Data Set Information
DATA_SET_NAME DEEP IMPACT 9P/TEMPEL ENCOUNTER - REDUCED ITS IMAGES V2.0
DATA_SET_ID DII-C-ITS-3/4-9P-ENCOUNTER-V2.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This data set contains version 2.0 of calibrated images of comet 9P/Tempel 1 acquired by the Deep Impact Impactor Target Sensor Visible CCD (ITS) after the impactor was released from the flyby spacecraft on 3 July 2005. Version 2.0 includes uncleaned radiance, cleaned radiance, and I-over-F data with improved geometry and revised image start and stop times. The data were collected on 3-4 July 2005. A summary of the comet observations in this data set is provided here: Mid-Obs Exposure IDs Date DOY Minimum Maximum Mission Activity ---------- --- ------- ------- --------------------------------- 2005-07-03 184 9000026 9000043 Release, Continuous Comet Imaging 2005-07-03 184 9000060 9000128 Continuous Comet Imaging 2005-07-04 185 9000130 9000710 Continuous Comet Imaging, Impact 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 ITS encounter data summary document which provides a log of the exposures beginning about 22 hours before impact. Both of these documents are included on the Deep Impact Documentation volume. 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] ITS_REDUCED_ENC_INDEX.* : Science-related index table for this data set ITS_ENCOUNTER_DATA_SUMMARY.* : Image log beginning about 22 hours before impact 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 AICD_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: DII-CAL-ITS-2-9P-CRUISE-V1.0 : Raw ITS cruise calibrations DII-C-ITS-2-9P-ENCOUNTER-V1.0 : Raw ITS encounter data DII-CAL-ITS-2-GROUND-TV3-V1.0 : ITS pre-flight calib data DI-C-SPICE-6-V1.0 : SPICE kernels Processing : The calibrated 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. For these data (version 2.0), geometric parameters were computed using the final kernels found in the PDS SPICE archive for Deep Impact. The pipeline performed the following reduction steps to produce the images in this data set: - Decompression of compressed images - Subtraction of a dark frame - Removal of electronic cross-talk - Application of a normalized flat field - Removal of CCD transfer smear - Conversion of data numbers to units of radiance for an absolute, radiometric calibration ('RADREV') - Interpolation over bad and missing pixels for partially cleaned, radiometric calibration ('RAD') - Conversion of cleaned radiance images ('RAD') to I-over-F images ('IF') The uncleaned radiance data, designated by the mnemonic 'RADREV', were provided in units of radiance as Watts/(meter**2 steradian micron). These data were considered reversible because the calibration steps could be removed to get back to the original, raw data numbers. Only the RADREV data were included in version 1.0 of this data set. The irreversibly cleaned radiance data, designated by the mnemonic 'RAD', were provided in units of radiance, Watts/(meter**2 steradian micron). Cosmic rays were not removed because the existing calibration routine was not robust. Finally, each cleaned radiance (RAD) image was divided by the solar spectrum at the target body's distance from the sun then multiplied by pi to produce a unitless I/F (I-over-F) image. These data were designated by the mnemonic 'IF'. Cosmic rays were not removed from these data. During the calibration process, the pipeline updated the pixel-by-pixel image quality map, the first FITS extension, to identify the following types of pixels: - 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 (missing pixels were identified when the raw FITS files were created) 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] included on the Deep Impact Documentation volume. Applied Coherent Technology Corporation in Herndon, VA, produced the PDS data labels by extracting parameters from the FITS headers. Data : File Naming Convention ---------------------- The naming convention for the image labels and FITS files is IVcccccccccc_eeeeeee_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 IVcccccccccc_9009001_001_RR.FIT and IVcccccccccc_9009001_002_RR.FIT. Finally, rr identifies the type of reduction: RR for RADREV data (radiance units, reversible) R for RAD data (radiance units, partially cleaned) I for IF data (unitless I-over-F, partially cleaned) 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 included on the Deep Impact Documentation volume. Imaging Modes ------------- A summary of the imaging modes is provided below. All image modes are unbinned. For a thorough description of the modes, please see the Deep Impact instrument paper by Hampton, et al. (2005) [HAMPTONETAL2005] included on the Deep Impact Documentation volume. X-Size Y-Size Mode Name (pix) (pix) Comments ---- ------ ------ ------ --------------------------------------- 1 FF 1024 1024 Full frame, shuttered 2 SF1 512 512 Sub-frame, shuttered 3 SF2S 256 256 Sub-frame, shuttered 4 SF2NS 256 256 Sub-frame, not shuttered 5 SF3S 128 128 Sub-frame, shuttered 6 SF3NS 128 128 Sub-frame, not shuttered 7 SF4O 64 64 Sub-frame, not shuttered 8 SF4NO 64 64 Sub-frame, not shuttered, no overclocks 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. Compression ----------- All data files in this data set were uncompressed. If the associated raw data file was compressed on board the flyby spacecraft (and thus received on the ground and archived as compressed) then the calibration pipeline used one of four lossy lookup tables to decompress raw image. 