A Gallery of HORSE Data and Results

Aerobraking Phase

MHSA observes the buffetted solar panel during descent into the upper Mars atmosphere. Note the oscillations caused by the solar panel flapping in the Martian breeze.

Below: a plot of typical viewing geometry during an aerobraking pass: emission angle (the angle between the field of view center and the nadir) versus latitude. The southbound pass begins at the right as the spacecraft slews to its aerobraking configuration, taking the MHSA field of view (one of the four) down to about 30 deg EMA at +75 deg latitude. At the end of the pass, the field is swept nearly straight down (0 deg EMA), and then rapidly off the planet disk. Note the fluctuations during the pass created by the force of the atmospheric drag.

Mapping Phase

Here is a typical day's worth of data. For each of the four quadrants, we plot the raw data numbers from the A, B, and S fields of view. The X axis shows hours from 0 to 24. You can see a repeating pattern every 2 hours, which is due to the fact that the orbit is not circular, so the horizon of the planet slowly moves up and down within our fields of view. Also, the poles tend to be cold, so there the A and B signals fall to nearly the lowest S (space viewing) values.

We now show you how the MHSA time coverage is used. As the seasons march along, indicated by Ls, which goes from 0 at the vernal equinox (start of northern spring) to 360 degrees, the Martian atmosphere temperatures change, depending on how warm the surface is, and especially on how much dust is suspended in the air. In the first frame below (upper left), the atmosphere is pretty much the same temperature all day long (see the key to the axes at the lower left), but it is somewhat warmer near the equator. Later (bottom left), we are starting to see a lunchtime warming in the south. As we get into the "Dust Storm Season" (upper right), the situation changes drastically. Not only is it a lot warmer, but there are now peak temperatures in the south in the late afternoon, and in the north in the late morning. Near the tail end of the dusty season, the atmosphere has cooled off again, but now, the warmest place on the planet is over the south pole! That is because it is sunny all day long there at this time of year.

Martian Movies: how the atmosphere changes with season

The following movies show the changing Martian atmosphere in two ways: as a standard Mars map, and as a latitude vs time-of-day plot. Both cover one Mars year, and have a 5 deg Ls interval between frames. The season is shown at the top. The button at the bottom can be slid to stop the movie at any desired point. Click the arrow at bottom left to start the movie. It plays at 2 frames per second. The temperature scale is in K. The night movie ( Nite107-100.MOV ) contains data from 18 hrs Martian local time to 6 hrs. West longitude is used.

The next movie ( Ls107-97DI.MOV ) presents the local time variation and how it changes with season. Here all longitudes have been averaged together. Because there is so much redundant data here in a 5 deg Ls period, we use only the first 2 deg of each 5 deg period. Note that time of day goes from right to left, and that for convenience we are putting hours from 0-24 into the same plotting space as longitudes 0-240. Thus, noon for example is 12 hrs = 120 on the graph.