Indeed, the 2009 AP English Language and Composition synthesis essay prompt is about space exploration:
"Explorers and tales of explorations tend to capture the human imagination. However, such explorations have financial and ethical consequences. Space exploration is no exception."
There is a list of eight sources that accompany the prompt--you do not need to use all the sources in your essay, but three to four are reasonable. Keep in mind that your ARGUMENT should be the central part of the essay--only uses the sources to SUPPORT the argument you make about space exploration.
Follow the link below directly to the College Board's AP Central website. Here you can find the prompt, the exact sources, the scoring rubric, and student sample essays that have been scored by the College Board readers. They also include comments on why essays have received the scores that they did. You should be able to get an idea about what the College Board (and your teacher) is looking for in the synthesis essay.