DATA_SET_DESCRIPTION |
Data Set Overview : This data set contains Raw data taken by New Horizons Multispectral Visible Imaging Camera instrument during the PLUTO mission phase. MVIC is a visible and near-infrared imager. MVIC comprises seven separate CCD two-dimensional arrays; all rows are 5024 pixels across with twelve pixels at either end of each row optically inactive. The single Pan Frame array is a panchromatic frame-transfer imager, 5024x128 pixels, that typically takes multiple frames in each observation. The common Pan Frame data product is an image cube in three dimensions: spatial; spatial; image frame, equivalent to time. Of the remaining six arrays, 5024x32 pixels each, two are panchromatic (unfiltered), and the remaining four are under filters and called the color arrays: Near-InfraRed (NIR); methane (CH4); Red; Blue. All six are operated in Time-Delay Integration (TDI) mode; the TDI arrays are in some ways similar to line cameras. In TDI mode, the spacecraft and MVIC boresight are scanned across the target at a rate that matches the charge transfer clock rate across the rows of the CCDs. Ideally the rates are matched, so as the charges are read by the analog-to-digital converter off the last line of the array, each pixel reading is near-proportional to the brightness of the same piece of the target as its image moved across the array, accumulating charge on each row. In TDI mode it is the product of the per-row charge clock rate and the duration of the observation that determines the number of rows each the image, and the image can be arbitrarily long; the number of rows (32) in each array is not relevant in determining the size of the image. The common data product for each of the TDI arrays is a 2-D image, of arbitrary length as noted earlier. During the Pluto mission phase starting in January, 2015, there were several sub-phases: three Approach sub-phases, (AP1, AP2 and AP3); a CORE sequence for the Pluto flyby on 14.July, 2015 (Day Of Year 195), sometimes also referred to as NEP (Near-Encounter Phase); three Departure sub-phases (DP1, DP2, DP3). For this first Ralph-MVIC delivery for the Pluto mission phase, this data set includes only the Approach data plus the subset of the CORE sequence data that was downlinked through the end of July, 2015. The rest of the Pluto data will be delivered in future versions of this data set according to the schedule worked out by the Project and NASA. On Approach during April, May and June of 2015, MVIC operations included the following: functional tests; full color observations of the Pluto, Charon and the other Plutonian satellites; Critical and Non-critical Optical Navication (OpNav or NAV) observations. The color observations were grouped over several 6-day periods to obtain a full rotation of Pluto and Charon. This dataset includes the first PC_VISUV_MAP for MVIC at about 19 days before encounter, a color TDI observation looking for changes in color and composition over multiple rotations, to meet the goal of understanding the time variability of Pluto's surface. These observations were repeated daily over that week leading up to encounter. From the day of encounter, this data set includes data from three CORE observations: (1) Pluto/Charon color map (PC_MULTI_MAP) about a day before the Time of Closest Approach (P-1d); (2) Pluto and Charon color scan at P-5h (PC_COLOR_1); (3) Nix color scan (N_COLOR_2). The PC_MULTI_MAP observation, the last one of which is included in this dataset, met multiple goals including imaging for color and surface composition maps of the Pluto and Charon hemispheres, Pluto and Charon phase integrals with resolved whole-disk images near 15 degrees, and imaging Pluto hazes on approach. Secondary goals are Pluto and Charon color high and low phase imaging to enable integrating over wavelength to determine the bolometric Bond albedo, and also to investigate the surface microphysics of Pluto and Charon, studying compositional and textural stratification in the surface as a function of terrain type. The N_COLOR series provided Nix high-resolution resolved color images. Every observation provided in this data set was taken as a part of a particular sequence. A list of these sequences has been provided in file DOCUMENT/SEQ_MVIC_PLUTO.TAB. N.B. Some sequences provided may have no corresponding observations. For a list of observations, refer to the data set index table. This is typically INDEX.TAB initially in the INDEX/ area