Mapping the Moon: Simulating LOLA in the Classroom

Introduction to LIDAR Mapping with LOLA.

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www.nasa.gov

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What is a satellite?

• Is it just a spacecraft?

• What do all satellites have in common?

• What do all those instruments do?

• And what kind of data is collected? They all have to do what?

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Examples of measurement quantities?

• Distance

• Volume

• Time

• Velocity/speed

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How are they all related?

• RADAR (Radio Detection and Ranging)

i.e. Our friendly neighborhood policeperson

• SONAR (Sound Navigation and Ranging)

i.e. Bathymetry of ocean floor

• LIDAR (Light Detection and Ranging)

i.e. LOLA (Lunar Orbiter Laser Altimeter)

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How does LOLA work?

• Laser pulses bounce off the surface.

• The time taken by the light to travel to the surface and back is measured.

LOLA is capable of timing pulses with a precision of 0.6 nanoseconds, corresponding to a distance error of no more than 10 cm.

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How do we “see” the topography?

• Signals that LOLA receives will be transferred to create a topographic map. But how is that actually constructed?

• One swath equals one cross-sectional slice of the surface.

• Multiple parallel scans can yield a contour representation

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Run1

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0.17-0.21675

0.21675-0.2635

0.2635-0.31025

0.31025-0.357

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• For each “satellite orbit” the motion detector is moved once across the surface

• The frame is then moved 5 cm, and the process is repeated until the entire surface has been scanned

• If Lunar Land is 150 cm x 150 cm, how many scans will be required to complete the map?

• If the “orbit” lasts for 15 seconds, what should the sampling rate be to collect 30 data points per orbit?

Mapping with the Ultra-Sound Motion detector

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