I pointed out the IRAS picture to Paul. It's interesting that the Pioneer drag data may be the only direct measurement of the dust density. I was a little surprised that it hadn't been considered before.

The IRAS picture has always been interesting to me because it dramatically shows that the projection of the plane of the ecliptic crosses the galactic plane right at the center of the galaxy. I've always wondered if there's a gravitational reason for this and if it is true for other planetary systems. Unfortunately, so far as I have been able to find out, there is not yet a way to determine the orbital planes of extrasolar planets.

We also studied the zodiacal light and gegenschein from Skylab. I collected the pictures for this chapter:
http://history.nasa.gov/SP-404/ch3.htm