four-month Mars Pathfinder-Sojourner mission had ended.
The delay results from an extended period of aerobraking manoeuvres needed by the Lockheed Martin MGS to enable it to reach its originally intended operational orbit around Mars.
The delay will cost NASA "several million" dollars.
The new regime was forced on NASA after a solar array malfunction ended the first aerobraking campaign (Flight International, 29 October-4 November).
Aerobraking uses the solar panels as "brakes" against the drag of the upper atmosphere, resulting in orbital alterations. One of the craft's two solar panels became unlatched, and there were fears that it could break off completely or that the MGS would have to be operated in a different orbit, degrading the expected scientific results.
After studies, NASA decided that the panel was strong enough to survive a more gentle, extended aerobraking regime, which will result in a six-month hiatus in manoeuvres in 1998 while Mars moves into the correct alignment with the Sun for global mapping.
The mapping will be conducted from the originally planned Sun-synchronous, 400km, circular orbit, but with the spacecraft imaging on a south-to-north pass over the equator at 02.00 rather than north-south at 14.00 Mars time.
Scientific observations and images will be obtained during the extended aerobraking regime, however. The MGS has already returned high-quality images.
Further solar-panel problems would cause the mission to be degraded, however, because the MGS would have to be operated from an elliptical orbit.o
Source: Flight International
