PDS_VERSION_ID = PDS3 RECORD_TYPE = "STREAM" LABEL_REVISION_NOTE = " 2011-04-27 EPOXI:McLaughlin New. This dataset supersedes version 1.0 and includes all inflight MRI calib data acquired during the EPOXI mission. 2011-08-31 EPOXI:McLaughlin Resolved liens from the Aug 2011 peer review. " OBJECT = DATA_SET DATA_SET_ID = "DIF-CAL-MRI-2-EPOXI-CALIBRATIONS-V2.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = " EPOXI INFLIGHT CALIBRATIONS - MRI RAW IMAGES V2.0" DATA_SET_COLLECTION_MEMBER_FLG = "N" START_TIME = 2007-10-04T22:26:24.270 STOP_TIME = 2010-11-28T13:05:25.799 DATA_SET_RELEASE_DATE = 2011-06-30 PRODUCER_FULL_NAME = "STEPHANIE MCLAUGHLIN" DETAILED_CATALOG_FLAG = "N" DATA_OBJECT_TYPE = "IMAGE" DATA_SET_TERSE_DESC = "Raw calibration images acquired by the Deep Impact Medium Resolution Visible CCD from 04 October 2007 through 28 November 2010 for the EPOXI mission." ABSTRACT_DESC = "This dataset contains raw calibration images acquired by the Medium Resolution Visible CCD (MRI) from 04 October 2007 through 28 November 2010 during the EPOCh, 103P/Hartley 2 Encounter, and cruise phases of the EPOXI mission." CITATION_DESC = " McLaughlin, S.A., B. Carcich, S.E. Sackett, K.P. Klaasen, and D.D. Wellnitz, EPOXI INFLIGHT CALIBRATIONS - MRI RAW IMAGES V2.0, DIF-CAL-MRI-2-EPOXI-CALIBRATIONS-V2.0, NASA Planetary Data System, 2011." DATA_SET_DESC = " Data Set Overview ================= This dataset contains version 2.0 of raw calibration images acquired by the Medium Resolution Visible CCD (MRI) from 04 October 2007 through 28 November 2010 during the EPOCh, 103P/Hartley 2 Encounter, and cruise phases of the EPOXI mission. This dataset supersedes version 1.0 which contained raw calibration only through July 2010. The purpose of these data are to monitor the MRI CCD and improve its calibration as needed. Therefore EPOXI calibration activities for the instrument generally followed those designed for Deep Impact. For example standard calibration targets continue to include the Moon, 16 Cyg A, 47 Tuc, Achernar, Beta Hyi, Canopus, HD 60753, HD 79447, NGC 3114, NGC 7027, Vega, sky frames, stim lamp frames, and dark frames. The Deep Impact calibration pipeline was the foundation for EPOXI until improvements were implemented for the Hartley 2 encounter as described in the Hartley 2 calibration summary report located in the DOCUMENT directory. For a detailed discussion of how the instruments were calibrated for EPOXI see Klaasen, et al. (2011, in preparation) [KLAASENETAL2011]. The Deep Impact instrument calibration is described by Klaasen, et al. (2008)[KLAASENETAL2006] and Klaasen, et al. (2005) [KLAASENETAL2005]. A list of the calibration activities relevant to this dataset is provided below and a description of each activity follows. The EPOXI in-flight calibrations summary chart in the DOCUMENT directory provides a quick-look at the activities. ------------------------------------------------------------------------ Phase and Exposure ID Calibration Activity Obs Date/DOY Target Start Stop ---------------------------- -------------- -------- ------- ------- Cruise 1 Instrument Checkout 2007-10-04/277 Sky 1010200 1010215 EPOCh Photometry Test 2007-11-04/308 HD 80607 9400000 9400000 Lunar Calibration 2007-12-29/363 Moon 1000000 1000058 Standard Cruise Cal 2008-01-09/009 Beta Hyi 2000000 2000009 HD 79447 2000010 2000019 47 Tuc 2000020 2000020 Achernar 2000021 2000029 Canopus 2000030 2000042 HD 60753 2002000 2002007 NGC 3114 2002008 2002019 Stim Lamp 2002020 2002029 Dark 2002030 2002039 Vega 2010000 2010008 16 Cyg A 2010009 2010016 NGC 7207 2010017 2010017 Cruise 2 HRII Subframe Gain Cal/Moon 2009-01-26/026 Moon 4000000 4000062 HRII Lunar Radiometry&Flats 2009-06-02/153 Moon 1000000 1000076 HRII Lunar Rad&Antisat Fltr 2009-06-09/160 Moon 1000000 1000012 1000300 1000311 Checkout after HRI Turnoff 2009-09-30/273 Sky 1010200 1010215 HRII Rad Cal #1 (Beta Hyi) 2009-10-13/286 Beta Hyi ExpIDs 2000000 through through 2000005 2009-10-24/297 repeately used HRII Lunar Flats/Rad Cal#1 2009-12-05/339 Moon 1000000 1000076 HRII Lunar Flats/Rad Cal#2 2009-12-12/346 Moon 1000000 1000076 HRII Lunar S.Pole Rad 2009-12-18/352 Moon 1000000 1000002 Standard Cruise Cal 2010-02-16/047 Beta Hyi 2000000 2000009 HD 79447 2000010 2000019 47 Tuc 2000020 2000020 