launch window
n.
A brief, specific period of time during which a spacecraft or projectile must be launched so that a desired mission or effect can be achieved.

[TahlilGaran] American Dictionary ▲

launch window
n., Space English, informal
1. A period of time when the line-up of planets, Sun, and Moon are such as to make favorable conditions for a specific space launch.
The mission was canceled until the next launch window which will be exactly six weeks from today.
2. A favorable time for starting some kind of ambitious adventure.
My next launch window for a European trip isn't until school is over in June.

[TahlilGaran] English Idioms Dictionary ▲