Mars Polar Lander Descent Imaging: Two Minutes of Work

Mars Polar Lander during terminal descent.

Descent imaging systems have a tough job. They wait around for a long time and are then asked to perform everything they will ever do in a very short time. There are no second chances. They have to work the first time.

For the Mars Polar Lander MARDI, descent imaging activities begin about 2.5 hours before entry, when the entry, descent, and landing (EDL) sequence powers-on the MARDI heater to bring the camera to its operating temperature. The following steps outline what happens next, all the way down to the surface of Mars:

The figure above shows a representative Mars Polar Lander descent profile, at two scales. The right graph shows the profile from heatshield jettision to touchdown, marked in 10 second increments (+). The small dark dots represent image acquisitions. The left graph is an enlargement of the terminal descent. The total descent can take from as short as 70 seconds to as long as 180 seconds, depending on events that occur earlier in the entry and descent. Powered descent, using the hydrazine engines, can last up to 45 seconds, although virtually all simulation scenarios limit powered descent to a window between 32 and 38 seconds in duration.

Artwork: NASA/JPL/Caltech; Chart: NASA/JPL/MSSS

©1999 Malin Space Science Systems, Inc.