Incidentally, there's an Easter Egg in The Martian that you can solve using the Martian launch window:
The level of simulation required to find a launch window for Weir’s proposed Mars mission that overlapped Thanksgiving also leads to a neat Easter egg in the novel—although the mission’s exact date is never given (not even the year is mentioned), Weir absolutely has a launch date for the story. No one has yet figured out what it is, but the clues to do so are buried in the text for anyone who wants to consult a solar system ephemeris and work it out. ("What I’m afraid of is that someone will try it and prove that I was wrong, like, 'No, you had Mars’s location off by ninety degrees and everything else is wrong!'")
I want to give a shout-out to a fellow nerd named Kenny Ray.
When writing The Martian, I was as scientifically accurate as possible. I even worked out the orbital trajectories that they took to get to and from Mars. I had to write software to help me work out a constantly-accelerating orbital path. I also had to find a launch window such that Earth and Mars were properly positioned.
So I had to pick a real-world date for the launch of Ares 3. I never specifically tell the reader any dates, but I had a spreadsheet to tell me the actual date of each sol. And of course everything that was date-sensitive is accurate (like transmission times, etc.)
Kenny was able to back-calculate the actual dates from information in the book. He emailed me his findings and he was absolutely right. So, for being the first person to work that out, he gets a free signed copy of the book.
smile emoticon
For the curious: Ares 3 launched on July 7, 2035. They landed on Mars (Sol 1) on November 7, 2035. The story begins on Sol 6, which is November 12, 2035.
"We construct a new type of transfer from the Earth to Mars, which ends in ballistic capture. This results in a substantial savings in capture Δv from that of a classical Hohmann transfer under certain conditions. This is accomplished by first becoming captured at Mars, very distant from the planet, and then from there, following a ballistic capture transfer to a desired altitude within a ballistic capture set. This is achieved by manipulating the stable sets, or sets of initial conditions whose orbits satisfy a simple definition of stability. This transfer type may be of interest for Mars missions because of lower capture Δv, moderate flight time, and flexibility of launch period from the Earth. "
