Extensive testing of NASA's Phoenix Mars Lander in preparation for an August launch has uncovered a potential data-handling problem in time to modify plans for use of a camera during the final minutes of arrival at Mars. The testing results led to a decision to take just one photograph with the spacecraft's Mars Descent Imager. The mission will still be capable of accomplishing all of its science goals.

The issue is not the camera itself, which is capable of taking multiple downward-looking images of the landing area during the final three minutes of flight. Tests of the assembled lander found that an interface card has a small possibility of triggering loss of some vital engineering data if it receives imaging data during a critical phase of final descent. That possibility is considered an unacceptable risk, and the potential problem with the interface card was identified too late for changing hardware. The card has circuitry that routes data from various parts of the payload.

The descent camera can store one image internally. The mission's science team plans to use that image to place in context observations of the landing site acquired by the lander's other tools -- including two cameras, two microscopes, a robotic arm and analytical instruments.

This single view will show smaller details of the terrain than will be discernable in images acquired by the High Resolution Imaging Science Experiment camera on NASA's Mars Reconnaissance Orbiter, which itself can resolve features smaller than the Phoenix lander.

Preparation of the spacecraft is moving on schedule toward loading propellant before encapsulating Phoenix into the third stage of its Delta II launch vehicle in mid-July. A three-week period of launch opportunity dates begins Aug. 3.

Phoenix will go to an arctic plain where an icy layer is expected to lie within arm's reach of the surface. There it will examine whether the environment beneath the surface has been a favorable habitat for microbial life. It will also investigate the history of the water in the ice and monitor Mars' arctic weather. Phoenix Mission site http://phoenix.lpl.arizona.edu/index.php