COSI Mission Selected by NASA to be Launched by SpaceX

On July 2, 2024, in an official update, NASA announced that it awarded a contract to SpaceX to provide the launch services for the Compton Spectrometer and Imager (COSI) mission. The contract has a value of $69 million, which includes Launch services and other related costs.

*SpaceX Falcon 9 standing vertical at SLC-4E for Starlink 2-8 mission. Credits: SpaceX*

The launch, originally planned for 2025, is currently scheduled for August 2027. COSI will fly on a Falcon 9 rocket from SLC-40 at Cape Canaveral Space Force Station. This delay is due to an extension of the Phase B design work aimed at reducing long-term costs.

The Mission

COSI’s mission is a collaboration between the University of California, Berkeley’s Space Sciences Laboratory, the Naval Research Laboratory, the University of California, San Diego, NASA’s Goddard Space Flight Center, and Northrop Grumman. It aims to bring to orbit the COSI telescope, a soft gamma-ray survey telescope designed to explore the origins of Galactic positrons. It will identify nucleosynthesis sites in the Galaxy, conduct groundbreaking gamma-ray polarization studies, and discover counterparts to multi-messenger sources.

*An illustration of the COSI spacecraft*. *Credits: NASA*

COSI was chosen as a part of NASA’s Astrophysics Explorers Program, which received 18 telescope proposals in 2019 and selected four for mission concept studies. After evaluations by scientists and engineers, in 2021, NASA officially selected COSI to proceed with the development.

From 2021 to 2023, the mission focused on detailed design and planning, achieving the Systems Requirements Review/Mission Definition Review (SRR/MDR) in January 2023, and the Preliminary Design Review (PDR) in February 2024.

In April 2024, COSI completed its Key Decision Point C (KDP-C) review. This allowed it to transition from the formulation phase to the implementation phase. This includes the assembly, integration, and testing of its components for the launch scheduled in 2027.

COSI Telescope

The COSI (Compton Spectrometer and Imager) telescope is an advanced gamma-ray observatory that delivers high sensitivity and resolution. Central to its design are sixteen 3D-imaging, high spectral resolution germanium detectors (GeDs), crucial for precise measurements of gamma-ray interactions. These detectors, housed within an evacuated aluminum cryostat and maintained at cryogenic temperatures by a mechanical cryocooler, offer a high energy resolution. Bismuth Germanate scintillator detectors surround the cryostat. These serve as an anti-coincidence shield to reduce background noise and improve detection accuracy.

*The Compton Spectrometer and Imager (COSI). Credits: UC Berkeley*

COSI utilizes a compact Compton telescope design, which integrates the scatterer and absorber within a single detector volume. This design allows for efficient imaging, spectroscopy, and polarization studies of gamma-ray sources. The telescope will be able to accurately measure the position and energy of gamma-ray interactions. Thus it will construct detailed maps of gamma-ray sources and analyze their properties with high precision.

The COSI mission is set to advance the field of gamma-ray astronomy by utilizing cutting-edge technology and collaborative efforts from multiple prestigious institutions. With the 2027 launch on a Falcon 9 rocket, the mission aims to provide valuable insights into gamma-ray sources within our galaxy. The contribution to our understanding of the universe is going to be significant.