Data Set Information
DATA_SET_TERSE_DESCRIPTION Calibrated clear-filter, C2, CN, OH and dust continuum images of comet C/Garradd (2009 P1) acquired by the Medium Resolution Visible CCD (MRI) from 20 February through 09 April 2012 during the Cruise 3 phase of the EPOXI mission.
Data Set Overview
    This dataset contains calibrated clear-filter, C2, CN, OH and dust
    continuum images of comet C/Garradd (2009 P1) acquired by the Medium
    Resolution Visible CCD (MRI) from 20 February through 09 April 2012
    during the Cruise 3 phase of the EPOXI mission.
    While DI Flyby spacecraft (DIF) was officially in hibernation after the
    encounter with comet 103P/Hartley 2 in November 2010, it continued to
    carry out observations of comets from a distance as the opportunity
    arises.  One such observing program was carried out in 2012 on comet
    C/Garradd (2009 P1).  Observations were obtained with the MRI CCD and
    the High Resolution Visible CCD (HRIV, archived separately) during a
    series of windows from 20 February through 09 April 2012 as the comet
    receded from 1.74 AU to 2.11 AU from the Sun and at a distance of
    1.88 AU to 1.30 AU from the spacecraft.
    Hourly sequences were obtained between 20 February and 07 March and
    again between 06-09 April with a few gaps for spacecraft maneuvers and
    data downloads.  During these windows, HRIV sequences consisted of a
    single Clear image, while each MRI sequence consisted of 13 broad- and
    narrowband images:  3 Clear, 3 CN, 2 C2, 2 OH and 2 Green Continuum.
    Images were unbinned 256x256-pixel subframe sections with the comet
    near the center of the frame.
    Modified visible imaging sequences were interspersed with the 1.05- to
    4.8-micron infrared spectral imaging scans (archived separately)
    obtained March 26-27 and April 2-3.  During these windows, 3 HRIV Clear
    images were obtained every hour, while the MRI sequences consisted of 1
    Clear and 1 CN image sampled every 15 minutes.
    Initial results based on the visible-wavelength imaging are presented
    in Farnham, et al. (2014) [FARNHAMETAL2014].  See the 'Related Data
    Sets' section below for a list of separately archived visible- and
    infrared-wavelength data.
    In the course of the observations of comet Garradd, a massive solar
    coronal ejection event occurred on 06 March 2012.  The effects of this
    event were seen in the data obtained on 07 March, with cosmic rays
    rapidly increasing until they eventually overwhelmed the detector.
    This was the last day of the collection period, so the images had
    returned to normal by the next collection period on 25 March 2012.
    Required Reading
      The documents listed below are essential for the understanding and
      interpretation of this dataset.  Although a copy of each document is
      provided in the DOCUMENT directory of this dataset, the most recent
      version is archived in the Deep Impact and EPOXI documentation set,
      DI-C-HRII/HRIV/MRI/ITS-6-DOC-SET-V4.0, available online at
        - The Archive Volume and Data Product Software Interface
          Specifications document (SIS) describes the EPOXI datasets, the
          science data products, and defines keywords in the PDS labels.
        - The EPOXI Calibration Pipeline Summary provides an overview
          of the final version of the calibration pipeline that generated
          the data products in this dataset.  For a thorough discussion
          of the pipeline, see 'EPOXI Instrument Calibration' by Klaasen,
          et al. (2013) [KLAASENETAL2011].
        - The Deep Impact instruments paper by Hampton, et al. (2005)
          [HAMPTONETAL2005] provides very detailed descriptions of the
        - This ASCII table provides image parameters such as the mid-obs
          Julian date, exposure time, image mode, filter, mission activity
          type, and description or purpose for each observation (i.e., data
          product) in this dataset.  This file is very useful for
          determining which data files to work with.
    Related Data Sets
      The following PDS datasets are related to this one and may be useful
      for research:
        - Raw MRI medium-resolution CCD images comet Garradd,
          including context images for the IR scans
        - Raw and calibrated HRIV high-resolution CCD images comet Garradd
        - Raw and calibrated HRII infrared spectral images of comet Garradd
        - EPOXI SPICE kernels
        - HRII, HRIV, and MRI instrument thermal telemetry data for EPOXI
          which may be useful for determining how temperature fluctuations
          affect the science instruments, in particular the IR spectrometer.
          N.B. The pipeline does not use these thermal data to calibrate
          IR spectra of the target.  Instead it uses instrument temperatures
          recorded in the FITS headers.
