Data Set Information
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| DATA_SET_NAME |
SURFACE TEMPERATURE MAPS OF COMET 9P/TEMPEL 1 V1.0
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| DATA_SET_ID |
DIF-C-HRII-5-TEMPEL1-SURF-TEMP-MAPS-V1.0
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| NSSDC_DATA_SET_ID |
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| DATA_SET_TERSE_DESCRIPTION |
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| DATA_SET_DESCRIPTION |
Data Set Overview : This data set contains two-dimensional infrared thermal maps of the surface of comet 9P/Tempel 1. The maps were derived from three spatially resolved scans of the nucleus acquired by the Deep Impact High Resolution Infrared Spectrometer (HRII) about 19, 12, and 5 minutes before the impact on 4 July 2005. A high-resolution, 120-m/pixel, thermal composite map is also included. Surface temperatures were derived from 1.0- to 4.0-micron data and ranged from 272K to 336K +/- 7K. This data set also includes the incidence and emission angle maps (mu0 and mu) associated with each thermal map and a table of temperatures assigned to plates in the Tempel 1 shape model that were illuminated and visible around the time of collecting the thermal data. For a thorough discussion of the maps, see Groussin, et al. 2007 [GROUSSINETAL2007]. Observations ------------ The characteristics of the three HRII scans acquired of the nucleus and used to derive the three temperature maps were extracted from Groussin, et al. 2007 [GROUSSINETAL2007] and provided below. The given values are with respect to the mid-point of a scan. An impact time of 05:44:34.265 UT 4 July 2005, at the flyby spacecraft, was used to calculate the time before impact. During the scans, 9P/Tempel 1 had a heliocentric distance of 1.5 AU. Exposure (scan) ID : 9000031 9000036 9000039 Image mode : 3 1 2 Number of frames in scan : 32 40 84 Percentage of visible nucleus covered : 90 100 50 Time at spacecraft (h:m:s UT) : 05:25:36 05:32:55 05:39:18 Time before impact (min) : 19.0 11.7 5.3 Scan duration (s) : 23 113 120 Slit length* (km) : 13 41 15 Minimum spectral resolution : 216 216 216 Target distance (km) : 20400 15900 12000 Spatial resolution (m/pixel) : 204 159 120 Phase angle (deg) : 62.88 62.89 62.91 * There is not correlation between the slit length and the resolution. The slit length only refers to the number of rows that are read out from the IR focal plane array (FPA); the physical length of the slit never changes. Therefore, as the spacecraft moved closer to the target, the spatial resolution improved. The value for slit length changes between the scans because the image mode is different for each set of frames. The image mode specifies the number of rows readout from the IR FPA in the along-slit (spatial) dimension. For image mode 1 the slit width is 256 2x2-binned pixels, for mode 2 it is 128 2x2-binned pixels, and for mode 3 it is 64 2x2 binned pixels. Additionally, the physical width of the slit is fixed at 10 microradians and cannot be changed. ** Please note the map associated with exposure ID 9000039 is truncated because of impact activities by the spacecraft. Related Data Sets ----------------- The following PDS data sets are related to this one: DIF-C-HRII-3-4-9P-ENCOUNTER-V2.0 : Calibrated HRII encounter data, version 2.0 DIF-C-HRIV/ITS/MRI-5-TEMPEL1-SHAPE-V1.0 : Tempel 1 shape model DI-C-HRII/HRIV/MRI/ITS-6-DOC-SET-V1.0 : Mission documentation Please note that the temperature maps were derived from version 2.0 of the calibrated HRII data. Version 2.0 includes improved geometric parameters, dark subtraction, and bad pixel identification. Data : Individual Thermal Maps and Related Geometry Maps ------------------------------------------------- Three individual thermal maps of the surface of Tempel 1 along with the related incidence- and emission-angle maps were generated from data for HRII scans 9000031, 9000036, and 9000039. Please note the map for scan 9000039 is truncated because of impact activities by the spacecraft. These two-dimensional maps are presented in the FITS image format. The data values in the maps have units of kelvin. The data files are listed here: map_9000031.fit : Temperature maps derived from the map_9000036.fit scans with exposure IDs of 9000031, map_9000039.fit 9000036, and 9000039 map_9000031_mu0.fit : Registered maps of the values of mu0 map_9000036_mu0.fit (cosine of the incidence angle) for map_9000039_mu0.fit each temperature map listed above map_9000031_mu.fit : Registered maps of the values of mu map_9000036_mu.fit (cosine of the emission angle) for map_9000039_mu.fit each temperature map listed above For context, a deconvolved image acquired by the HRI visible CCD is included in the documentation for this data set. Composite Thermal Map and Related Geometry Maps ----------------------------------------------- The composite thermal map and its related geometry maps for mu0 (cosine of the incidence angle) and mu (cosine of the emission angle) were generated from the highest-resolution thermal maps derived from data for scans 9000036 and 9000039. The two-dimensional maps are presented in the FITS image format. The data values in the maps have units of kelvin. thermal_composite.fit : Composite thermal map at 120 m/pixel made from the highest-resolution thermal maps (map_9000036.fit and map_9000039.fit) thermal_composite_mu0.fit : Registered map of values of mu0 (cosine of the incidence angle) for the composite thermal map thermal_composite_mu.fit : Registered map of values of mu (cosine of the emission angle) for the composite thermal map Plate Temperature Table ----------------------- The plate_temp.tab file is a fixed-width, ASCII table that provides a temperature for each plate of the Tempel 1 shape mode that was visible near impact. The first column in the table identifies the plate index (0-based) within the archived shape model for Tempel 1. The second column provides the corresponding temperature in units of Kelvin. The PDS data set, DIF-C-HRIV/ITS/MRI-5-TEMPEL1-SHAPE-V1.0, includes the Tempel 1 shape model used for this analysis. It is available