Emily Lakdawalla • Dec 30, 2013
Lunar Reconnaissance Orbiter spies Chang'e 3 and Yutu
As promised, Lunar Reconnaissance Orbiter's sharp eyes spotted the Chang'e 3 lander and Yutu rover on the lunar surface on December 25. The hardware shows up as a few bright pixels throwing long, dark shadows, clearly visible in a before-and-after comparison. The lander is the bigger blob, the rover a much smaller one.
These photos are not as high-resolution as previous Lunar Reconnaissance Orbiter images of lunar landing sites, because after the completion of its primary mission the spacecraft was moved from its low-altitude circular orbit to a higher and more stable elliptical orbit in order to lengthen its life at the Moon.* The orbit approaches to within 30 kilometers of the lunar surface near the south pole, with a maximum altitude of 200 kilometers near the north pole. As the Chang'e 3 mission landed relatively far to the north of the equator, the orbiter was at a relatively high 150 kilometers altitude when it took the photos. At a higher altitude, the spacecraft's orbit is not as strongly affected by the lunar "mascons," regions of relatively high gravity that tug orbits out of shape. But its camera can no longer get half-meter resolution all over the surface; it now gets a maximum of about 1.5 meters' resolution where Chang'e 3 landed. But that's good enough to spot hardware, as it has done here!
The Lunar Reconnaissance Orbiter Camera explainer on these images is great; I suggest it for further reading!
* An earlier version of this blog post incorrectly implied that Lunar Reconnaissance Orbiter was in a 150-kilometer circular orbit.
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