Data Set Overview
    =================

      This data set contains Calibrated data taken by New Horizons
        Radio Science Experiment
      instrument during the JUPITER mission phase.

      The REX instrument measures the amplitude and phase of radio signals
      captured by the New Horizons high-gain antenna.  The main investigation
      is an occultation experiment which uses radio signals transmitted from
      Earth to probe the atmosphere and ionosphere of Pluto and Charon.
      Ancillary investigations include measurements of the 4 cm wavelength
      radiothermal emission from planets or other radio sources.  Phase data
      may also be combined with Pluto encounter tracking data, derived from
      the Radio Science Subsystem separately from REX and to be archived in
      separate non-REX data set(s), to infer the influence of gravitational
      fields on the spacecraft as it moves through the Pluto system.

      The main investigation requires coordinated use of the Earth-based
      transmitters and the spacecraft receiver as the two physical elements
      of the REX instrument.  The 'Ground Element' comprises DSN (Deep Space
      Network) hardware and operations facilities on Earth, and the 'Flight
      Element' includes signal processing hardware and software onboard the
      spacecraft.

      Unless inclusion of tuning profiles for one-way uplink transmissions is
      noted below, this data set includes only samples taken and measurements
      made by the REX system hardware on-board the New Horizons spacecraft --
      either of one-way uplink signals or of 4cm-wavelength thermal emission.

      #######################################################################
      #######################################################################
      REQUIRED UNDERSTANDING:  THE REX AND THE NEW HORIZONS (NH) REGENERATIVE
      RANGING TRACKER [DEBOLTETAL2005] ARE

         *****SEPARATE***** AND *****INDEPENDENT*****

      SUBSYSTEMS THAT BOTH USE THE RADIO FREQUENCY (RF) AND TELECOMMUNICATION
      SUBSYSTEMS.  TRACKING DATA WILL NOT BE ARCHIVED IN REX DATA SETS.
      #######################################################################
      #######################################################################

The New Horizons Jupiter encounter afforded no occultation or bi-static
scattering geometries for which REX had sufficient sensitivity.  The main REX
activity during Jupiter flyby was a pair of radiometric scans of the High Gain
Antenna (HGA), across the Jovian disk for the purpose of calibrating the REX
radiometer experiment.  The scans were conducted with New Horizons at ~100 Rj
both in-bound and out-bound, when the angular size of Jupiter was closely
matched to the beamwidth of the HGA.  The Jovian radiometric profile
downlinked from the first scan exhibits high precision, and has been used to
calibrate the REX radiometric response.

Other activities during the mission phase, not associated with the proximity
to Jupiter and with the main purpose of characterizing the instrument, were
standard checkout operations, looking for weak tones in the REX band by using
a large gain, mapping the HGA beam pattern, and an interference test with
other instruments.

Although one-way uplink data signals were sent from the Ground Element to REX,
the characteristics of those signals are not needed to analyze these REX
observations comprising instrument checkout, characterization and calibration
activities.  So no uplink tuning profiles are included in this data set.

      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_REX_JUPITER.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.


    Known issues in REX data
    ========================

        The following item assumes familiarity with the REX, REX terminology
        and the required reading and other documentation provided with this
        data set.

        Time tag anomalies in ROF sequences
        -----------------------------------

        REX places ten incrementing time tags in each REX Output Frame (ROF).
        The time tags can be used both to identify any breaks in a sequence of
        ROFs, and to determine the time between any two ROFs within a
        sequence.

        The normal sequence for time tags is to start at zero in the first ROF
        and increment ten times per ROF, so the first time tag of the second
        ROF is 10, that of the third ROF is 20, etc.  In practice, the first
        and last ROFs in a sequence do not always show simple zero starts and
        clean finishes, respectively, indicating data corruption in just those
        ROFs.  There is no indication of corruption elsewhere in ROF streams,
        and REX commanding ensures there are always adequate ROFs before and
        after any observation, so discarding starting and ending ROFs in a
        sequence based on simple inspection of time tags is the way to handle
        this issue.

        For more detail, refer to the REX Instrument Description section in
        the SOC Instrument Interface Control Document (ICD).


    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 Operations Center (SOC) at
      the Southwest Research Institute (SwRI), Department of Space Operations.
      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.



    Calibration
    ===========


      Detailed information about calibration of REX data is available
      in the SOC Instrument Interface Control Document (ICD) and
      in the NH_REX_RADIOMETER_CALIB_V4P7 calibration report in the
      DOCUMENT section of this data set; refer to these documents for
      REX calibration details.

      Note also that for REX data the Calibrated dataset is one version
      behind the Raw dataset, so for example the Calibrated dataset would
      be at Version 1.0 while the Raw dataset would be at Version 2.0.
      There was an initial delivery to the PDS of the Raw dataset before
      the Calibrated dataset was completed.


    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.

         REX_0123456789_0X7B0_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
         |        |          N.B. ApIDs are case-insensitive
         |        |
         |        +--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 **
        ===========  ==================================  =============
         REX          REX                                0X7B0 - 0X7B3 *

         * Not all values in this range are in this data set
         ** ApIDs are case insensitive

         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 types of files generated by each ApID
        (N.B. ApIDs are case-insensitive) along with the instrument
        designator that go with each ApID:


         ApIDs   Data product description/Prefix(es)
         =====   ===================================
         0x7b0 - REX Lossless Compressed Data (CDH 1)/REX
         0x7b1 - REX Packetized Data (CDH 1)/REX
         0x7b2 - REX Lossless Compressed Data (CDH 2)/REX
         0x7b3 - REX Packetized Data (CDH 2)/REX


      Instrument description
      ----------------------

        Refer to the following files for a description of this instrument.

