PDS_VERSION_ID = PDS3 LABEL_REVISION_NOTE = "2014-06-01, S. MURCHIE, edited; 2014-06-11, J. WARD, edited; 2014-09-11, S. MURCHIE, edited; 2016-03-16, S. MURCHIE, edited" RECORD_TYPE = STREAM OBJECT = DATA_SET DATA_SET_ID = "MESS-H-MDIS-5-RDR-MP5-V1.0" OBJECT = DATA_SET_INFORMATION DATA_SET_NAME = "MESS MDIS MAP PROJ 5-COLOR MULTISPECTRAL RDR V1.0" DATA_SET_TERSE_DESC = "5-color multispectral reduced data records for the wide-angle MDIS camera on MESSENGER." DATA_SET_COLLECTION_MEMBER_FLG = "N" DATA_OBJECT_TYPE = "IMAGE" START_TIME = 2004-08-19T18:01:23 STOP_TIME = 2015-04-30T11:07:43 DATA_SET_RELEASE_DATE = 2016-05-06 PRODUCER_FULL_NAME = "CHRISTOPHER HASH" DETAILED_CATALOG_FLAG = "N" CITATION_DESC = "C. Hash, MESS MDIS MAP PROJ 5-COLOR MULTISPECTRAL RDR V1.0, NASA Planetary Data System, 2016" ABSTRACT_DESC = " Abstract ======== The Mercury Dual Imaging System (MDIS) consists of two cameras, a Wide Angle Camera (WAC) and a Narrow Angle Camera (NAC), mounted on a common pivot platform. This dataset includes 5-Color Multispectral Reduced Data Records for the WAC. The 5-Color Map Projected Multispectral RDR (MP5) data set consists of a 5-color map of northern latitudes acquired during MESSENGER's Extended Mission, and includes I/F in the 5 filters used for this map. This product has higher spatial resolution than, and complements, an 8-color multispectral map acquired during the primary mission (in MDR data products). It has better spectral sampling and the same spatial resolution, and complements, a 3-color multispectral map also acquired during the Extended Mission (in MD3 data products). It is intended to search for spatial variations in color properties of the northern volcanic plains. This product is photometrically normalized to a solar incidence angle (i) = 30 degrees, emission angle (e) = 0 degrees, and phase angle (g) = 30 degrees at a spatial sampling of 128 pixels per degree. The map consists of a single tile covering the north polar quadrangle or 'Mercury chart' already defined by the USGS (H01), plus the northern parts of the 4 Mercury charts immediately to the south (H02-H05). The tile is composed of 5 bands corresponding to 5 of the 11 WAC filters. The tile also contains 6 backplanes describing ancillary information. The subset of 5 of 11 available multispectral filters samples albedo and spectral slope over MDIS's wavelength range. Unlike the 3- and 8-color products, which were acquired with the WAC pointed near nadir, the 5-color map was acquired pointed at a nearly uniform phase angle near 30 degrees to minimize shadowing at the high latitudes of the Northern Volcanic Plains." DATA_SET_DESC = " Data Set Overview ================= MDIS 5-color imaging of Mercury is mosaicked into a single 128 pixel/degree tile (MP5). This tile corresponds to the pre-existing Mercury chart H01, plus the northern part of the chart to the immediate south, H02-H05. Map tiles are named based on the quadrant of the Mercury chart they span: MDIS_ppp_rrrPPD_Hxxddv.IMG where: ppp = product type = MP5 rrr = resolution in pixels/degree (PPD) Hxx = Mercury chart designation dd = quadrant within Mercury chart (NW, NE, SW, or SE), or a polar chart (NP, SP) v = version number The following is an example file name with a description of the individual components: MDIS_MP5_128PPD_H01NP0.IMG For this image: Product type = MP5 (MP5) Resolution = 128 pixels/degree (128PPD) Mercury chart = Borealis (H01) Quadrant = North Polar (NP) Version = 0 The MP5 directory, present in the MP5 archive volume, contains the 5-Color MDIS Map Projected Multispectral Reduced Data Record (MP5). MP5 files are located in a subdirectory based on Mercury Chart. Latitude and longitude limits of Mercury Charts overlapped by the MD5, as named at the end of mission, are: Quadrangle Subdirectory Lat. (degrees) Long. (deg. east) H-1 Borealis H01 65 to 90 0 to 360 H-2 Victoria H02 22.5 to 65 270 to 360 H-3 Shakespeare H03 22.5 to 65 180 to 270 H-4 Raditladi H04 22.5 to 65 90 to 180 H-5 Hokusai H05 22.5 to 65 0 to 90 The center latitude and center longitude of the MP5 is located in H01 so only that directory is populated. An MP5: - Consists of map-projected photometrically normalized I/F CDRs mosaicked into a multispectral map tile; - Contains image data in I/F corrected photometrically to i=30 degrees, e=0 at a resolution of 