Mars Global Surveyor aerobreaking phases, required to
achieve its mapping orbit, have yielded vertical profiles
of thermospheric densities, scale heights and temperatures
covering a broad range of local times, seasons and
spatial coordinates [Keating et al. 1998, 2001]. Phase
I covered local times from 11 to 16 h (assuming 24
"martian hours” per martian day or sols), with a latitude
coverage of approximately 40deg to 60deg N. Seasons
observed during this phase were centered around winter
solstice and altitudes of periapsis range from 115 to
135 km. The altitudes for Phase II were lower, with a
minimum around 100 km and a maximum around 120.
Martian spring was the season covered during this phase
and the local time was between 15 and 16 h. The latitude
covered by Phase II, however, was more extense
than that seen during Phase I, with a coverage from 60deg N
to basically the South Pole
