The phrase "a main mission" is correct and usable in written English.
It can be used to refer to the primary objective or goal of a project, organization, or individual.
Example: "The team's focus for this quarter is to complete a main mission of improving customer satisfaction."
Alternatives: "a primary objective" or "a key goal."
Homeschoolers are not the most obvious raw material for a college whose main mission, since its founding, five years ago, has been to train a new generation of Christian politicians.
After all, if we set up a system whose main mission is to satisfy boards of directors and to provide acceptable profits to stockholders, how can we expect that patient concerns will enter into the consciousness of the providers?
It stated: "At the time of a kidnapping the main mission becomes forcing the release of the abducted soldiers from their kidnappers, even if that means injury to our soldiers".
It may be crass force of habit to assume a band's main mission should be to increase their size and status but, even if Sonic Youth wanted to go for gold, it's difficult to see how they'd facilitate it.
Another Libyan guard said he saw Mr. Stevens escorted to the office in a wing off the main mission building, the room with an iron gate behind a wooden door.
The player is given a starship, and the main mission is to fight an alien race called the Distilled Evil and their slaves, the Sporg.
Although a diversion to the main mission, it proved to be an extremely productive one.
Instead, two weeks before graduation, he opted to seek a slot in the 147th Fighter Group, a Texas Air National Guard unit whose main mission was to defend the Gulf Coast.
Assuming ESA ENVISAT ASAR as main mission, a small satellite (BISSAT) equipped with a receiving-only antenna and flying in formation with ENVISAT is studied in details.