128 pixels per degree (~332 m/pixel at the equator); - Is composed of 5 bands corresponding to the 5 of the 11 WAC filters; and - Contains 6 backplanes: (a) image count, the number of image sets averaged at a given latitude/longitude coordinate, and (b-f) standard deviations of the values used to determine average normalized I/F in each of the 5 bands. Versions ======== Version numbers of the MP5 increment on reprocessing or addition of new data. The map tile is in polar stereographic projection. Version 1 is released at PDS release 15. It is controlled and projected onto a global digital elevation model. It uses a Kasseleinin-Shkuratov photometric model, whose parameters are the same for any given wavelength band across all MESSENGER end-of-mission map data products. I/F is taken from version 5 CDRs. Parameters ========== MDIS observing variables pertaining to the MP5 are as follows. Pixel Binning: Some images are unbinned and 1024x1024 pixels. Some images are 2x2 pixel binned in the focal plane hardware (also known as 'on-chip' binning), resulting in 512 x 512 images. Images can be further compressed 2x2 using the MP, in addition to DPU binning, yielding 256x256 images. Images used in 5-color MP5 products are mostly not binned although some taken at the lowest altitudes are binned 2x2 'on-chip'. This less aggressive binning strategy than in the Primary Mission 8-color products results in nearly a >2x reduction in the native pixel scale of the data. 12-8 bit compression: Images are read off the detector in 12-bit format. 12 bit images may converted to 8 bit images using one of eight lookup tables (LUTs). All WAC images collected as part of the 5-color multispectral map have been converted to 8 bits. FAST/DPCM compression: All images are compressed losslessly using FAST/DCPM compression as they are read out of the DPU, to conserve recorder space. Once the data are written to the recorder, they can be uncompressed and recompressed more aggressively in the MP. Wavelet compression: Images may be integer wavelet transform- compressed in the MP, typically at 3:1 for color data. Color imaging was taken losslessly compressed when downlink volume permitted it. Exposure Control: The exposure time of MDIS images can be set manually by command, or automatically by the software. In manual mode, exposure times from 1-989, 1001-1989, ..., to 9001-9989 ms are available. In autoexposure mode the exposure time of the next image is computed by the DPU software, and cannot exceed 989 ms in duration. If the time of the next image occurs before the calculation can be completed, and pixel binning or filter position change, then the algorithm compensates for predicted changes in scene brightness and filter transmission using an onboard data structure. All images in the MP5 were acquired using automatic exposure. Pointing: The MDIS imagers are mounted on a pivot platform, which is itself mounted to the MESSENGER spacecraft deck. The pivot platform is controlled by a stepper motor, which is controlled by the Data Processing Unit (DPU). The pivot platform can move in either direction. The total range of motion is 240 degrees, limited by mechanical 'hard' stops, and is further constrained by 'soft' stops applied by the software. The nominal pointing position for MDIS is defined as 0 degrees, aligned with the spacecraft +Z axis and the boresight for several other instruments. The range of the soft stops is set to 40 degrees in the spacecraft -Y direction (toward the MESSENGER sunshade) and +50 degrees in the +Y direction (away from the sunshade). The pivot position can be commanded in intervals of 0.01 degrees within this range. During acquisition of the 5-color multispectral map, the pivot was used to point the WAC to near-constant low phase angles near 30 degrees, allowing emission angle to vary. Filter selection: The WAC imager contains a 12 position filter wheel to provide spectral imaging over the spectral range of the CCD detector. Five of the filters were chosen for the map and appear in the MP5 in order of increasing wavelength: WAC filter 6 (filter F), 430 BP 40 WAC filter 4 (filter D), 560 BP 5 WAC filter 7 (filter G), 750 BP 5 WAC filter 12 (filter L), 830 BP 5 WAC filter 9 (filter I), 1000 BP 15 Processing ========== A sequence of processing creates an MP5 from CDRs and DDRs. A Derived