Pasadena scientists say the three orbiters will not only watch the landing from above, but relay radio data to Earth from the Phoenix, as the lander hits the Mars air an initial speed of 12,750 miles per hour.
Longtime Mars planetary scientist Peter Smith at the University of Arizona said the Phoenix lander will use its heat shield, a parachute, and finally a rocket thruster to touch down on the surface of Mars.
Orbiting overhead will be the trio of spacecraft controlled from Pasadena, including the Odyssey spacecraft. Powerful radio transmitters using dish-shaped antennae will relay telemetry from the Phoenix to ground stations on Earth.
"We will have diagnostic information from the top of the atmosphere to the ground that will give us insight into the landing sequence," said JPL Phoenix deputy project manager David Spencer.
One of the three orbiting satellites would be on the exact wrong side of Mars when the Phoenix lands, were it not for a carefully-measured series of rocket firings commanded from Pasadena to alter its orbit, he said. Those firing began this week.