Launch window

The definitions given here are as used by launch directors and trajectory analysts at NASA and other space agencies.

In more complex cases, including the use of gravitational slingshots, launch periods are irregular.

Sometimes rare opportunities arise, such as when Voyager 2 took advantage of a planetary alignment occurring once in 175 years to visit Jupiter, Saturn, Uranus, and Neptune.

[14] Launch windows and days are usually calculated in UTC and then converted to the local time of where the rocket and spacecraft operators are located (frequently multiple time zones for USA launches).

[15] For trips into largely arbitrary Earth orbits, no specific launch time is required.

Achieving the correct orbit requires the right ascension of the ascending node (RAAN).

RAAN is set by varying a launch time, waiting for the earth to rotate until it is in the correct position.

The launch vehicle will have a target, and the guidance system will alter the steering commands to attempt to get to the final end state.

[18] Due to the relationship between an orbiting object's beta angle (in this case, the ISS) and the percent of its orbit that is spent in sunlight, solar power generation and thermal control are affected by that beta angle.