Data Record (DDR) consists of multiband images whose line and sample dimensions and coordinates correspond one-for-one with those of a CDR. It has 5 bands of data used to help create an MP5, including for every image pixel: (a) latitude, (b) longitude, (c) incidence angle, (d) emission angle, and (e) phase angle. The DDRs are an intermediate product used to create MP5s and other map products, are defined as a distinct data product in the MDIS CDR/RDR Software Interface Specification, and are delivered to the PDS. The sequence of processing is as follows: (a) Experiment Data Records (EDRs) are assembled from raw data. (b) Radiance images are created from the EDRs and calibration files. (c) Radiance is converted to I/F CDRs by dividing by (pi * solar flux at 1 AU / heliocentricdistance_in_AU^2). (d) I/F is photometrically corrected to i = 30 degrees, e = 0 degrees. (e) Pivot positions are extracted from the spacecraft housekeeping and formatted as a pivot C kernel. (f) Using the pivot C kernel and other SPICE kernels, DDRs are created. The surface intercept on a model of Mercury's surface is calculated for each spatial pixel. The angles of this pixel relative to the equatorial plane and reference longitude constitute the latitude and longitude of the pixel. For that latitude and longitude, solar incidence, emission, and phase angles are determined. (g) I/F corrected to i = 30 degrees, e = 0 degrees is map projected into multiband MP5s using the latitude and longitude information in the DDRs. Backplanes are populated using statistics on the count and standard deviations of images that are averaged to populate each of the bands of normalized I/F. For the version 1 MP5, at any location, all images that fall within the following criteria are averaged, to reduce residuals from the time- variable instrument calibration. This results in a spatially variable number of images having been averaged: - Controlled images are only used, with the G filter images part of the control set, and other filters in any given color set registered to the G filter images - Only uses images from the 3-color mapping campaign - For tiles north of 75N latitude: - Incidence angle at the center of the images is < 86.5 degrees - Image ID > 4000000 to avoid some high-incidence early data - For tiles south of 75N latitude: - Incidence angle at the center of the images is < 83 degrees - Image ID > 4460000 to avoid some high-incidence early data For the MP5 delivered at the end of the mission, the form of the photometric correction used is a Kasseleinen-Shkuratov function described by [DOMINGUEETAL2016]. The form of the function is given as: I/F = AN*exp[-(g*mu)]{c_sub_l[2cos i/(cos i + cos e)]+[1-c_sub_l]cos i} where i is solar incidence angle, e is emission angle, g is phase angle, AN is normal albedo at a given wavelength, mu and c_sub_l are wavelength-dependent parameters. Parameter values were fit using multiple regions between 24 degrees and 46 degrees south latitude and 330 degrees and 353 degrees east longitude. These regions sample incidence angle (i), emission angle(e), and phase angle (g) coverage commensurate with global mapping campaigns. In addition whole-disk Mercury images taken at a large number of geometries during the Mercury flybys expand the phase angle range. Parameter values were fit in the same manner as the parameters for the Hapke model. The values are given in the table below: WAC filter, wavelength, AN, mu, c_sub_l F, 433.2, 0.0700, 0.6363, 0.6293 D, 558.9, 0.0911, 0.5976, 0.6186 G, 748.7, 0.1111, 0.5628, 0.6424 L, 828.4, 0.1194, 0.5570, 0.6369 I, 996.2, 0.1250, 0.5200, 0.6303 Data ==== There is one data type associated with this volume, an MP5 consisting of mosaicked, photometrically corrected WAC CDRs acquired through 5 spectral filters, appended with 5 backplanes describing the component CDRs, their native spatial sampling scale, and their photometric geometries. Ancillary Data ============== There are two types of ancillary data provided with this dataset: 1. The CALIB directory contains bandpasses of the spectral filters of MDIS used to collect the images in the dataset, to facilitate comparison with other data sets. See CALINFO.TXT in that directory for more details. 