NASA has awarded a contract to SpaceX for the launch of the Compton Spectrometer and Imager (COSI) spacecraft. This contract, valued at approximately $69 million, covers the launch and related activities, scheduled for August, 2027.
The COSI mission, a Small Explorer (SMEX) class mission in low-Earth orbit, includes a gamma-ray telescope designed to study gamma rays emitted by massive star explosions at the end of their lives. These supernova explosions generate nucleosynthesis, fusing new atomic nuclei of heavier elements.
Scientists will use data from the COSI spacecraft to map the formation of these elements in the Milky Way. In addition, COSI’s observations will provide new insights about the annihilation of positrons, the antimatter equivalent of electrons, which appears to originate in the center of the galaxy. Another goal of COSI is to quickly report the location of short gamma-ray bursts, which are extremely violent explosions that light up and then disappear in just a few seconds, likely caused by the merging of neutron stars.
With a design previously tested on research balloons, the COSI telescope will focus on the so-called soft gamma rays, a relatively unexplored segment of the electromagnetic spectrum. After being selected by NASA in 2021 as the next mission of the Explorers program, COSI received formal approval for its development and launch in 2027, with a total budget of between $267 and $294 million.
The COSI spacecraft, built by Northrop Grumman, weighs less than a ton, but it’ll travel alone to orbit on a Falcon 9 rocket. The mission will operate at about 550 kilometers (342 miles) above the equator, in an orbit chosen to avoid radiation interference over the South Atlantic Anomaly. The Falcon 9 will place the COSI directly into its operational orbit and then perform a lateral maneuver to align with the equator, a maneuver that requires a lot of energy.
