Data Set Information
DATA_SET_NAME MRO CRISM EXPERIMENT DATA RECORD V1.0
DATA_SET_ID MRO-M-CRISM-2-EDR-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This volume contains portions of the CRISM Experiment Data Record (EDR) Archive, a collection of image cubes from the Compact Reconnaissance Imaging Spectrometer for Mars on the Mars Reconnaissance Orbiter spacecraft. Images are stored with PDS labels, but are otherwise unprocessed and uncalibrated. This volume also contains ancillary data files and browse images in PNG format, HTML documents that support a web browser interface to the volume, an index file ('imgindx.tab') that tabulates the contents of the volume, and documentation files. 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 : CRISM observing scenarios are constructed using a set of key variables ('configurations') which include the following: (All are selectable separately for the VNIR and IR detectors). Image source: Image data may be generated using digitized output from the detector, or using one of up to seven test patterns. Row selection: All detector rows having useful signal can be saved, or alternatively an arbitrary, commandable subset of rows can be saved. The number of rows with useful signal is 545, 107 in the VNIR and 438 in the IR. The nominal number of rows for multispectral mode was 73, 18 in the VNIR and 55 in the IR prior to 10 Dec 2006. On that date an extra channel was added to the VNIR for a total of 19. For each detector, there are four options of channel selection to choose from rapidly by command: hyperspectral (545 total channels), multispectral (73 total channels prior to 10 Dec 2006, 74 total channels on and after 10 Dec 2006), and two sets of expanded multispectral (84 and 92 channels prior to 10 Dec 2006, 85 and 93 channels on and after 10 Dec 2006). An analogy is a car radio preset button. New options are set by uploading a data structure to the DPU. Data with any wavelength selection may have a corresponding TRDR, but the wavelength selection affects the wavelength continuity and dimensionality of a TRDR. Pixel binning: Pixels can be saved unbinned or binned 2x, 5x, or 10x in the spatial direction. No pixel binning in the spectral direction is supported. Compression: All CRISM data are read off the detector in 14-bit format and are compressed real-time in hardware. Compression options, in succession, are: (1) Subtraction of an offset, on a line by line basis. Offsets are set by uploading a data structure to the DPU. (2) Multiplication by a gain, on a line by line basis, with the output in 12-bit format. Gains are set by uploading a data structure to the DPU. (Raw 12-bit data are stored onground in data products as 16-bit numbers.) (3) Optionally, conversion from 12 to 8 bits using one of eight look-up tables (LUTs) specified on a line by line basis. These choices are set by uploading a data structure to the DPU. (4) Optionally, lossless Fast + differential pulse-code modulation (DPCM) compression. Pointing: CRISM has two basic gimbal pointing configurations and two basic superimposed scan patterns. Pointing can be (1) fixed (nadir-pointed in the primary science orbit) or (2) dynamic, tracking a target point on the surface of Mars and taking out ground track motion. Two types of superimposed scans are supported: (1) a short, 4-second duration fixed-rate ('EPF-type') scan which superimposes a constant angular velocity scan on either of the basic pointing profiles, or (2) a long, minutes-duration fixed-rate ('target swath-type') scan. Frame rate: Frame rates of 1, 3.75, 5, 15, and 30 Hz are supported. The 1 Hz frame rate is used for hyperspectral measurements of the onboard integrating sphere, because the long exposures possible at 1 Hz are needed for appreciable SNR at the shortest wavelengths. 3.75 Hz is used for hyperspectral measurements of Mars; this is the highest frame rate at which the DPU electronics support onboard compression options over the range of wavelengths imaged onto the detectors with useful SNR. 15 and 30 Hz frame rates are used for nadir-pointed multispectral measurements that return only selected wavelengths. The 5 Hz frame rate is not planned for use in flight, because at that rate the electronics do no support compression of a hyperspectral wavelength selection, and it would produce excessive along-track smear in a nadir-pointed observation. Integration time: Integration times are in increments of 1/480th of the inverse of the frame rate. At 1 Hz, for example, available integration times are 1/480th sec, 2/480th sec...480/480th , and at 15 Hz, 1/7200th sec, 2/7200th sec...480/7200th sec. Calibration lamps: 4095 levels are commandable in each of two lamps at each focal plane, and in two lamps in the integrating sphere. All lamps can be commanded open-loop, meaning that current is commanded directly. For the integrating sphere only, closed loop control is available at 4095 settings. For closed loop control, the setting refers to output from a photodiode viewing the interior of the integrating sphere; current is adjusted dynamically to attain the commanded photodiode output. Note: lamps reach maximum current at open- or closed-loop settings <4095. Shutter position: Open, closed, or viewing the integrating sphere. The shutter is actually commandable directly to position 0 through 32. In software, open:3, sphere:17, closed:32. NOTE: during integration and testing, it was discovered that at positions <3 the hinge end of the shutter is directly illuminated and creates scattered light. Position 3 does not cause this effect, but the other end of the shutter slightly vignettes incoming light. Pointing: CRISM has two basic gimbal pointing configurations and two basic superimposed scan patterns. Pointing can be (1) fixed (nadir-pointed in the primary science orbit) or (2) dynamic, tracking a target point on the surface of Mars and taking out ground track motion. Two types of superimposed scans are supported: (1) a short, 4-second duration fixed-rate ('EPF-type') scan which superimposes a constant angular velocity scan on either of the basic pointing profiles, or (2) a long, minutes-duration fixed-rate ('target swath-type') scan. Pointing configuration affects the contents but not the dimensionality of an EDR. Processing : The CRISM data stream downlinked by the spacecraft unpacks into a succession of compressed image frames with binary headers containing housekeeping. In each image, one direction is spatial and one is spectral. There is one image for the VNIR focal plane and one image for the IR focal plane. The image