        CATALOG

          REX.CAT

        DOCUMENTS

          REX_SSR.*
          SOC_INST_ICD.*


      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
            /DOCUMENT/NH_TRAJECTORY.*           - Jupiter-centric



      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.  PDS-SBN
      practices 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.  TARGET_NAME may be N/A (Not Available or Not
      Applicable) for a few observations in this data set; typically that
      means the observation is a functional test so N/A is an appropriate
      entry for those targets, but the PDS user should also check the
      NEWHORIZONS:OBSERVATION_DESC and NEWHORIZONS:SEQUENCE_ID keywords in
      the PDS label, plus the provided sequence list (see Ancillary Data
      below) to assess the possibility that there was an intended target.
      These two keywords are especially useful for STAR targets as often
      stars are used as part of instrument calibrations, and are
      included as part of the sequencing description which is captured
      in these keywords.



    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-JUPITER-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_REX_JUPITER.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.  Some
      sequences may have failed to execute due to spacecraft events (e.g.
      safing).  No attempt has been made during the preparation of this data
      set to identify such empty sequences, so it is up to the user to
      compare the times of the sequences to the times of the available
      observations from INDEX/INDEX.TAB 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) was 65.184s at
      NH launch, and the first three additional leapseconds occurred
      in at the ends of December, 2009, June, 2012 and June, 2015.
      Refer to the NH SPICE data set, NH-J/P/SS-SPICE-6-V1.0, and the
      SPICE toolkit documentation, for more details about leapseconds.

      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 REX Principal Investigator:

      Ivan Linscott, Stanford University
      David Packard Building - Room 319
      350 Serra Mall
      Stanford, CA   94305-9515
      USA

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
      may not have corresponding data products in the calibrated data set.


      Note that the REX Raw V2.0 dataset corresponds with the REX
      Calibrated V1.0 dataset. The Raw data had been certified once before
      the calibrated data was able to be certified.

    Data coverage and quality
    =========================
      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_REX_JUPITER.TAB.  N.B. Some sequences
      provided may have zero corresponding observations.

      Refer to the Confidence Level Overview section above for a summary
      of steps taken to assure data quality.

      The calibrated radiometry values in the data products of this data
      set are supplied in units of dBm.  The conversion to dBm includes the
      logarithm of a raw power value.  For cases where that raw power value
      is zero, the logarithm function used returns the IEEE_REAL floating
      point special value for negative infinity (-Inf).  This is correct
      behavior, and that IEEE_REAL special value for negative infinity is
      stored in the data file. However, PDS3 has no way to recognize this
      as negative infinity, and will instead interpret the bits in the data
      as -340282366920938463463374607431768211456.0, or about -3.4E+38.  To
      deal with this, the radiometry COLUMN OBJECT will contain the
      VALID_MINIMUM keyword with a value sufficiently small to flag the
      IEEE-754 -Inf values as invalid, whether they are interpreted as the
      special IEEE-754 value negative infinity or as the numeric -3.4E+38.
      In practice, this only occurs in situations where the raw accumulated
      power is being initialized, or where the raw power data are zeroed
      because REX has been shut down before completion of a final REX
      Output Frame (ROF; see the ICD), or where the instrument input is a
      non-physical synthetic signal used to validate correct operation of
      the REX instrument.  In all of these cases, this behavior is easily
      identified and will have no effect on any science analysis.

      The Time Tag counter values included with REX data normally increment
      nine times within each data file and once between consecutive frames.
      However, there are sometimes anomalous departures from this behavior at
      the start and end of contiguous runs of data files (see REX.CAT for a
      brief discussion of such an issue related to compression).  Files with
      such anomalies are few compared to the total number of data files, and
      excluding those files with anomalous Time Tag data from data analysis
      will not significantly affect the results of the REX investigation.
      Refer to the Science Operations Center/instrument interface control
      document for more detail about REX Time Tags; there is adequate
      information there for users to identify anomalous files.
      In addition, products with Time Tag anomalies are listed in file
      ERRATA.TXT provided with this data set.


    Observation descriptions in this data set catalog
    =================================================

      Some users will expect to find descriptions of the observations
      in this data set here, in this Confidence Level Note.  This data
      set follows the more common convention of placing those
      descriptions under the Data Set Description (above, if the user is
      reading this in the DATASET.CAT file) of this data set catalog.


    Caveat about TARGET_NAME in PDS labels and observational intent
    ===============================================================

      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 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.

      Finally, note that, within the FITS headers of the data products,
      the sequence tables, and other NH Project-internal documents used
      in this data set and/or inserted into the data set catalog,
      informal names are often used for targets instead of the canonical
      names required for the TARGET_NAME keyword.  For example, during
      the Pluto mission phase, instead of the TARGET_NAME '15810 ARAWN
      (1994 JR1)' there might be found any of the following:  1994JR1;
      1994 JR1; JR1.  For all values where the PDS keyword TARGET_NAME
      is used (e.g. in PDS labels and in index tables), the canonical,
      PDS-approved names are used (if not, please bring this to the
      attention of PDS so it can be rectified).  However, within the
      context of this data set, these project abbreviations are not
      ambiguous (e.g. there is only one NH target with 'JR1' in its
      name), so there has been, and will be, no attempt to expand such
      abbreviations where they occur outside formal PDS keyword values.


    Review
    ======
      This dataset was peer reviewed and certified for scientific use on
      December 4, 2017.