2. There may be a BROWSE directory containing browse images in PNG and/or GeoTIFF format. See BROWINFO.TXT in that directory for more details. Coordinate System ================= The cartographic coordinate system used for the MDIS data products conforms to the J2000 celestial reference frame for star imaging, and the IAU planetocentric system with East longitudes being positive for planetary surfaces. The IAU2000 reference system for cartographic coordinates and rotational elements is used for computing latitude and longitude coordinates of planets. The value for Mercury radius is 2439.4 km. Media/Format ============ The MDIS archive is organized and stored in the directory structure described in the Mercury Dual Imaging System (MDIS) Calibrated Data Record (CDR) and Reduced Data Record (RDR) Software Interface Specification (SIS). The contents of the archive, along with fiduciary checksums, are compressed into a single 'zip archive' file for transmittal to the PDS Imaging node. The zip archive preserves the directory structure internally so that when it is decompressed the original directory structure is recreated at the PDS Imaging node. The zip archive is transmitted to the PDS Imaging node via FTP to the URL specified by the node for receiving it." CONFIDENCE_LEVEL_NOTE = " Confidence Level Overview ========================= Known issues of concern are described below. Review ====== This archival data set was examined by a peer review panel prior to its acceptance by the Planetary Data System (PDS). The peer review was conducted in accordance with PDS procedures. Data Coverage and Quality ========================= Only a subset of raw EDR data are calibrated to CDRs and then incorporated into MP5 products. Briefly, the following criteria are met: (a) The data represent a scene and not the instrument test pattern, as indicated by data quality index (DQI) byte 0. (b) The exposure time is greater than zero (zero exposures occur in some images due to software features), as indicated by DQI byte 1. (c) Less than 20 percent of the image is saturated (empirically this is a threshold dividing wholly corrupted images from everything else). (d) The target of the image is MERCURY. (e) The image was taken as part of the 5-color mapping campaign represented by MP5 data products. The MP5 is based on version 5 CDRs which correct a number of earlier calibration artifacts. Those images may be subject to some or all of the following issues. (1) COMPRESSION ARTIFACTS. Wavelet compression applied to science images is lossy. At higher compression ratios, compression artifacts will degrade data precision over spatial scales comparable to or smaller than several pixels. The degradation can be greater proportionally to the image dynamic range of brightness, if the data are converted from 12 to 8 bits in such a way that a 1 DN error occupies a greater fraction of the digital dynamic range. Wavelet compression was used minimally prior to Mercury orbit. The initial configuration in Mercury orbit was to perform 12 to 8 bit conversion using LUT0 for the WAC and LUT2 for the NAC, with a wavelet compression ratio of 4:1 for color imaging. Initial images exhibited unexpectedly visible compression artifacts. Beginning 19 April 2011, LUT0 and LUT2 were replaced with LUT1 which better preserves image dynamic range. Beginning 19 May 2011, targeted color images began to be acquired with lossless compression. Beginning 31 May 2011, the wavelet compression ratio for color images was reduced to 3:1 for global mapping. All MP5 images are taken with LUT1 and a compression ratio of 3:1 or less. (2) RADIOMETRIC ACCURACY. The radiometric calibration of the WAC was updated several times over the mission to iteratively reduce residuals from 3 sources of error: (a) time-variable responsivity of the detector, (b) residuals in the flat-field correction, and (c) residuals in the correction to responsivity for detector temperature. For multispectral products, the residuals from time-variable responsivity initially led to distinct seams; correction of this artifact is treated in more detail below. In version 5 CDRs an improved temperature correction was derived empirically, by fitting as a function of CCD temperature, the median values of images acquired throughout Mercury orbit at a wide range of temperatures but a narrow range of photometric geometries. The flat field was updated empirically using the median of thousands of