Roamy here. 21 years ago, as Voyager 1 was leaving the solar system, it looked back and took a solar system family portrait. Earth was just a small blue dot, only a few pixels. Now the MESSENGER spacecraft, which has been studying Mercury since 2008, has done the same thing, but from the opposite angle. (click to embiggen)
MESSENGER stands for MErcury Surface, Space ENvironment, GEochemistry and Ranging and was launched in 2004. It will enter orbit around Mercury March 18. It has already discovered water in Mercury’s exosphere and evidence of volcanic activity on the surface.
I did some kind of testing for MESSENGER but can’t recall if it was the solar cells or optical property measurements. I’ll update if I get a brain wave.