One Apollo 11 Experiment Is Still Going 50 Years Later

The Lunar Laser Ranging Experiment lets NASA precisely measure the distance between Earth and the moon

5 min read
Image of the laser deployed from the facility and pointing toward the sky.
Goddard’s Laser Ranging Facility in Greenbelt, Md., directing a laser (green beam) toward the Lunar Reconnaissance Orbiter spacecraft in orbit around the moon (white disk). The moon has been deliberately over-exposed to show the laser.
Photo: Tom Zagwodzki/Goddard Space Flight Center

THE INSTITUTEIf nothing else will convince someone that humans once walked on the moon, NASA’s lunar ranging experiment (LURE) should. It’s because of that experiment that scientists know the precise distance between the Earth and the moon with centimeter accuracy.

The LURE’s first demonstration began on 1 August 1969, when a pulse of trillions of photons was shot out of a telescope at Lick Observatory on Mount Hamilton, outside of San Jose, Calif. The laser pulse traveled to the moon and returned after reflecting off a 1-meter-wide array of mirrors—retroreflectors—that Apollo 11 astronauts had placed on the lunar surface 12 days earlier.

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How the FCC Settles Radio-Spectrum Turf Wars

Remember the 5G-airport controversy? Here’s how such disputes play out

11 min read
This photo shows a man in the basket of a cherry picker working on an antenna as an airliner passes overhead.

The airline and cellular-phone industries have been at loggerheads over the possibility that 5G transmissions from antennas such as this one, located at Los Angeles International Airport, could interfere with the radar altimeters used in aircraft.

Patrick T. Fallon/AFP/Getty Images
Blue

You’ve no doubt seen the scary headlines: Will 5G Cause Planes to Crash? They appeared late last year, after the U.S. Federal Aviation Administration warned that new 5G services from AT&T and Verizon might interfere with the radar altimeters that airplane pilots rely on to land safely. Not true, said AT&T and Verizon, with the backing of the U.S. Federal Communications Commission, which had authorized 5G. The altimeters are safe, they maintained. Air travelers didn’t know what to believe.

Another recent FCC decision had also created a controversy about public safety: okaying Wi-Fi devices in a 6-gigahertz frequency band long used by point-to-point microwave systems to carry safety-critical data. The microwave operators predicted that the Wi-Fi devices would disrupt their systems; the Wi-Fi interests insisted they would not. (As an attorney, I represented a microwave-industry group in the ensuing legal dispute.)

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