Stardust Navigation Camera:
The Navigation Camera (NC) is an engineering subsystem used to optically navigate the Stardust-NExT spacecraft upon approach to the comet. This will assist the spacecraft in achieving a proper comet Tempel 1 flyby distance, near enough to the nucleus to assure adequate dust collection, while keeping it out of danger. The camera will also serve as an imaging camera to collect science data. This will include capturing high-resolution color images of the comet nucleus, on approach and on departure, and broadband images at various phase angles while nearby.
The Navigation Camera images will be used to construct a 3-D map of the comet nucleus in order to better understand its origin, morphology and mechanisms, and to search for mineralogical irregularities on the nucleus. It could potentially supply information on the nucleus rotation state too. The camera will provide images, taken through different filters, to provide information on the gas and dust coma during approach and departure phases of the mission. These images may be able provide information on gas composition, gas and dust dynamics and possible jet phenomena.
Navigation Camera. Courtesy: NASA
In order to meet these science and optical navigation objectives the NC design was developed utilizing a Voyager Wide Angle Optical Assembly. Additionally, the NC has a newly developed scan mirror mechanism to vary the camera viewing angle and a periscope to protect the scanning mirror while the spacecraft flies through the comet coma. The NC is a framing charge coupled device (CCD) imager with a focal length of 200 mm. The NC has a focal plane shutter and filter changing mechanism of the Voyager/Galileo type.
At the heart of the camera is a charge-coupled device (CCD) used as a detector, cooled to suppress dark current and shielded from protons and electrons. The electronics contain the signal chain and CCD drivers located in the sensor head, command and control logic, power supplies, mechanism drivers, a digital data compressor and two UARTs too interface with the spacecraft Command and Data Handling (C&DH).
NC command and telemetry functions will also be handled by the electronics, including storage of science commands, collection of science imaging data and telemetry, transmission of imaging data and telemetry to C&DH and receipt of commands from C&DH. The NC uses a data rate of 300 k pixels for transferring data to the C&DH. There is also the option for data reduction with 12 bit to 8 bit square root compression, windowing and error free compression within windows.