Planetes, Futatsu no Spica Recommendations
Both Planetes and Twin Spica deal with astronauts, although in Twin Spica's case, they are astronauts-in-training. Both are serious dramas involving the emotional growth of the main characters, but Planetes offers far more in the way of comic relief. Twin Spica, on the other hand, is a fairly intense emotional drama with little in the way of comic relief. Fans of the more serious moments of Planetes will probably find much to enjoy in the oftentimes sad tale of Twin Spica.
Human drama about space exploration, which faces tragedy as often as it faces success.