SpaceCast
Pathfinder Special Reports ....................................... July 4 , 1997
Pathfinder Reaches Mars
WASHINGTON, DC - JULY 4 1:02 PM EDT Mars Pathfinder is now in the Martian atmosphere, speeding towards landfall in an ancient dried river valley. Now some 80 miles above the surface, Pathfinder is traveling at 7.5 km/sec., with heat building up on its shield of 100 megawatts of thermal energy. The atmosphere of Mars will slow the spacecraft to 900 mph, or 400 meters/sec.

From this point on, the only likely signal from the spacecraft will be the carrier wave, a single frequency radio wave. The shifting frequency of the carrier, known as the Doppler shift, will provide an indication of the decelerations occurring during entry and parachute deployment. The spacecraft is also designed to send back a frequency-keyed signal following certain key events; this signal is called a semaphore. The semaphore is very weak, and is not expected to be received in real time. However, careful analysis after-the-fact of the broad frequency spectrum recording of the radio signal will give the operations team considerable information on how events unfolded during the rapid descent to the surface.

Landing events during decent will happen quickly. A 24-ft diameter parachute will deploy now to slow the vehicle down to 65 meters/sec. Some 20 seconds later the top of the heat shield will drop away, its work today completed. The lander will then drop on a bridle below the backshell of its shield, and will drop down a metal tape on a centrifugal breaking system that is designed into one of the lander's "petals". Once it has dropped onto the bridle, Pathfinder will use its radar altimeter to time the inflation sequence of the airbag landing system.

This radar ranging will happen when Pathfinder is at 1.5 km above the surface and 32 seconds before touchdown. When that has occurred, the airbag complex will inflate at 8 seconds before landing. Following inflation, a rocket motor on the backshell will fire to slow the descent rate to nearly zero, at which point the bridle will be severed and the lander, encased in the airbags, will drop down onto the surface. Landing is expected at 1:07pm EDT. Accelerometer data should be able to confirm the braking sequence of parachutes, bridles, airbags and landing had occurred.

Washington , DC - July 4, 12:32PM EDT NASA reports that the Cruise Stage has pulled away on schedule from the Mars Pathfinder entry heat shield at 12:32pm EDT today. Signals were to be received from the Deep Space Network at Madrid, Spain. Pathfinder is now about 8500 km above Mars. Forces of up to 20 Gs, or 20 times the pull of gravity, are expected on the hull of the craft as it plunges into the atmosphere of Mars. NASA now standing by for data from the accelerometers as the first reports are received that Pathfinder has first touched the atmosphere of Mars. This side of the red planet is now in predawn darkness, awaiting sunrise.
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