Improving the Accuracy of Satellite-Derived Data

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In this research we are aiming at improving the accuracy of satellite-derived data through developing a novel technique for vicarious calibration. The technique uses an optical sensor with enhanced traceability to the SI units. The spectrometer, together with supporting equipment, will be mounted on-board a remote controlled helicopter as an efficient and low cost remote sensing tool. The on-board instruments are controlled using a mini-computer that is connected with a ground-based computer through remote network connection, so real time measurements can be observed and controlled on the ground by the operator. The spectrometer, that is required to be a palm-size detector, is operating in the VIS-NIR spectral range. The technique has the potential to provide accurate and low cost reference surface measurements for large and difficult terrains over a short period of time, which can subsequently be used to calibrate and validate satellite-derived measurements.

The optical sensor, selected to be a photodiode array spectrometer, will be calibrated against a fixed-point blackbody. This blackbody provides a high emissivity and high stability reference source of known spectral radiance over the emitted spectral range. However, the highest fixed-point that is defined by the current International Temperature Scale (ITS-90) is the copper point at 1357.77 K [10], which is not high enough to provide sufficient optical power at short wavelengths.

It is proposed in this work to calibrate the spectrometer against a eutectic fixed-point, which uses metal carbon alloy rather than pure metals [11]. These fixed-points have the potential to provide a spectral radiance blackbody source with melting points up to 3500 K [12]. However, the thermodyn...

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... sources, rather than lasers, will be studied. This approach provides a cheap, thus available, system that can be used to correct for stray light in these photodiode arrays on commercial scales.

5- The radiometric performance of the photodiode array spectrometer has to be evaluated. Correction for any inconsistency between laboratory and in-the-field measurements should be provided

6- Identify the temperature of the blackbody at the photodiode array spectrometer can be calibrated and develop a system to calibrate the spectrometer against it.

7- Develop the helicopter-based system and identify the supporting equipment that can be used a long with photodiode array instrument. These are required to include an imaging camera, and a global positioning system, so the spectral and imaging characteristics of the site can be presented along with its spatial information.

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