Data Set Information
DATA_SET_NAME EPOXI EXOPLANET TRANSIT OBS - HRIV RAW IMAGES V1.0
DATA_SET_ID DIF-X-HRIV-2-EPOXI-EXOPLANETS-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview : This data set set contains raw images of eight known transiting extrasolar planetary systems (hot Jupiters) acquired by the Deep Impact High Resolution Visible CCD (HRIV) during the EPOCh phase of the EPOXI mission. From 22 January through 31 August 2008, EPOCh took advantage of the permanent on-orbit defocus of the HRI telescope by using the HRIV CCD to collect over 172,000 usable, photometric-quality, visible light images of these exoplanet systems: HAT-P-4, HAT-P-7, GJ 436, TrES-2, TrES-3, XO-2, XO-3, and WASP-3. Time series of continuous 50-second integrations in a subframe mode of 128x128 or 256x256 pixels with the clear #6 optical filter (350 to 1000 nanometers) were used to observe each system for about three weeks, typically covering five or more transits as well as secondary eclipses; an exception is XO-3 which was observed only briefly before the spacecraft unexpectedly entered safe mode. For most observations the 128x128-pixel subarray was used. The larger subarray of 256x256 pixels was commanded during some transit and secondary eclipse periods to ensure that pointing jitter did not cause the star to fall beyond the edges of the subarray. The transiting planet systems were observed in the integrated light of the planet and star; no spatially resolved image of the planet was possible. The out-of-focus HRIV telescope defocuses the images to about 10 pixels or 4 arcseconds at full-width half-max and introduces visible structure. The following table chronologically lists the EPOCh transiting exoplanet observations. For most targets, preview imaging was performed to determine if the pointing bias needed to be modified for that target series. Target Start Date/DOY Stop Date/DOY Comments ------- -------------- -------------- -------------------------- HAT-P-4 2008-01-22/022 2008-02-12/043 XO-3 2008-02-12/043 2008-02-17/048 S/C entered safe mode TRES-3 2008-03-06/066 2008-03-08/068 XO-2 2008-03-09/069 2008-03-11/071 Preview for pointing bias TRES-3 2008-03-11/071 2008-03-18/078 XO-2 2008-03-20/080 2008-03-28/088 GJ 436 2008-05-04/125 2008-05-27/148 TRES-2 2008-06-28/180 2008-06-29/181 Preview for pointing bias HAT-P-4 2008-06-29/181 2008-07-08/190 TRES-2 2008-07-08/190 2008-07-17/199 WASP-3 2008-07-17/199 2008-07-19/201 Preview for pointing bias TRES-2 2008-07-20/202 2008-07-30/212 WASP-3 2008-07-30/212 2008-08-08/221 HAT-P-7 2008-08-08/221 2008-08-10/223 Preview for pointing bias WASP-3 2008-08-10/223 2008-08-16/229 HAT-P-7 2008-08-16/229 2008-08-31/244 The time series for each target was typically bracketed by a set of dark and internal stimulator lamp frames to monitor changes in the CCD detector and to aid transit photometry. These data are archived separately in the raw EPOXI calibrations data set, DIF-CAL-HRIV-2-EPOXI-CALIBRATIONS-V1.0. The general characteristics of the observed planetary systems as described by Ballard, et al. (2009) [BALLARDETAL2009] is provided here: Stellar #Transits Target V_mag Observed Points of Interest ------- ----- --------- ------------------------------------------- HAT-P-4 11.22 10 Low density planet, large radius for its mass XO-3 9.91 1 Eccentric orbit, second planet suspected TrES-3 12.40 7 Short period (31 hours), reflected light target XO-2 11.18 3 Fainter component in wide visual binary, metal rich GJ 436 10.67 8 Eccentric orbit, unseen planet suspected, star is M-dwarf TrES-2 11.41 7 Kepler target, additional planets possible WASP-3 10.64 8 Strongly heated, reflected light and visible thermal emission possible HAT-P-7 10.50 8 Kepler target, even more strongly heated than WASP-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. EPOCH_OVERVIEW.PDF - This presentation provides an overview of the EPOCh phase of the EPOXI mission. EPOCH_TRANSIT_OBS.PDF - This document describes of the EPOCh stellar transit observations although most of the information is captured in this data set catalog file you are reading. EPOCH_TRANSIT_OBS_SCLK2BJD.PDF - This report describes the calibration of spacecraft clock timing and reduction to Barycentric Dynamic Time Julian Date for EPOCh observations of transiting extrasolar planets. HRIV_2_EPOXI_GJ436.TAB HRIV_2_EPOXI_HATP4.TAB HRIV_2_EPOXI_HATP7.TAB HRIV_2_EPOXI_TRES2.TAB HRIV_2_EPOXI_TRES3.TAB HRIV_2_EPOXI_WASP3.TAB HRIV_2_EPOXI_XO2.TAB HRIV_2_EPOXI_XO3.TAB - These ASCII tables provide 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. Publications of the preliminary photometry results based on the transiting planet observations include Ballard, et al. (2009) [BALLARDETAL2009B] and Christiansen, et al. (2009) [CHRISTIANSENETAL2009]. Related Data Sets ----------------- The following PDS data sets are related to this one and may be useful for research: DIF-E-HRIV-3-EPOXI-EXOPLANETS-V1.0 - Calibrated HRIV extrasolar planet transit observations DIF-CAL-HRIV-2-EPOXI-CALIBRATIONS-V1.0 - Raw HRIV dark frames (exposure IDs 9600000 and 9600001) and internal stimulator lamp images (exposure IDs 9600002 and 9600003) acquired to monitor changes in the CCD detector for EPOCh transit photometry purposes 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 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 HRIV 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 HVyymmddhh_eeeeeee_nnn.LBL or FIT where 'HV' identifies the HRIV 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 1000001, the first FITS file name would be HV08051200_9200003_000.FIT and the last would be HV08051200_9200003_032.FIT. Image Compression ----------------- Although raw data numbers for HRIV frames could be compressed on board the flyby spacecraft by use of a lookup table then downlinked, processed, and archived in the same format, EPOCh exoplanet transit images acquired during the time period covered by this data set were never compressed. Therefore the COMPRESSED_IMAGE_VALUE keyword in the data labels is always set to 'UNCOMPRESSED'. 