Data Set Information
DATA_SET_NAME EPOXI INFLIGHT CALIBRATIONS - MRI RAW IMAGES V1.0
DATA_SET_ID DIF-CAL-MRI-2-EPOXI-CALIBRATIONS-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This data set contains version 1.0 of raw calibration data acquired by the Medium Resolution Visible CCD (MRI) during the EPOXI mission. The data for this version were collected from 04 October 2007 through 09 January 2008, during the first cruise phase of the mission. Additional MRI calibrations were not taken during the EPOCh phase and 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 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. 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]. A list of the calibration activities relevant to this data set is provided here and a description of each activity follows. 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 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 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. 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. 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. 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 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-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-C-MRI-2-EPOXI-HARTLEY2-V1.0 DIF-C-MRI-3/4-EPOXI-HARTLEY2-V1.0 - Raw and calibrated MRI 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-MRI-2-9P-CRUISE-V1.0 DIF-CAL-MRI-2-9P-ENCOUNTER-V1.0 - Deep Impact raw MRI calibrations data sets 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 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 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 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 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. For more information about this topic, see the image compression section of the Deep Impact instrument calibration document. 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 Deep Impact instrument calibration document. Also the EPOXI SIS has a brief discussion of this topic. 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 relative boresight alignments section 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. 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 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 list of the characteristics of the MRI filters is provided below. For more information about the filters, see the Deep Impact instruments document or the Deep Impact instrument calibration document. Also the EPOXI SIS has a brief discussion of this topic. 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 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.
DATA_SET_RELEASE_DATE 2009-09-30T00:00:00.000Z
START_TIME 2007-10-04T10:26:24.270Z
STOP_TIME 2008-01-09T11:06:30.435Z
MISSION_NAME EPOXI
MISSION_START_DATE 2007-09-26T12:00:00.000Z
MISSION_STOP_DATE 2013-09-20T12:00:00.000Z
TARGET_NAME CALIBRATION
TARGET_TYPE CALIBRATION
INSTRUMENT_HOST_ID DIF
INSTRUMENT_NAME DEEP IMPACT MEDIUM RESOLUTION INSTRUMENT - VISIBLE CCD
INSTRUMENT_ID MRI
INSTRUMENT_TYPE CCD CAMERA
NODE_NAME Small Bodies
ARCHIVE_STATUS SUPERSEDED
CONFIDENCE_LEVEL_NOTE 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 : 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 biased during integration so that the centers of the two halves are apparently 1/6 pixel closer to the center, and the two boundary rows show a decrease in sensitivity of 1/6. Reconstructed image files space all lines evenly, so the true image is erroneously vertically pushed apart by 1/3 pixel at its center in these reconstructions. When making science measurements from MRI images, one must therefore be very careful to properly account for the two flaws introduced by the apparently narrow central lines on the CCD - a geometric error that separates the image by an extra 1/3 pixel at the horizontal quadrant boundary, and 2) insertion of extra total radiance into calibrated images due to the flat-field correction, which corrects for an apparent radiance deficit in the two central rows because of the smaller number of photons actually incident on those rows. 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 Deep Impact instrument calibration document or the EPOXI SIS document.
CITATION_DESCRIPTION McLaughlin, S.A., B. Carcich, K.P. Klaasen, and D.D. Wellnitz, EPOXI INFLIGHT CALIBRATIONS - MRI RAW IMAGES V1.0, DIF-CAL-MRI-2-EPOXI-CALIBRATIONS-V1.0, NASA Planetary Data System, 2009.
ABSTRACT_TEXT This data set contains raw calibration images acquired by the Deep Impact Medium Resolution Visible CCD from 04 October 2007 through 09 January 2008 for the EPOXI mission.
PRODUCER_FULL_NAME STEPHANIE MCLAUGHLIN
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