Data Set Overview : This dataset contains version 2.0 of raw calibration spectra acquired by the High Resolution Infrared Spectrometer (HRII) from 04 October 2007 through 07 February 2011 during the EPOCh, 103P/Hartley 2 Encounter, and cruise phases of the EPOXI mission. This dataset supersedes version 1.0 which contained raw calibration data only through May 2010.  The purpose of these data are to monitor the HRII spectrometer and improve its calibration as needed. EPOXI calibration activities generally followed those designed for the Deep Impact mission. For example standard calibration targets continued to include the Moon, 16 Cyg A, 47 Tuc, Beta Hyi, HD 79447, NGC 7027, Vega, sky 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 1010100 1010107 Instrument Checkout Retest 2007-12-04/338 Sky 1010200 1010208 Lunar Calibration 2007-12-29/363 Moon 1000005 1070000 Standard Cruise Cal 2008-01-09/009 Beta Hyi 2000000 2000001 HD 79447 2000002 2000002 47 Tuc 2000003 2000004 Vega 2010000 2010001 16 Cyg A 2010002 2010003 Dark 2011000 2012010 NGC 7207 2012011 2012012 Dark Retake for Lunar Cal 2008-01-16/016 Dark 1000000 1000054 2008-01-17/017 Dark 1000005 1000154 EPOCh Darks for Earth Obs #1 2008-03-18/078 Dark 1000000 1000001 2008-03-19/079 Dark 1002024 1002025 Darks for Earth Obs #4 2008-05-28/149 Dark 1000000 1000001 2008-05-29/150 Dark 1002024 1002025 Darks for Earth Obs #5 2008-06-04/156 Dark 1000000 1000001 2008-06-05/157 Dark 1002024 1002025 Standard Cruise Cal 2008-06-23/175 Vega 2010000 2010001 16 Cyg A 2010002 2010003 NGC 7207 2010004 2010005 Dark 2011000 2012020 2008-06-24/176 Beta Hyi 2000000 2000001 HD 79447 2000002 2000002 47 Tuc 2000003 2000004 Cruise 2 HRII Reciprocity Test 2008-09-18/262 Dark 3200000 3200019 HRII Dark Flush Test 2008-09-26/270 Dark 3000001 3000011 HRII Encounter Darks Rerun 2008-10-02/276 Dark 9000030 9020002 HRII Dark Gap Test 2008-10-08/282 Dark 3100000 3100024 HRII Subframe Gain Cal/Moon 2009-01-26/026 Moon 4000001 4000153 Dark 4100001 4100335 EPOCh Earth N.Pole Darks 2009-03-27/086 Dark 1000000 1000001 2009-03-28/087 Dark 1002024 1002025 HRII Lunar Flats&Radiometry 2009-06-01/152 Moon 1000000 1000000 2009-06-02/153 Moon 1000000 1000076 HRII Lunar Antisat Fltr&Rad 2009-06-09/160 Moon 1000000 1000519 HRII Linearity Cal 2009-06-18/169 Dark 2011000 2012020 EPOCh Earth S.Pole #1 Darks 2009-09-27/270 Dark 1000000 1000001 Checkout after HRI Turnoff 2009-09-30/273 Sky 1010100 1010107 EPOCh Earth S.Pole #2 Darks 2009-10-04/277 Dark 1000000 1000001 2009-10-05/278 Dark 1002024 1002025 HRII Rad Cal #1 (Beta Hyi) 2009-10-13/286 Beta Hyi ExpIDs 2000000 through through 2000005 2009-10-24/297 repeatedly used HRII Dark Subframe Test 2009-11-20/324 Dark 4000001 4000293 EPOCh Mars Darks 2009-11-20/324 Dark 1000000 1000001 2009-11-21/325 Dark 1002024 1002025 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 Dark 2011000 2012020 Vega 2010000 2010001 16 Cyg A 2010002 2010003 NGC 7027 2010004 2010005 Beta Hyi 2000000 2000001 HD 79447 2000002 2000002 47 Tuc 2000003 2000004 HRII NoSave Flush Test 2010-04-20/110 Dark 4000000 4000227 HRII Rad Cal #2 (Beta Hyi) 2010-05-03/123 Beta Hyi ExpIDs 2000000 to through 2000005 2010-05-17/137 repeatedly used Hartley 2 Encounter Standard Cruise Cal 2010-09-28/271 Dark 2011000 2012020 (pre-encounter) Vega 2010000 2010001 16 Cyg A 2010002 2010003 NGC 7027 2010004 2010005 Beta Hyi 2000000 2000001 HD 79447 2000002 2000002 47 Tuc 2000003 2000004 Standard Cruise Cal 2010-11-27/331 Dark 2011000 2012020 (post-encounter) to Vega 2010000 2010001 2010-11-28/332 16 Cyg A 2010002 2010003 NGC 7027 2010004 2010005 Beta Hyi 2000000 2000001 HD 79447 2000002 2000002 47 Tuc 2000003 2000004 IR 50-Frame Extended LinCal 2011-02-05/036 Darks 5000000 5000084 (pre-encounter) to 2011-02-06/037 ------------------------------------------------------------------------  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 HRII spectrometer confirmed the mechanical components were functioning. The instrument exhibited nominal behavior of background levels although several detector pixels had an odd response when compared to Deep Impact.  