# The 2016 Super Pressure Balloon flight of the Compton Spectrometer and Imager

## TL;DR

The 2016 Super Pressure Balloon flight of COSI demonstrated its capabilities as a gamma-ray imager and polarimeter, achieving preliminary results in line with its scientific objectives during a 46-day flight.

## Contribution

This paper reports the first flight of COSI on a Super Pressure Balloon, showcasing its design, performance, and initial scientific results in gamma-ray astronomy.

## Key findings

- Successful 46-day flight on Super Pressure Balloon
- Preliminary detection of gamma-ray signals aligned with science goals
- Validation of instrument performance and sensitivity

## Abstract

The Compton Spectrometer and Imager (COSI) is a balloon-borne, soft-gamma ray imager, spectrometer, and polarimeter with sensitivity from 0.2 to 5 MeV. Utilizing a compact Compton telescope design with twelve cross-strip, high-purity germanium detectors, COSI has three main science goals: study the 511 keV positron annihilation line from the Galactic plane, image diffuse emission from stellar nuclear lines, and perform polarization studies of gamma-ray bursts and other extreme astrophysical environments. COSI has just completed a successful 46-day flight on NASA's new Super Pressure Balloon, launched from Wanaka, New Zealand, in May 2016. We present an overview of the instrument and the 2016 flight, and discuss COSI's main science goals, predicted performance, and preliminary results.