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] included on the Deep Impact Documentation volume. 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 left, ecliptic North is up, and the Sun is to the right. This was also the convention used when displaying ITS images of Tempel 1 in published papers. For a comparison of the orientation of ITS flight images with those from ground-based calibrations as well as those from the High and Medium Resolution Instrument CCDs (HRIV and MRI, respectively), see the quadrant nomenclature section of the 'Deep Impact Instrument Calibration' document. Parameters : Data Units ---------- Reduced RADREV and RAD data are in units of radiance, W/(m**2 steradian micron). I/F data are unitless. Time-Related Keywords --------------------- All time-related keywords in the data labels, except EARTH_RECEIVED_TIME, are based on the clock on board the impactor spacecraft. EARTH_RECEIVED_TIME provides the UTC when an Earth-based observer should have been able to see an event recorded by the instrument. The TIME_FROM_IMPACT_VALUE keyword in the data labels was based on the best estimate of the time of impact based on the clock onboard the impactor was UTC 05:44:34.200 on 4 Jul 2005. The analysis that lead to this estimate is discussed in the spacecraft clock correlation document included on the Deep Impact documentation volume. Geometry-Related Keywords ------------------------- The SOLAR_NORTH_POLE_CLOCK_ANGLE in the data labels specified the the direction of ecliptic north as projected onto the image plane. It is measured from the 'upward' direction, clockwise to the direction toward ecliptic north when the image is displayed as defined by the SAMPLE_DISPLAY_DIRECTION and LINE_DISPLAY_DIRECTION keywords. The SDC pipeline was not able to automatically determine the proper geometric information for the target of choice in many cases. When these parameters could not be computed, the corresponding keywords in the PDS data labels were set to a value of unknown (UNK). Geometry-related keywords for most calibration targets were set to UNK. 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. After a detailed analysis of the timing problem in early 2006, improved self-consistent SPICE kernels were generated by the Deep Impact project to correlate the spacecraft clocks; there is still a 1-2 second uncertainty between the in-situ data and the ground- based observations and an uncertainty of about one half of a second between the clocks on the flyby and impactor spacecraft. These improved kernels were included in the DI SPICE data set and were used to calculate the geometric parameters in the PDS data labels. For more information about this discrepancy, please see the spacecraft clock correlation report provided on the DI documentation volume, DIDOC_0001. The SPICE kernels used to calculated the geometric parameters are provided by the SPICE_FILE_NAME keyword in the PDS data labels. The kernels were listed in the order they were loaded into memory for processing. Ancillary Data : Geometric parameters included in the data labels were computed using the final version of the kernel files 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.
DATA_SET_RELEASE_DATE 2006-12-22T00:00:00.000Z
START_TIME 2005-07-03T07:44:28.368Z
STOP_TIME 2005-07-04T05:44:29.555Z
MISSION_NAME DEEP IMPACT
MISSION_START_DATE 2005-01-12T12:00:00.000Z
MISSION_STOP_DATE 2005-07-13T12:00:00.000Z
TARGET_NAME 9P/TEMPEL 1 (1867 G1)
TARGET_TYPE COMET
INSTRUMENT_HOST_ID DII
INSTRUMENT_NAME DEEP IMPACT IMPACTOR TARGETING SENSOR - VISIBLE CCD
INSTRUMENT_ID ITS
INSTRUMENT_TYPE CCD CAMERA
NODE_NAME Small Bodies
ARCHIVE_STATUS SUPERSEDED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : There are no gaps in this data set. All raw images of Tempel 1 that were received on the ground were successfully reduced and included in this data set. 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 report included on the Deep Impact Documentation 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 was peer-reviewed in April 2007 and was accepted for the PDS archive pending resolution of liens (completed in July 2007). 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 : CCD Horizontal Gap ------------------ There is a 1/3-pixel, horizontal gap for a clocking phase between the upper and lower halves of the CCD. It was inserted by the manufacturer to facilitate the simultaneous upward and downward reading of the upper and lower quadrants. The gap causes a 10 percent reduction in the sensitivity of the two central rows (i.e., one row immediately above the gap and one below it). 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 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 paper included on the Deep Impact Documentation volume.
CITATION_DESCRIPTION McLaughlin, S. A., B. Carcich, T. McCarthy, M. Desnoyer, and K.P. Klaasen, DEEP IMPACT 9P/TEMPEL ENCOUNTER - REDUCED ITS IMAGES V2.0, DII-C-ITS-3/4-9P-ENCOUNTER-V2.0, NASA Planetary Data System, 2006.
ABSTRACT_TEXT This data set contains version 2.0 of calibrated images of comet 9P/Tempel 1 acquired by the Deep Impact Impactor Target Sensor Visible CCD after the impactor was released from the flyby spacecraft on 3 July 2005. Version 2.0 includes uncleaned radiance, cleaned radiance, and I-over-F data with improved geometry and revised image start and stop times. The data were collected on 3-4 July 2005.
PRODUCER_FULL_NAME STEPHANIE MCLAUGHLIN
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