Instrument Checkout Retest: On 4 December 2007 a retest of the October instrument checkout sequence was performed for the three science instruments. The focus of this retest was to determine if HRII pixels that had an odd response during checkout had changed or improved.  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. The sequence included along- and cross-slit HRII scans of the moon for flat fields and characterization of the HRII anti-saturation filter. (Please note the flat-field data were mostly saturated at long wavelengths). Due to a minor error in the lunar calibration sequence, a series of HRII dark frames were not recorded. A retest to acquire the missing HRII darks was scheduled for 16-17 January 2008.  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.  HRII Dark Retake for Lunar Cal: Due to a minor error in the lunar calibration sequence that was executed in December, a series of HRII dark frames was not recorded. However the darks were successfully rerun for the HRII spectrometer on 16-17 January 2008. The darks help characterize the IR background level.  EPOCh Earth Obs Darks: At the beginning and end of each EPOCh Earth observation period in 2008, HRII dark frames were acquired for calibration purposes and included in this dataset.  Standard Cruise Calibration: A second standard cruise calibration was performed on 23-25 June 2008 for the HRII and HRIV instruments. The sequence was very similar to that used for the calibration performed on 9 January 2008, except the MRI instrument was turned off because of thermal and telecommunication concerns.  HRII Reciprocity Test: On 18 September 2008, an HRII reciprocity test was performed to determine the background signal level of the READ and RESET frames of the IR spectrometer as a function of the past history of integration delay times and the timing gap between sets of frames using the diagnostic imaging mode (number 6). The ultimate objective of this test along with the HRII Dark Flush, HRII Dark Gap, and HRII Subframe Gain tests performed over the next four months is to develop a more accurate model of the variation in the background level of the IR spectrometer.  HRII Dark Flush Test: On 26 September 2008, an HRII dark frame flush test was performed to determine the type of IR spectrometer instrument operation needed to remove all traces of the residual (previous) image.  HRII Encounter Darks Rerun: On 02 October 2008 a set of HRII dark frames for several exposure IDs from the Deep Impact Tempel 1 encounter sequence was acquired. The exposures were those acquired from about 19 minutes before the impact with Tempel 1 through the first few hours of lookback imaging.  HRII Dark Gap Test: On 08 October 2008, an HRII dark gap test was performed to characterize the change in the residual image and the dark level in the IR spectrometer as a function of wait time and number of readouts after acquiring data in the subframe imaging modes (numbers 2 and 3).  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.  EPOCh Earth North Pole Darks: At the beginning and end of this campaign on 27-28 March 2009, HRII dark frames were acquired for calibration purposes and included in this dataset.  HRII Lunar Flats and Radiometry: On 1-2 June 2009, the HRII spectrometer acquired a series of east/west scans of the moon along the IR slit for flats. These data were the best obtained to date for the purpose of generating flat fields for the IR spectrometer. Also three cross-slit north/south scans of the moon were acquired for lunar radiometry. Please note these data have poor signal-to-noise at short wavelengths.  HRII Lunar Antisat Filter and Radiometry: On 9 June 2009, the HRII spectrometer imaged the moon using cross-slit north/south scans to better characterize the effects of the anti-saturation filter in the IR spectra. These data were also used for radiometry.  HRII Linearity Calibration: On 18 June 2009, HRII darks were acquired to check the linearity of the IR spectrometer. The sequence was identical to the one used during standard cruise calibrations for linearity.  EPOCh Earth South Pole #1 Darks (partial): At the beginning of this campaign on 27-28 September 2009, HRII dark frames were acquired for calibration purposes and included in this dataset. However the sequence ended prematurely because HRI was turned off by fault protection although the spacecraft was fine. The set of HRII darks scheduled for the end of this sequence were never acquired.  