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the purpose of lro is to provide data

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and information to safely go back to the

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moon and our experience in the past this

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includes apollo but it's also true of

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the martian landers where we've worked

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on the same kind of work there is that

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a lander is built in such a way with an

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assumption that

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when it lands it there are going to be

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rocks underneath and it can only take a

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certain size of rock and the ones that

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on

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if there was a 30 centimeter rock which

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is about one foot

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and it landed on top of it it would be

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just okay

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all right so

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they're interested to know how how high

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these rocks are to see whether in fact a

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particular area is safe to land because

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if you have a roughness as we call it a

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rocks

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of three or four feet there's no way a

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lola is a laser altimeter

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it sends a short pulse of light from the

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spacecraft it is then split into five

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separate pulses

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so actually five pulses go down to the

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surface hit the surface come back again

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and come to five different detectors on

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the spacecraft and hence derive the

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distance of the surface below the

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spacecraft and we do this

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in addition to the altimetric

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measurement which is the distance

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measurement to the surface we measure

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something we call this pulse spreading

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which is the fact that the laser pulse

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that goes out is is is shaped rather

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like a

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pulse a a

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a gaussian curve that cur that pulse

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goes to the surface and because of the

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surface features it gets distorted it

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gets

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spread as we call it if it's like a

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sheet of ice or let's say water or glass

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there'll be no spraying of the pulse if

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in fact it's all got rocks and lumps and

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bumps on it then the pulse will come

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back spread and although we don't know

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exactly the distribution of the rocks or

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the bumps we can say approximately what

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the

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heights if you like within that five

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it was not easy to do this instrument as

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quickly as as we needed to we knew

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approximately what they would need and

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so myself and and colleagues got

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together and and sat down and thought

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about the stringent requirements that

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clearly were going to come along for

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this mission in terms of say an

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altimeter and

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we like most of these things you have a

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hiccup along the way at least once or

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twice but uh we have a great instrument

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team and uh they worked very hard

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weekends as well trying to get this

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thing together so right now the