Hi all, 

I'm doing some Earth science textbook work, and have to do an illustration that incorporates a space satellite and a satellite dish on the ground. For both, I used NASA photos as reference. The client seems to be very picky about having things appear "realistic" - so I even took pains to make sure the satellite itself was appropriate for the content. 

The comments from the editor came back asking if I had "traced" photos for the satellite and dish (I did not) - but they do look realistic, which is what the client wants. She said that "tracing photos" is not allowed due to copyright issues.

My understanding is that government stuff, like NASA, NOAA, etc. - is in the public domain - so even if I HAD traced them, I would have been OK in doing so, as long as the finished product does not duplicate the photo. But even if I did want the object to look like the photo, I would be OK in making it look like the photographed object. 

Is my understanding correct on this? What IS the policy on using govt photos as reference. Are they indeed public domain? What if I did want to use an element that was part of a govt. photo in an illustration? Could I do so?

Thanks much,