Sequence of Events:
07/04/97 17:05:09 Nominal Time of Parachute Deploy
07/04/97 17:05:29 Heat Shield Separation
07/04/97 17:05:59 Nominal Time of Lander Separation
07/04/97 17:06:56 Approximate Time-Radar Altimeter Ground Acquisition - 1 mile above ground
At approximately 17:05:09 the parachute will deploy at an altitude of 8.6 kilometers or 5.3 miles. When a parachute is deployed in the Earth's thick atmosphere there is a short period of rapid deceleration. However, because the Martian atmosphere is so thin the rate of deceleration is gradual. When the chute deploys, Pathfinder is traveling at a speed of 900 miles per hour, or 392 meters per second. Approximately 83 seconds later, Pathfinder has reached a terminal, or steady state, velocity of 134 miles per hour, or 64 meters per second. At this point more pyrotechnics fire to release the heat shield from the back shell which forms the upper cone shaped surface of the entry vehicle. At approximately 17:05:59 the lander separates away from the back shell and descends on a tether. Approximately one minute later the radar altimeter in the lander will determine the height of Pathfinder above the surface of Mars. As Pathfinder descends through the atmosphere, the radar altimeter updates the flight computer to establish the exact times of the remaining sequences.