Data Set Information
DATA_SET_NAME MESSENGER H XRS 5 REDUCED DATA RECORD (RDR) FOOTPRINTS V1.0
DATA_SET_ID MESS-H-XRS-5-RDR-FOOTPRINTS-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION The MESSENGER XRS RDR Footprint data set contains a single footprint for each CDR observation. Each footprint contains a set of points that form the perimeter of the planetary footprint from which the corresponding CDR spectra were obtained.
DATA_SET_DESCRIPTION 
Data Set Overview
   =================
     Each observation is calibrated and processed into the CDR data
     set. The orbital mechanics of the instrument and field-of-view of
     each measurement are used in the computation of the footprints.

   Instrument Overview
   ===================
     The X-Ray Spectrometer (XRS) experiment is comprised of three
     identical gas proportional counters (GPC) that measure X-rays
     emitted from the surface of Mercury in the energy range from about
     1 to 10 keV.  X-rays in this energy range sample the planetary
     surface to depths of a few tens of microns.

     See the INSTRUMENT.CAT file for more information and
     [SCHLEMMETAL2007] for full details.

   Calibration Overview
   ====================
     The supernova remnant X-ray source Cassiopeia-A (Cas-A) was
     used for periodic in-flight calibration because of its relatively
     high intensity in the XRS energy range. Once or twice a year XRS
     was pointed to Cas-A for about 48 hours and then away from that
     source for another 48 hours to accumulate background
     measurements. These measurements provided an evaluation and
     calibration of the XRS anti-coincidence and rise-time
     discrimination background rejection systems.

   Parameters
   ==========
     The principal parameters when observing with the XRS are as
     follows:

     * Integration Period: Normal (quiet Sun) or Flare. In Normal mode
     three different integration intervals are used, depending on
     distance to the planet. These may be set over a wide range, but
     the default values are:

                  Integration  Collection Time
       Closest:        40 s       2000 s
       Mid-Range:     200 s      10000 s
       Greatest:      450 s      31200 s

     In flare mode integration periods are automatically shortened to a
     pre-determined level, typically 20 s, for 60 minutes or less.

     * Veto Event: Accept or reject events with a simultaneous signal
     from the anti-coincidence wires.

     * Rise-Time Validation: Accept or reject events with an invalid
     rise time measurement.

     Creation of the footprint perimeters uses the HEALPix library
     [GORSKIETAL2004]. HEALPix tessellates the surface of a sphere
     into 12 base pixels of equal area distributed on bands of constant
     latitude, each pixel a curvilinear quadrilateral. The base pixels
     are divided into subpixels based on a parameter, NSIDE, which
     determines the number of subpixels along the edge of each base
     pixel. The resolution of the HEALPix maps is set based on the
     altitude at the midpoint of the observation in kilometers. At
     altitudes at or below 10 km, the HEALPix NSIDE parameter is set
     to 4096; between 10 and 60 kilometers, NSIDE is set to 1024; at
     altitudes above 60 km, NSIDE is set to 256.

   Data
   ====
     The XRS instrument telemetry conveys science data, configuration
     data and status (housekeeping) data. Several telemetry packets are
     used to downlink this information:

        Status Housekeeping Packets
        Uncompressed Science Packets
        Compressed Science Packets
        Raw Sensor Data Packets

     The useful science and housekeeping measurements from the
     telemetry are decompressed and decomutated and are correlated and
     accumulated into one binary table, which constitutes the primary
     experimental data record (EDR).

     Each record of the table contains four energy spectra,
     housekeeping, status, and rate data for one integration period.
     The spectra correspond to the Mg-filtered detector (GPC1), the
     Al-filtered detector (GPC2), the unfiltered detector (GPC3), and
     the solar monitor (SAX). All the spectra have 256 bins, but only
     the highest 244 bins for the GPC and the highest 231 bins for the
     SAX are telemetered. All bins are 16 bits deep. There are five
     32-bit rate counters for SAX and nine 24-bit rate counters for
     each of the three gas proportional counters.

     Rate counters for all four detectors include raw, valid event,
     analyzed, pileup, and high-energy rates. The gas detectors also
     have counters for the veto-anode, veto, rise-pileup, and
     rise-rejection rates.

     Housekeeping data provide voltage, current, and temperature
     readings measured at the end of each integration period. Also
     reported are record and software status, hardware settings and
     integration and reporting times.

