Data Set Information
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| DATA_SET_NAME |
DEEP IMPACT 9P/TEMPEL ENCOUNTER - REDUCED MRI IMAGES V1.0
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| DATA_SET_ID |
DIF-C-MRI-3/4-9P-ENCOUNTER-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
Data Set Overview : This data set contains reduced images of comet 9P/Tempel 1 acquired by the Deep Impact Medium Resolution Instrument Visible CCD (MRI) during the encounter phase of the mission. The 9P/Tempel 1 data are described in 'Deep Impact: The Anticipated Flight Data' by Klaasen, et al. (2005) [KLAASENTAL2005]. For more details about the images taken around impact, refer to the MRI encounter data summary document which provides a log of the exposures taken from 28 hours before impact through lookback. A list of the comet observations in this data set is provided here: Mid-Obs Exposure IDs Date DOY Minimum Maximum Mission Activity ---------- --- ------- ------- -------------------------- 2005-05-01 121 5000104 5000111 Daily Comet Imaging 2005-05-07 127 5000704 5000723 Daily Comet Imaging 2005-05-08 128 5000804 5000847 Daily Comet Imaging 2005-05-15 135 5001504 5001599 Daily Comet Imaging 2005-05-16 136 5001604 5001671 Daily Comet Imaging 2005-05-17 137 5001704 5001771 Daily Comet Imaging 2005-05-18 138 5001804 5001871 Daily Comet Imaging 2005-05-19 139 5001904 5001971 Daily Comet Imaging 2005-05-25 145 5002504 5002571 Daily Comet Imaging 2005-05-26 146 5002604 5002659 Daily Comet Imaging 2005-05-27 147 5002700 5002759 Daily Comet Imaging 2005-05-28 148 5002800 5002835 Daily Comet Imaging 2005-05-29 149 5002900 5002971 Daily Comet Imaging 2005-05-30 150 5003000 5003071 Daily Comet Imaging 2005-05-31 151 5003100 5003123 Daily Comet Imaging 2005-06-03 154 6000300 6000371 Daily Comet Imaging 2005-06-04 155 6000400 6000471 Daily Comet Imaging 2005-06-05 156 6000500 6000523 Daily Comet Imaging 2005-06-10 161 6001012 6001035 Daily Comet Imaging 2005-06-11 162 6001100 6001147 Daily Comet Imaging 2005-06-12 163 6001200 6001223 Daily Comet Imaging 2005-06-13 164 6001300 6001359 Daily Comet Imaging 2005-06-14 165 6001400 6001447 Daily Comet Imaging 2005-06-15 166 6001500 6001571 Daily Comet Imaging 2005-06-16 167 6001600 6001635 Daily Comet Imaging 2005-06-17 168 6001700 6001759 Daily Comet Imaging 2005-06-18 169 6001800 6001847 Daily Comet Imaging 2005-06-19 170 6001900 6001971 Daily Comet Imaging 2005-06-20 171 6002000 6002071 Daily Comet Imaging 2005-06-21 172 6002100 6002171 Daily Comet Imaging 2005-06-22 173 6002200 6002271 Daily Comet Imaging 2005-06-23 174 6002300 6002371 Daily Comet Imaging 2005-06-24 175 6002400 6002471 Daily Comet Imaging 2005-06-25 176 6002500 6002559 Daily Comet Imaging 2005-06-26 177 6002600 6002647 Daily Comet Imaging 2005-06-27 178 8000003 8000143 Daily Comet Imaging 2005-06-28 179 8000168 8000176 Daily Comet Imaging 8100000 8100140 Daily Comet Imaging 2005-06-29 180 8100165 8100173 Daily Comet Imaging 8200000 8200107 Daily Comet Imaging 8300003 8300011 Daily Comet Imaging 2005-06-30 181 8400042 8400050 Daily Comet Imaging 8400129 8400482 Daily Comet Imaging 2005-07-01 182 8400561 8400569 Daily Comet Imaging 8500000 8500437 Daily Comet Imaging 2005-07-02 183 8500477 8500533 Daily Comet Imaging 8600000 8600167 Daily Comet Imaging 8800015 8800179 Radiometry and Imaging 2005-07-03 184 9000003 9000340 Continuous Comet Imaging 2005-07-04 185 9000341 9001067 Impact Imaging 9010000 9080000 Lookback Imaging 2005-07-05 186 9080000 9120000 Lookback Imaging 2005-07-06 187 9120000 9150017 Lookback Imaging Essential Reading ----------------- The following documents, located on the Deep Impact Documentation volume, DIDOC_0001, are essential for the understanding and interpretation of this data set: ANTICIPATED_FLIGHT_DATA.* : Anticipated flight data by Klaasen, et al. (2005) [KLAASENTAL2005] MRI_ENCOUNTER_DATA_SUMMARY.* : Image log from 28 hours before impact through lookback INFLIGHT_CALIBRATION_SUMMARY.* : Summary of in-flight calibrations CALIBRATION_DOC.* : Instrument calibration by Klaasen, et al. (2006) [KLAASENETAL2006] INSTRUMENTS_HAMPTON.* : Instrument paper by Hampton, et al. (2005) [HAMPTONETAL2005] MISSION_OVERVIEW_AHEARN.* : Mission overview by A'Hearn, et al. (2005) [AHEARNETAL2005B] SCLK_CORRELATION.* : Discussion of the discrepancy between the spacecraft clocks and UTC AIDC_FLIGHT_HRIV_MRI_ITS.