PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = " 2017-07-29, Joy, Modified from FC1 L1b cruise ds.cat; 2017-09-22, Joy, Updated after peer review;" OBJECT = DATA_SET DATA_SET_ID = "DAWN-A-FC1-3-RDR-CERES-IMAGES-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "DAWN FC1 CALIBRATED CERES IMAGES V1.0" DATA_SET_TERSE_DESC = "Reduced data records for Framing Camera 1 during the Dawn Ceres extended mission." DATA_SET_COLLECTION_MEMBER_FLG = N START_TIME = 2017-02-19T00:00:00 STOP_TIME = 2017-04-30T00:00:00 PRODUCER_FULL_NAME = "PABLO GUTIERREZ-MARQUES" DATA_SET_RELEASE_DATE = 2017-09-01 DETAILED_CATALOG_FLAG = N DATA_OBJECT_TYPE = "IMAGE" CITATION_DESC = " Nathues, A., H. Sierks, P. Gutierrez-Marques, S. Schroeder, T. Maue, I. Buettner, M. Richards, U. Chistensen, U. Keller, DAWN FC1 RAW (EDR) CRUISE CHECKOUT/CALIBRATION IMAGES V1.0, DAWN-X-FC1-2-EDR-CRUISE-IMAGES-V1.0, NASA Planetary Data System, 2017." ABSTRACT_DESC = " Abstract ======== This dataset contains calibrated Framing Camera 1 (FC1) images sometimes called level-1b or reduced data. It includes images from the Dawn Ceres eXtended Mission Orbit 3 (XMO3, aka Ceres Extended GRaND - CXG) phase on 2017-02-19 and the Ceres eXtended Mission Orbit 4 (XMO4, aka Ceres Extended Opposition - CXO) phase on 2017-04-29. FC1 is one of two identical units flying on Dawn spacecraft. It was designated as the backup system to be used only in the event of a failure of the primary system, FC2. Prior to the Ceres extended mission, FC1 had only been used for in-flight calibration and to periodically exercise its various mechanisms (door, filter wheel, etc.). This is the only science dataset generated by FC1." DATA_SET_DESC = " Dataset overview ================ This dataset contains calibrated Framing Camera 1 (FC1) images sometimes called level-1b or reduced data. It includes images from the Dawn Ceres eXtended Mission Orbit 3 (XMO3, aka Ceres Extended GRaND - CXG) phase on 2017-02-19 and the Ceres eXtended Mission Orbit 4 (XMO4, aka Ceres Extended Opposition - CXO) phase on 2017-04-29. FC1 is one of two identical units flying on Dawn spacecraft. It was designated as the backup system to be used only in the event of a failure of the primary system, FC2. Prior to the Ceres extended mission, FC1 had only been used for in-flight calibration and to periodically exercise its various mechanisms (door, filter wheel, etc.). This is the only science dataset generated by FC1. As in the original raw data sets, in addition to the imagery, ancillary information is stored within the image headers, as well as a detailed account of all the reference files used for the calibration. Calibration files needed for further processing are archived as a separate data set. The images in this dataset have been radiometrically calibrated by means of fully reversible procedures, transforming the value of the pixels from digital units to applicable engineering units without modification of the geometry. For more information on the contents and organization of the volume set refer to the aareadme.txt file located in the root directory of the data volumes. Parameters ========== Compression: FC images may optionally be compressed by wavelet transformation. Wavelet compression: Images may be integer or floating point wavelet transform-compressed in the DPU. The integer approach produces lossless compression, while the floating point can induce distortions of +/-1 DN. The encoding of the wavelets ensures that any length of the data starting at the beginning can be decoded, thus allowing to compress further by discarding the trailing part. Windowing: In order to manage downlink resources, up to 10 portions of the image can be selected in the DPU and downlinked as subframes. The subframes are allowed to overlap. During EDR construction each subframe is stored separately and also mosaicked into the original image. Exposure Control: The exposure time of FC images is set by command for each image. Pointing: The Framing Cameras are fixed mounted onto the Dawn Instrument deck, with the nominal alignment of the optical axis with the +Z axis of the spacecraft. Deviations from the nominal are documented in the calibration data. Filter selection: The FC has 8 filters at its disposal, numbered from F1 to F8. F1 is a broadband (clear) filter, sensitive in the wavelength interval from 400 to 1100 nm peaking at 700 nm. The narrow-band color filters are of the interference type, and have wavelengths ranging