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Didymos Reconnaissance and Asteroid Camera for OpNav (DRACO)

NSSDCA ID: 2021-110A-01

Mission Name: Double Asteroid Redirection Test


The Didymos Reconnaissance and Asteroid Camera for OpNav (DRACO) has two primary functions. The first is to provide approach images of the Didymos system to the SMARTNav navigation algoriithm to allow precise targeting of the asteroid. The second is to provide high-resolution images (better than 20 cm/pixel at impact) of the surface of the asteroid to aid in characterizing the makeup of the body.

DRACO consists of three subsystems. The optical telescope assembly is rigidly mounted to the spacecraft body and points with the spacecraft movement. The focal plane and focal plane electronics (FPE) have the focal plane attached to the OTA and the FPE mounted on the spacecraft deck. The image processing and software is contained in the spacecraft computer.

The DRACO telescope is a Ritchey-Chretien design, with hyperbolic primary and secondary mirrors and a field-flattening lens. It uses a lightweight, extremely low coefficient of thermal expnsion design to maintain focus over a large low-temperature range, utilizing an M46J/R53 composite. The mirrors are composed of a glass ceramic substrate, Zerodur, with an enhanced silver coating mounted on INVAR flexures. the field flattening lens is fused silica with a VIS-NIR BBAR coating. The interior of the telescope is coated with Aeroglaze-Z-306 black paint.

The main tube, with the primary mirror mounted at one end and the secondary held at the other end by a spider mount, is 264 mm in diameter and 483 mm long. A baffle tube extends 64 mm past the secondary mirror. A smaller interior baffle tube, 32 mm in diameter and 241 mm long, is mounted in the center of the main tube, affixed at one end to the field flattening lens.

The main tube has five vanes, including the aperture stop, inside. The aperture is 208.28 mm, the telescope is f/12.60 with a field of view of 0.29 degrees. The 2560 x 2160 pixel CMOS focal plane array (2048 x 2048 optical format) is mounted at the end of the telescope, giving an instantaneous field-of-view of 2.48 microradians (0.51 arcsec). The instrument is sensitive to wavelengths from 400-1000 nm. Total mass of the instrument is 9.55 kg, it uses 4.95 W power for the electronics and 5.2 W for the heaters.

Light enters the main tube at the front end and reflects off the primary mirror at the end back to the secondary mirror at the front. From the secondary mirror it is reflected through the secondary baffle and passes through the field flattening lens at the back of the tube and is focused on the focal plane. The focal plane data is digitized into two 11-bit readouts, one in high gain mode and one in low gain mode. These two streams are sent to the Focal Plane Electronics, which combines them into a single 16-bit stream which passes to the Single Board Computer. Multiple data volume reductions (binning, compression, windowing) are available before transmission, allowing roughly one image to be sent to Earth every 5 seconds during proximity imaging operations. The images are also used on-board for closed loop guidance navigation.

Alternate Names

  • DoubleAsteroidRedirectionTest(DART)/DidymosReconnaissanceandAsteroidCameraforOpNav(DRACO)
  • urn:nasa:pds:context:instrument:dart.draco
  • urn:nasa:pds:context:instrument:dart.hga

Facts in Brief

Mass: 9.55 kg
Power (avg): 5 W

Funding Agency

  • National Aeronautics and Space Administration (United States)


  • Planetary Science: Geology and Geophysics

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail

Selected References

  • Fletcher, Z. J., et al., Design of the Didymos Reconnaissance and Asteroid Camera for OpNav (DRACO) on the double asteroid redirection test (DART), in Space Telescopes and Instrumentation 2018: Optical, Infrared, and Millimeter Wave, Proc. SPIE Vol. 10698, 106981X, doi:10.1117/12.2310136, Jul. 2018.
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