WASHINGTON — Orbital Sciences Corp. is protesting a $400 million NASA engineering services contract awarded to SGT Inc. in May to support the Joint Polar Satellite System and other projects at the agency’s Goddard Space Flight Center in Greenbelt, Md.

The Joint Polar Satellite System is the next-generation U.S. polar-orbiting weather satellite system.

SGT underbid Orbital and QinetiQ North America of Fairfax, Va., to win the Omnibus Multidiscipline Engineering Services (OMES) contract, a five-year indefinite-delivery, indefinite-quantity contract to help Goddard’s Applied Engineering and Technology Directorate develop hardware and software for agency Earth and space science missions.

NASA took nearly a year to evaluate OMES proposals, narrowing the field to SGT and Orbital in April before ultimately selecting SGT on the basis of cost.

SGT, a Greenbelt-based company that holds several large Goddard support contracts, has grown to 1,500 employees since winning its first NASA contract in the mid-1990s.

Goddard Deputy Director Arthur “Rick” Obenschain, writing in the May 29 OMES selection statement posted in late June on NASA’s procurement website, said the SGT and Orbital proposals both received high marks for mission suitability and past performance, but “SGT offered a significantly lower proposed and probable cost than Orbital.”

QinetiQ North America “was eliminated from the competition” after the three bidders submitted their final proposal revisions in mid-April, according to the OMES selection statement.

Orbital formally protested NASA’s decision June 18 to the U.S. Government Accountability Office, which has until Sept. 26 to resolve the case. NASA’s response to the complaint is due July 18, with Orbital’s comments due 10 days later, according to the congressional watchdog agency, which handles contract bid protests.

Goddard contracting officer Antwan Reid said July 12 that the OMES contract is on hold pending resolution of the protest. In the meantime, he said, Goddard’s Applied Engineering and Technology Directorate will rely on various discipline-specific engineering contracts to support its activities.

Orbital spokesman Barron Beneski said July 10 that the company does not comment on bid protests.