online at the Small Bodies Node. Map Orientation --------------- When displaying the thermal or geometry maps, a true-sky view can be achieved by displaying the image using the standard FITS convention where the fastest-varying axis (samples) increase to the right in the display window and the slowest-varying axis (lines) increases to the top. This convention is also defined by these keywords in the PDS data labels: SAMPLE_DISPLAY_DIRECTION : RIGHT LINE_DISPLAY_DIRECTION : UP When using this convention to display the maps, the Sun is to the right, ecliptic north is toward the right, celestial north is toward the upper-right, and celestial east is toward the upper-left. The projected positive spin axis of the nucleus points toward the top. This is the orientation used by Groussin, et al. (2007) [GROUSSINETAL2007]. Processing : Thermal Maps ------------ Frames for each scan (9000031, 9000036, and 9000039) were selected from version 2.0 of HRII reversibly calibrated data in units of radiance (W/(m**2 micron steradian)). Because scattered light is not negligible for the HRII spectrometer, the calibrated data were then manually corrected (cleaned) for bad pixels and scattered light for this analysis. The contribution from the coma was negligible compared to that of the nucleus and was therefore not subtracted. See Groussin, et al. (2007) [GROUSSINETAL2007] for details about the scattered light model and the analysis of the coma contribution. See the Deep Impact Instrument Calibration document by Klaasen, et al. (2006) [KLAASENETAL2006] for a discussion of the stray light for the HRII instrument and the calibration pipeline. To derive the temperature maps from the spectra of the nucleus, a process that combined the scattered light from the Sun with the thermal infrared emission of the nucleus was used to fit the data. The best fit was achieved by using a least squares method in the thermal infrared range of 3.0 to 4.0 microns. This method was applied to each frame of one scan to derive a temperature map of the nucleus for that scan. Details about the process and the analysis of the maps using a thermal model are described by Groussin, et al. (2007) [GROUSSINETAL2007] Geometry Maps (mu0 and mu) for the Thermal Maps ----------------------------------------------- The mu0 and mu maps were calculated with the shape model of Tempel 1 archived in PDS for the time of impact. The sub-spacecraft longitude and latitude are 295 deg and -26 degrees, respectively. The sub-solar longitude and latitude are 349 deg and 9.2 degrees, respectively. The thermal data used to construct the thermal maps were collected 19, 12, and 5 minutes before the impact, when the change in the viewing geometry was less than 2 degrees. To register the geometry maps with thermal maps as precisely as possible, the geometry maps were first rendered at a pixel scale of 16m/pix, and the thermal maps were rescaled to this resolution for the purpose of registration. The geometry maps and thermal maps were then registered by shifting and slightly rotating according to the limb/terminator and a few large features. Finally the registered geometry maps were scaled down to the original pixel scale of their corresponding thermal maps. If a pixel was in shadow, its value was set to zero. The uncertainty of these geometry maps was affected by the uncertainty of the shape model and registration error. Close to the limb and terminator, the uncertainty of angles can be large. Thus pixels with value less then 0.17 (80 deg angle) should probably be discarded for practical purposes. Composite Thermal Map --------------------- The composite thermal map was constructed from the two highest-resolution thermal maps for scans 9000036 and 9000039. First, the thermal map for 9000036 at 159 m/pixel was scaled to 120 m/pixel, the scale of the thermal map for exposure 9000039. Then the rescaled map for 9000036 was registered against the thermal map for 9000039 by shifting and rotating to align the limb and terminator profile and some large surface thermal features. Six lines (35-40) of thermal map 9000039 appeared to be bad during a visual inspection and were therefore discarded. Finally the upper half of the nucleus in thermal map 9000036 that was covered by map 9000039 was replaced by lines from the latter and were therefore not used. The geometry maps (mu0 and mu) for the composite thermal map were calculated using the procedure as described above for each individual thermal map. Plate Temperature Table ----------------------- As in the plate shape model, the surface of the nucleus of Tempel 1 was represented by a collection of triangle plates. From the thermal maps, the temperatures of the illuminated and visible plates at the time of impact could be calculated. To do this, the composite thermal map with pixel scale 120 m/pixel was used. A map of plate numbers was rendered using the geometry of impact, where the value of a pixel represented the index of the plate that was projected onto this pixel in the composite thermal map. The pixel scale of the resulting plate map was 16m/pix, a scale that was finer than the sizes of most plates (so that every pixel fell into one plate). The composite thermal map was then rescaled to this resolution, so that the plate map could be registered to it by comparing the limb/terminator profile and a few large features. Comparing the composite thermal map with the registered plate map, the temperatures of illuminated and visible plates were extracted. Due to the uncertainty of the plate shape model and the low signal close to the limb and terminator of the nucleus in the thermal map, the edge of the plate map and thermal map could not be aligned everywhere. Therefore, all plates with their average values of mu0 or mu smaller than 0.17 (80 degrees) were discarded from this data table. For the plates included, the uncertainties in the temperature were dominated by the composite thermal map, which was in turn affected by the registration error during composition, as well as by the uncertainty of original thermal maps. This data set overview was provided by O. Groussin and J.-Y. Li.
