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NASA's Lunar Orbiter Spots China's Lander Chang'e-3 On The Moon

First Posted: Jan 02, 2014 04:37 PM EST

China's moon lander Chang'e 3 successfully landed on the lunar Mare Imbrium (Sea of Rains) just east of a 450 m diameter impact crater on 14 December 2013 -- and it was spotted on Christmas Eve by NASA's Lunar Reconnaissance Orbiter as seen in this before-after-image.

Soon after landing, a small rover named Yutu (or Jade Rabbit in English) was deployed and took its first tentative drive onto the airless regolith. At the time of the landing LRO's orbit was far from the landing site so images of the landing were not yet possible.

Ten days later on 24 December, LRO approached the landing site, and LROC was able to acquire a series of six LROC Narrow Angle Camera (NAC) image pairs during the next 36 hours (19 orbits). The highest resolution image was possible when LRO was nearly overhead on 24 December 22:52:49 EST. At this time LRO was at an altitude of ~150 km above the site, and the pixel size was 150 cm.

The rover is only about 150 cm wide, yet it shows up in the NAC images for two reasons: the solar panels are very effective at reflecting light so the rover shows up as two bright pixels, and the Sun is setting thus the rover casts a distinct shadow (as does the lander). Since the rover is close to the size of a pixel, how can we be sure we are seeing the rover and not a comparably sized boulder?

Fortuitously, the NAC acquired a "before" image of the landing site, with nearly identical lighting, on 30 June 2013. By comparing the before and after landing site images, the LROC team confirmed the position of the lander and rover, and derived accurate map coordinates for the lander (44.1214°N, 340.4884°E, -2640 meters elevation).

The lander set down about 60 meters east of the rim of a 450 meter diameter impact crater (40 meters deep) on a thick deposit of volcanic materials. -- Source: University of Arizona

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