WASHINGTON: "One of two teams building competing payload designs for the U.S. Space Force’s next missile warning satellites completed critical design review, clearing the way for fabrication. The payload will be incorporated into one of the first two satellites in the Next Generation Overhead Persistent Infrared constellation, a new space-based missile warning system being built to replace the Space Based Infrared System, or SBIRS. Like the current constellation, Next Gen OPIR will be able to detect and track ballistic missiles all over the globe. The first block of the new constellation will be made up of five satellites, three in geostationary orbit, and two more in highly elliptical orbits to provide polar coverage.

Lockheed Martin, the prime contractor for the three geostationary satellites, has subcontracted for two competing designs for the mission payload itself, which it will integrate with its bus. Northrop Grumman and Ball Aerospace are working together on one design, with Raytheon Technologies working on a separate effort. In addition to designing one of the payloads for the geostationary satellites, Northrop Grumman is also developing the polar satellites. The Space Force has already begun work on the next block of Next Gen OPIR satellites, which could be placed in medium Earth orbit rather than geostationary orbit."

https://www.c4isrnet.com/battlefield-tech/space/2021/08/06/northrop-grumman-ball-aerospace-clear-milestone-for-missile-warning-payload/