* : Description of the data set and definitions of label keywords Initial results from the encounter and impact were presented in 'Deep Impact: Excavating Comet Tempel 1' by by A'Hearn, et al. (2005) [AHEARNETAL2005A]. Related Data Sets ----------------- The following PDS data sets are related to this one: DIF-CAL-MRI-2-9P-CRUISE-V1.0 : Raw MRI cruise calibrations DIF-C-MRI-2-9P-ENCOUNTER-V1.0 : Raw MRI encounter data DIF-CAL-HRII/HRIV/MRI-2-GROUND-TV4-V1.0 : MRI ground calibrations DI-C-SPICE-6-V1.0 : SPICE kernels Processing : The reduced, two-dimensional FITS images in this data set were generated by the Deep Impact calibration pipeline, maintained by the project's Science Data Center (SDC) at Cornell University. The pipeline performed the following reduction steps to produce the images in this data set: - Calibration of temperatures and voltages in the FITS headers - Decompression of compressed images - Correction for uneven bit weighting due to analog-to-digital (ADC) conversion (a unit correction) - Subtraction of a dark frame - Removal of electronic cross-talk removal - Application of a flat field - Normalization of quadrant gains - Removal of CCD transfer smear - Conversion of data numbers to units of radiance for an absolute, radiometric calibration The resulting data were provided in physical units of radiance, Watts/(meter**2 steradian micron). These data, designated by the pneumonic ''RADREV'', were not cleaned and are considered reversible because the calibration steps can be removed to get back to the original, raw data numbers. During the calibration process, the pipeline updated the pixel-by-pixel image quality map, the first FITS extension, so the following types of pixels could be identified: - Pixels where the raw value was saturated - Pixels where the analog-to-digital converter was saturated - Pixels that were ultra-compressed and thus contain very little information - Pixels considered bad as indicated by bad pixel maps The pipeline also created a FITS image extension for a signal-to-noise ratio map. The calibration steps and files used to reduce each raw image are listed in the PROCESSING_HISTORY_TEXT keyword in the PDS data label for that image. For a detailed discussion of the calibration pipeline and the resulting data, see the instrument calibration document by Klaasen, et al. (2006) [KLAASENETAL2006]. Applied Coherent Technology Corporation in Herndon, VA, produced the PDS data labels by extracting parameters from the FITS headers. Data : CCD Images ---------- The two-dimensional, CCD images in this data set are in FITS format. The primary data array contains the image, followed by two image extensions that are pixel-by-pixel maps which provide additional information about the primary image: - The first extension uses one byte of eight, bit flags to describe the quality of each pixel in the primary image. The PDS data label defines the purpose of each bit. - The second extension provides a signal-to-noise ratio for each pixel in the primary image. Each image FITS file is accompanied by a detached PDS label. For more information about the FITS primary image and extensions, refer to the instrument calibration document. Compression ----------- The calibration pipeline used one of four lossy lookup tables to decompress raw images that were compressed onboard the spacecraft. For information about data compression, see the Deep Impact instruments document by Hampton, et al. (2005) [HAMPTONETAL2005] or the instrument calibration paper by Klaasen, et al. (2006) [KLAASENETAL2006]. True-Sky ''As Seen By Observer'' Display ---------------------------------------- A true-sky view is achieved by displaying the image using the standard FITS convention: the fastest-varying axis (samples) increasing to the right in the display window and the slowest- varying axis increasing to the top. This convention is also defined in the data labels: SAMPLE_DISPLAY_DIRECTION : 'RIGHT' LINE_DISPLAY_DIRECTION : 'UP' The direction to Celestial North and Ecliptic North, measured clockwise from the top of the displayed image, is provided in PDS labels by CELESTIAL_NORTH_CLOCK_ANGLE and SOLAR_NORTH_POLE_CLOCK_ANGLE, both of which assume the correct display defined by SAMPLE_DISPLAY_DIRECTION and LINE_DISPLAY_DIRECTION. Using this convention for Tempel 1 approach images, ecliptic East is toward the top, ecliptic North is toward the right, and the Sun is down. After impact, the Flyby spacecraft came out of shield mode and turned around to lookback at the comet. For lookback images, ecliptic East is toward the top, ecliptic North is toward the left, and the Sun is down. For a comparison of the orientation of MRI flight images with those from ground-based calibrations as well as those from the High Resolution Instrument CCD (HRIV) and the Impactor Targeting Sensor CCD (ITS), see the quadrant nomenclature section of the 'Deep Impact Instrument Calibration' document. It is important to note that, in published results about the encounter, the project elected to rotate MRI images such that ecliptic East is to the left, ecliptic North is up, and the Sun is to the right for approach images. This is equivalent