Last night, the Lunar Atmosphere and Dust Environment Explorer impacted the surface of the moon in a controlled crash.
Developed by NASA’s Ames Research Center in California, LADEE (pronounced laddie) was a $280 million robotic mission to orbit the moon, gathering details about the structure and composition of the lunar atmosphere and determining if dust is lofted into the lunar sky. "It's bittersweet knowing we have received the final transmission from the LADEE spacecraft after spending years building it in-house at Ames, and then being in constant contact as it circled the moon for the last several months,” LADEE project manager Butler Hine says in a news release.
The vending machine-sized dust probe was launched in September 2013 from NASA's Wallops Flight Facility in Virginia. It began orbiting the moon in October and gathering science data in November. Scientists hope to use the data to address a long-standing mystery: Was lunar dust, when electrically charged by sunlight, responsible for the pre-sunrise glow seen above the lunar horizon during several Apollo missions?
Earlier this month, LADEE maneuvered its way down to about two kilometers (or a mile) above the moon’s surface -- that’s lower than most commercial airplanes fly here. LADEE was actually the first to successfully fly more than 100 orbits at extremely low altitudes. And over its lifetime, LADEE has made the best measurements ever of dust kicked up when micrometeorites slam into the moon.
Another LADEE first, in its short but highly productive career: hosting NASA’s dedicated system for two-way communication using laser instead of radio waves. A pulsed laser beam transmitted data from the moon to Earth at a record-breaking download rate of 622 Mbps. Then, an error-free data upload rate of 20 Mbps was transmitted from the ground station back aboard LADEE. "We had a really high rate of data transmission,” Mihaly Horanyi at the University of Colorado, Boulder, tells New Scientist. “You could have watched Netflix on the moon if you wanted to.” Future versions could allow hi-def streaming of videos from space.
But all good things must come to an end. Because LADEE lacked the fuel to maintain a long-term lunar orbit or continue operations, it was intentionally sent into the moon’s surface. On April 11, LADEE performed a final maneuver to ensure a trajectory that’ll allow it to impact the far side of the moon -- where we can’t see or communicate with it. On Tuesday, the total lunar eclipse robbed LADEE’s solar panels of their electricity-generating ability and drained its batteries. “It was a nail-biting event,” Hine tells the New York Times. “I’ve never seen that many yellow and red alarms going off simultaneously.” But LADEE survived the cold and darkness (unexpectedly) and made some final measurements.
On April 17 at 10:59 pm Pacific time, Ames researchers confirmed LADEE’s crash, which took place between 9:30 and 10:22 pm. The spacecraft likely broke apart and heated up several hundred degrees (maybe even vaporized) at the surface. Anything that’s left is probably buried in shallow craters. "At the time of impact, LADEE was traveling at a speed of 3,600 miles [around 5,800 kilometers] per hour -- about three times the speed of a high-powered rifle bullet," LADEE project scientist Rick Elphic says in a news release. "There’s nothing gentle about impact at these speeds -- it’s just a question of whether LADEE made a localized craterlet on a hillside or scattered debris across a flat area." The Lunar Reconnaissance Orbiter team hopes to capture images of the impact site later.
Farewell, LADEE. May you rest in pieces knowing you left your mark.
Image: NASA Ames/Dana Berry
Correction: An earlier version stated that 3,600 miles is equivalent to 58,000 kilometers. This is of course wrong. The extra 0 has been deleted.