This document contains the high-level overview of the DRACO Raw Data Collection. Data Set Overview =============================================================================== This collection consists of DRACO raw images contained in FITS files. The Level-0 raw DRACO image format is a single HDU, 1024 (sample) x 1024 (line), 32-bit floating point FITS file, 2x2 binned from the original 2048 x 2048 window1, in units of DN. Metadata contained in the FITS header and mapping to class and attribute in the PDS4 xml label structure is in the jhuapl_dart_draco_uncalibrated_calibrated_sis document. Refer to the jhuapl_dart_draco_uncalibrated_calibrated_sis document for more details on the data product structure. Instrument Overview =============================================================================== DRACO is a narrow-angle, panchromatic, visible light imager consisting of an optical telescope assembly, a focal plane array with associated electronics, and image processing software. DRACO has a Ritchey-Chretien telescope with an aperture of 208 mm, operates at f/12.6, and has a field of view of 0.29 deg. The focal plane array is a 2560 x 2160 pixel, panchromatic, front-side illuminated complementary metal–oxide–semiconductor (CMOS) sensor with 6.5 micrometer pixels with digital output. The instantaneous field of view (IFOV) is 2.48 microradian unbinned, or 4.96 microradian binned. The detector is sensitive to light from 400–1000 nm. DRACO was designed to support optical navigation of the spacecraft and ensure impact with Dimorphos (the secondary member of the Didymos system), to refine system properties (e.g., orbit, rotation rate, pole), to characterize the surface characteristics and shape of Dimorphos during the Terminal and Final mission phases, and to constrain the location of the impact site. The latter observations will allow insight into target properties, presence or absence of blocks at the impact site, and impact angle, which will feed into the estimation of dynamical changes in the Didymos system resulting from the DART impact. The DRACO detector runs in both global and rolling shutter readout modes and has dual high and low gain output, although only one output can be recorded at a time. There are four possible gain settings: low gain amplification can be set to 1x or 2x; high gain amplification can be set to 10x or 30x. DRACO typically employs high gain, 30x when operating in rolling shutter mode to maximize the SNR, and low gain, 1x when operating in global mode during the Terminal and Final mission phases to prevent saturation and maximize the dynamic range of the images. Data =============================================================================== Each final Level-0 raw PDS4 data product will consist of: 1) A 32-bit floating point fits file with one Header Data Unit (HDU) containing the metadata header fields and the data unit of the array (1024 pixels x 1024 pixels). The data are represented as DN. 2) A browse PNG created from the raw FITS file. Pixel values indicating “outside of window”, “missing data”, or identified as a "bad pixel" will be set to zero in the browse PNG. Saturated pixel values will be set to 255 in the browse PNG. DRACO images are acquired at a 1.04 Hz rate (0.962 seconds per image). The shutter mode, gain, and exposure time are defined for every imaging sequence. All DRACO images start out 2560 x 2160 pixels, are windowed to 2048 x 2048 pixels, and are 2 x 2 binned to 1024 x 1024 pixels. The data can be further windowed to 512 x 512 pixels to reduce file size and allow for continuous image downlinking before impact during the Terminal and Final phases of the mission. The position of this second window is centered on the region of interest (ROI). Upon receipt at the MOC, each 512 x 512 image is placed back into its original location within the binned, 1024 x 1024 image display frame. The PXOUTWIN keyword defines the pixel value used by ground software to populate all pixels within the 1024 x 1024 image that are outside the 512 x 512 second window. A 1024 x 1024 calibration table can be subtracted from binned data (unsigned, minimum pixel value = 0). This calibration table is stored onboard and also contains a map of bad pixels. The calibration table subtraction is effectively a bias subtraction, and improves the performance of SMART Nav targeting. The baseline plan is to subtract the on-board calibration table from all images during the Terminal and Final phases of the mission and during SMART Nav tests. The raw collection includes these types of images ‘as-is’. Calibrated images created from raw images with on-board calibration subtraction will reverse the on-board calibration table on the ground. See the data_dracocal collection for these images. Refer to the jhuapl_dart_draco_calibration_pipeline_description_v1.pdf document for more details on the calibration process. DRACO uncalibrated data products are identified with file names in the format of: dart_SSSSSSSSSS_sssss_##_. SSSSSSSSSS 10-digit value of IMGTMSEC sssss 5-digit value of IMGTMSUB ## two digit version number, e.g., “01” defines product as one of the following types: raw the file extension: .fits for fits file format .png for PNG files