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Field Calibration 
Field calibration of instruments just prior and immediately after (and sometimes during) data collection can be essential to assure quantitative analysis of the measurement data. Most instruments are known to suffer from drift, aging, and changes as a result of transportation and handling. Using a calibration that was performed in the lab prior to shipping an instrument may produce inaccurate results. Similar results may be experienced from a calibration that is performed on the instrument after shipping back from a field event.  

It is desirable to build calibration capabilities into the sensor operation. As a minimum, we often collect “bright” and “dark” fields for various radiometric sensors. Spectral calibration can be achieved using well known atmospheric and stellar bands. MODTRAN can provide reference spectral bands. Star calibration can also be to verify radiometric calibration accuracy
(See Atmospheric Based Spectral Calibration.)  

In the case shown below, an OKSI MWIR imaging spectrometer is calibrated in the field using a blackbody source and a collimator. The calibration rig is designed so that it can be easily mounted in line with the sensor for the calibration, and then removed. This allows the sensor to remain focused in "mission configuration". The use of such techniques assures high data fidelity in critical field experiments.

 

 
In addition to calibration, field instruments can be equipped with GPS and AHRS (Attitude and Heading Reference System) or simpler IMU units. These provide precise position and aiming data. If a target is being tracked, each frame of data can be stamped with the specific line of sight (LOS) parameters (the tracker mount may often provide similar azimuth and elevation data). IRIG or GPS time are also a part of a typical instrumentation system.  

Please contact OKSI to design a field calibration and recording system to best fit specific requirements of your work.

 
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Last modified: March 12, 2008