to rotating an image counter-clockwise by 90 degrees with respect to the convention provided above. Published lookback images were rotated clockwise by 90 degrees with with respect to the convention provided above such that ecliptic East to the right, ecliptic North up, and the Sun to the left. File Naming Convention ---------------------- The naming convention for the image labels and FITS files is MVcccccccccc_iiiiiii_nnn_RR.LBL or FIT where cccccccccc is the spacecraft clock count at the mid-point of the observation, eeeeeee is the exposure ID (OBSERVATION_ID in data labels). Up to 999 individual images could be commanded for one exposure ID. Therefore, nnn in the file name provides the sequentially increasing image number within an exposure ID and corresponds to IMAGE_NUMBER in the data labels. For example, if two images were commanded for exposure ID 9009001, the two FITS files names would be MVcccccccccc_9009001_001_RR.FIT and MVcccccccccc_9009001_002_RR.FIT. Finally, RR identifies the reduction level, RADREV: reversible data in units of radiance (RADREV). This reduction level is described in the instrument calibration document. Parameters : Data Units ---------- Reduced RADREV data are in units of radiance, W/(m**2 steradian micron). The data are reversible and are not cleaned. Imaging Modes and Filters ------------------------ For descriptions of the imaging modes and filters, please see the Deep Impact instrument paper by Hampton, et al. (2005) [HAMPTONETAL2005]. Most image modes had a set of bias overclock rows and columns, located around the edges of the image array. All overclock pixels were excluded from the calculation of the values for MINIMUM, MAXIMUM, MEDIAN, and STANDARD_DEVIATION in the data labels. Time-Related Keywords --------------------- All time-related keywords in the data labels, except EARTH_RECEIVED_TIME, are based on the clock on board the flyby spacecraft. EARTH_RECEIVED_TIME provides the UTC when an Earth-based observer should be able to see an event recorded by the instrument. The TIME_FROM_IMPACT_VALUE keyword in the data labels was based on the estimated impact time at the flyby spacecraft of UTC 05:44:35.821 on 4 Jul 2005, as published by A'Hearn, et al. (2005) [AHEARNETAL2005A]. Geometry-Related Keywords ------------------------- The SDC attempted to calculate geometric parameters relating to the target only when it was within several fields of view of the instrument boresight. When these parameters could not be calculated, the corresponding keywords in the PDS data labels were set to a value of unknown (UNK). Geometric parameters were computed using the best SPICE kernels available at the time of calibration and the results were stored in the FITS header. For impact images, geometric parameters such as the target-to-spacecraft distance were computed with respect to the impact site, not the center of the comet. Geometric parameters provided in the data labels were computed at the epoch specified by MID_IMAGE_TIME, except for the target-to-sun and earth-observer-to-target parameters. Target-to-sun values were calculated for the time when the light left the sun while earth-observer-to-target were calculated for the time when the light left the target. Geometry-related parameters in the PDS data labels are uncertain at a level of a few seconds because of a known 2-second discrepancy between the clocks on board the flyby and impactor spacecraft and between in-situ data and ground-based observations. The Deep Impact project generated self-consistent SPICE kernels, outside of NAIF, to help account for the discrepancy. The November 2005 version of these kernels was used to calculate the image times and geometric information in PDS data labels. After further analysis of the timing problem in early 2006, improved self-consistent SPICE kernels were generated by the Deep Impact project. The improved kernels were included in the DI SPICE data set. For more information about this discrepancy, please see the spacecraft clock correlation document included on the Deep Impact document volume. The SPICE kernels used to calculated the geometric parameters are provided by the SPICE_FILE_NAME keyword in the PDS data labels. The kernels are listed in the order they were loaded into memory for processing. Ancillary Data : Geometric parameters included in the data labels were computed using the November 2005 version of the SPICE data. These were the best available data at the time of image creation. Since image creation, some SPICE kernels were improved, and these were archived in the Deep Impact SPICE data set. Coordinate System : Earth Mean Equator and Vernal Equinox of J2000 (EME J2000) was the inertial reference system used to specify observational geometry parameters in the data labels.
