If it makes you feel better, the Earth missions are not shown. There are a lot. Also, they seem to have left out missions that end in the Lagrange points. L1

If it makes you feel better, the Earth missions are not shown. There are a lot. Also, they seem to have left out missions that end in the Lagrange points. L1 is about 1% of the way to the Sun, and SoHO (for one) went there in 1996 and is still operating there. L2 is 1% in the opposite direction, and WMAP and Planck are/were there in 2009 when that map was made. Finally, I think Stereo A and B may not be not there either; they trail/lead the Earth in its orbit; now they are almost on the opposite side of the Sun compared to Earth (http://stereo-ssc.nascom.nasa.gov/where.shtml http://stereo-ssc.nascom.nasa.gov/where.shtml).