Odyssey GRS Derived Neutron Data (DND)

DND – Derived Neutron Data

Instrument: Odyssey Gamma Ray Spectrometer

PDS Data Set ID: ODY-M-GRS-4-DND-V2.0DOI: 10.17189/1522867

For more information about GRS DND products, see the Data Set Catalog File.

For more information about GRS DND processing, see the Neutron Data Processing document and mons2_pds_final.pdf.

For more information about GRS IDR products, see the GRS IDR Product SIS.

The Gamma Ray Spectrometer Intermediate Data Record (GRSIDR) Derived Neutron Data (DND) data products are composed of the derived neutron data and the associated timing, spatial, and engineering information for each ~19.7 second collection interval. The objective of compiling the DND is to create a series of neutron data that have been processed to yield normalized neutron counting rates for all four of the Neutron Spectrometer (NS) prisms, from which thermal and epithermal neutron counting rates are determined (AND).

The raw neutron data (NEUTNS) is processed in the following way to produce the Version 1.0 of the DND data products. Detailed processing information can be found in the Neutron Data Processing document.

  1. The raw data are processed to determine time-dependent parameters such as peak channel numbers and overload counting rates. These data are used to screen out periods of time where the data are not useful and also provide information for subsequent analysis of pulse height spectra.

  2. A time series of net counting rates is determined from the raw pulse height spectra for each prism. A number corrections are applied, including gain, differential nonlinearity, and background subtraction. Selection criteria are applied to eliminate invalid data.

  3. Normalization constants are determined independently for each counting data product from data acquired at equatorial latitudes within a time interval (roughly ±1/2 day) of each measurement.

  4. Valid counting data and normalization constants are combined using IDL programs to produce time series data for each prism.

The DND product is intended to be the first intermediate data product available for the NS portion of the GRS data. These data should be useful to those scientists who are experienced in neutron spectroscopy.

The DND data have been completely reprocessed in Version 2.0. See mons2_pds_final.pdf in the DOCUMENT directory of the archive. New processing algorithms have allowed inclusion of many observations that were previously rejected, and improved data fitting methods provide a significant improvement in data quality and a reduction in noise. The updated data products allow researchers to more accurately detect and measure the amount of water ice, carbon dioxide ice, and hydrated minerals in the first half meter below the surface of Mars.

GRS DND products have the following file names:

DND_yyyymmdd.DAT (with detached PDS label)

where:

yyyy = year

mm = month (01-12)

dd = day (01-31)

In ODE, DND products have the following Product IDs:

DND_YYYYMMDD