        - Deep Impact and EPOXI documentation set
    The calibrated two-dimensional FITS CCD images and PDS labels in this
    data set were generated by the Deep Impact/EPOXI data pipeline,
    maintained by the project's Science Data Center (SDC) at Cornell
    University.  The final version of the pipeline for MRI processing,
    dated January 2013, was used. (This version is identical to the one
    used in June 2011 to process comet Hartley 2 data.) Known limitations
    and deficiencies of the pipeline and the resulting data are discussed
    in the EPOXI Calibration Pipeline Summary document in this dataset and
    by Klaasen, et al. (2013) [KLAASENETAL2011].
    For each CCD image, the pipeline generates two types of calibrated
      - Uncleaned radiance data provided in units of
        Watts/(meter**2 steradian micron) and identified by the
        mnemonic 'RADREV'.  The RADREV data are considered to be
        reversible because the calibration steps can be backed out to
        return to the original, raw data numbers.  A RADREV image can
        be converted to unitless I-over-F by multiplying by the value
        assigned to the DATA_TO_IOVERF_MULTIPLIER keyword in the PDS
        label.  Alternatively, a RADREV image can be converted from
        radiance units to calibrated data numbers by multiplying by the
        value assigned to the DATA_TO_DN_MULTIPLIER in the PDS label.
      - Irreversibly cleaned radiance data provided in units of
        Watts/(meter**2 steradian micron) and identified by the
        mnemonic 'RAD'.  The RAD data are considered to be
        irreversible because the calibration steps, such as smoothing
        over bad pixels, cannot easily be backed out to return to the
        original, raw data numbers.  A RAD image can be converted
        to unitless I-over-F by multiplying by the value assigned to
        the DATA_TO_IOVERF_MULTIPLIER keyword in the PDS label.
        Alternatively, a RAD image can be converted from radiance units to
        calibrated data numbers by multiplying by the value assigned to
        the DATA_TO_DN_MULTIPLIER in the PDS label (though interpolated
        pixels will not be real data).  Please note that values in the
        overclock rows and columns bordering the active CCD area are
        set to 0 in the RAD product.
    The calibration pipeline performed the following processes, in the
    order listed, on the raw MRI FITS data to produce the RADREV and
    RAD products found in this data set (the process uses the image
    mode and filter to select the appropriate set of calibration files):
      - Decompression of compressed images (all images in this dataset
        were never compressed, so this step was bypassed)
      - Correction for bias
      - Subtraction of a dark frame
      - Removal of horizontal, instrumental striping
      - 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 that is reversible (RADREV)
      - Interpolation over bad and missing pixels identified in the
        RADREV data to make a partially cleaned, irreversible, radiometric
        calibration with units of radiance (RAD);  Steps for despiking
        (i.e., cosmic ray removal) and denoising the data which are part
        of the RAD stream were not performed because the existing routines
        are not robust
      - Calculation of multiplicative factors to convert a RADREV or RAD
        image to I-over-F
    As part of the calibration process, the pipeline updated the
    pixel-by-pixel image quality map, the first FITS extension, to identify:
      - 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, and
      - Pixels considered to be anomalous 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 to capture the
    signal-to-noise ratio map and another extension to capture the values
    used to remove horizontal striping.  The calibration steps and files
    applied to each raw image are listed in the PROCESSING_HISTORY_TEXT
    keyword in the PDS data label.
    FITS Images and PDS Labels
      Each calibrated image is stored as FITS.  The primary data unit
      contains the two-dimensional CCD image which is followed by two
      image extensions that are two-dimensional pixel-by-pixel maps
      providing additional information about the CCD image:
        - The first extension uses one byte consisting of eight,
          single-bit flags to describe the quality of each pixel
          in the primary image.  The PDS data label defines the
          purpose of each single-bit flag.
        - The second extension provides a signal-to-noise ratio for
          each pixel in the primary image.
        - The third extension contains the two columns of DN values that
          were subtracted from every non-overclock column in the left
          and right halves of the primary image array by the stripe
          removal process.
      Each FITS file is accompanied by a detached PDS data label.  The
      EPOXI SIS document provides definitions for the keywords found in
      a data label and provides more information about the FITS primary
      image and the extensions.  Many values in a data label were
      extracted from FITS image header keywords which are defined in the
      document EPOXI_FITS_KEYWORD_DESC.ASC found in the Deep Impact and
      EPOXI documentation dataset, DI-C-HRII/HRIV/MRI/ITS-6-DOC-SET-V4.0.
