The first scene of "The Martian" a storm kicks up on the surface of Mars and the crew of the Ares 3 decide they need to abandon their mission and return to the Hermes. They quickly board the MAV and launch, somehow successfully getting back to the Hermes.
It's established later that the MAV are suborbital craft, and aren't intended to reach orbit (at-least not without heavy modifications).
If the Hermes is set to orbit Mars while the crew works on the surface (assuming the Hermes is in a "sub-orbital orbit", otherwise the MAV would never reach the altitude to reach the Hermes in the first place), there seems to be a pretty good chance the Hermes is no where near where the MAV would need it to be to pick up the crew.
At-least within the context of the movie, we don't see the crew check on the position of the Hermes when they launch.
My question: What is the likely-hood the Hermes is right where it needs to be to pick up the crew. Is there any science behind the crew being able to abandon the planet at a moment's notice and be able to make it back to the Hermes safely, or would the science conclude that they could only abandon the planet in a very small window of time, when the Hermes is in prefect position to retrieve the crew?