photometrically corrected images of relatively bland field-filling images of Mercury. (3) SCATTERED LIGHT. The WAC is subject to scattered light originating from within the field-of-view or just outside it. One source is multiple reflections off of 13 optical surfaces (2 sides of each of 4 lenses, the spectral filter, and the CCD cover glass, as well as the CCD surface itself). The scatter becomes worse at longer wavelengths. Just off the limb of a large extended source near 1 field-of-view in size, like Venus or Mercury, measured radiance increases with wavelength from 2% to 7% of the value measured on the extended source. The value decreases with distance off the target more quickly at shorter than at longer wavelengths, but remains at 1% hundreds of pixels from the source. Conversely, light must be scattering from bright parts of an image to dark parts of an image. Averaged over sources tens of pixels in area, and away from abrupt brightness contrasts, scattered light affects shapes of spectra measured from WAC data at least at the 1-2% level, worse near brightness boundaries or for small, bright crater ejecta. The expected effect is enhanced brightness at <650 nm in dark areas, and decreased brightness at >650 nm in small bright areas. In the end-of-mission delivery 15, a forward model of the expected WAC scatter from a given scene was derived using optical design software modeling CCD structure and hardware, with magnitudes of scatter calibrated against flight measurements. The ray trace analysis reveals an in-scene component from light diffracted by the CCD and reflected by the CCD cover glass, and an out-of-scene component from light reflected off metallic surfaces alongside the CCD and back off the cover glass. Images with the worst scattered light were excluded from multispectral map products. (4) TIME-VARIABLE WAC RESPONSIVITY. During Mercury orbit it was recognized that filter-dependent changes in WAC responsivity on the order of +/- 15% occurred over timescales as short as several days. Because those variations were not consistent from filter to filter, they led to spurious spectral features, which were particularly conspicuous near 750 nm. The cause(s) of these variations in responsivity are not known, but they could include transient radiation effects on the detector or electronics, aging of filters, periodic deposition and burn-off of contaminants on filters, or incorrect recording of exposure time. For version 5 WAC CDRs used to create the MP5, an updated correction covers the full duration of the orbital phase. Overlaps between color image sets in color mapping campaigns were used to derive a multiplicative correction factor for each filter and for each Earth day (2-3 orbits). The version 1 MP5 uses CDRs with this updated correction. An analysis of overlap among individual images shows that residual differences (which include errors from calibration, scattered light, and possible incomplete correction of photometric variation) average <2% for the majority of the planet. (5) MAP PROJECTION ERRORS. The MP5 is constructed from images controlled using c-smithed kernels and a global digital elevation model (DEM), both derived using a least-squares bundle adjustment of common features, measured as tie point coordinates in overlapping NAC and WAC-G filter images of Mercury at favorable solar incidence and emission angles. Empirically, misregistration errors between images are generally at the pixel scale of the map (0.2 km) in most locations. Derivation of smithed kernels and the DEM for end of mission data products is described by [BECKERETAL2016]. Limitations =========== None" END_OBJECT = DATA_SET_INFORMATION OBJECT = DATA_SET_MISSION MISSION_NAME = "MESSENGER" END_OBJECT = DATA_SET_MISSION OBJECT = DATA_SET_TARGET TARGET_NAME = "MERCURY" END_OBJECT = DATA_SET_TARGET OBJECT = DATA_SET_HOST INSTRUMENT_HOST_ID = MESS INSTRUMENT_ID = "MDIS-WAC" END_OBJECT = DATA_SET_HOST OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "HAWKINSETAL2007" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "HAWKINSETAL2009" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "DOMINGUEETAL2016" END_OBJECT = DATA_SET_REFERENCE_INFORMATION OBJECT = DATA_SET_REFERENCE_INFORMATION REFERENCE_KEY_ID = "BECKERETAL2016" END_OBJECT = DATA_SET_REFERENCE_INFORMATION END_OBJECT = DATA_SET END