Design of the Didymos Reconnaissance and Asteroid Camera for OpNav (DRACO) on the double asteroid redirection test (DART)

The Double Asteroid Redirection Test (DART) is a spacecraft that will impact the smaller body of the binary asteroid Didymos. As a technology demonstration, this will be the first time a kinetic impactor is used to perturb the motion of a near earth object. This technique could someday be used to deflect a dangerous asteroid on a future collision course with Earth. As the only instrument aboard DART, the Didymos Reconnaissance and Asteroid Camera for OpNav (DRACO) serves two purposes. First, DRACO provides images to the Small-body Maneuvering Autonomous Real-Time Navigation (SMARTNav) algorithm, allowing the spacecraft to precisely locate and impact the target. In its final moments, DRACO will also characterize the impact site by providing high resolution, scientific imagery of the surface. Derived from the Long Range Reconnaissance Imager (LORRI) on New Horizons, the telescope is a 208 mm aperture, f/12.6, catadioptric Ritchey-Chrétien, with a 0.29 degree field of view. A lightweight opto-mechanical structure, with low CTE mirror substrates and a composite baffle tube, maintains telescope focus in the low temperature environment of deep space. At the focal plane is a 2560 by 2160 pixel, panchromatic, front-side illuminated complementary metal oxide semiconductor (CMOS) image sensor, with digital output, global shutter, and low read noise. A highly integrated focal plane electronics (FPE) module controls the sensor and relays data to the spacecraft.