Uncalibrated Gamma Spectra

The uncalibrated gamma spectra data, or "raw" gamma spectra, are composed of the raw, uncorrected gamma spectra obtained by the Gamma Subsystem (GS), or gamma sensor head, which includes associated timing and spatial information. The spectra consists of the cumulative counts of gamma rays at the detector over one pixel, binned into 16,384 channels, based on energy. The times listed (sc_ev_time, UTC time, and spatial fields) all denote the center of the collection interval (also called a "pixel").

More information on all uncalibrated data types, including gamma data, may be found in the EDR Dataset Description.

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:
  1. The Gamma Subsystem (GS), or gamma sensor head, which obtains raw uncalibrated gamma spectra

  2. The Neutron Spectrometer (NS), which obtains the uncalibrated Neutron Spectra, and

  3. The High-Energy Neutron Detector (HEND), which collects the raw HEND data.

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.