Three will operate instruments on board the mission, the first step in the planned return of humans to the moon decades after the last Apollo mission. The fourth scientist is already gathering data from a satellite in orbit around the moon.

The lunar orbiter launch was to have taken place Wednesday, but the space shuttle Endeavour developed a hydrogen leak. Its liftoff had been postponed until Wednesday, and NASA did not want to conduct two launches on the same day. As it turns out, Endeavour’s problem could not be fixed in time, so for orbital and mechanical reasons the shuttle now will have to depart on Saturday or wait until July 11.

Mike Wyatt, one of the Brown scientists, speaking by telephone from Cape Canaveral, said that due to the weather, there is a 60 percent chance of a successful launch on Thursday.

James Head III, a veteran who trained astronauts for the Apollo missions, is part of a team that will operate the Lunar Orbiter Laser Altimeter, or LOLA. The instrument will provide high-resolution, three-dimensional maps of the moon.

Peter Schultz, a planetary scientist, is on a team that will operate the Lunar Crater Observation and Sensing Satellite, or LCROSS, which is designed to search for water.

When it comes time, probably in October, LCROSS will separate from the parent Lunar Reconnaissance Orbiter and take a suicide dive onto the lunar surface at twice the speed of a bullet. The ejected material will be analyzed for the presence of water.

“The idea is to smash an impactor into the shadowed floor of a crater,” Schultz said in an interview last month. “We want to dig below the surface to see if we’ve got ice.” If so, he said, “it makes a difference in terms of bringing your own water with you or process what’s already there.”

The target will be a crater at the lunar south pole, where permanent shadows may have preserved water in its frozen form from eons ago.

Wyatt, a member of the Brown faculty since 2006, specializes in thermal imaging. He is on a team called Diviner, with a goal of measuring day and night surface temperatures over a wide area.

The results are expected to help NASA pick a good landing spot for astronauts who would establish a long-term base.

Wyatt said the Diviner instrument can locate areas too hazardous for human landing. It does so by checking how slowly rocks lose their temperature in the lunar night. Larger rocks lose their heat more slowly than smaller ones.

He said the instrument also will be looking for water traces.

“We can pinpoint where ice might be stable in permanently shadowed craters, near the north and south poles, that have never seen the light of day for billions and billions of years because they are deep and at such high latitudes,” he said. “It’s so cold that water would be stable as ice.”

The instrument also will probe the surface to determine which minerals are present.

Carle Pieters also will be keeping an eye on the Lunar Orbiter mission.

As the lead scientist for one of the two NASA instruments aboard Chandrayaan-1, the first Indian satellite to orbit the moon, she is already one step ahead of her colleagues.

“We have an instrument orbiting the moon — the moon mineralogy mapper,” Pieters said in an interview in May. “We measure reflected solar light and analyze it in 240 colors. Our eyes can only detect red, green and blue and combinations. With this instrument, we take a spectrum that includes both visible lightwaves and longer wavelengths where the eye can’t see.”

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