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.  EPOCh Earth South Pole #2 Darks (Full): On 04-05 October 2009, EPOCh successfully acquired a full set of observations (24 hours) of Earth at high southern latitudes. At the beginning and end of this campaign, HRII dark frames were acquired for calibration purposes and included in this dataset.  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 absolute spectral radiometric calibration for that instrument.  HRII Dark Subframe Test: On 20 November 2009, the HRII spectrometer acquired dark frames to further characterize the background signal of the subframe imaging modes (numbers 2 and 3) versus the integration time and the time between IR frames.  EPOCh Mars Obs Darks: On 20-21 November 2009, EPOCh observed Mars for 24 hours with the HRIV CCD and the IR spectrometer. At the beginning and end of this campaign, HRII dark frames were acquired for calibration purposes and included in this dataset.  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 cross-slit scans of the moon for radiometry and east/west scans along the slit for lunar flats and a radiometric calibration. Please note the flat-field data are very good.  HRII Lunar South Pole Radiometry: On 18 December 2009, about 10 days before the distant flyby of Earth the IR spectrometer made north/south cross-slit scans of the lunar south pole for radiometric analysis.  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 NoSave Flush Test: On 20 April 2010, an HRII dark frame sequence designed to reduce the amount of charge buildup that results in abnormally high signals in the first 1 to 4 images of a multi-frame IR exposure was tested. The sequence consisted of flushing the IR detector before science imaging by alternating between saving frames of one exposure ID for science and not saving those from the next exposure (i.e., flush frames).  HRII Radiometric Cal #2 (Beta Hyi): From 03 May to 17 May 2010, the HRII spectrometer repeatedly scanned the star Beta Hyi to improve the absolute spectral radiometric calibration for that instrument.  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.  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.  HRII 50-Frame Extended Linearity Calibration: From 05 to 06 February 2011, the HRII spectrometer took 50 dark frames for a set of integration times and for each imaging mode to gather enough data to perform a thorough analysis of the linearity of each active pixel in the IR focal plane array.   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.  HRII_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-HRII-2-EPOXI-EARTH-V1.0 DIF-E-HRII-3/4-EPOXI-EARTH-V1.0 - Raw and calibrated HRII Earth observations  DIF-M-HRII-2-EPOXI-MARS-V1.0 DIF-M-HRII-3/4-EPOXI-MARS-V1.0 - Raw and calibrated HRII Mars observations  DIF-C-HRII-2-EPOXI-HARTLEY2-V1.0 DIF-C-HRII-3/4-EPOXI-HARTLEY2-V1.0 - Raw and calibrated HRII 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-V2.0 - 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-HRII-2-9P-CRUISE-V1.0 DIF-CAL-HRII-2-9P-ENCOUNTER-V1.0 - Deep Impact raw HRII calibrations datasets from 2005  DIF-CAL-HRII-2-GROUND-TV1-V1.0 DIF-CAL-HRII/HRIV-2-GROUND-TV2-V1.0 DIF-CAL-HRII/HRIV/MRI-2-GROUND-TV4-V1.0 - Deep Impact raw HRII pre-launch calibrations from 2002 and 2003   Processing : The raw two-dimensional (wavelength and spatial/along-slit) FITS spectral images and PDS labels in this dataset 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 spectral image is stored as FITS. The primary data unit contains the two-dimensional spectral image, with the fastest varying axis corresponding to increasing wavelengths from about 1.05 to 4.8 microns and the slowest varying axis corresponding to the spatial or along-slit dimension. The primary array 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 HIyymmddhh_eeeeeee_nnn.LBL or FIT where 'HI' identifies the HRII 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 can be commanded for one exposure ID. Spectral scans often had 32 or more frames for one specific exposure. 