NSSDCA ID: PSSB-00546
Availability: Archived at NSSDC, accessible from elsewhere
Time span: 2010-11-04 to 2010-11-04
This description was generated automatically using input from the Planetary Data System.
This dataset contains deconvolved High Resolution Visible CCD (HRIV) images of the nucleus of comet 103/P Hartley 2. Clear and color filter (350-950 nanometer) images, which were acquired within +/- one hour of closest approach on 04 November 2010 at 13:59:47 UTC during the EPOXI mission, have been restored to retrieve much of the resolution that was lost due to the defocus of the HRI telescope. Image scales range from 1.4 to 85.5 meters/pixel. All images were deconvolved using the Richardson-Lucy method because it preserves global photometry as described by Lindler, et al. (2013) [LINDLERETAL2013]. This publication along with Lindler, et al. (2007) [LINDLERETAL2007] discuss the positive and negative attributes of the Richardson-Lucy algorithm and should be read before using the deconvolved images in this dataset. Although the nucleus in many of the images was severely saturated, these frames were deconvolved and included in this dataset because there may be useful ice grain information (e.g., see Kelley, et al., 2013 [KELLEYETAL2013]). HRIV frames that captured only the grains but not the nucleus were also deconvolved and included in this dataset. Data ==== The deconvolved images located in the /DATA/ directory were produced from 106 reversibly calibrated, radiance (RADREV) FITS images archived in the PDS dataset, DIF-C-HRIV-3/4-EPOXI-HARTLEY2-V1.0. (See Klaasen, et al., 2013 [KLAASENETAL2011] for a description of the RADREV calibration.) The deconvolution process applied the filter-dependent point spread functions for the EPOXI stellar target Canopus that are archived in the the PDS dataset DIF-CAL-HRIV-6-EPOXI-STELLAR-PSFS-V1.0. For each RADREV image, results after 25, 50, 100, 200, and 400 iterations of the Richardson-Lucy algorithm were stored as separate FITS files of the following format: - The primary data unit is the 2-dimensional, deconvolved RADREV image in units of Watts/(meter^2*steradian*micron). Its header was extracted the original RADREV file. - The first image extension is a residual image of the deconvolution process. It provides the residual for each pixel as a number of sigma error, which is described by Lindler, et al. (2013) [LINDLERETAL2013]. The residual is computed as (input RADREV image) minus (restored image reconvolved with the PSF), normalized by the estimated error in the pixel. Pixels with bad data have their residual set to a sigma of zero. - The second image extension is a mask of the pixels used in deconvolution. Saturated data, detected cosmic rays, and bad pixels that were ignored are set to zero in this extension. A value of one indicates good data. A preview JPEG image of the 200 iteration result for each of the 106 HRIV exposures is included in the /DOCUMENT/PREVIEW/ directory. The JPEGs were generated with a square root intensity scale after clipping between 0 to 4 Watts/(meter^2*steradian*micron). The square root scale was chosen so that grains could be seen in the images without the nucleus. File Naming Convention ---------------------Each FITS file in the /DATA/ directory is accompanied by a detached PDS label file. The naming convention for the deconvolved data products is HVyymmddhh_eeeeeee_nnn_Diii.ext 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 the label), 'nnn' is the image number (IMAGE_NUMBER in the label) within the exposure ID, 'D' indicates a deconvolved image, 'iii' gives the number of deconvolution iterations, and 'ext' is set to FIT for a FITS file or LBL for a label file. 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 specified in the data labels, where 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. Parameters ========== Imaging Modes ------------The general properties of the two HRIV modes used for the images in this dataset are provided below. Please note that HRIV images are never binned. For more information, see Hampton, et al. (2005) [HAMPTONETAL2005] and Klaasen, et al. (2013) [KLAASENETAL2011]. X-Size Y-Size Mode Name (pix) (pix) Comments ---- ------ ------ ------ --------------------1 FF 1024 1024 Full frame, shuttered 2 SF1 512 512 Sub-frame, shuttered Filters ------The general properties of the eight HRIV filters used for the images in this dataset are provided below. For more information, including the effective wavelength for the radiance calibration, see Hampton, et al. (2005) [HAMPTONETAL2005] and Klaasen, et al. (2013) [KLAASENETAL2011]. Filter Center Width # Name (nm) (nm) Comments - ---------- ----- ----- ---------------1 CLEAR1 650 >700 Not band limited 2 BLUE 450 100 3 GREEN 550 100 4 VIOLET 350 100 Shortpass coating 5 IR 950 100 Longpass 7 RED 750 100 8 NIR 850 100 9 ORANGE 650 100 Ancillary Data ============== Observational parameters, such as filter, exposure time, range, and pixel scale, have been extracted from the PDS data label of the 200 iteration result for each of the 106 images and stored in a fixed-width ASCII table named DECONV_IMAGE_PARAMETERS.TAB, which is located in the /DOCUMENT/ directory. 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. Observational geometry parameters in the data labels and FITS headers were extracted from the archived RADREV products. The parameters were computed by the EPOXI data pipeline at the epoch specified by the mid-obs UTC, IMAGE_MID_TIME, in the labels. The exceptions are 1) the target-to-sun values evaluated at the time light left the target that reached the spacecraft at mid-obs time and 2) 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. Additionally, the parameters were computed using the best available SPICE kernels at the time the RADREV products were generated; the kernels are specified in the SPICE_FILE_NAME keyword in the data labels. The most recent version of the kernels are archived in the PDS 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.
These data are available on-line from the Planetary Data System (PDS) at:
http://pdssbn.astro.umd.edu/holdings/dif-c-hriv-5-epoxi-hartley2-deconv-v1.0/
Questions and comments about this data collection can be directed to: Dr. David R. Williams
Name | Role | Original Affiliation | |
---|---|---|---|
Dr. Michael F. A'Hearn | Data Provider | University of Maryland | |
Mr. Don J. Lindler | General Contact | NASA Goddard Space Flight Center |