Data Set Information
DATA_SET_NAME LRO MOON CRATER EDR RAWDATA VERSION 1.0
DATA_SET_ID LRO-L-CRAT-2-EDR-RAWDATA-V1.0
NSSDC_DATA_SET_ID
DATA_SET_TERSE_DESCRIPTION
DATA_SET_DESCRIPTION Data Set Overview ================= The Cosmic Ray Telescope for the Effects of Radiation (CRaTER) is a stacked detector-absorber cosmic-ray telescope designed to answer key questions to enable future human exploration of the Solar System. CRaTER's primary measurement goal is to measure directly the average lineal energy transfer (LET or 'y') spectra caused by space radiation penetrating and interacting with shielding material. Such measured LET spectra are frequently unavailable. In the absence of measurements, numerical models are used to provide estimates of LET; the reliability of the models require experimental measurements to provide a ground truth. The CRaTER Level 0 dataset consists of files containing the raw primary science, secondary science, and housekeeping telemetry packets and packet headers created by the instrument. The Level 0 data are meant to be used only for archival purposes in order to reconstruct the other CRaTER data products in the future, should that become necessary. The Level 0 data are not intended to be used directly in data analyses or scientific investigations--the data are stored in binary data structures and have not been converted to appropriate engineering or science values. Users seeking CRaTER data are strongly encouraged to use the Level 1 or Level 2 datasets. See the MISSION.CAT file for more information on the LRO mission. See the CRAT_INST.CAT file for more information on the CRaTER instrument. See SPENCEETAL2010 for detailed description of LRO flight version of the instrument, its operations, and data processing. Science Objectives and Observation Strategy ------------------------------------------- CRaTER is designed to achieve characterization of the global lunar radiation environment and its biological impacts and potential mitigation as well as investigation of shielding capabilities and validation of other deep space radiation mitigation strategies involving materials. CRaTER will fill knowledge gaps regarding radiation effects, provide fundamental progress in knowledge of the Moon's radiation environment, and provide specific path-finding benefits for future planned human exploration. Parameters ---------- LRO CRaTER flight instrument identification: --instrument model = Flight Model 1 (FM1); --instrument serial number (S/N) = 02; --FPGA revision code = 3. Data ---- CRaTER's principal measurement is the energy deposited in the 3-pairs of silicon detectors by charged particles and photons passing through the instrument's 'telescope' unit. Whenever the coulombic charge signal re- sulting from the energy deposited in a detector exceeds a predefined and fixed threshold, the instrument's electronics performs a detailed measurement of the signals from all of the detectors. The resulting detector signal amplitudes are compared to the values of the 'lower level discriminators' (LLDs). LLDs establish minimum amplitudes for signals to qualify as valid charged-particle or photon interactions. The LLD values are generally set to insure that the desired charged-particle or photon measurements are not contaminated by system electronic noise. Seperate LLD settings are required for the thick and thin detectors due to the difference in their sensitivities; the thin and thick detector LLD values are reported in the 'DiscThin' and 'DiscThick' parameters as part of the secondary science packet. In addition to the LLD settings, measurement filtering is achieved through detector coincidence requirements--the combination of detectors registering valid signals to qualify as a charged-particle or photon measurement 'event'. To measure all charged particles arriving from the instrument's zenith or nadir directions, for example, the coincidence requirements would be valid signals in at least detectors 1, or 2, or 5, or 6. Conversely, a coincidence consisting of valid signals in all six detectors would ensure only zenith- or nadir-arriving charged particles with high energies are reported. For CRaTER's six axially-coaligned detectors there are 64 possible coincidence combinations. The desired set of coincidence combinations are stored as a coincidence mask parameter in the instrument's memory; the coincidence mask setting is reported in the 'Mask' parameter as part of the secondary science packet. To qualify as an 'event', therefore a charged particle or photon passing through CRaTER's telescope must interact and deposit sufficient energy to generate signals with amplitudes in excess of the specified LLDs in a specified combination of detectors; only data for valid 'events' are re- ported in the instrument's telemetry. The measured interaction event data is written as a series of primary science packets to the instrument's output telemetry buffer for the spacecraft to read. At ~1 second intervals CRaTER receives a timing pulse from the spacecraft, at which time it flushes the primary science data from the output buffer and writes a secondary science packet for the spacecraft to read. Every 16 seconds a housekeeping packet is also created and written to the output buffer. This Level 0 dataset is composed of the three types of time-sequential, raw CRaTER data records: (1) primary science, (2) secondary science, and (3) housekeeping. The primary science raw data consists of the signal pulse heights from each of the six detectors produced during an 'event'. The raw event data in the primary science packets are the scalar channel numbers output by the detector-amplifier strings' analog-to-digital converters (ADCs) fol- lowing signal pulse height analysis. The secondary science raw data contain the majority of instrument config- uration settings, status flags, and event counters. Reported configura- tion settings include the last command sent to CRaTER, detector LLD set- tings, and coincidence mask values. Status flags available in the secon- dary science raw data include detector bias status, selected pulse am- plitude range and rate for the internal calibration pulser, and detector processing status. Counters report the number of 'singles' for each de- tector as well as the number of 'good', 'rejected', and total events re- corded by CRaTER during the monitoring period. The housekeeping raw data contains the output of internal monitors used to assess the operating health of the instrument, such as power supply voltage monitors, detector bias voltages and bias currents, pulse ampli- tudes from the internal calibration pulser, and temperatures at five locations inside of the instrument's housing. The analog output from radiation monitor is also included in the housekeeping data packets. The primary science, secondary science, and housekeeping packets are written to seperate files in binary format. Each file begins with a 64-byte header and continues with one or more CCSDS packets. Each packet begins with a 6-byte CCSDS header that defines the type (ApID 120, 121, or 122) and length of the packet, followed by a 6-byte secondary header containing a time tag and instrument-specific flags. Each of the files contains all of the data from a single UTC day. The files' binary structures are documented in CRaTER SPDR and Archive Volume Software Interface Specification (Document 32-01211), sections 5.2.6 and Appendix C.