     The CDR data products are aggregated to produce the RDRs; in
     combination with the relevant SPICE kernels and the instrument's
     field-of-view parameters, a planetary footprint can be calculated
     for each CDR observation.
DATA_SET_RELEASE_DATE 2017-05-12T00:00:00.000Z
START_TIME 2011-03-24T12:54:09.000Z
STOP_TIME 2015-04-30T11:10:57.000Z
MISSION_NAME MESSENGER
MISSION_START_DATE 2004-08-03T12:00:00.000Z
MISSION_STOP_DATE 2015-04-30T12:00:00.000Z
TARGET_NAME MERCURY
TARGET_TYPE PLANET
INSTRUMENT_HOST_ID MESS
INSTRUMENT_NAME XRAY SPECTROMETER
INSTRUMENT_ID XRS
INSTRUMENT_TYPE XRAY SPECTROMETER
NODE_NAME Geosciences
ARCHIVE_STATUS ARCHIVED - ACCUMULATING
CONFIDENCE_LEVEL_NOTE 
Confidence Level Overview
   =========================
     The XRS CDR data are the calibrated data records released for the
     XRS. They include all of the EDR data plus other information such
     as detector energy calibration, engineering data conversions, and
     spatial data necessary to convert raw XRS counts to planetary
     surface compositions. The XRS RDR maps and footprints are created
     using the calibrated XRS CDR products.

   Review
   ======
     The XRS CDR was reviewed internally by the XRS team prior to
     release to the PDS.  PDS also performed an external review of the
     XRS CDR. Likewise, the XRS RDR products are reviewed both
     internally by the XRS science team and by PDS.

   Data Coverage and Quality
   =========================
     XRS RDR products are generated from data collected only while in
     orbit at Mercury, which is from phases Mercury Orbit through
     Mercury Orbit Year 5. It is, however, helpful to review the
     larger mission from which these data are derived.

     Nineteen mission phases: Launch, Earth Cruise, Earth Flyby,
     Venus 1 Cruise, Venus 1 Flyby, Venus 2 Cruise, Venus 2 Flyby,
     Mercury 1 Cruise, Mercury 1 Flyby, Mercury 2 Cruise,
     Mercury 2 Flyby, Mercury 3 Cruise, Mercury 3 Flyby,
     Mercury 4 Cruise, Mercury Orbit, Mercury Orbit Year 2,
     Mercury Orbit Year 3, Mercury Orbit Year 4, and
     Mercury Orbit Year 5. These mission phases are defined as:

                           Start time          End time
     Phase Name            Date (DOY)          Date (DOY)
     -------------------   -----------------  -----------------
     Launch                03 Aug 2004 (216)  12 Sep 2004 (256)
     Earth Cruise          13 Sep 2004 (257)  18 Jul 2005 (199)
     Earth Flyby           19 Jul 2005 (200)  16 Aug 2005 (228)
     Venus 1 Cruise        17 Aug 2005 (229)  09 Oct 2006 (282)
     Venus 1 Flyby         10 Oct 2006 (283)  07 Nov 2006 (311)
     Venus 2 Cruise        08 Nov 2006 (312)  22 May 2007 (142)
     Venus 2 Flyby         23 May 2007 (143)  20 Jun 2007 (171)
     Mercury 1 Cruise      21 Jun 2007 (172)  30 Dec 2007 (364)
     Mercury 1 Flyby       31 Dec 2007 (365)  28 Jan 2008 (028)
     Mercury 2 Cruise      29 Jan 2008 (029)  21 Sep 2008 (265)
     Mercury 2 Flyby       22 Sep 2008 (266)  20 Oct 2008 (294)
     Mercury 3 Cruise      21 Oct 2008 (295)  15 Sep 2009 (258)
     Mercury 3 Flyby       16 Sep 2009 (259)  14 Oct 2009 (287)
     Mercury 4 Cruise      15 Oct 2009 (288)  03 Mar 2011 (062)
     Mercury Orbit         04 Mar 2011 (063)  17 Mar 2012 (077)
     Mercury Orbit Year 2  18 Mar 2012 (078)  17 Mar 2013 (076)
     Mercury Orbit Year 3  18 Mar 2013 (077)  17 Mar 2014 (076)
     Mercury Orbit Year 4  18 Mar 2014 (077)  17 Mar 2015 (076)
     Mercury Orbit Year 5  18 Mar 2015 (077)  30 Apr 2015 (120)

     No XRS data were collected during Earth Flyby or Venus 1 Flyby
     phases. The XRS was on for some of each of the other seventeen
     mission phases. During these planned operational periods, the XRS
     functioned nominally and the data quality was good. Specific XRS
     operational periods were:

