LADEE will explore the makeup of the moon’s flimsy atmosphere and test a cutting-edge communications system
NASA’s Lunar Atmosphere and Dust Environment Explorer spacecraft (LADEE) safely entered lunar orbit yesterday and will soon test its futuristic laser communications system. The Lunar Laser Communications Demonstration aboard LADEE will link up with ground stations in New Mexico, California and the Canary Islands, sending data packets back to Earth at the rate of hundreds of megabits per second.
After the testing is complete, NASA will lower LADEE’s orbit to begin its 100-day mission measuring the composition of the moon’s extremely tenuous atmosphere, where atoms are so few they never collide. LADEE will also explore the dust environment closer to the surface. Scientists hope to explain what causes the mysterious glow along the sunrise and sunset horizons seen by Apollo astronauts back in the 1960s and 70s. A leading theory holds that dust gets electrostatically levitated after being charged by solar radiation.
As the spacecraft begins its mission, we can turn toward the crescent moon, now making its return to the evening sky at dusk. Tonight and tomorrow night it joins Venus – don’t miss the opportunity to see the two brightest nighttime sky objects together against a colorful twilight sky.
Every month we get two opposing crescents – one in the evening after sunset, with the crescent’s horns pointing to the left or east, and the other at dawn shaped like the letter “C” with horns pointed west. These two crescent regimes flank either side of the new moon phase, when the moon lies almost directly between the sun and Earth. Except during a solar eclipse, we can’t see a new moon because it’s nearly in the same line of sight as the sun and lost in the glare of day.
A day or two before and after new, the moon lies far enough to one side of the Earth-sun line for its edge to turn into the sunlight. We see a shining crescent. As the moon continues along its orbit, the angle it makes to Earth and sun widens, and its phase waxes from crescent to half to full before returning to morning crescent and new.
With tonight’s crescent a brand new cycle begins. Watching the moon’s changing phases we become more familiar with its orbital motion and spatial relationship to the Earth and sun.