LRO LEND Derived Data

Lunar Exploration Neutron Detector (LEND) Derived product types

Instrument: LRO Lunar Exploration Neutron Detector

PDS3 Data Set ID: LRO-L-LEND-4/5-V1.0DOI: 10.17189/1520636

PDS4 Bundle: urn:nasa:pds:lro_lendDOI: 10.17189/p89b-8w72

LRO PDS3 to PDS4 Migration Status: Complete

For more information about LEND Derived products, see the RDR Product SIS.

For more information about the PDS3 volume, see the LEND Archive Volume SIS.

Note: The product SIS was created for PDS3, but it is still applicable to the data after the PDS4 migration.

The LRO Lunar Exploration Neutron Detector (LEND) derived product consists of Derived LEND Counts Data (RDRDLD4), extended Derived LEND Counts Data (RDRDLX4), and Averaged LEND Counts Data (RDRALD4).

The Derived LEND Counts Data (RDRDLD4) contain a time-series of Neutron Detector science data that has been processed to account for instrument warm up and efficiency saturation effects, variation of Galactic Cosmic Ray (GCR) flux, clearance for Solar Particle Events (SPE), separation between charged particles and neutrons, temperature and altitude corrections.

The Extended Derived LEND Counts Data (RDRDLX4) contain a time-series of Neutron Detector science data that contains supplemental values useful for interpretation of RDRDLD4 data, including uncertainties for neutron counts on each detector.

No spacecraft background subtraction is made for RDRDLD4 and RDRDLX4 in the derived data collection. The time series measurements of each of the un-collimated LEND neutron signals are corrected for altitude.

Once the altitude correction has been made to the data, it is examined to determine if data collection occurred during a solar particle event (SPE). SPEs significantly influence the LEND detectors’ counting rates, often increasing the counting rates by several orders of magnitude. Any data collected during times of intense solar activity are flagged and excluded from further routine data processing.

The following circumstances lead to a value of -1 being assigned to the count rate in the corresponding derived record:

  • Measurements obtained with the nadir angle of the spacecraft greater than 1.9° are ignored.

  • Raw counts from each of the detectors are examined for ‘outlier’ values, which could be produced either due to some micro-discharge in the HV circuit of a counter, or due to some corruptions in the instrument memory. Measurements are defined as outlier events based upon a specific count threshold for each detector (11 cps for CSETN1-4; 30 cps for SETN; and 49 cps for STN1-3).

  • Single or multiple detectors do not have high voltage applied for a period of time.

Data is also corrected for instrument warm-up, separation of charged particles and neutrons, and variation of galactic cosmic rays.

The RDRDLD4 data product is a time-series collection of neutron counts and backgrounds derived from the 9 neutron detectors aboard the LEND instrument. The derived data product is structured as a single 27-column, time-ordered data file for each collection day. The RDRDLX4 data product is a time-series collection of neutron count uncertainties derived from the 9 neutron detectors aboard the LEND instrument, as well as a calculated sum of neutron counts and uncertainty across the four collimated sensors of epithermal neutrons, CSETN1-4. The data product is structured as a single 12-column, time-ordered data file for each collection day.

The Averaged LEND Counts Data (RDRALD4) contain Neutron Detector science data that is processed by normalizing and averaging derived data to yield science data in a counts/second format for each Lunar map pixel.

Background subtracted, non-Solar Particle Event (SPE) influenced time series data are used to create temporally and spatially binned counting rate data for each of the five un-collimated LEND neutron signals and one for the four collimated sensors. The creating of spatially averaged counting rates requires the time series collection interval data to be distributed between the .5-degree x .5-degree latitude longitude map cells. The time series data distribution is accomplished by registering each collection interval to the projection of the spacecraft orbital trajectory on the surface of the Moon. The time series data distribution is accomplished by registering each collection interval to the projection of the spacecraft orbital trajectory on the surface of the Moon. The spacecraft trajectory projection during a single ~1 second collection interval is fit with a straight line. The projected straight line spacecraft trajectory is used to determine the fraction of the data collection interval that resides inside each .5x.5 degree map cell. The fractions of each collection interval within a given map cell are then used to calculate the total number of counts and collection time in each map cell.

The RDRALD4 data products are a collection of averaged, normalized neutron counting rates and errors for the neutron spectra collected by the 9 neutron detectors aboard the LEND instrument. The data products are structured as a single 23-column data file for each of the poles and for the equatorial region.

LEND Derived products have the following file names:

LEND_RDR_DLD_yyyymmdd.DAT (with detached PDS label) - for RDRDLD4

LEND_RDR_DLX_yyyymmdd.DAT (with detached PDS label) - for RDRDLX4

LEND_RDR_ALDt_yyyymmdd.DAT (with detached PDS label) - for RDRALD4

where:

t = product type

E = equirectangular

N = north polar

S = south polar

yyyymmdd = 8-digit date specifier

 

In ODE, LEND Derived products have the following product IDs:

lend_rdr_dld_yyyymmdd - for RDRDLD4

lend_rdr_dlx_yyyymmdd - for RDRDLX4

lend_rdr_aldt_yyyymmdd - for RDRALD4