Mission Profile
After launch on a Med-Lite with a Delta II 7425 configuration (the 25 day launch window opens on 3 January 1999) and an 11 month cruise phase to Mars, the Mars Polar Lander will separate from its cruise stage just before atmospheric entry on 3 December 1999. The two probes will be separated from the cruise stage by mechanical pyros approximately 18 seconds later. The probes have no active control or propulsion systems, but are designed to passively orient themselves during free fall with the forebody front forward. Impact is expected to occur at 160 to 200 m/s with an angle of attack of less than 12 degrees. On impact, the aeroshell will shatter and the forebody will separate and penetrate to 0.3 to 2 meters below the surface depending on the constitution of the underlying material. The 3-axis accelerometer measures the deceleration of the forebody, which will help determine the depth of probe penetration and may provide data on the hardness and layering of the material.
A few minutes after impact, a small drill will be deployed out the side of the forebody. The drill will bring approximately 0.1 grams of sample into the water experiment sample cup inside the forebody, where it will be examined for the presence of ice. The sample will then be heated in 10 degree C increments and measurements of the amount of water vapor released at each stage will be made using a tunable diode laser, giving information on the water-bearing minerals within the sample. The temperature sensor in the forebody will measure thermal properties of the martian soil and allow estimates to be made of the conductivity. A sun detector on the aftbody will be used.to verify that the aftbody remained on the surface after landing. Atmospheric pressure and subsurface temperature measurements will be made every hour for the two day nominal mission in conjunction with measurements made by the Mars Polar Lander, and continue as long as the batteries hold out, which should be about an additional 20 days. Data will be stored on board and then transmitted to the Mars Global Surveyor spacecraft and relayed to Earth.
The target area is located within the northern boundary of the martian polar layered terrain, near 73 degrees south latitude, 210 degrees west longitude. The landing area for both probes should be about 50 to 100 km from the Mars Surveyor '98 Lander touchdown site. This area is considered to be an important reservoir of water, carbon dioxide and other volatiles on Mars.