Uncalibrated High-Energy Neutron Detector (HEND) Spectra
High-Energy Neutron Detector (HEND) spectral data is obtained by the
High-Energy Neutron Detector instrument, and consists of HEND records
and associated timing and spatial information.
HEND records, also called frames, may be one of three types:
The timing and spatial data provided with the HEND data includes spacecraft clock values
and spacecraft geometry data. The SC_EV_TIME, UTC time and spatial fields are all recorded
at the center of the collection interval.
- Nominal, or spectra, frames consist of six spectra with sixteen channels each
at two bytes per channel.
- Profile, or time series, frames consist of the six spectra pus two time profiles.
The inner scintillator profile is thirty seconds in duration, with a count for each second.
The outer scintillator profile is also thirty seconds in duration, but has a time resolution
of 0.25 seconds, with a count for each interval. Note: This is not related to Profile,
or Gamma-Ray Burst data.
- Status frames, or HEND instrument commands.
For more information on uncalibrated (raw) HEND and other GRS data, please see the
EDR Dataset Description document.
Overview of Uncalibrated Data
Uncalibrated data are raw data that has had associated timing and spatial information added.
A full description may be found in the
2001 Mars Odyssey Gamma Ray Spectrometer EDR
NASA Level 0 Software Interface Specification (EDR SIS).
Gamma-Ray Spectrometer Instruments Background
The Mars Odyssey Gamma-Ray Spectrometer (GRS) is a suite of
three instruments working together to collect data that
map the elemental concentrations on the surface of
Mars. The three instruments are:
These three instruments work differently but are complementary.
The neutron instruments have better counting statistics and
sample to a greater depth than the GS, but the GS determines the
abundance of many more elements. A full description of the Mars
Odyssey Gamma-Ray Spectrometer instruments may be found in
Boynton, et. al, 2004.
- The Gamma Subsystem (GS), or gamma sensor head, which obtains
raw uncalibrated gamma spectra
- The Neutron Spectrometer (NS), which obtains the uncalibrated
Neutron Spectra, and
- The High-Energy Neutron Detector (HEND), which collects the
raw HEND data.