DATA_SET_RELEASE_DATE 2010-03-15T00:00:00.000Z
START_TIME 2009-06-29T12:00:00.000Z
STOP_TIME 2025-06-30T11:59:59.820Z
MISSION_NAME LUNAR RECONNAISSANCE ORBITER
MISSION_START_DATE 2009-06-18T12:00:00.000Z
MISSION_STOP_DATE N/A (ongoing)
TARGET_NAME MOON
TARGET_TYPE SATELLITE
INSTRUMENT_HOST_ID LRO
INSTRUMENT_NAME COSMIC RAY TELESCOPE FOR THE EFFECTS OF RADIATION
INSTRUMENT_ID CRAT
INSTRUMENT_TYPE ENERGETIC PARTICLE DETECTOR
NODE_NAME planetary plasma interactions
ARCHIVE_STATUS ARCHIVED - ACCUMULATING
CONFIDENCE_LEVEL_NOTE Confidence Level Overview ------------------------- No confidence level information is provided for the Level 0 data since it consists of only the raw instrument binary data and is not intended for direct use in data analyses. Confidence level information is provided with the Level 1 and Level 2 sets. Review ------ A minimal set of automated quality control steps are used by the data processing system to verify the integrity of the data. During the creation of the Level 0 data files from the downlinked instrument data files, each data packet's CCSDS header is checked for format and content. Packets are discarded if their headers are corrupted, incorrectly formatted, or containing invalid values. All packets are sorted into time order and checked for temporal gaps. Duplicate packets are also discarded. Metrics plus any detected anomalies are written to process log files for review by scientists and engineers from the instrument team. Anomalies noted during the processing are investigated. Anomalies due to missing input files (e.g., instrument science and housekeeping data files, spacecraft housekeeping data files, spacecraft ephemeris kernels, and ancillary files such as leap second and spacecraft clock kernels) are corrected by locating the missing input and reprocessing the data. Data Coverage and Quality ------------------------- Start date for the initial version of the LRO-L-CRAT-2-EDR-RAWDATA-V2.0 archival volume is 2009-06-29T00:00:00.000. This date/time is the begin- ning of the first full UTC day following completion of LRO lunar orbit insertion (LOI) maneuvers and transition to the nominal nadir-pointing observation attitude. It is also the first day for which complete re- constructed ephemeris ('SPK') data was available from the LRO Mission Operations Center. There is only limited re-constructed ephemeris data currently available for the period between initial instrument power-up (2009-06-20) and LOI completion/transition to the nominal observing attitude. CRaTER data obtained during Cruise Phase (instrument power-up - 2009-06-23), Lunar Orbit Acquisition (2009-06-23), and the initial Commissioning Period (2009-06-23 - 2009-06-28) will be included when more complete ephemeris data becomes available. Data gaps are identified during initial data processing. Each gap's beginning and end times are recorded in gap files stored in the DOCUMENT directory--there are seperate gap files for primary science, secondary science, and house-keeping data. Each gap file contains a cumulative listing of the missing data up to and including the time span covered for the data current volume. The minimum duration between successive data packets to qualify as a data gap is specified during data processing. The default gap duration specifications are: --primary science = 2 seconds; --secondary science = 2 seconds; --and housekeeping =20 seconds. These default gap duration values may be over ridden at the time of data processing. The gap duration specifications used while processing a specific day's data are recorded in the corresponding process log files and stored in the DATA subdirectoy directory containing the data products. Limitations ----------- The LRO-L-CRAT-2-EDR-RAWDATA-V1.0 data set includes all data obtained by the CRaTER instrument, including data from periods when the instrument was placed into special configurations. Special configurations include the instrument start-up tests that occur whenever the instrument is power cycled to (e.g., initial instrument start-up, recovery following space- craft transition to sun-safe mode) as well routine calibrations (90-degree off-nadir GCR background measuerments, internal pulser sweeps, LLD zero crossing measurements, and LLD sweeps). As specified in CRaTER Standard Product Data Record and Archive Volume Software Interface Specification, Document 32-01211, the Level 0 house- keeping data files contain the voltage (V28BUS) and current draw (I28bus) measured at the instrument side of the instrument-spacecraft 28 VDC bus interface. For the LRO CRaTER instrument, the voltage (V28BUS) and cur- rent (I28BUS) values are UNDEFINED. Immediately prior to instrument delivery, the signal leads from these two monitors were removed to reduce excessive EMI emmission; however, the instrument software still processes the signals from these open leads and includes them in the housekeeping packets stored in the instrument housekeeping files. Although no longer defined, these values have been retained in the Level 0 housekeeping files in order to preserve the structure defined for the instrument's housekeeping packets (LRO telemetry ApID = 122). Although values can be retrieved for the voltage (V28BUS) and current (I28BUS) parameters from the Level 0 housekeeping data files, they are UNDEFINED and should be discarded from any analyses.
CITATION_DESCRIPTION Spence, H.E., LRO MOON CRATER EDR RAWDATA VERSION 1.0, LRO-L-CRAT-2-EDR-RAWDATA-V1.0, NASA PLANETARY DATA SYSTEM, 2010
ABSTRACT_TEXT This data set comprises the raw binary data from from the LRO Cosmic Ray Telescope for the Effects of Radiation (CRaTER) instrument. The data consists of the unconverted primary science, secondary science, and housekeeping CCSDS-formatted data packets and data headers.
PRODUCER_FULL_NAME PROF. HARLAN SPENCE
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