WASHINGTON — NASA tapped United Launch Alliance (ULA) and Space Exploration Technologies Corp. (SpaceX) to launch a total of four Earth Science missions between 2014 and 2016, the agency said in a pair of press releases issued late July 16.

United Launch Alliance of Littleton, Colo., got a $412 million contract to launch three of the missions aboard Delta 2 rockets from Space Launch Complex 2 at Vandenberg Air Force Base, Calif. ULA will launch NASA’s Soil Moisture Active Passive spacecraft in October 2014, the Orbiting Carbon Observatory-2 in July 2014, and the Joint Polar Satellite System-1 in November 2016. NASA in March said that ULA was likely to get a contract for these missions.

Hawthorne, Calif.-based SpaceX, meanwhile, will get $82 million to launch Jason-3, which is a Europe-U.S. satellite that will measure the height of global sea surfaces. The mission will ride to space aboard a Falcon 9 in December 2014 from Vandenberg’s Space Launch Complex 4, NASA said. The missions stands to be SpaceX’s first launch of a NASA science satellite. SpaceX also bid on the trio of Earth Science launches that went to ULA.

ULA’s Delta 2 was once the go-to medium-lift vehicle for NASA and the Air Force. The Air Force, which footed the bill for most of the rocket’s support costs, stopped using Delta 2 in 2009. NASA subsequently said it could not absorb those costs and also decided to stop using Delta 2, which is no longer in production.

ULA has parts for five Delta 2 rockets left in its inventory. The rocket last flew in October, when it launched NASA’s Suomi NPP weather and climate satellite from Vandenberg.

NASA Earth Science officials have said that they are willing to pay a premium price for launch reliability to avoid losing any more payloads. Back-to-back failures of Orbital Sciences Corp.’s Taurus XL rocket in 2009 and 2011 doomed two Earth science satellites at a cost of about $1 billion to the agency, NASA Earth Science Director Michael Freilich said July 10.

Dan Leone is a SpaceNews staff writer, covering NASA, NOAA and a growing number of entrepreneurial space companies. He earned a bachelor’s degree in public communications from the American University in Washington.