Achernar 2000021 2000029 Canopus 2000030 2000042 Vega 2010000 2010008 16 Cyg A 2010009 2010016 NGC 7027 2010017 2010017 HD 60753 2002000 2002007 NGC 3114 2002008 2002019 Stim Lamp 2002020 2002031 Dark 2002032 2002039 HRII Rad Cal #2 (Beta Hyi) 2010-05-03/123 Beta Hyi ExpIDs 2000000 through through 2000005 2010-05-17/137 repeatedly used MRI Dosido Fast Slew Test 2010-07-12/193 Dark ExpIDs 2100100 through 2100110 repeatedly used Hartley 2 Encounter Standard Cruise Cal 2010-09-28/271 Vega 2010000 2010008 (pre-encounter) to 16 Cyg A 2010009 2010016 2010-09-29/272 NGC 7027 2010017 2010017 Beta Hyi 2000000 2000009 HD 79447 2000010 2000019 47 Tuc 2000020 2000020 Achernar 2000021 2000029 Canopus 2000030 2000042 HD 60753 2002000 2002007 NGC 3114 2002008 2002019 Dark 2002020 2002029 Stim Lamp 2002030 2002039 Darks for E-34Days to 2010-10-01/274 Dark Various ExpIDs E+12Days *to*2010-11-16/320 Standard Cruise Cal 2010-11-27/331 Vega 2010000 2010008 (post-encounter) to 16 Cyg A 2010009 2010016 2010-11-28/332 NGC 7027 2010017 2010017 Beta Hyi 2000000 2000009 HD 79447 2000010 2000019 47 Tuc 2000020 2000020 Achernar 2000021 2000029 Canopus 2000030 2000042 HD 60753 2002000 2002007 NGC 3114 2002008 2002019 Dark 2002020 2002029 Stim Lamp 2002030 2002039 ------------------------------------------------------------------------ Instrument Checkout: On 4 October 2007, the three science instruments were turned on for the first time in more than two years. Sky frames acquired by the MRI CCD confirmed the mechanical components such as the shutter and filter wheel were functioning. The instrument exhibited nominal behavior of background levels. EPOCh Photometry Test: On 4-9 November 2007, EPOCh photometry tests were performed for the HRIV instrument to check pointing and photometric stability. One MRI frame of the target, HD 80607, was acquired. Lunar Calibration: On 29 December 2007 as the spacecraft approached Earth, the three science instruments used the Moon as a target to acquire data for recalibration purposes (radiometry and scattered light). Standard Cruise Calibration: On 9 January 2008, the first of the standard cruise calibrations for the three science instruments was performed. The calibration sequence included observations of several standard stars, both solar analogs and hot stars with few absorption lines in their spectra for absolute calibration of all instruments, a stellar cluster for checking geometric distortion in the cameras, and a planetary nebula for checking the wavelength calibration of the spectrometer. This sequence was designed such that it could be rerun, with few if any changes, after completion of the EPOCh observations and then again just before and just after the observing program for comet 103P/Hartley 2. Good radiometry, geometric, and linearity data were obtained. HRII Subframe Gain Calibration: On 26 January 2009, an HRII subframe gain calibration was conducted to observe differences in the IR spectrometer signal response rates when observing an external radiance source to differentiate between gain and offset effects when using the various subframe modes. The test was performed by scanning the spectrometer across the moon (cross slit) at multiple speeds with various subframe modes while the HRI telescope barrel was warm. MRI frames were acquired to provide context for the IR scans. HRII Lunar Radiometry and Flats: On 1-2 June 2009, the HRII spectrometer acquired a series of north/south scans (cross slit) of the moon for lunar radiometry and east/west scans along IR slit for flats. These data were the best obtained to date for the purpose of generating flat fields for the IR spectrometer. MRI frames were acquired to provide context for the IR scans. HRII Lunar Radiometry and Antisat Filter: On 9 June 2009, the HRII spectrometer imaged the moon using north/south scans (cross slit) to better characterize the effects of the anti-saturation filter in the IR spectra. MRI frames were acquired to provide context for the IR scans. Checkout after HRI Turnoff: Before repeating the Earth South Pole observation, a standard imaging checkout of the HRII, HRIV, and MRI instruments was performed after HRI was powered up on 30 September 2009. The data included HRII spectra of the sky. HRII Radiometric Cal #1 (Beta Hyi): From 