Laser marksmanship

Laser marksmanship
Date:1 February 2010 Tags:,

A 400 000 km-long beam of light pinpoints an orbiter circling the moon.
By Alex Hutchinson

Astronauts will need excellent maps to safely explore the Moon. One unexpected boulder or incline could disable a lander or rover – and possibly ruin a multi-billion-dollar mission. Nasa launched the Lunar Reconnaissance Orbiter (LRO) last June to chart the landscape in unprecedented detail. Mapmakers on Earth need to know the LRO’s exact location as it spins around the Moon at 5 800 km/h, but conventional tracking methods that use microwaves are only accurate to within about 20 m. To get a better fix, researchers at Goddard Space Flight Centre in Maryland, USA, are locating the orbiter with a laser that flickers 28 times a second. An onboard detector records each pulse’s arrival and radios that information to Earth, enabling the researchers to calculate the position of the LRO, 400 000 km away, to within 10 cm.

No trick photography or digital manipulation was used, says Thomas Zagwodzki, who captured this image for NASA.

Camera: Olympus SP-565 UZ, 10-megapixel digital.
Exposure: 15 seconds, mid-range F-stop.
Condition: Fog helped make the beam visible.
Pointer: The beam’s original diameter is only about 30 cm, but it spreads to 19 km by the time it intercepts the LRO.

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