Iris is the name of a probe that's being sent by NASA to Mars to provide Watney with some much-needed food supplies. This is an acutely urgent necessity now that the potato farm is dead. Even so, it's calculated that the probe will still take over 400 days to reach its destination. That's presuming, of course, that Iris is successfully launched, which, unfortunately, it isn't.
This is largely because the NASA administrator, Teddy, chooses not to carry out the necessary inspections prior to the probe's launch. The results of such negligence are catastrophic. The protein cubes on board the probe liquefy and the shifting of the liquid to one side of the probe throws it off balance. At ground control, the signal has been lost, and to make matters worse, debris can be seen falling from the sky. The launch of Iris has been a complete, unmitigated disaster.