13 October to 24 October 2009, the HRII spectrometer repeatedly scanned the star Beta Hyi to improve the radiometric calibration for that instrument. MRI frames were acquired to provide context for the IR scans. HRII Lunar Flats/Radiometric Cal #1 and #2: On 05 and 12 December 2009 as the spacecraft approached Earth, the IR spectrometer made north/south scans of the moon for radiometry and east/west scans along the slit for lunar flats and a radiometric calibration. MRI frames were acquired to provide context for the IR scans. HRII Lunar South Pole Radiometry: On 18 December 2009, about 10 days before the distant flyby of Earth the IR spectrometer made north/south scans of the lunar south pole for radiometric analysis. MRI frames were acquired to provide context for the IR scans. Standard Cruise Calibration: A full, standard cruise calibration for HRII, HRIV, and MRI was completed on 16 February 2010. The sequence was very similar to that used for the standard cruise calibrations in 2008. HRII Radiometric Cal #2 (Beta Hyi): From 03-17 May 2010, the HRII spectrometer repeatedly scanned the star Beta Hyi to improve the radiometric calibration for that instrument. MRI frames were acquired to provide context for the IR scans. MRI Dosido Fast Slew Test: On 12 July 2010, the MRI Dosido fast slew sequence involved a test of the observing strategy planned from 8 days to 1 day before the Hartley 2 encounter that included periods during which the spacecraft attitude was maneuvered once per hour between the Earth downlink attitude and the comet viewing attitude. The spacecraft was slewed at a high rate between these two attitudes, and the Deep Space Network was required to lockup on the downlink quickly every hour. MRI images of random space were taken each hour at the comet viewing attitude as they will be during the actual encounter sequence in early November 2010. Pre-Encounter Standard Cruise Calibration: A full, standard cruise calibration for HRII, HRIV, and MRI was performed on 28-29 September 2010. The sequence was very similar to that used earlier in 2010. Darks for E-34 Days to E+12 Days: The imaging sequences that were executed from 01 October through 16 November 2010 for the encounter of Hartley 2 included MRI dark frames for background and stripe removal analyses. Post-Encounter Standard Cruise Calibration: A full post-encounter standard cruise calibration for HRII, HRIV, and MRI was performed on 27-28 November 2010. The sequence was nearly identical to the pre-encounter calibration performed in September. 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-V3.0, available online at http://pds.nasa.gov. EPOXI_SIS.PDF - 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. HARTLEY2_CAL_PIPELINE_SUMM.PDF - The EPOXI Hartley 2 Calibration Pipeline Summary provides an overview the calibration pipeline as of June 2011 used for processing data acquired during the Hartley 2 Encounter. EPOXI_INFLIGHT_CAL_SUMMARY.PDF - The EPOXI In-Flight Calibrations Summary provides an overview of the instrument calibrations performed during the entire EPOXI mission. INSTRUMENTS_HAMPTON.PDF - The Deep Impact instruments paper by Hampton, et al. (2005) [HAMPTONETAL2005] provides very detailed descriptions of the instruments. MRI_2_EPOXI_CALIBRATIONS.TAB - This ASCII table provides image parameters such as the mid-obs Julian date, exposure time, 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 calibration purposes: DIF-E-MRI-2-EPOXI-EARTH-V1.0 DIF-E-MRI-3/4-EPOXI-EARTH-V1.0 - Raw and calibrated MRI Earth observations, used mainly for context purposes. DIF-M-MRI-2-EPOXI-MARS-V1.0 DIF-M-MRI-3/4-EPOXI-MARS-V1.0 - Raw and calibrated MRI Mars observations, used mainly for context purposes. DIF-C-MRI-2-EPOXI-HARTLEY2-V1.0 DIF-C-MRI-3/4-EPOXI-HARTLEY2-V1.0 - Raw and calibrated MRI comet Hartley 2 observations DI-C-HRII/HRIV/MRI/ITS-6-DOC-SET-V3.0 - Deep Impact and EPOXI documentation set including a draft of the Deep Impact instrument calibration paper by Klaasen, et al. (2008) [KLAASENETAL2006] DIF-C/E/X-SPICE-6-V1.0 - EPOXI SPICE kernels DIF-CAL-HRII/HRIV/MRI-6-EPOXI-TEMPS-V1.0 - 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 DIF-CAL-MRI-2-9P-CRUISE-V1.0 DIF-CAL-MRI-2-9P-ENCOUNTER-V1.0 - Deep Impact raw MRI calibrations datasets