Transcripts of LOLAvideo_portal.wmv

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[Smith] The purpose of LRO is to provide data and information to safely go back to the Moon. And our experience in the past, this includes Apollo but it's also true of the Martian landers where we've worked on the same kind of work. A lander is built in such a way with an assumption that when it lands there are going to be rocks underneath and it can only take a certain size of rock. The ones on the Mars landers for example, I think if there was a 30 centimeter rock which is about one foot and if it landed on top of it it would be just OK. So they're interested in how high these rocks are to see if that particular area is safe to land. Because if you have a roughness as we call it, or rocks of three or four feet there's no way a lander can get down.

[music] LOLA is a laser altimeter. It sends a short pulse of light from the spacecraft. It is then split into five separate pulses So actually five pulses go down to the surface, hit the surface, hit the surface, come back again and come to five different detectors on the spacecraft. And hence derive the distance of the surface below the spacecraft. And we do this about a hundred and forty times per second. In addition to altimetric measurement as we call it, which is the distance measurement to the surface, we measure something we call the pulse spreading, which is the laser pulse that goes out is shaped rather like a pulse, a Gaussian curve. That pulse goes to the surface and because of the surface features it gets distorted, it gets spread as we call it. If it's like a sheet of ice or water or glass, there'll be no spreading of the pulse. If in fact it's all got rocks and bumps in it then the pulse will come back spread. and although we don't know exactly the distribution of the rocks or the bumps we can say approximately what the spread of the heights, if you like, within that five meter spot are. It was not easy to do this instrument as quickly as we needed to. We knew approximately what they would need and so myself and colleagues got together and elements that clearly were going to come along for this mission in terms of say an altimeter. And we, like most of these things you have a hiccup along the way at least or twice, but we have a great instrument team. And they worked very hard, weekends as well, trying to get this thing together. So right now the instrument's on the spacecraft and it's beautiful; it's spectacular.

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