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; 2019-01-31, Joy, Updated for XM2;" 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 = 2018-09-29T05:35:00 PRODUCER_FULL_NAME = "PABLO GUTIERREZ-MARQUES" DATA_SET_RELEASE_DATE = 2016-09-01 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 1 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. In addition, there are images from eXtended Mission 2 (XM2), orbits XMO6 (C2I - intermediate), and XMO7 (C2E - elliptical) as well as some checkout and end-of-mission star calibration images. FC1 is one of two identical units flying on the 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 1 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. In addition, there are images from eXtended Mission 2 (XM2), orbits XMO6 (C2I - intermediate), and XMO7 (C2E - elliptical) as well as some checkout and end-of-mission star calibration images. FC1 is one of two identical units flying on the 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 ============= The FC1 camera was used extensively in the XMO4 observations of extended mission 1, and during the C2I phase and first 14 orbits of the C2e phase of extended mission 2. FC1 images were acquired to protect against the possibility of an FC2 reset that would have resulted in the loss of unique/critical images that could not be reacquired. However, in most cases, there was insufficient DSN bandwidth to downlink both FC2 and all FC1 images. The science plan included contingency products that would have returned the FC1 images in case of a reset, and to flush from instrument memory any images that could not be returned. This stratgey placed highest priority on the newest data rather than those previously acquired. The FC2 camera did not reset during XM2. The only FC1 images returned were those that the plan indicated could be returned in addition to the FC2 images. The imaging strategy for both cameras made use of the FC internal priorization ability, based on the science objectives. During XM2, images around periapsis were the highest priority, with the priority dropping as the time before/after periapsis increased. The combination of the internal prioritization and limited downlink results in large gaps in the image numbers of FC1 images returned. Images numbers are incremented each time an image is acquired, regardless of it's priority. The RDR (L1B) dataset does not contain 'engineering' images like 'darks', 'cal_lamps', and other checkout images when the FC door is not open. These images are provided in the EDR (L1A) dataset and this is one reason why the number of images included in the two datasets may differ. In addition, some images that are damaged (partial downlink, etc.) may be included in the EDR dataset but they cannot be calibrated and included here. The table below gives the number of images acquired in each activity, and if different, the number returned. -------------------------------------------------------------------------- Dawn Ceres Extended Mission 1 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 ========================================================================== Extended Mission 2 Science Observations with FC1 -------------------------------------------------------------------------- 17-07-01 CX2 XMO5 Ceres Extended Mission 2 Phase (range ~15000 km) -------------------------------------------------------------------------- 18-01-13 Checkout 19 non-pointed clear and color -------------------------------------------------------------------------- 18-04-15 CTI TRANSFER_ Ceres Transfer to Intermediate Orbit TO_INTERMEDIATE -------------------------------------------------------------------------- No FC science observations in this phase -------------------------------------------------------------------------- 18-05-15 C2I XMO6 Ceres Extended 2 Intermediate (range ~1950 km) -------------------------------------------------------------------------- 18-05-15 C2I XMO6 501 of 1338 nadir clear+color (3+ of 10 orbits) ------------------------------------------------------------------------ 18-05-31 CTE TRANSFER_ Ceres Transfer to Elliptical Phase TO_ELLIPTICAL ------------------------------------------------------------------------ No FC science observations in this phase ------------------------------------------------------------------------ 18-06-09 C2E XMO7 Ceres Extended 2 Elliptical (peri range ~35 km) ------------------------------------------------------------------------ 18-06-09 C2E da942 498 of 902 nadir clear only (5 orbits) 18-06-15 C2E da942 629 of 895 nadir clear only (5 orbits) 18-06-21 C2E da942 553 of 553 nadir Cerelia at Periapsis (3 orbits) 18-09-29 C2E Star Cal 117 of 117 images ------------------------------------------------------------------------- * 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