Corrected Gamma Spectra

The gamma data are time series records taken over the course of a day. Data files are labeled with the date. Individual records are composed of corrected gamma spectra and the associated timing, spatial, and engineering information. The gamma spectra consists of the cumulative counts of gamma rays at the detector over one collection interval binned into 16384 channels based on energy. The collection interval is approximately 19.7 seconds, but may vary over the course of mapping. The timing and spatial data provided with the gamma spectra 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.

Detailed Information

Column Descriptions
Column Name Type Bytes Units
SC_RECV_TIME MSB_UNSIGNED_INTEGER 8
The time the raw spectrum packet was received by the spacecraft, in ticks (256 per second).
SC_EV_TIME MSB_UNSIGNED_INTEGER 8
Spacecraft time at the middle of the pixel, in ticks.
CEB_TIME MSB_UNSIGNED_INTEGER 8 MILLISECOND
Clock count from the GRS Common Electronics Box at the beginning of the pixel.
UTC CHARACTER 23
SC_EV_TIME converted to UTC, stored as yyyy-mm-ddThh:mm:ss.sss.
PIXEL_DURATION MSB_UNSIGNED_INTEGER 2 MILLISECOND
Length of the collection period in milliseconds.
GRS_PIXEL_NUMBER MSB_UNSIGNED_INTEGER 4
Sequential counter of accumulation intervals, starts with one as grs orbit begins. Special case on reboot when the the CEB is in orbit 0, pixel 0.
GRS_ORBIT_NUMBER MSB_UNSIGNED_INTEGER 4
Sequential counter of orbits from GRS CEB boot.
ODY_ORBIT_NUMBER MSB_UNSIGNED_INTEGER 4
Orbit number common to all instruments aboard Odyssey. This orbit number is incremented by one as the spacecraft passes through the orbital descending node.
AREOCENTRIC_LATITUDE IEEE_REAL 8 DEGREE
Sub spacecraft latitude in Mars fixed coordinates at the middle of the pixel.
AREOCENTRIC_LONGITUDE IEEE_REAL 8 DEGREE
Sub spacecraft longitude in Mars fixed coordinates at the middle of the pixel. Longitude increases towards the East.
INSTR_BORESIGHT_MARS IEEE_REAL 24 KILOMETER
Sub instrument boresight (x,y,z) in Mars fixed coordinates at the middle of the pixel.
SUB_SCPOS_MARS IEEE_REAL 24 KILOMETER
Sub spacecraft vector (x,y,z) in Mars fixed coordinates at the middle of the pixel.
SCALT IEEE_REAL 8 KILOMETER
Areocentric altitude of the sub-spacecraft point in Mars-fixed rotating frame at the middle of the pixel.
DELTA_ANGLE IEEE_REAL 8 DEGREE
Difference between instrument +y direction and true north at the middle of the pixel.
MARS_SOL IEEE_REAL 8
Longitude of the Sun at 0 hours UT on the date of the record. Taken from the Association of Lunar and Planetary Observers 'Ephemeris for Physical Observation of Mars'.
DAY_INDEX MSB_UNSIGNED_INTEGER 2
Day of Martian year.
LOCAL_HOUR MSB_UNSIGNED_INTEGER 1
Local Sun hour at the sub-spacecraft point.
LOCAL_MINUTE MSB_UNSIGNED_INTEGER 1
Local Sun minute at the sub-spacecraft point.
POINTING BOOLEAN 1
True if pointing data was available.
INTERSECTING BOOLEAN 1
True if the pointing vector intersects Mars.
BAD_CODE MSB_UNSIGNED_INTEGER 4
If non-zero, the data has been flagged bad. Definitions in bad_code.txt.
IS_TEMP_A IEEE_REAL 4 CELSIUS
Inner Stage A temperature, smoothed and interpolated to the center of the pixel.
IS_TEMP_B IEEE_REAL 4 CELSIUS
Inner Stage B temperature, smoothed and interpolated to the center of the pixel.
OS_TEMP_A IEEE_REAL 4 CELSIUS
Outer Stage A temperature, smoothed and interpolated to the center of the pixel.
OS_TEMP_B IEEE_REAL 4 CELSIUS
Outer Stage B temperature, smoothed and interpolated to the center of the pixel.
B170K_TEMP IEEE_REAL 4 CELSIUS
The 170K card temperature, smoothed and interpolated for the middle of the pixel.
B170K_NORM_TEMP IEEE_REAL 4 CELSIUS
Temperature used to normalize the 170K card gain.
IS_NORM_TEMP IEEE_REAL 4 CELSIUS
Temperature used to normalize the detector gain.
GPA_TEMP IEEE_REAL 4 CELSIUS
Gamma Pulse Analyzer temperature, smoothed, and interpolated to the center of the pixel.
GAMMA_VREF_TEMP IEEE_REAL 4 CELSIUS
V-reference temperature smoothed, and interpolated to the center of the pixel.
HVBS_MONITOR IEEE_REAL 4 VOLT
High voltage bias supply value smoothed, and interpolated to the center of the pixel.
IS_TEMP_COEFFICIENT IEEE_REAL 4
Temperature coefficient of gain for the detector (parts-per-million/degree C)
B170K_TEMP_COEFFICIENT IEEE_REAL 4
Temperature coefficient of gain for the 170K card (parts-per-million/degree C).
APPS_GAIN_DHK MSB_UNSIGNED_INTEGER 2
APPS shaping amp gain setting from gamma digital housekeeping.
LLD_CNTR MSB_UNSIGNED_INTEGER 2
Lower level discriminator count.
ULD_CNTR MSB_UNSIGNED_INTEGER 2
Upper level discriminator count.
L1_CNTR MSB_UNSIGNED_INTEGER 2
Total number of gamma events within the L1 energy range.
L2_CNTR MSB_UNSIGNED_INTEGER 2
Total number of gamma events within the L2 energy range.
L3_CNTR MSB_UNSIGNED_INTEGER 2
Total number of gamma events within the L3 energy range.
PHA_CNTR MSB_UNSIGNED_INTEGER 4
Pulse Height Analyzer counter.
PHA_TIMER MSB_UNSIGNED_INTEGER 8
Pulse Height Analyzer timer.
FIRST_CHANNEL MSB_UNSIGNED_INTEGER 2
First valid channel in the spectrum.
LAST_CHANNEL MSB_UNSIGNED_INTEGER 2
Last valid channel in the spectrum.
FIRST_FULL_CHANNEL MSB_UNSIGNED_INTEGER 2
First channel with real counts.
LAST_FULL_CHANNEL MSB_UNSIGNED_INTEGER 2
Last channel with real counts.
GAIN IEEE_REAL 4
Target gain after correction, as determined by, as determined by instrument settings and spectral analysis. Units are KeV/channel.
OFFSET IEEE_REAL 4
Target offset after correction, as determined by instrument settings and spectral analysis. Units are KeV.
GAIN_CORRECTION IEEE_REAL 4
After summing the corrected spectra, we may find that due to aging, drift, etc. we did not correct to the target gain. This field is then set to the ratio of the actual to the target gain, and the spectrum is recorrected with this factor included.
OFFSET_CORRECTION IEEE_REAL 4
Set to the ratio of the actual to the target offset.
GPA_COEFFICIENTS IEEE_REAL 24
Temperature coefficients for the GPA.
INL_COEFFICIENTS IEEE_REAL 120
Coefficients of the polynomial used to correct the INL for this spectrum. Calculated from GAMMA_VREF_TEMP.
CORRECTED_SPECTRUM IEEE_REAL 65536
Gamma spectrum, corrected counts for each channel.