The Mars Reconnaissance Orbiter (MRO) spacecraft was launched toward
Mars from the Kennedy Space Center in Florida on August 12, 2005, and
will arrive at Mars about March 10, 2006. After being captured into a
gravitationally bound orbit around Mars, achieved via spacecraft
deceleration induced by the firing of onboard engines, orbit
modification via the process of aerobraking will commence and nominally
continue for six months. At the conclusion of a successful aerobraking
phase, the spacecraft will be in a near-circular (250 x 320 km) near-
polar sun synchronous orbit, which is desired for the mapping phase of
the mission. The ability to anticipate the atmospheric conditions MRO
will experience in the 100-200 km altitude range as it passes through
Mars? upper atmosphere is an important component for successful
completion of aerobraking. Previous aerobraking experience at Mars
provides one indication of conditions MRO might experience. Numerical
models provide an additional tool, and enable investigation of possible
conditions more specific to the space and time domain for which MRO will
be aerobraking.

The MRO aerobraking plan calls for aeropasses to occur during the
Martian season approaching Northern summer (Ls ~ 25-110) spanning
nearly 550 spacecraft orbits. Periapsis (closest approach) for each 
orbit will progress from high Southern latitudes (70-80S) near the
terminator (local mean solar time, LMST = 2000 to 1800), over the 
South pole (80-90S) traversing dayside to nightside local times 
(LMST = 1800 to 2400 to 0300) and equatorward (80-20S) deep on the
nightside (LMST = 0300). See Figures 1-4.  Periapsis altitudes during
the main phase of aerobraking are planned for 100-110 km (see Figures
5-6).  The solar activity anticipated during this main phase of
aerobraking calls for solar minimum conditions (F10.7-cm = 70-100 
solar flux units at Earth). A solar flux unit = 10^-22 m^-2 Hz^-1.
This aphelion season (Ls ~ 90) also is characterized by rather low 
dust opacities in the Martian atmosphere.

This MRO modeling website contains plots and tables from coupled 
MGCM-MTGCM simulations of the Mars upper atmosphere (for solar and dust
conditions described above) for the main phase of MRO aerobraking 
(Ls = 25-110). Simulations are partitioned into two cases, appropriate
for:

I.        Early Aerobraking (Ls = 25-60)
        -- Periapsis latitude = 70-80S
        -- Periapsis LMST     = 2000 to 1800

II.        Mid-to-Late Aerobraking (Ls = 60-110)
        -- Periapsis latitude = 80S to 90S to 20S
           (over the S. pole and onto the nightside)
        -- Periapsis LMST     = 1800, 2000, 2200, 2400, 0300


Key MGCM-MTGCM generated plots are chosen to illustrate the upper
atmosphere conditions (densities and temperatures) that the MRO
spacecraft may encounter during the main phase of aerobraking.

I.        MRO plots of densities (kg/km3) and temperatures (K)
        for constant LMST (1800, 2000, 2200, 2400, 0300) at a
        given UT = 12. These plots provide a "snap shot" of 
        the Mars upper atmosphere at a single time during the 
        Martian day to capture altitude versus latitude
        variations. Each MRO aeropass through the thermosphere
        (below ~200 km) will traverse both latitude and altitude
        on inbound (descending) and outbound (ascending) segments.
        Several adjacent aeropasses will occur at roughly the
        same LMST while precessing in longitude about the planet.

II.        MRO plots of density (kg/km3) at constant altitudes
        (110 and 130 km) and LMST (1800, 2200, 2400, 0300).
        These density (latitude versus longitude) plots 
        approximate what the MRO spacecraft will observe as it
        precesses in longitude around the planet for several
        orbits at roughly the same LMST. "Longitude fixed"
        wave features, previously observed during Mars Global
        Surveyor aerobraking, may also be visible during MRO
        aerobraking. These features should vary with LMST
        according to the underlying tidal modes responsible
        for their existence. Current MGCM-MTGCM simulations
        predict significant longitude variations of density
        at 130 km.

General MRO aerobraking descriptive plots are shown below. 
Open = opening of MRO launch window, and Close = Closing
of MRO aerobraking launch window.