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| DATA_SET_RELEASE_DATE |
2006-11-01T00:00:00.000Z
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| START_TIME |
2005-07-04T05:25:23.325Z
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| STOP_TIME |
2005-07-04T05:40:20.251Z
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| MISSION_NAME |
DEEP IMPACT
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| MISSION_START_DATE |
2005-01-12T12:00:00.000Z
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| MISSION_STOP_DATE |
2005-07-13T12:00:00.000Z
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| TARGET_NAME |
9P/TEMPEL 1 (1867 G1)
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| TARGET_TYPE |
COMET
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| INSTRUMENT_HOST_ID |
DIF
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| INSTRUMENT_NAME |
DEEP IMPACT HIGH RESOLUTION INSTRUMENT - IR SPECTROMETER
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| INSTRUMENT_ID |
HRII
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| INSTRUMENT_TYPE |
INFRARED SPECTROMETER
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| NODE_NAME |
Small Bodies
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| ARCHIVE_STATUS |
ARCHIVED
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| CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview : The overall uncertainty for the reduction processes was estimated to be 20 percent. See Groussin, et al. (2007) [GROUSSINETAL2007]. This corresponds to an overall uncertainty of 7K for the surface temperatures. Review : This data set was originally peer-reviewed in November 2006 and accepted for the PDS archive pending the resolution of liens which were resolved in June 2007. Because new data products (the mu0 and mu files) were added, this data set was peer reviewed again in June 2008 and was accepted for the PDS archive pending the resolution of minor, cosmetic liens which were resolved in late June 2008. Limitations : Known Deficiencies for the IR Calibration ----------------------------------------- There are known deficiencies with the version of the IR calibration pipeline that reduced these data. These are described in the HRII calibration limitations document included on the Deep Impact documentation data set, DI-C-HRII/HRIV/MRI/ITS-6-DOC-SET-V1.0. HRI Telescope Focus ------------------- Early images of stars using the HRI visible CCD indicated the HRI telescope was out of focus. However, this focus problem minimally affected the HRII instrument because the IR spectrometer was over sampled by a factor of five when compared to the visible CCD. For more details, please see the instrument calibration paper by Klaasen, et al. (2006) [KLAASENETAL2006] included on the Deep Impact documentation data set, DI-C-HRII/HRIV/MRI/ITS-6-DOC-SET-V1.0.
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| CITATION_DESCRIPTION |
Groussin, O. and J-Y. Li, SURFACE TEMPERATURE MAPS OF COMET 9P/TEMPEL 1 V1.0, DIF-C-HRII-5-TEMPEL1-SURF-TEMP-MAPS-V1.0, NASA Planetary Data System, 2006.
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| ABSTRACT_TEXT |
This data set contains two-dimensional infrared thermal maps of the surface of comet 9P/Tempel 1. The maps were derived from three spatially resolved scans of the nucleus acquired by the Deep Impact High Resolution Infrared Spectrometer (HR II) about 19, 12, and 5 minutes before the impact on 4 July 2005. A high-resolution, 120 m/pixel, thermal composite map is also included. Surface temperatures were derived from 1.0- to 4.0-micron data and ranged from 272K to 336K +/- 7K. This data set also includes the incidence and emission angle maps associated with each thermal map and a table of temperatures assigned to plates in the Tempel 1 shape model that were illuminated and visible near the time of impact.
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| PRODUCER_FULL_NAME |
Stephanie A. McLaughlin
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| SEARCH/ACCESS DATA |
SBN Comet Website
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