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) 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. Parameters : Data Units ---------- Raw image data have units of raw data numbers. Imaging Modes ------------- Two HRIV image modes were used for the EPOCh transiting planet observations: X-Size Y-Size Mode Name (pix) (pix) Comments ---- ------ ------ ------ ------------------------------- 3 SF2S 256 256 Sub-frame, shuttered 5 SF3S 128 128 Sub-frame, shuttered All modes are unbinned. For most observations the 128x128 mode was used. The larger subarray of 256x256 pixels was commanded during some transit and secondary eclipse periods and for preview imaging to ensure that pointing jitter did not cause the star to fall beyond the edges of the subarray. 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. 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 ------- One HRIV image mode was used for the EPOCh transiting planet observations: Filter Center Width # Name (nm) (nm) Comments - ---------- ----- ----- ------------------------------- 6 CLEAR6 650 >700 Not band limited For more information about the filter, see the Deep Impact instruments document or the Deep Impact instrument calibration document. Also the EPOXI SIS has a brief discussion of this topic. 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. It is important to note that the spacecraft clock is affected by a systematic drift relative to ground clocks due to the changing thermal environment of the spacecraft. The EPOCh team calibrated the spacecraft clock versus ground clocks, and the corrected times were computed for each transiting system (giving Julian Date and Barycentric Julian Date by image file name). However to aid transit timing analysis, the computation was implemented in the data pipeline, and the EPOCh team verified that the resulting values were consistent with theirs. Thus the Barycentric Dynamic Time Julian Date (BJD) for the mid-point of an observation when light reaches the solar system barycenter is provided by the KPKSSBJT keyword in the FITS header of each data product. For more information about calculating the BJD, please see the document EPOCH_TRANSIT_OBS_SCLK2BJD.PDF. The pipeline also computed the Barycentric Dynamic Time at the mid-point of the observation at the spacecraft; it is provided as a Julian Date in the FITS header keyword OBSMIDJT. The project elected to omit these two barycentric-related values from the PDS labels. 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. For example, some HAT-P-4 observations have inaccurate values for boresight RIGHT_ASCENSION and DECLINATION because only predicted pointing information, and not final reconstructed pointing, was available to the data pipeline. 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, unless specified otherwise (e.g, SUB_SPACECRAFT_LONGITUDE). 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 2008-01-22T12:22:53.769Z
STOP_TIME 2008-08-31T12:44:54.196Z
MISSION_NAME EPOXI
MISSION_START_DATE 2007-09-26T12:00:00.000Z
MISSION_STOP_DATE 2013-09-20T12:00:00.000Z
TARGET_NAME GJ 436
HAT-P-4
HAT-P-7
TRES-2
TRES-3
WASP-3
XO-2
XO-3
TARGET_TYPE STAR
INSTRUMENT_HOST_ID DIF
INSTRUMENT_NAME DEEP IMPACT HIGH RESOLUTION INSTRUMENT - VISIBLE CCD
INSTRUMENT_ID HRIV
INSTRUMENT_TYPE CCD CAMERA
NODE_NAME Small Bodies
ARCHIVE_STATUS ARCHIVED
CONFIDENCE_LEVEL_NOTE Confidence Level Overview : The data files in this data set were reviewed internally by the EPOXI project. 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 Earth 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. In-flight bakeouts during late February and early March 2005 reduced the defocus from about 1.0 cm to about 0.6 cm, resulting in a decrease in the width of stars from about 12 pixels to 9 pixels. For more details, please see the Deep Impact instrument calibration paper by Klaasen, et al. (2006) [KLAASENETAL2006] and the Deep Impact image restoration paper by Lindler, et al. (2007) [LINDLERETAL2007]. 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 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 HRIV 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. Out-of-Frame Target ------------------- Some exoplanet transit images in this data set do not contain the star because of deviations in pointing. However the intended target is specified by the TARGET_NAME keyword in the data labels. 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, D. Deming, D.D. Wellnitz, and K.P. Klaasen, EPOXI EXOPLANET TRANSIT OBS - HRIV RAW IMAGES V1.0, DIF-X-HRIV-2-EPOXI-EXOPLANETS-V1.0, NASA Planetary Data System, 2009.
ABSTRACT_TEXT This data set set contains raw images of eight known transiting extrasolar planetary systems (hot Jupiters) acquired by the Deep Impact High Resolution Visible CCD during the EPOCh phase of the EPOXI mission. From 22 January through 31 August 2008 the HRIV CCD collected over 172,000 usable, photometric-quality visible light images of these transiting planet systems: HAT-P-4, HAT-P-7, GJ 436, TrES-2, TrES-3, XO-2, XO-3, and WASP-3. Time series of continuous 50-second integrations were used with the clear filter (#6) to observe each system for about three weeks, typically covering five or more transits as well as secondary eclipses. An exception was XO-3 which was only observed briefly due to the spacecraft entering safe mode. The transiting planet systems were observed in the integrated light of the planet and star; no spatially resolved image of the planet was possible.
PRODUCER_FULL_NAME STEPHANIE MCLAUGHLIN
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