of the data set. There is also a file SLIMINDX.TAB in INDEX/ that summarizes key information relevant to each observation, including which sequence was in effect and what target was likely intended for the observation. Version : This is VERSION 1.0 of this data set. Processing : The data in this data set were created by a software data processing pipeline on the Science Operation Center (SOC) at the Southwest Research Institute (SwRI), Department of Space Studies. This SOC pipeline assembled data as FITS files from raw telemetry packets sent down by the spacecraft and populated the data labels with housekeeping and engineering values, and computed geometry parameters using SPICE kernels. The pipeline did not resample the data. Data : The observations in this data set are stored in data files using standard Flexible Image Transport System (FITS) format. Each FITS file has a corresponding detached PDS label file, named according to a common convention. The FITS files may have image and/or table extensions. See the PDS label plus the DOCUMENT files for a description of these extensions and their contents. This Data section comprises the following sub-topics: - Filename/Product IDs - Instrument description - Other sources of information useful in interpreting these Data - Visit Description, Visit Number, and Target in the Data Labels Filename/Product IDs -------------------- The filenames and product IDs of observations adhere to a common convention e.g. MC0_0123456789_0X530_ENG.FIT ^^^ ^^^^^^^^^^ ^^^^^ ^^^\__/ | | | | ^^ | | | | | | | | | +--File type (includes dot) | | | | - .FIT for FITS file | | | | - .LBL for PDS label | | | | - not part of product ID | | | | | | | +--ENG for CODMAC Level 2 data | | | SCI for CODMAC Level 3 data | | | | | +--Application ID (ApID) of the telemetry data | | packet from which the data come | | | +--MET (Mission Event Time) i.e. Spacecraft Clock | +--Instrument designator Note that, depending on the observation, the MET in the data filename and in the Product ID may be similar to the Mission Event Time (MET) of the actual observation acquisition, but should not be used as an analog for the acquisition time. The MET is the time that the data are transferred from the instrument to spacecraft memory and is therefore not a reliable indicator of the actual observation time. The PDS label and the index tables are better sources to use for the actual timing of any observation. The specific keywords and index table column names for which to look are * START_TIME * STOP_TIME * SPACECRAFT_CLOCK_START_COUNT * SPACECRAFT_CLOCK_STOP_COUNT Instrument Instrument designators ApIDs : : : MVIC MC0, MC1, MC2, MC3, MP1, MP2, MPF 0X530 - 0X54A * * Not all values in this range are in this data set There are other ApIDs that contain housekeeping values and other values. See SOC Instrument ICD (/DOCUMENT/SOC_INST_ICD.*) for more details. Here is a summary of the meanings of each instrument designator: Instr Dsgn. Description : : MC0 MVIC, Color TDI, Red filter MC1 MVIC, Color TDI, Blue filter MC2 MVIC, Color TDI, Near-InfraRed (NIR) filter MC3 MVIC, Color TDI, Methane (CH4) filter MP1 MVIC, Panchromatic TDI CCD 1 MP2 MVIC, Panchromatic TDI CCD 2 MPF MVIC, Panchromatic frame (5024 pixels) See SOC Instrument ICD (/DOCUMENT/SOC_INST_ICD.*) for details Here is a summary of the types of files generated by each ApID along with the instrument designator that go with each ApID: ApIDs Data product description/Prefix(es) : : 0x530 - MVIC Panchromatic TDI Lossless (CDH 1)/MP1,MP2 0x53f - MVIC Panchromatic TDI Lossless (CDH 2)/MP1,MP2 0x531 - MVIC Panchromatic TDI Packetized (CDH 1)/MP1,MP2 0x540 - MVIC Panchromatic TDI Packetized (CDH 2)/MP1,MP2 0x532 - MVIC Panchromatic TDI Lossy (CDH 1)/MP1,MP2 0x541 - MVIC Panchromatic TDI Lossy (CDH 2)/MP1,MP2 0x533 - MVIC Panchromatic TDI 3x3 Binned Lossless (CDH 1)/MP1,MP2 * 0x542 - MVIC Panchromatic TDI 3x3 Binned Lossless (CDH 2)/MP1,MP2 * 0x534 - MVIC Panchromatic TDI 3x3 Binned Packetized (CDH 1)/MP1,MP2 * 0x543 - MVIC Panchromatic TDI 3x3 Binned Packetized (CDH 2)/MP1,MP2 * 0x535 - MVIC Panchromatic TDI 3x3 Binned Lossy (CDH 1)/MP1,MP2 * 0x544 - MVIC Panchromatic TDI 3x3 Binned Lossy (CDH 2)/MP1,MP2 * 0x536 - MVIC Color TDI Lossless (CDH 1)/MC0,MC1,MC2,MC3 0x545 - MVIC Color TDI Lossless (CDH 2)/MC0,MC1,MC2,MC3 0x537 - MVIC Color TDI Packetized (CDH 1)/MC0,MC1,MC2,MC3 0x546 - MVIC Color TDI Packetized (CDH 2)/MC0,MC1,MC2,MC3 0x538 - MVIC Color TDI Lossy (CDH 1)/MC0,MC1,MC2,MC3 0x547 - MVIC Color TDI Lossy (CDH 2)/MC0,MC1,MC2,MC3 0x539 - MVIC Panchromatic Frame Transfer Lossless (CDH 1)/MPF 0x548 - MVIC Panchromatic Frame Transfer Lossless (CDH 2)/MPF 0x53a - MVIC Panchromatic Frame Transfer Packetized (CDH 1)/MPF 0x549 - MVIC Panchromatic Frame Transfer Packetized (CDH 2)/MPF 0x53b - MVIC Panchromatic Frame Transfer Lossy (CDH 1)/MPF 0x54a - MVIC Panchromatic Frame Transfer Lossy (CDH 2)/MPF * as of October, 2014, 3x3 modes have not been used Instrument description ---------------------- Refer to the following files for a description of this instrument. CATALOG MVIC.CAT DOCUMENTS RALPH_SSR.