    File Naming Convention
      The naming convention for the raw data labels and FITS files is
      MVyymmddhh_eeeeeee_nnn_rr.LBL or FIT where 'MV' identifies the MRI
      instrument, yymmddhh provides the UTC year, month, day, and hour at
      the mid-point of the observation, eeeeeee is the exposure ID
      (OBSERVATION_ID in data labels), nnn provides the image number
      (IMAGE_NUMBER in the data labels) within the exposure ID, and
      rr identifies the type of reduction:
        RR for RADREV data (reversibly calibrated, radiance units)
        R  for RAD data (partially cleaned RADREV data, radiance units)
      Up to 999 individual images or frames can be commanded for one
      exposure ID.  Therefore, nnn in the file name provides the
      sequentially increasing frame number within an exposure ID and
      corresponds to IMAGE_NUMBER in the data labels.  For example, if 6
      frames were commanded for a scan with an exposure ID of 4010000, the
      first FITS file name would be MV12022019_4010000_001_RR.FIT and the
      last would be MV12022019_4010000_006_RR.FIT.
    Image Compression
      All data products in this dataset are uncompressed.  Specifically
      all raw CCD images, from which these data products are derived,
      were never compressed on board the spacecraft.
    Image Orientation
      A true-sky 'as seen by the observer' view is achieved by displaying
      the image using the standard FITS convention:  the fastest-varying
      axis (samples or wavelength) increasing to the right in the display
      window and the slowest-varying axis (lines or spatial/along-slit)
      increasing to the top.  This convention is identified in the data
      labels:  the SAMPLE_DISPLAY_DIRECTION keyword is set to RIGHT and
      The direction to celestial north, ecliptic north, and the Sun is
      provided in data labels by CELESTIAL_NORTH_CLOCK_ANGLE,
      and are measured clockwise from the top of the image when it is
      displayed in the correct orientation as defined by
      the aspect of the North celestial pole in an image can be computed
      by adding 90 degrees to the boresight declination given by
      DECLINATION in the data labels.
      For a comparison of the orientation FITS image data from the three
      science instruments, see the quadrant nomenclature section of the
      the EPOXI SIS document.
    Instrument Alignment
      For a comparison of the field of view and the relative boresight
      alignment of MRI to the High Resolution Instrument Visible CCD
      (HRIV) and the slit of the High Resolution IR Imaging Spectrometer
      (HRII), see the instrument alignment section of the EPOXI SIS
      document or Klaasen, et al. (2011) [KLAASENETAL2011].
    Data Units
      The calibrated RADREV and RAD image data have units of radiance,
      W/(m**2 steradian micron).
    Imaging Modes
      One mode was used for all images in this dataset:
                    X-Size  Y-Size  Bin
        Mode Name   (pix)   (pix)  Type  Comments
        ---- ------ ------  -----  ----- ------------------
          3  SF2S      256    256    Sub-frame, shuttered
      For more information see Hampton, et al. (2005) [HAMPTONETAL2005],
      Klaasen, et al. (2008) [KLAASENETAL2006] and Klaasen, et al. (2013)
      [KLAASENETAL2011].  All modes are unbinned.
      Several MRI filters were used for the images in this dataset:
        Filter         Center Width
        #  Name        (nm)   (nm)   Comments
        -  ----------  -----  -----  -------------------------------
        1  CLEAR1       650   >700   For context; not band limited
        2  C2           514   11.8   For C2 in coma
        3  GREEN_CONT   526    5.6   For dust in coma
        6  CLEAR6       650   >700   For context; not band limited
        7  CN           387    6.2   For CN in coma
        9  OH           309    6.2   For OH in coma
      For more information about the filters, see Hampton, et al. (2005)
      [HAMPTONETAL2005], Klaasen, et al. (2008) [KLAASENETAL2006] and
      Klaasen, et al. (2013) [KLAASENETAL2011]. For the effective center
      wavelengths and the corresponding full-width-half-max values see
      Klaasen, et al. (2013) [KLAASENETAL2011].
    Time- and Geometry-Related Keywords
      All time-related keywords in the data labels, except
      EARTH_OBSERVER_MID_TIME, are based on the clock on board the flyby
      spacecraft.  EARTH_OBSERVER_MID_TIME provides the UTC when an
      Earth-based observer should have been able to see an event recorded
      by the instrument.
      The SDC pipeline was not able to automatically determine the proper
      geometric information for the target of choice in some cases.  When
      these parameters could not be computed, the corresponding keywords
      in the data labels are set to a value of unknown, 'UNK'.  Also if
      GEOMETRY_QUALITY_FLAG is set to 'BAD' or GEOMETRY_TYPE is set to
      'PREDICTED' in the PDS labels, then this indicates the geometry
      values may not be accurate and should be used with caution.  The
      value 'N/A' is used for some geometry-related keywords in the data
      labels because these parameters are not applicable.
      Observational geometry parameters provided in the data labels were
      computed at the epoch specified by the mid-obs UTC, IMAGE_MID_TIME,
      in the data labels.  The exceptions are the target-to-sun values
      evaluated at the time light left the target that reached the
      spacecraft at mid-obs time, and the earth-observer-to-target values
      evaluated at the time the light that left the target, which reached
      the spacecraft at mid-obs time, reached Earth.
