TUCSON, Ariz. - A robotic spacecraft scheduled to land tomorrow on Mars will be operated by NASA. But calling the shots on what the robot does will be up to scientists at a University of Arizona lab.

If the Phoenix Mars Lander makes a successful touchdown in the planet's northern polar region, NASA's Jet Propulsion Laboratory in California will turn over scientific control to the Tucson researchers. The university's Lunar and Planetary Laboratory has been dealing with missions to Mars since 1964.

It will be the first time a public university has led a Mars mission. Principal scientist Peter H. Smith and his colleagues in Arizona will make decisions about the robot's actions; NASA will send those commands to the robot.

The Phoenix lander will study whether the ice beneath the Martian surface ever melted and look for traces of organic compounds in the permafrost to determine if life could have emerged at the site.

"If we could find it, and if we can convince ourselves it's Martian and not something we carried from Earth, then we literally have the smoking gun for present or past life on Mars," lab director Michael Drake said.

The university and Smith are veterans of space and Mars explorations. In fact, this will be Smith's third crack at trying to place a lander on Mars.

The Mars Polar Lander, carrying cameras built by Smith, crashed in December 1999 on its landing approach at the Martian south pole.

He also worked on the microscope and the robotic arm camera built for the Mars Surveyor Lander mission that had been scheduled for 2001 but was canceled because of the 1999 crash landing.

The laboratory's scientists have been involved at some level with virtually every successful Mars mission.

Smith has been focusing much of his work on Mars since 1993, when he developed a camera used in NASA's Pathfinder mission. It sent back images beginning July 4, 1997, from the Sojourner Rover.

He was part of the science team for the rovers Spirit and Opportunity, which have been researching on Mars since early 2004. He was also project manager for the 2005 Mars Reconnaissance Orbiter's sophisticated camera that has returned more than 25,000 images and 3,500 radar observations since 2006.

"His optimism is rather contagious and his enthusiasm is contagious," said Barry Goldstein, program manager of Phoenix at the Jet Propulsion Laboratory, who has known Smith for a decade.

The historic operations during the Phoenix mission will be run out of a converted 50,000-square-foot warehouse near the University of Arizona campus. It also holds two full-scale models of the Phoenix Mars lander, one on a platform surrounded by a rocky landscape depicting the terrain where the real lander is expected to come to rest.

Researchers will have magnums of champagne chilled as they tensely await the landing. "I just hope we get to actually use them to celebrate, not to drown our sorrows," said Drake, the lab director.

William Boynton, who has worked on three previous Mars missions, said scientists were confident.

"... The odds are certainly well in our favor that this will be a good success," he said.