Didymos Reconnaissance and Asteroid Camera for OpNav (DRACO): design, fabrication, test, and operation

DRACO is the only instrument on the Double Asteroid Redirection Test (DART) spacecraft. DRACO is a narrow angle camera designed to provide final images of the Didymos system at less than 0.50 m/px ground scale as well as provide images to be used for the Small-body Maneuvering Autonomous Real Time Navigation (SMARTNav) targeting system on board the DART spacecraft. DRACO includes an F/12.6, 2625mm focal length Ritchey-Chrétien telescope with a field-flattening lens. Images are taken with a 6.5um CMOS image sensor, the BAE CIS2521F, by the DRACO Focal Plane Electronics (FPE) and transferred to the spacecraft. Images are then processed for blobs and centroids for use in SMARTNav and either downlinked in real-time or recorded on the spacecraft for later playback. DRACO is thermally isolated and operated at -80°C to -20°C. Alignment was completed at room temperature, with additional checks after vibration testing and a focus shim was added for operation at cold temperature. Performance is near-diffraction limited and in-flight performance matches well with ground measurements. The BAE CIS2521 is measured to have very low read noise (< 2 e-) and negligible dark current. DRACO was integrated on the DART spacecraft in June 2021 after a successful instrument development and test campaign. DRACO is currently in use on the DART spacecraft after a successful commissioning. It will be used as the primary guidance sensor for the DART impact in September 2022 and provide high-resolution images of the Didymos system.