DAN data sets

Data Set Overview

The Dynamic Albedo of Neutrons (DAN) is an active/passive neutron spectrometer that measures the abundance and depth distribution of H- and OH-bearing materials (e.g., adsorbed water, hydrated minerals) in a shallow layer (~1 m) of Mars' subsurface along the path of the MSL rover. In active mode, DAN measures the time decay curve (the 'dynamic albedo') of the neutron flux from the subsurface induced by its pulsing 14 MeV neutron source. A detailed description of the DAN instrument and scientific investigation can be found in Litvak et al. (2008).

The MSL DYNAMIC ALBEDO OF NEUTRON DETECTOR consists of 3 EDR data types. Each is a time series collection of science and housekeeping data from the MSL rover. Data are sorted by type and by time, with each data file containing one sol's worth of data from midnight to midnight UTC. Measurements are assigned to a particular sol based on the end of the collection interval.

Parameters

The DAN EDR data set is composed of three data types. The objective of compiling the DAN EDR is to create a record of the primary data collected by DAN.

Standby

The DAN standby data set is produced when the instrument low voltage is on with no science observations.

Passive

The PASSIVE data set is produced with high voltage applied to the detectors but when the Pulsing Neutron Generator (PNG) is not pulsing.

Active

The ACTIVE data is produced with high voltage applied to the detectors when the PNG is pulsing.

Processing

DAN's Experiment Data Records (EDR), NASA Level 0 products are generated from the reconstructed data products, which are produced by the Multi-Mission Data Processing and Control System (MPCS) on MSL. MPCS is a component of Real Time Operations (RTO), which itself is part of the MSL Ground Data System (GDS).

Data

The DAN EDR data product contains three types of data.

DAN_STANDBY DAN housekeeping data DAN_PASSIVE DAN housekeeping and passive neutron data DAN_ACTIVE DAN housekeeping and active neutron data

All three types are time series of DAN housekeeping and science data.

Coordinate System

Not applicable for this data set.

Software

No DAN specific software is provided with this data set.

PDS-labeled images and tables can be viewed with the program NASAView, developed by the PDS and available for a variety of computer platforms from the PDS web site http://pds.nasa.gov/tools/nasa-view.shtml. There is no charge for NASAView.

Confidence Level Overview

The data presented in the DAN EDR is intended to be the least processed, most primitive data set released for DAN. Data presented here are an accurate representation of DAN data as received from the rover.

Review

The DAN EDR was reviewed internally by the DAN team prior to release to the PDS. PDS will also performed an external peer review of the DAN EDR.

Data Coverage and Quality

Data reported are the minimally processed data received from the rover during nominal DAN operations. All data received are reformatted into one of the EDR data types. Data are by definition of good quality, as damaged telemetry packets are sequestered upon receipt from the spacecraft. We do not expect to receive many (if any) damaged data packets.

Limitations

The major limitation of this data set is that it is level 0, minimally processed data. The data are received from the spacecraft telemetry and ingested into a database. If gaps exist in the telemetry, data are lost.

Data Compression

No data compression is used.

Data Set Overview

The Dynamic Albedo of Neutrons (DAN) is an active/passive neutron spectrometer that measures the abundance and depth distribution of H- and OH-bearing materials (e.g., adsorbed water, hydrated minerals) in a shallow layer (~1 m) of Mars' subsurface along the path of the MSL rover. In active mode, DAN measures the time decay curve (the dynamic albedo) of the neutron flux from the subsurface induced by its pulsing 14 MeV neutron source (Figure 1 shows an example). A detailed description of the DAN instrument and scientific investigation can be found in Litvak et al. (2008).

The MSL DYNAMIC ALBEDO OF NEUTRON DETECTOR consists of 5 RDR data types. Three are a time series collection of science and housekeeping data from the MSL rover. Data are sorted by time, with each data file containing one sol's worth of data. Measurements are assigned to a particular sol based on the start of the collection interval.

Parameters

The DAN RDR data set is composed of five data types. The objective of compiling the DAN RDR is to create a record of the reduced data derived from the EDR data collected by DAN. The following paragraphs discuss the parameters of interest in each of the data types.

Derived Engineering

The DAN engineering data set is produced from the housekeeping data that is in all EDR data types. The raw values are converted to engineering units of volts, amp, or Celsius.

Derived Passive

The PASSIVE data set is produced with high voltage applied to the detectors but the PNG is not pulsing. The sum of the counts in the CTN and CETN spectra which are background corrected and adjusted for detector efficiency.

Derived Active

The ACTIVE data is produced with high voltage applied to the detectors and the PNG is pulsing. The sum of the counts in the CTN and CETN spectra which are background corrected and adjusted for detector efficiency.

Averaged Passive

The PASSIVE data set is produced with high voltage applied to the detectors but the PNG is not pulsing. The average of the Derived Passive data set over some period time. The time over which the data is averaged is included in the data set.

Averaged Active

The ACTIVE data is produced with high voltage applied to the detectors and the PNG is pulsing. The average of the Derived Active data set over some period time. The time over which the data is averaged is included in the data set.

Processing

DAN's Reduced Data Records (RDR), NASA Level 1 and above products are generated by the DAN team from the EDR data products, which are produced by the Multi-Mission Data Processing and Control System (MPCS) on MSL. MPCS is a component of Real Time Operations (RTO), which itself is part of the MSL Ground Data System (GDS).

Data

The DAN RDR data product contains five types of data.

DAN_DERIVED_ENG DAN housekeeping data in engineering units DAN_DERIVED_PASSIV DAN reduced passive neutron data DAN_DERIVED_ACTIVE DAN reduced active neutron data DAN_AVERAGED_PASSIV DAN averaged reduced passive neutron data DAN_AVERAGED_ACTIVE DAN averaged reduced active neutron data

The first three types are time series of DAN housekeeping and science data. The last two are averaged over some time period.

Coordinate System

This data set will use the standard Mars latitude and an easting longitude to specify location. This spatial information will be calculated using the SPICE tool set along with MSL specific SPICE kernels.

Software

No DAN specific software is provided with this data set.

PDS-labeled images and tables can be viewed with the program NASAView, developed by the PDS and available for a variety of computer platforms from the PDS web site http://pds.nasa.gov/tools/software_download.cfm. There is no charge for NASAView.

Confidence Level Overview

The data presented in the DAN RDR is intended to be processed, and reduced data set released for DAN. Data presented here are an accurate reduction of DAN data using the a derived processing technique.

Review

The DAN RDR was reviewed internally by the DAN team prior to release to the PDS. PDS will also performed an external peer review of the DAN RDR.

Data Coverage and Quality

Data reported are the processed data received from OPGS in the form of EDR. All data received is processed into one of the RDR data types. Data are of good quality as the processing is based on the best available knowledge of the reduction algorithms used.

Limitations

The major limitation of this data set is that gained knowledge as data is received from Mars may require the reprocessing of data alreay delivered the PDS due to modifications in the algorithms used in the data production.

Data Compression

No data compression is used.