MRO Snaps Phoenix

May 27, 2008 / Written by: Henry Bortman

Sure, it just looks like a picture of two little white dots and a line on a mottled gray background. But it’s actually one of the most amazing photographs ever taken.

As NASA’s Phoenix spacecraft made its descent through the martian atmosphere on Sunday, May 25, another spacecraft, the Mars Reconnaissance Orbiter (MRO), orbiting high above, snapped this image of Phoenix suspended beneath its 40-foot-wide parachute. At the time, Phoenix was hurtling through the martian atmosphere at about 250 miles per hour; MRO was traveling at more than 7500 mph. The two spacecraft were about 450 miles apart. And Phoenix was off-course.

Phoenix Project Manager Barry Goldstein unveiled the surprise image at a press conference Monday morning. “What you see here is a spectacular image taken by the Mars Reconnaissance Orbiter … of Phoenix on the parachute through its descent phase.” The image was captured by MRO’s HiRISE camera. HiRISE is the highest-resolution camera ever put in orbit around Mars. It is capable of resolving surface details as small as an office desk. “This is an engineer’s delight,” Goldstein said.

Getting the shot involved a combination of careful planning – and plain old good luck. “Our most important goal was to make sure that, during entry, descent and landing, we actually recorded all the data that Phoenix sent,” said Jim Erickson, MRO project manager. “Everything else was gravy.” To that end, MRO’s UHF antenna, the antenna it uses to receive data from Phoenix, was pointed toward the incoming spacecraft’s expected path.

Fortunately, HiRISE is mounted near the UHF antenna, and points in the same direction. That meant that attempting to take the picture of Phoenix wouldn’t compromise receiving critical data from it.

“The picture really wasn’t designed to be media-friendly,” Erickson said. It was intended to provide engineers with information in the event something went awry during the Phoenix descent, so that “we had something to enable us to figure out what had gone wrong. Now it’s going to enable us to figure out better what went right.”

The planning made it likely that, if Phoenix set down in the dead center of its targeted landing area, MRO would capture the image. But Phoenix, for reasons that are not yet fully understood, landed some 13.5 miles off-course. That’s where the good luck came in, because it happened to be off-course in the direction HiRISE was already pointing. Still, Erickson, said, “We weren’t sure at all that we had gotten it until we found it in the image.”

MRO still has a critical role to play in the Phoenix mission. Along with NASA’s Odyssey orbiter, it is responsible for relaying all of Phoenix’s scientific data back to Earth. To keep the Phoenix payload as light as possible, engineers chose not to include an antenna with enough power to broadcast to Earth directly.

MRO will also be sending back more Phoenix snapshots. It already has been sent orders to photograph Phoenix on the ground. This will help the Phoenix team pinpoint the lander’s precise location. In addition, by comparing before and after pictures of the landing site, Phoenix scientists will be able to study how the lander’s thrusters affected the surrounding terrain. Those images are expected soon.

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