from 2005 DIF-CAL-HRII/HRIV/MRI-2-GROUND-TV4-V1.0 - Deep Impact raw MRI pre-launch calibrations from 2002 and 2003 Processing ========== The raw 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 FITS data were assembled from raw telemetry packets sent down by the flyby spacecraft. Information from the embedded spacecraft header (the first 100 bytes of quadrant A image data) was extracted and stored in the primary FITS header. Geometric parameters were computed using the best available SPICE kernels and the results were also stored in the FITS header. If telemetry packets were missing, the corresponding pixels were flagged as missing in the quality map included as a FITS image extension. The quadrant nomenclature and the image quality map are described in the EPOXI SIS document. The SDC did not apply any type of correction or decompression algorithm to the raw data. Data ==== FITS Images and PDS Labels -------------------------- Each raw MRI image is stored as FITS. The primary data unit contains the two-dimensional CCD image. It is followed by one image extension that contains a two-dimensional pixel-by-pixel quality map. This extension uses one byte of eight bit flags to indicate the quality of each pixel in the primary image. The data label provides a short description of each bit. For more information about the FITS primary image and its extension or for examples of how to access and use the quality flags, refer to the EPOXI SIS document. Each FITS file is accompanied by a detached PDS data label. The EPOXI SIS document provides definitions for the keywords found in a PDS data label. Many values in a 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-V3.0. File Naming Convention ---------------------- The naming convention for the raw data labels and FITS files is MVyymmddhh_eeeeeee_nnn.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), and nnn provides the image number (IMAGE_NUMBER in the data labels) within the exposure ID. 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 32 frames were commanded for a scan with an exposure ID of 1000000, the first FITS file name would be MV07122918_1000000_001.FIT and the last would be MV07122918_1000000_032.FIT. Image Compression ----------------- For some MRI calibration frames the raw data numbers were compressed on board the flyby spacecraft by use of a lookup table then downlinked, processed, and archived in the same format. A compressed image is identified by the value 'COMPRESSED' in the COMPRESSED_IMAGE_VALUE keyword in the data labels or the COMPRESS keyword in the FITS headers. See the EPOXI SIS and EPOXI Hartley 2 Calibration Pipeline Summary documents as well as Klaasen, et al. (2008) [KLAASENETAL2006] for more information. 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) increasing to the right in the display window and the slowest-varying axis (lines) increasing to the top. This convention is identified in the data labels: the SAMPLE_DISPLAY_DIRECTION keyword is set to RIGHT and LINE_DISPLAY_DIRECTION to UP. The direction to celestial north, ecliptic north, and the Sun is provided in data labels by CELESTIAL_NORTH_CLOCK_ANGLE, ECLIPTIC_NORTH_CLOCK_ANGLE, and SUN_DIRECTION_CLOCK_ANGLE keywords and are measured clockwise from the top of the image when is displayed in the correct orientation as defined by SAMPLE_DISPLAY_DIRECTION and LINE_DISPLAY_DIRECTION. Please note 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]. Parameters ========== Data Units ---------- Raw image data are in units of raw data numbers. Target Name and Description --------------------------- The TARGET_NAME keyword in the data labels is set to the intended target, 'CALIBRATION', for each observation in this dataset. The TARGET_DESC keyword provides the name of the specific calibration target, such as 'DARK' or 'VEGA'. Imaging Modes ------------- A summary of the imaging modes is provided here. For more information see the EPOXI SIS and EPOXI Hartley 2 Calibration Pipeline Summary documents, Hampton, et al. (2005) [HAMPTONETAL2005] and Klaasen, et al. (2011) [KLAASENETAL2011]. 