                           Start time         End time
     Phase Name            Date (DOY)         Date (DOY)
     -----------------     ----------------   ----------------
     Launch                30 Aug 2004 (243)  30 Aug 2004 (243)
     Earth Cruise          07 Feb 2005 (038)  11 Feb 2005 (042)
                           14 Apr 2005 (104)  14 Apr 2005 (104)
                           09 Jul 2005 (190)  13 Jul 2005 (194)
     Earth Flyby           No Data
     Venus 1 Cruise        16 Jan 2006 (016)  13 Feb 2006 (044)
                           06 Sep 2006 (249)  10 Sep 2006 (253)
     Venus 1 Flyby         No Data
     Venus 2 Cruise        27 Jan 2007 (027)  31 Jan 2007 (031)
     Venus 2 Flyby         26 May 2007 (146)  20 Jun 2007 (171)
     Mercury 1 Cruise      21 Jun 2007 (172)  08 Aug 2007 (220)
                           17 Aug 2007 (229)  25 Aug 2007 (237)
                           21 Dec 2007 (355)  30 Dec 2007 (364)
     Mercury 1 Flyby       31 Dec 2007 (365)  21 Jan 2008 (021)
     Mercury 2 Cruise      28 Mar 2008 (088)  02 Jun 2008 (154)
                           11 Jun 2008 (163)  21 Sep 2008 (265)
     Mercury 2 Flyby       22 Sep 2008 (266)  20 Oct 2008 (294)
     Mercury 3 Cruise      21 Oct 2008 (295)  19 Nov 2008 (324)
                           15 Jan 2009 (015)  04 May 2009 (124)
                           07 May 2009 (127)  17 May 2009 (137)
                           28 Aug 2009 (240)  01 Sep 2009 (244)
                           04 Sep 2009 (247)  15 Sep 2009 (258)
     Mercury 3 Flyby       16 Sep 2009 (259)  29 Sep 2009 (272)
     Mercury 4 Cruise      22 Jan 2010 (022)  03 Dec 2010 (337)
                           06 Dec 2010 (340)  03 Mar 2011 (062)
     Mercury Orbit         04 Mar 2011 (063)  16 Mar 2011 (075)
                           23 Mar 2011 (082)  07 Mar 2012 (067)
                           12 Mar 2012 (072)  17 Mar 2012 (077)
     Mercury Orbit Year 2  23 Mar 2012 (083)  17 Mar 2013 (076)
     Mercury Orbit Year 3  18 Mar 2013 (077)  17 Mar 2014 (076)
     Mercury Orbit Year 4  18 Mar 2014 (077)  17 Mar 2015 (076)
     Mercury Orbit Year 5  18 Mar 2015 (077)  30 Apr 2015 (120)

     The XRS detectors were on continuously during orbital mission
     phases except where spacecraft operations (eclipses) and
     instrument health and safety (temperature and count rate)
     required some or all of the detectors to be turned off.  Details
     of these off periods and other operational issues may be found in
     the XRS EDR and CDR data confidence notes.

   Limitations
   ===========
     This is a calibrated data set. It includes the data that are
     received from the spacecraft telemetry as well as calibration
     information and other ancillary data necessary for data analysis.
     The XRS RDRs are created using the calibrated XRS CDR
     products.
CITATION_DESCRIPTION L. R. Nittler, MESSENGER H XRS 5 REDUCED DATA RECORD FOOTPRINTS V1.0, NASA Planetary Data System, 2017.
ABSTRACT_TEXT Abstract ======== This data set consists of the MESSENGER XRS reduced data record (RDR) footprints which are derived from the navigational meta-data for each calibrated data record (CDR) whose FOV_STATUS is 1 or 3; that is, when the field of view intersects the planet and is either partially or entirely sunlit. Each XRS observation results in four X-ray spectra. When an X-ray interacts with one of the four detectors, a charge or voltage pulse is generated. This signal is converted into one of 2^8 (256) channels, which are correlated to energy. Over a commanded integration time period a histogram of counts as a function of energy (channel number) is recorded. The EDRs are the number of events in each channel of the four detectors accumulated over the integration period. Channels above or below the useful energy range of the detectors are not transmitted. The result is three 244-channel GPC histograms and one 231-channel solar monitor histogram, each of which is designated as a single X-ray spectrum. Each observation is calibrated and processed into the CDR data set. For each CDR whose field of view is contained or partially contained on the planetary surface, a footprint is computed that corresponds to the perimeter of the planetary region within the instrument field of view during the integration time of the observation.
PRODUCER_FULL_NAME LARRY R. NITTLER
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