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 1000001, the first FITS file name would be HI08060416_1000001_001.FIT and the last would be HI08060416_1000001_032.FIT.   Image Compression ----------------- Although raw data numbers for HRII frames could be compressed on board the flyby spacecraft by use of a lookup table then downlinked, processed, and archived in the same format, all calibration-related spectra acquired during the time period covered by this dataset were never compressed.   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 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.   IR Slit Location ---------------- For a comparison of the relative locations of the IR slit with respect to the fields of view of the Medium Resolution Instrument Visible CCD (MRI) and the High Resolution Instrument Visible CCD (HRIV), see the instrument alignment section of the EPOXI SIS document or Klaasen, et al. (2011) [KLAASENETAL2011].   Timing for Spectra ------------------ It is important to note that the readout order of the IR detector affects the timing of the spectra. When a HRII spectral image is displayed using the true-sky convention, the wavelength increases horizontally to the right and the spatial or along-slit direction is vertical. In this orientation, the IR detector was read out from the left and right edges and toward the center and starting with the first row at the bottom and ending with the last row at the top of the display. Since the detector is reset and read out on a pixel-by-pixel basis, the read out order affects the time at which each pixel is exposed although each pixel has the same exposure duration -- except for the ALTFF mode that has different read and reset causing the effective exposure time to vary with line number, i.e., along the slit in the spatial direction. Additionally, the end of the spectrometer slit that always points roughly towards the sun is the first line to be readout and the last line to be read out is furthest from the sun, assuming the spacecraft is in its usual orientation with the solar panels pointing roughly toward the sun. For more information about the timing of the spectra, see the zero exposure background section of the EPOXI instrument calibration paper by Klaasen, et al. (2011) [KLAASENETAL2011]. A brief discussion about how the calibration pipeline handles the ALTFF mode is included in the EPOXI Hartley 2 Calibration Pipeline Summary document.   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]. In the table below, X-Size is the spectral dimension and Y-Size is the spatial dimension.  X-Size Y-Size Bin Mode Name (pix) (pix) Type Comments ---- ------ ------ ----- ----- ------------------------------------ 1 BINFF 512 256 2x2 Binned full frame 2 BINSF1 512 126 2x2 Binned sub-frame 3 BINSF2 512 64 2x2 Binned sub-frame 4 UBFF 1024 512 1x1 Unbinned full frame 5 ALTFF 512 256 2x2 Alternate mode 1 (min. exposure time is 1/2 of mode 1) 6 DIAG 1024 512 1x1 Diagnostic, one reset frame followed by a separatly-stored read frame such that odd IMAGE_NUMBERs are reset frames and even IMAGE_NUMBERs are read frames 7 MEMCK 1024 512 1x1 Memory Check  Note the subframe modes are binned (2x2), reduce the spatial (LINE) extent of the image FOV, and have a shorter readout time which reduces the exposure time for bright objects and keeps the detector from saturating.   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. The kernels are archived in 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 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 May 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.   HRI Telescope Focus ------------------- Images of stars acquired early during the Deep Impact mission in 2005 indicated the HRI telescope was out of focus. However, this focus problem does not significantly affect the HRII instrument. For more details please see the Deep Impact instrument calibration paper by Klaasen, et al. (2008) [KLAASENETAL2006].   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 reference rows and columns located around the edge of the spectral image. For more information, see the quadrant nomenclature section of the EPOXI SIS document.