Tuesday, July 13, 2010

A Landing on Mars

Our last view of Space. 62 km over Mars, this is the view from the ARES spacecraft at 5:55 PM Universal Time, 10 minutes from a landing scheduled for 6:05 PM UT. Because of the speed of light, this image will not reach Earth until 6:07 PM UT, by which time ARES will have landed. The dark area near the horizon is Gusev Crater, our target and site of the Spirit Rover.

Rendezvous and landing is a complex three-body dance involving Sun, Mars and spacecraft. Since leaving Earth orbit, ARES has been in an elliptical Hohmann transfer orbit to intercept Mars. Because ARES has been near the aphelion in her course, Mars has been overtaking the spacecraft from astern at 2.65 km/sec. In addition, Mars' gravity has been slowly pulling the spacecraft in, adding to the relative velocity. There is no turning back fron landing, neither has there been since Earth escape. Like unmanned probes of the past, ARES will use Mars' atmosphere to cancel her velocity.

Reentry is a fascinating problem in itself. 12 minutes from touchdown, ARES deploys a 20 meter diameter inflatable heat shield. A communications blackout begins as plasma builds around the spacecraft and the crew experiences deceleration up to 9 gees. In a matter of seconds the spacecraft slows from Mach 5 to less than Mach 1. 12 km from the surface the 3 main parachutes deploy, followed by heat shield separation. Less than 1 km from the surface, landing jets will fire. If all goes well, the spacecraft will touch down softly on the plains of Gusev Crater.

We would hear from the landed crew at 6:17 Universal Time.


Locations of visitors to this page