"invaluable mission" is a correct and usable phrase in written English.
You can use it when you want to refer to a task or purpose as having great value and importance. For example, "The volunteers took on an invaluable mission to deliver food to those in need."
Postwar efforts to fly helicopters as short-haul passenger transports foundered, although they became invaluable in specialized missions (medevac, police patrol, traffic monitoring) and in sundry utility roles.
Similarly, the Thatcherite right's portrayal of Wilson as the personification of the failure of the postwar settlement provided an invaluable justification for its mission to remodel its relationship with the citizen.
Sam Loover, a family friend and an agent of World Intelligence Network (WIN), persuades Mac to dedicate the services of Joe and the BIG RAT to the organisation: Joe will become a WIN operative with a difference, the unlimited possibilities offered by the BIG RAT serving as an invaluable tool for completing missions.
Through her caring, insight and dedication to Women At Risk's mission, Inez provided invaluable support to countless people with cancer.
Through her caring, insight and dedication to Women At Risk's mission, Laura provided invaluable support to countless people with cancer.
Today, this data guides our mission and provides invaluable feedback on our programs.
His assertion that U.N.-led peacekeeping missions have made "invaluable contributions in stabilizing conflicts in Africa" was undercut by his criticism that "too often, the focus of this organization has not been on results but on bureaucracy and process".
Religious groups have been notably successful in placing and acclimating new immigrants, for example, and mission outposts have proved invaluable for the distribution of American famine relief overseas.
"Locally engaged Afghan staff working for our armed forces and civilian missions in Afghanistan make an invaluable contribution to the UK's efforts to help support the spread of security, stability and development in their country.
The space agencies say the data will be invaluable as they plan towards eventually mounting a mission to Mars.
