Calibration and In-flight Performance of DART’s Didymos Reconnaissance and Asteroid Camera for OpNav (DRACO)

Abstract The Didymos Reconnaissance and Asteroid Camera for OpNav (DRACO) was the only instrument on board NASA’s Double Asteroid Redirection Test spacecraft. DRACO had a 2628.326 mm focal length Ritchey–Chrétien telescope with a 208.28 mm aperture and a 0.29° field of view (FOV). The camera used a front-side-illuminated complementary metal–oxide–semiconductor (CMOS) sensor, BAE CIS2521F, with 2048 × 2048 illuminated pixels. DRACO worked with an onboard image processor to support autonomous targeting and ensure impact with Dimorphos, the secondary asteroid in the 65803 Didymos system, on 2022 September 26. This paper covers the calibration and in-flight performance of DRACO, including descriptions of ground and in-flight activities, instrument characterization, the calibration pipeline, and delivered Planetary Data System (PDS) products. DRACO exhibited low read noise and dark current that enhanced the instrument’s sensitivity, although the sensor’s nonlinearity and popcorn noise in global shutter mode required careful characterization and compensation to optimize terminal navigation performance. DRACO had a relatively circular point-spread function of less than two binned pixels across the full FOV. The combined calibration efforts achieved an absolute radiometric calibration (in both rolling and global shutter modes) of better than 20% and a relative calibration across an image of <0.2%, despite no formal radiometric requirements. DRACO acquired 259,290 images in flight, which have been delivered to the PDS in both raw and calibrated forms. DRACO’s excellent performance indicates that similar off-the-shelf CMOS detectors would be well suited for future planetary missions in low-radiation environments.