Data Set Overview : This data set contains version 1.0 of raw calibration data acquired by the High Resolution Infrared Spectrometer (HRII) during the EPOXI mission. The data for this version were collected from 04 October 2007 through 08 October 2008, during the first cruise and EPOCh phases of the mission as well as the early part of the second cruise phase. Future versions of this data set will include calibrations acquired during the remaining part of the second cruise phase and the 103P/Hartley 2 encounter phase of the EPOXI mission.  The purpose of these data are to monitor the HRII spectrometer 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, Beta Hyi, HD 79447, NGC 7027, Vega, sky frames, and dark frames. For a detailed discussion of how these data are used to calibrate the instrument, see the Deep Impact instrument calibration publication by Klaasen, et al. (2008) [KLAASENETAL2006]. The calibration observations for EPOXI are based on those designed for Deep Impact which are discussed by Klaasen, et al. (2005) [KLAASENETAL2005].  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  Instrument Checkout: On 4 October 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. 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 that sequence was successfully rerun for the HRII spectrometer on 16-17 January 2008.  EPOCh Earth Obs Darks: At the beginning and end of each EPOCh Earth observation period, HRII dark frames were acquired for calibration purposes and included in this data set.  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. Data from the HRII Subframe Gain test performed in late January 2008 will be included in version 2.0 of this data set.  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 10 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).   Required Reading --------------- The following documents are essential for the understanding and interpretation of this data set. Please note the most recent version of these documents, including other formats such as ASCII text, can be found in the Deep Impact and EPOXI documentation data set, DI-C-HRII-HRIV-MRI-ITS-6-DOC-SET-V2.0.  EPOXI_SIS.PDF - The Archive Volume and Data Product Software Interface Specifications document (SIS) describes the the data set, the science data products, and defines keywords in the PDS labels.  CALIBRATION_PAPER_DRAFT.PDF - The Deep Impact instrument calibration paper by Klaasen, et al. (2008) [KLAASENETAL2006] describes how the instruments were calibrated for Deep Impact and similarly for EPOXI and explains the calibration process used for both missions. The published version should be available online in the Review of Scientific Instruments by the American Institute of Physics. The EPOXI archive provides only an incomplete draft.  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 data set. This file is very useful for determining which data files to work with.   Related Data Sets ----------------- The following PDS data sets 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-C-HRII-2-EPOXI-HARTLEY2-V1.0 DIF-C-HRII-3/4-EPOXI-HARTLEY2-V1.0 - Raw and calibrated HRII comet Hartley 2 observations (to be delivered in 2011)  DI-C-HRII-HRIV-MRI-ITS-6-DOC-SET-V2.0 - Deep Impact and EPOXI documentation set  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-HRII-2-9P-CRUISE-V1.0 DIF-CAL-HRII-2-9P-ENCOUNTER-V1.0 - Deep Impact raw HRII calibrations data sets 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 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 Deep Impact instrument calibration document and the EPOXI SIS document included in this data set. 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 or the Deep Impact instrument calibration document.  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.   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 data set were never compressed. 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. For more information about this topic, see the image compression section of the Deep Impact instrument calibration documents.   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 Deep Impact instrument calibration document. Also the EPOXI SIS has a brief discussion of this topic.   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 relative boresight alignments section of the Deep Impact instrument calibration document.   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. 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 pointing roughly toward the sun. For more information about the timing of the spectra, see the IR focal plane and quadrant nomenclature sections of the Deep Impact instrument calibration 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 data set. The TARGET_DESC keyword provides the name of the specific calibration target, such as 'DARK' or 'VEGA'.   Imaging Modes ------------- For a thorough description of the imaging modes, please see the Deep Impact instruments document or the Deep Impact instrument calibration document. Also the EPOXI SIS has a brief discussion of this topic. A summary of the imaging modes is provided here. 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 separate read frame 7 MEMCK 1024 512 1x1 Memory Check   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 that were calculated for the time when the light arrived at the target and the earth-observer-to-target values that were calculated for the time when the light left the target.  The flyby spacecraft clock SPICE kernels (SCLK) used to convert to UTC and to calculate geometry-related parameters for this data set have a known accuracy of no better than 0.5 seconds. However as this data set was being produced, the mission operations team figured out how to correct raw clock correlation data for the flyby spacecraft to allow timing fits that are accurate to at least the sub-second level. The project plans to generate a complete, corrected set of 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 data sets for the two missions and posted on the NAIF/SPICE web site at http://naif.jpl.nasa.gov/naif/.   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 data set, 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 data set 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.

Confidence Level Overview : The FITS files in this data set were reviewed internally by the EPOXI project and were used extensively by the science teams to improve the calibration of instrument.   Review : This data set is archived at the PDS Small Bodies Node (SBN) and the Multi-Mission Archive at STScI (MAST). It passed a peer review held by SBN on 23 July 2009; MAST personnel participated.   Data Coverage and Quality : There are no unexpected gaps in this data set. All calibration observations received on the ground were processed 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 EPOXI SIS document.   Limitations :  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 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 Deep Impact instrument calibration document or the EPOXI SIS document.