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
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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