GRS Data Types InformationThe information in these help pages is provided as a brief introduction to the GRS data types only; for more detailed and technical information, see the official documents:
A Pixel By Any Other Name is NOT The Same...
The GRS collects a new spectrum (pixel) approximately every 19.7 seconds, at 360 times per orbit of Mars. These spectra represent detected gamma rays from the planet during the time interval within the detector's range. These spectra are binned by energy level, and each gamma ray detected does not have a particular set of coordinates to identify where it collided with the planet, but an individual gamma-ray does originate in the pixel area. Approximately 4200 spectra are received each Earth day from the Odyssey spacecraft and the Gamma-Ray Spectrometer instruments.
For all data, the collection interval, or pixel, is approximately 19.7 seconds in length, but can vary over the course of mapping. This is a much different definition for the word "pixel" than is used in image processing, traditional image manipulations, or visual camera terminology, where a pixel (or picture element) is equal to the smallest discrete component of an image or picture on a CRT screen (usually a colored dot). In this case, a pixel is a geographic region of the planet's surface over which the instruments have collected data (spectra) for the approximate interval.
The data collected by the GRS suite of instruments includes corrected, or calibrated, spectra, which are intermediate scientific data products from the different instruments. Uncalibrated, or raw data with spatial information added are also available. Profile data from Gamma Ray Bursts may be downloaded, as well as hardware and engineering data from the spacecraft and the GRS instruments. See the categories on the control bar to the left of this page.
More detailed information is contained in documents located in the section of the GRS PDS Node software.