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 9 FFD 1024 1024 Full-frame diagnostic, shuttered All modes are unbinned. Most image modes have 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. These overclock areas described in the Deep Impact instruments document and the Deep Impact instrument calibration document. Filters ------- A summary of the MRI filters is provided here. For more information see the EPOXI SIS and EPOXI Hartley 2 Calibration Pipeline Summary documents, Hampton, et al. (2005) [HAMPTONETAL2005] and Klaasen, et al. (2011) [KLAASENETAL2011]. 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 4 RED 750 100 For context 5 IR 950 100 For context; longpass 6 CLEAR6 600 >700 For context; not band limited 7 CN 387 6.2 For CN in coma 8 VIOLET_CONT 345 6.8 For dust in coma 9 OH 309 6.2 For OH in coma 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 for certain calibration targets. 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. Ancillary Data ============== The 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. NAIF used these kernels to produce the EPOXI SPICE dataset, DIF-C/E/X-SPICE-6-V1.0. 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. Software ======== 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 dataset. " CONFIDENCE_LEVEL_NOTE = " Confidence Level Overview ========================= The FITS files in this dataset were reviewed internally by the EPOXI project and were used extensively by the science teams to improve the calibration of instrument. Review ====== This dataset, Version 2.0, was peer reviewed and certified for scientific use on 15 August 2011. It supersedes Version 1.0 which contained data only from October 2007 through July 2010. Data Coverage and Quality ========================= There are no unexpected gaps in this dataset. All calibration observations received on the ground were processed and included in this dataset. 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. Limitations =========== Timing ------ The flyby spacecraft clock SPICE kernels (SCLK) used to convert to UTC and to calculate geometry-related parameters for this dataset have a known accuracy of no better than 0.5 seconds. However the latest SCLK (science version 84) applied to the Hartley 2 encounter data is good to within 0.01 seconds for converting the spacecraft timestamps to ephemeris time for observations acquired around closest approach. Please note that the SCLK (version 65) used to compute UTC values and geometry for calibration data acquired from January 2009 through July 2010 has known discontinuities of up to a second. Those discontinuities have been corrected in the latest SCLK, science version 84, applied to Hartley data. The mission operations team has figured out how to correct raw clock correlation data for the Deep Impact flyby spacecraft to allow timing fits that are accurate to well under the sub-second level as evidenced by the 0.01-second accuracy around the time the Hartley 2 encounter. The EPOXI project plans to use this method to generate a complete and highly accurate set of UTC correlations for the flyby spacecraft since the launch, resulting 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 http://naif.jpl.nasa.gov/naif/. The EPOXI project will provide more precise times for archived data as time and funding permit. CCD Horizontal Gap ------------------ Calibration analysis combining Deep Impact and early EPOXI data determined the two halves of the HRIV 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 resolution. 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 raw FITS images. Since the values in these pixels vary dramatically, it is recommended that the values of the MINIMUM and 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. " END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_TARGET TARGET_NAME = "CALIBRATION" END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = "DIF" INSTRUMENT_ID = "MRI" END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_MISSION MISSION_NAME = "EPOXI" END_OBJECT = DATA_SET_MISSION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BELTONETAL2011" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "HAMPTONETAL2005" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "KLAASENETAL2005" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "KLAASENETAL2006" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "KLAASENETAL2011" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END