Launch Period vs. Launch Window
(1:41) audio

Boeing's Kris Walsh describes the difference between the launch period and the launch window. The launch period is the number of days specified in which a mission can be launched to arrive at the proper orbit within a specific time period. The launch window occurs each day within the launch period.

TRANSCRIPTION of LAUNCH PERIOD VS. LAUNCH WINDOW audio:

One is the launch period, which is how many days we can launch a mission to the proper orbit. For low earth orbit, basically there's no concern. That launch period is 365 days a year. To go to Mars, or to go to L1 such as Genesis, or to an asteroid, you're severely limited because you need a certain energy to be imparted to that satellite. They might use another planet, or the moon to get into the proper orbit. So we work with the satellite provider. We work with the NASA [National Aeronautics and Space Administration] organization that give[s] us targets -- we get the satellite to that target with a certain energy and then the mission designers take over from there. We also have a launch window on a day-to-day basis. And that can range from one second to over an hour. All our Mars missions were one-second windows and we got those all off in the first or second day. When we do have 12 minutes or more, if we have a problem with the launch countdown we can safe the vehicle, recycle, and attempt again on the same day. If we have a one-second window, if we have any problems in the last four minutes of the countdown, we are down for 24 hours.