      Since the pole of comet Garradd is not well known, the pipeline
      used the default SPICE kernel, GARRADD_0001.TPC, which specifies
      a non-rotating body with the positive pole aligned with EMEJ2000.
  Ancillary Data
    The timing and geometric parameters included in the data labels and
    FITS headers were computed using the best available SPICE kernels at
    the time the data products were generated.  Most kernels are available
    in the EPOXI SPICE dataset, DIF-C/E/X-SPICE-6-V1.0; others that had
    not yet been archived in the PDS when this dataset was produced are
    available online at the Operational Flight Project Kernels website
    maintained by the NASA Navigation and Ancillary Information Facility
  Coordinate System
    Earth Mean Equator and Vernal Equinox of J2000 (EME J2000) is the
    inertial reference system used to specify observational geometry
    parameters in the data labels.
    The observations in this dataset are in standard FITS format with PDS
    labels, and can be viewed by a number of PDS-provided and commercial
    programs.  For this reason no special software is provided with this
DATA_SET_RELEASE_DATE 2013-08-23T00:00:00.000Z
START_TIME 2012-02-20T07:04:17.708Z
STOP_TIME 2012-04-09T01:46:55.253Z
MISSION_START_DATE 2007-09-26T12:00:00.000Z
MISSION_STOP_DATE 2013-09-20T12:00:00.000Z
NODE_NAME Small Bodies
Confidence Level Overview
    The data files in this dataset were reviewed internally by the EPOXI
    This dataset was peer reviewed and certified for scientific use on
    21 March 2014.
  Data Coverage and Quality
    There are no unexpected gaps in this dataset.  All observations
    received on the ground were processed and included in this dataset.
    Any 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 EPOXI SIS document.
      The EPOXI project plans to generate a complete and highly accurate
      set of UTC correlations since launch.  This will ultimately result
      in a future version of a SCLK kernel that will retroactively change
      correlation for **all** Deep Impact and EPOXI data.  When this
      kernel is available, it will be added to the SPICE datasets for
      the two missions and posted on the NAIF/SPICE web site at
   CCD Horizontal Gap
      Calibration analysis combining Deep Impact and early EPOXI data
      determined the two halves of the MRI CCD - the boundary being the
      two horizontal central lines 511 and 512 (zero based) - while
      physically consistent across the boundary, are 1/6 of a pixel
      smaller vertically than a normal row.  Therefore, reconstructed
      images, which have uniform row spacing, have a 1/3-pixel extension
      introduced at the center of the array.  Thus for two features on
      either side of the midpoint line, the vertical component of the
      actual angular separation between those features is one-third of a
      pixel less than their measured difference in vertical pixels in the
      image.  As for all geometric distortions, correction of this
      distortion will require resampling of the image and an attendant
      loss in spatial resolution.  The standard pipeline process does
      not perform this correction so as to preserve the best spatial
      The two 1/6-pixel narrower central rows collect only 5/6 of the
      charge of a normal row.  This effect is corrected by the flat-field
      division for calibrated science images so that the pixels in these
      rows have the correct scene radiance assigned to them.  However,
      point-source or disk-integrated photometric measurements using
      aperture photometry areas that include these central rows will be
      slightly distorted unless special adjustments are made.  For
      example, the aperture photometry process for comet 9P/Tempel 1 added
      an extra 1/6-pixel worth of signal to the to the pixels in each of
      these two rows in the reconstructed, calibrated images as described
      in Appendix A of Belton, et al., (2011) [BELTONETAL2011].
    Displaying Images
      Flight software writes an image header over the first 100 bytes of
      quadrant A.  These image header pixels were included in the calibrated
      FITS images.  Since the values in these pixels vary dramatically,
      it is recommended that the values of the EPOXI:MINIMUM and EPOXI:MAXIMUM
      keywords in the 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 CCD image.  For more information,
      see the quadrant nomenclature section of the EPOXI SIS document.
CITATION_DESCRIPTION McLaughlin, S.A., B. Carcich, S.E. Sackett, K.P. Klaasen, and T. Farnham EPOXI C/GARRADD (2009 P1) - MRI CALIBRATED IMAGES V1.0, DIF-C-MRI-3/4-EPOXI-GARRADD-V1.0, NASA Planetary Data System, 2014.
ABSTRACT_TEXT This dataset contains calibrated clear-filter, C2, CN, OH and dust continuum images of comet C/Garradd (2009 P1) acquired by the Medium Resolution Visible CCD (MRI) from 20 February through 09 April 2012 during the Cruise 3 phase of the EPOXI mission.
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