from each focal plane has a header with 220 housekeeping items that contain full status of the instrument hardware, including data configuration, lamp and shutter status, gimbal position, a time stamp, and the target ID and macro within which the frame of data was taken. These parameters are stored as part of an Experiment Data Record (EDR), which consists of raw data. The data in one EDR represent a series of image frames acquired with a consistent instrument configuration (shutter position, frame rate, pixel binning, compression, exposure time, on/off status and setting of different lamps). Each frame has dimensions of detector columns (spatial samples) and detector rows (wavelengths, or bands). The multiple image frames are concatenated, and are formatted into a single multiple-band image (suffix *.IMG) in one file, plus a detached list file in which each record has housekeeping information specific to one frame of the multiple-band image (suffix *.TAB). The text file is based on the 220 housekeeping items. Five of theitems are composite in that each byte encodes particular information on gimbal status or control. These separate items are not broken out, except for the gimbal status at the beginning, middle, and end of each exposure, from which gimbal position is broken out (3 additional items). The housekeeping is pre-pended with 10 additional frame-specific items useful in data validation, processing, and sorting, for a total of 233 items per frame. Further information can be found in the data product SIS in the DOCUMENT directory. The multiple-band image has dimensions of sample, line, and wavelength. The size of the multiple-band image varies according to the observation mode but is deterministic given the macro ID. A typical multiple-band image might have XX pixels in the sample (cross-track) dimension, YY pixels in the line (along-track) dimension, and ZZ pixels in the wavelength dimension, where: XX (samples) : 640/binning, where 640 is the number of columns read off the detector, and binning is 1, 2, 5, or 10; YY (lines) : the number of image frames with a consistent instrument configuration; and ZZ (bands) : the number of detector rows (wavelengths) whose read-out values are retained by the instrument. Data : There is only one data type associated with this volume, the raw uncalibrated DNs. Ancillary Data : There are various types of ancillary data provided with this dataset: 1. SPICE kernels, used to interpret observational geometry, are available in the GEOMETRY directory. See GEOMINFO.TXT for more details. 2. The EXTRAS directory contains materials that may be helpful but are beyond the scope of the required elements of the archive. This includes a time ordered history of observations and the characteristics of the sites observed, as well as the configuration-managed history of the hardware and software state of the CRISM instrument. See EXTRINFO.TXT for more details. 3. The BROWSE directory contains browse images in PNG format, and HTML documents that support a web browser interface to the volume. See BROWINFO.TXT for more details. Coordinate System : The cartographic coordinate system used for the CRISM data products conforms to the IAU planetocentric system with East longitudes being positive. The IAU2000 reference system for Mars cartographic coordinates and rotational elements was used for computing latitude and longitude coordinates. Media/Format : The CRISM archive will be made available online via Web and FTP servers. This will be the primary means of distribution. Therefore the archive will be organized as a set of virtual volumes, with each data set stored online as a single volume. As new data products are released they will be added to the volume's data directory, and the volume's index table will be updated accordingly. The size of the volume will not be limited by the capacity of the physical media on which it is stored; hence the term virtual volume. When it is necessary to transfer all or part of a data set to other media such as DVD for distribution or for offline storage, the virtual volume's contents will be written to the other media according to PDS policy, possibly dividing the contents among several physical volumes.
DATA_SET_RELEASE_DATE 2007-06-08T00:00:00.000Z
START_TIME 1965-01-01T12:00:00.000Z
STOP_TIME N/A (ongoing)
MISSION_NAME MARS RECONNAISSANCE ORBITER
MISSION_START_DATE 2005-08-12T12:00:00.000Z
MISSION_STOP_DATE N/A (ongoing)
TARGET_NAME MARS
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID MRO
INSTRUMENT_NAME COMPACT RECONNAISSANCE IMAGING SPECTROMETER FOR MARS
INSTRUMENT_ID CRISM
INSTRUMENT_TYPE IMAGING SPECTROMETER
NODE_NAME Geosciences
ARCHIVE_STATUS IN QUEUE
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : This is a TBD data set. Known problems are TBD. Review : This archival data set will be examined by a peer review panel prior to its acceptance by the Planetary Data System (PDS). The peer review will be conducted in accordance with PDS procedures. Data Coverage and Quality : For each observation, every EDR is compared against frame-by-frame predictions of commanded instrument state. The results of the comparison are written as a data validation report that accompanies the EDRs for that observation. In the case of a hardware or configuration discrepancy (shutter position, lamp status or level, pixel binning, frame rate, channel selection, power status of detectors), processing of the image data to RDR level does not occur in order to avoid introducing invalid results. Missing frames or portions of frames are replaced with a value of 65535 (this cannot be a valid data value) and only that portion of the EDR is not further processed. If an expected calibration data set (background, focal plane lamp, or sphere) is not successfully acquired and downloaded, the next closest in time calibration can be used. In this case there is a discrepancy between the predicted EDR processing table and the actual one, and this is recorded in the data quality index upon processing of the scene EDR to the TRDR level. Limitations : None.
CITATION_DESCRIPTION Murchie, S., Mars Reconnaissance Orbiter Compact Reconnaissance Imaging Spectrometer for Mars Experiment Data Record, MRO-M-CRISM-2-EDR-V1.0, NASA Planetary Data System, 2006.
ABSTRACT_TEXT This dataset is intended to include raw IR and VNIR data cubes from the CRISM instrument on MRO.
PRODUCER_FULL_NAME SCOTT MURCHIE
SEARCH/ACCESS DATA
  • Geosciences Web Services
  • Mars Orbital Data Explorer
  • Geosciences Online Archives
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