* SOC_INST_ICD.* NH_RALPH_V###_TI.TXT (### is a version number) Other sources of information useful in interpreting these Data -------------------------------------------------------------- Refer to the following files for more information about these data NH Trajectory tables: /DOCUMENT/NH_MISSION_TRAJECTORY.* - Heliocentric RALPH Field Of View definitions: /DOCUMENT/NH_FOV.* /DOCUMENT/NH_RALPH_V###_TI.TXT Visit Description, Visit Number, and Target in the Data Labels --------------------------------------------------------------- The observation sequences were defined in Science Activity Planning (SAP) documents, and grouped by Visit Description and Visit Number. The SAPs are spreadsheets with one Visit Description & Number per row. A nominal target is also included on each row and included in the data labels, but does not always match with the TARGET_NAME field's value in the data labels. In some cases, the target was designated as RA,DEC pointing values in the form ``RADEC:123.45,-12.34'' indicating Right Ascension and Declination, in degrees, of the target from the spacecraft in the Earth Equatorial J2000 inertial reference frame. This indicates either that the target was either a star, or that the target's ephemeris was not loaded into the spacecraft's attitude and control system which in turn meant the spacecraft could not be pointed at the target by a body identifier and an inertial pointing value had to be specified as Right Ascension and Declination values. The PDS standards do not allow putting a value like RADEC:... in the PDS TARGET_NAME keyword's value. In those cases the PDS TARGET_NAME value is set to CALIBRATION. Ancillary Data : The geometry items included in the data labels were computed using the SPICE kernels archived in the New Horizons SPICE data set, NH-X-SPICE-6-PLUTO-V1.0. Every observation provided in this data set was taken as a part of a particular sequence. A list of these sequences has been provided in file DOCUMENT/SEQ_MVIC_PLUTO.TAB. In addition, the sequence identifier (ID) and description are included in the PDS label for every observation. N.B. While every observation has an associated sequence, every sequence may not have associated observations; that is, some sequences may have failed to execute due to spacecraft events (e.g. safing) and there will be observations associated with those sequences. No attempt has been made during the preparation of this data set to identify if any, or how many, such empty sequences there are, so it is up to the user to compare the times of the sequences to the times of the available observations from the INDEX/INDEX.TAB table to identify such sequences. Time : There are several time systems, or units, in use in this dataset: New Horizons spacecraft MET (Mission Event Time or Mission Elapsed Time), UTC (Coordinated Universal Time), and TDB Barycentric Dynamical Time. This section will give a summary description of the relationship between these time systems. For a complete explanation of these time systems the reader is referred to the documentation distributed with the Navigation and Ancillary Information Facility (NAIF) SPICE toolkit from the PDS NAIF node, (see http://naif.jpl.nasa.gov/). The most common time unit associated with the data is the spacecraft MET. MET is a 32-bit counter on the New Horizons spacecraft that runs at a rate of about one increment per second starting from a value of zero at 19.January, 2006 18:08:02 UTC or JD2453755.256337 TDB. The leapsecond adjustment (DELTA_ET : ET - UTC) over this dataset is 65.184s. The data labels for any given product in this dataset usually contain at least one pair of common UTC and MET representations of the time at the middle of the observation. Other portions of the products, for example tables of data taken over periods of up to a day or