from 430 to 980 nm. Processing ========== An FC image downlinked by the spacecraft unpacks into a succession of one or more compressed image subframes with an attached PDS headers containing housekeeping items that include full status of the instrument hardware, software configuration, temperature, voltage and current readings. The data in one EDR consists of one or more reconstructed image frames, with the accompanying header translated into text format in the label. The dimensions and location (pixel coordinates) of each frame are included for proper further processing. Each frame is formatted into one file (suffix *.IMG), with an attached label. Subframes are retained as separate entities and also are reassembled into their original coordinates in the 'summary' image. Parts of the reconstructed image not included in the subframes are given a value of zero. The label contains all relevant housekeeping information in calibrated form (e.g. degrees Celsius, volts, or amperes. For further details on the layout of the data and the possible combinations of frames, please refer to the Software Interface Specification. The calibration process is divided into several steps that aim to remove the effect of different source of noise: conversion from 16-bit integer to 32-bit floating point, read-out bias, dark current, read-out smear, flat field non-uniformity, correction of under-sensitive pixels, exposure normalization, radiometric calibration. For more detailed information on the calibration process, please refer to [SCHROEDER&GUTIER2011]. For a discussion of which calibration images to use for a given activity, please refer to the data set catalog file for DAWN-CAL-FC1-2-EDR-CALIB-IMAGES-V1.0. " CONFIDENCE_LEVEL_NOTE = " Exposure times ============== Due to an idiosyncrasy of the proximity electronics, that takes approximately 193 milliseconds from the commanding of the image acquisition to the actual start of the exposure, the images report the commanding time and the end of exposure. This results in a difference of 193 milliseconds between the usual calculation of exposure time (STOP_TIME - START_TIME) and the reported EXPOSURE_DURATION, which is always shorter than the difference of the other two. Calibration files ================= All the files involved in the calibration of this data set have been subsequently delivered as part of the calibration data set. Furthermore, the history part of the PDS header of each image lists which calibration files was used for each of the calibration steps. Since FC1 had not been previously used for science, new flats and composite darks were generated specifically to be used with these data (see calibration volume. Data Coverage ============= -------------------------------------------------------------------------- Dawn Ceres Science Observations with FC1 -------------------------------------------------------------------------- Start Mission Activity Activity Date Phase Name Description -------------------------------------------------------------------------- 16-12-14 CXG XMO3 Ceres Extended GRaND Phase (range ~8000-9500 km) -------------------------------------------------------------------------- 17-02-19 CXG CYCLE3 296 FC2~nadir clear+color (1 orbit) 96 FC1~nadir clear+color -------------------------------------------------------------------------- 17-04-28 CXO XMO4 Ceres Extended Opposition Phase (range 14-55E3 km) -------------------------------------------------------------------------- 17-04-29 CX0 Opposition 194 FC2~nadir clear+color (range ~20,000 km) 188* FC1~nadir clear+color -------------------------------------------------------------------------- * FC1 clear images were interleaved with the FC2 clear images by acquiring them at the same cadence (5 minutes) but offset in time 2.5 minutes later. FC1 color images were acquired inbound to minimum phase and FC2 images were acquired on the outbound leg providing functional redundancy while maximizing science return. " END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = "1 CERES" END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = DAWN INSTRUMENT_ID = "FC1" END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_MISSION MISSION_NAME = "DAWN MISSION TO VESTA AND CERES" END_OBJECT = DATA_SET_MISSION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "SIERKSETAL2011B" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "SCHROEDER&GUTIER2011" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END