NASA Podcasts

LCROSS Mission
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Hello, my name is Brian Day. I am the education and public outreach lead for NASA's LCROSS Lunar Impactor mission. One of the really important resources that we will need to have for people living on the Moon is water. Now, it would be nice if we could actually find water on the Moon. So how do we go about looking for water?

Well, we're going to do it with two robotic space probes, the lunar reconnaissance orbiter (LRO) and the Lunar CRater Observation and Sensing Satellite (LCROSS).

Lunar Reconnaissance Orbiter (LRO)

We'll talk about LRO first.

The Lunar Reconnaissance Orbiter is going to go into orbit around the Moon and it’s going to map the Moon in finer detail than we've ever done before. As a matter of fact if your coffee table were on the surface of the Moon, LRO would probably be able to see it. It's really pretty fantastic. But in addition to mapping the Moon with this beautiful photographic camera LRO is also going to look at the temperature environment on the Moon (What are the high temperatures and lows?) and the radiation environment on the Moon. These are all things that we'll really want to know before we have people living on the surface of the Moon.

So the plan for LRO is that it will use its own propulsion system to enter into a circular orbit around the Moon, a polar orbit going around the north and south poles at about 50 kilometers high. From this for one year it will map the surface of the Moon for what we call the Exploration Systems Mission Directorate, the people who are planning our future presence on the Moon. After that one-year mission it will be turned over to the Science Mission Directorate at NASA who will use it to do lunar science and study the history of the Moon's surface and how it came to be the way it is.

Lunar CRater Observation and Sensing Satellite (LCROSS)

LCROSS is a very different concept. The LCROSS system consists of two main components. You have the centaur upper stage of our Moon rocket, which again that has the motor that takes us out of Earth orbit and propels us toward the Moon. And then later on we'll use that empty upper stage as our impactor. Then we also have the shepherding spacecraft. This is what guides and targets that upper stage toward its target crater and it also carries the scientific instrumentation on board that will measure and analyze the plume we create. There is a range of instrumentation on board. We have cameras and spectrometers, both working in the visible and infrared wavelengths.

Both LRO and LCROSS are scheduled to launch together in the spring of 2009. They'll launch aboard an Atlas 5 rocket flying out of Cape Canaveral in Florida. As they launch and climb out of the Earth's atmosphere they'll jettison or get rid of the lower stage of the Atlas 5 rocket, and it will fall back to Earth in the ocean. We'll climb into Earth orbit, and after being there a very brief time, fire the engine of the centaur. The centaur will take LRO and LCROSS out of Earth orbit on its way toward the Moon. About two hours after launch LRO separates and it will now take its own path to the Moon to conduct its mission.

Five days after launch, LCROSS, still attached to that centaur upper stage, will do a fly-by of the Moon and will use the Moon's gravity to fling us into a very highly tilted, highly inclined orbit around the entire Earth/Moon system. Each one of these big loops takes about 38 days. We call this an LGALRO orbit: Lunar Gravity Assist Lunar Return Orbit.

The idea is that when we meet up with the Moon again we'll do so so that we're coming in at a very steep angle relative to the Moon's pole. That centaur upper stage is going to hit at 2.5 kilometers per second, about 5600 miles-per-hour. When it hits the floor of that crater, it will create a huge plume of debris arching maybe 10 kilometers or so into the Moon's sky. LCROSS is going to be perfectly situated to be able to look down and see that impact.

Over the next four minutes, the LCROSS shepherding spacecraft will actually fly down, descend through the plume of debris sampling it and letting us know what it's made of. Is there in fact any water ice and if so, how much? Four minutes after the centaur hits, the LCROSS shepherding spacecraft will also hit creating a second plume of debris. That plume of debris, actually both plumes of debris, will be observed from the surface of the Earth through some of the greatest telescopes on the Earth, from telescopes in Earth orbit such as possibly the Hubble space telescope and from instruments in orbit around the Moon such as the Lunar Reconnaissance Orbiter.

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