more, will only have the MET time associated with a given row of the table. For the data user's use in interpreting these times, a reasonable approximation (+/- 1s) of the conversion between Julian Day (TDB) and MET is as follows: JD TDB : 2453755.256337 + ( MET / 86399.9998693 ) For more accurate calculations the reader is referred to the NAIF/SPICE documentation as mentioned above. Reference Frame : Geometric Parameter Reference Frame ----------------------------------- Earth Mean Equator and Vernal Equinox of J2000 (EMEJ2000) is the inertial reference frame used to specify observational geometry items provided in the data labels. Geometric parameters are based on best available SPICE data at time of data creation. Epoch of Geometric Parameters ----------------------------- All geometric parameters provided in the data labels were computed at the epoch midway between the START_TIME and STOP_TIME label fields. 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. Contact Information : For any questions regarding the data format of the archive, contact New Horizons RALPH Principal Investigator: Alan Stern, Southwest Research Institute S. Alan Stern Southwest Research Institute Department of Space Studies 1050 Walnut Street, Suite 400 Boulder, CO 80302 USA
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CONFIDENCE_LEVEL_NOTE |
Confidence Level Overview : During the processing of the data in preparation for delivery with this volume, the packet data associated with each observation were used only if they passed a rigorous verification process including standard checksums. In addition, raw (Level 2) observation data for which adequate contemporary housekeeping and other ancillary data are not available may not be reduced to calibrated (Level 3) data. This issue is raised here to explain why some data products in the raw data set, NH-P-MVIC-2-PLUTO-V1.0, may not have corresponding data products in the calibrated data set, NH-P-MVIC-3-PLUTO-V1.0. Data coverage and quality : Caveat about TARGET_NAME in PDS labels and observational intent : A fundamental truth of managing data from some spacecraft missions is that the intent of any observation is not suitable for insertion into the command stream sent to the spacecraft to execute that observation. As a result, re-attaching that intent to the data that are later downlinked is problematic at best. For New Horizons that task is made even more difficult as the only meta-data that come down with the observation is the unpredictable time of the observation. The task is made yet even more difficult because uplink personnel, who generate the command sequences and initially know the intent of each observation, are perpetually under deadlines imposed by orbital mechanics and can rarely be spared for the time-intensive task of resolving this issue. To make a long story short, the downlink team on New Horizons has created an automated system to take various uplink products, decode things like Chebyshev polynomials in command sequences representing celestial body ephemerides for use on the spacecraft to control pointing, and infer from those data what the most likely intended target was at any time during the mission. This works well during flyby encounters and less so during cruise phases and hibernation. The point to be made is that the user of these PDS data needs to be cautious when using the TARGET_NAME and other target-related parameters stored in this data set. This is less an issue for the plasma and particle instruments, more so for pointing instruments. To this end, the heliocentric ephemeris of the spacecraft, the spacecraft-relative ephemeris of the inferred target, and the inertial attitude of the instrument reference frame are provided with all data, in the J2000 inertial reference frame, so the user can check where that target is in the Field Of View (FOV) of the instrument. Furthermore, for pointing instruments with one or more spatial components to their detectors, a table has been provided in the DOCUMENT/ area with XY (two-dimensional) positions of each inferred target in the primary data products. If those values are several thousand pixels off of a detector array, it is a strong indication that the actual target of that observation is something other than the inferred target, or no target at all e.g. dark sky. Review : This dataset was peer reviewed and certified for scientific use on TBD.
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