Probing the Galactic Diffuse Continuum Emission with COSI

The under-explored energy range between 0.2 - 5 MeV will soon be probed with improved sensitivity by the Compton Spectrometer and Imager (COSI), a Small Explorer satellite mission selected by NASA and scheduled to launch in 2027. Although not one of its primary science goals, COSI will be capable of measuring the Galactic diffuse continuum emission (GDCE) with unprecedented sensitivity. These observations will provide a unique probe of the cosmic ray (CR) electron intensity throughout the Galaxy, having implications for the source density, injection, and propagation. In turn, COSI will help to address long-standing questions about the origin of CR electrons in the Galaxy. In preparation for measuring the GDCE with the satellite mission, we are analyzing data from the 2016 COSI balloon flight using the latest state-of-the-art models from the CR propagation code, GALPROP (v57). Our preliminary results show that the COSI balloon likely detected the GDCE, and that the observed flux toward the Galactic center is above the model predictions by a factor of ~2-4, in agreement with past results from COMPTEL and INTEGRAL. In this talk I will present the results and discuss plausible implications. I will also summarize the prospects for measuring the GDCE with the COSI satellite mission.