May 9, 2008 -- The last time NASA dispatched a spacecraft to a polar region of Mars, it fell into a radio silence seconds before landing. What happened during Polar Lander's descent has been the subject of countless debates, a top-level investigation and Congressional hearings.
Suffice it to say that whatever happens when the replacement craft Phoenix hones in on Mars on May 25, Earthlings will be watching.
Technically speaking, listening would more accurately describe what a trio of orbiters already circling Mars will be doing for flight controllers as Phoenix descends toward the planet's north pole.
NASA hopes to land the craft so it can burrow down into the frozen tundra and retrieve ice samples that may determine if conditions were suitable for life to develop.
Mars Odyssey will relay the descent and landing live, or what passes for live when the action takes place 171.5 million miles away. At that distance, radio signals traveling at the speed of light take 15.3 minutes to reach Earth. By the time flight controllers know if Phoenix began the descent through the planet's atmosphere, it should have already landed.
Mars Reconnaissance Orbiter and Europe's Mars Express are the backups. They will record signals from Phoenix during the descent and landing which can be relayed to Earth for later analysis.
"The intent and the plan is to have Odyssey relay each bit of the descent and landing that is available to Earth," said NASA spokesman Guy Webster, with the Jet Propulsion Laboratory in Pasadena, Calif., which oversees the probe.
Odyssey needed to skirt about halfway around the planet to be in position to monitor Phoenix's arrival. MRO and Mars Express likewise fired their steering engines to reach observational posts.
Even the Mars rovers, Spirit and Opportunity, which are poking around the ground on opposite sides of the equator looking for signs of past water, were called in for support, simulating transmissions from Phoenix for tests with the orbiters.
Mars Reconnaissance Orbiter already has been tapped for active duty. In addition to relaying pictures of the target landing site, the spacecraft has been keeping an eye on the weather.
The latest dispatch shows dust devils in sight, but they are not expected to be an issue for landing. Dust devils are common on Mars and are created when columns of warm air rise from the planet's surface, gathering dust as they grow tall in the planet's low gravity.
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