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| DATA_SET_RELEASE_DATE |
2005-12-31T00:00:00.000Z
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| START_TIME |
2005-05-01T08:02:39.004Z
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| STOP_TIME |
2005-07-06T06:16:45.149Z
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| MISSION_NAME |
DEEP IMPACT
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| MISSION_START_DATE |
2005-01-12T12:00:00.000Z
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| MISSION_STOP_DATE |
2005-07-13T12:00:00.000Z
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| TARGET_NAME |
9P/TEMPEL 1 (1867 G1)
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| TARGET_TYPE |
COMET
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| INSTRUMENT_HOST_ID |
DIF
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| INSTRUMENT_NAME |
DEEP IMPACT MEDIUM RESOLUTION INSTRUMENT - VISIBLE CCD
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| INSTRUMENT_ID |
MRI
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| INSTRUMENT_TYPE |
CCD CAMERA
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| NODE_NAME |
Small Bodies
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| ARCHIVE_STATUS |
SUPERSEDED
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| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview : As noted above, the geometry-related parameters in the PDS data labels are uncertain at a level of a few seconds because of a known 2-second discrepancy between the clocks on board the flyby and impactor spacecraft and between in-situ data and ground-based observations. For more information about this discrepancy, please see the spacecraft clock correlation document included on the Deep Impact document volume. The FITS files in this data set were reviewed internally by the Deep Impact project and were used extensively by the science team. Review : This data set passed a PDS peer review that took place on April 5, 2006. Reviewers stated these data should be archived pending resolution of the liens produced during the review. Data Coverage and Quality : There are no gaps in this data set. All raw, Tempel 1 images were successfully reduced and included in this data set. Horizontal striping through some images indicates missing data. The image quality map extension identifies where pixels are missing. If the second most-significant bit of a pixel in the image quality map is turned on, then data for the corresponding image pixel is missing. For more information, refer to the notes about image quality map in the PDS data label or to the instrument calibration document. Limitations : Displaying Images ----------------- Flight software overwrote the first 50 uncompressed (or 100 compressed) pixels of first quadrant read out from the instrument with an image header. These header pixels were included in the reduced FITS images. Since the values in these pixels vary dramatically, it is recommended that the values of the MINIMUM and MAXIMUM keywords in the PDS data label (or the MINPVAL and MAXPVAL in the FITS header) be used to scale an image for display because these values exclude the header bytes as well as the overclock rows and columns located around the edge of the image. The location of the header bytes in a FITS image depends on the readout order of the instrument, as discussed in the quadrant nomenclature section of the instrument calibration document.
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| CITATION_DESCRIPTION |
McLaughlin, S. A., B. Carcich, T. McCarthy, M. Desnoyer, and K.P. Klaasen, DEEP IMPACT 9P/TEMPEL ENCOUNTER - REDUCED MRI IMAGES V1.0, DIF-C-MRI-3/4-9P-ENCOUNTER-V1.0, NASA Planetary Data System, 2005.
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| ABSTRACT_TEXT |
This data set contains reduced images of comet 9P/Tempel 1 acquired by the Deep Impact Medium Resolution Instrument Visible CCD during the encounter phase of the mission.
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| PRODUCER_FULL_NAME |
STEPHANIE MCLAUGHLIN
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| SEARCH/ACCESS DATA |
SBN Comet Website
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