Last week, NASA's Lunar Atmosphere and Dust Environment Explorer (LADEE) beamed back its first images of the moon. But the images were a happy coincidence; the low-flying satellite was actually using its onboard camera systems to track stars, and orient itself by their positions.
According to NASA, "The main job of a star tracker is to snap images of the surrounding star field so that the spacecraft can internally calculate its orientation in space" – a task it completes multiple times per minute. "The accuracy of each of LADEE's instruments' measurements depends on the star tracker calculating the precise orientation of the spacecraft."
"Star tracker cameras are actually not very good at taking ordinary images," explains Butler Hine, LADEE project manager at NASA's Ames Research Center in California, in a statement. "But they can sometimes provide exciting glimpses of the lunar terrain."
This series of images was taken at one-minute intervals on February 8 at around 23:45 UTC, during lunar night. Earthshine, however – whereby the moon is not illuminated directly by the Sun, but indirectly by sunlight reflected off the Earth – was still illuminating the moon's surface, allowing LADEE to capture features in the northern western hemisphere. NASA gives the following play-by-play of what you can seen in each shot:
The initial image captured the smooth-floored crater Krieger, about 14 miles (23 km) in diameter, on the horizon, with four mile (seven km) wide Toscanelli, in the foreground.
The second image shows Wollaston P, about two-and-a-half miles (4 km) diameter, near the horizon, and the southeastern flank of the lunar mountain Mons Herodotus.
The third image caught a minor lunar mountain range, Montes Agricola, which is northwest of the large bright crater Aristarchus (out of view), as well as the flat-floored crater Raman, about six miles (10 km) diameter.
Image four in the series captures Golgi, about four miles (6 km) in diameter, and three-mile-wide (5 km) Zinner.
The final image views craters Lichtenberg A and Schiaparelli E in the smooth mare basalt plains of Western Oceanus Procellarum, west of the Aristarchus plateau.