The anime is a 12-parter, and I believe it covers the first two books. The description of the second book at Amazon and elsewhere is a bit off - the girls have to fix a space probe that's going to Pluto, but Amazon makes it sound like the girls are going to Pluto themselves.

And in the midst of my googling, I also found an interview with Housuke Nojiri at the JAXA website:

http://www.jaxa.jp/article/interview/vol33/index_e.html