Abstract
Stress in vegetation causes a small shift of the point of maximum slope in the spectral reflectance between 680nm and 750nm ?the so-called "red-edge" position (REP). This shift has been used as an indication of stress, both in the laboratory and in field measurements. The shift of the REP can be between 3 and 7 nm and is directly related to variations in the chlorophyll content and health condition of the plant and its leaves. The fundamental theory for this research has been the evaluation of the "red-edge" effect as a suitable means for detecting and monitoring vegetation stress using a small-satellite-borne remote sensing instrument as a cost-effective solution to global plant stress monitoring. In this work the design of a low cost instrument that uses the REP is proposed. The paper describes the fundamental theory that supports the design, and explains the main aspects of the proposed low-cost, compact hyperspectral instrument. The instrument is compatible with a small satellite platform and is proposed as a cost-effective solution for vegetation stress monitoring. Towards the instrument design, a radiometric analysis combined with the estimation of the red-edge position under different scenarios have proven to be very useful in the design of a hyperspectral solution for monitoring stress in vegetation. The existing solutions have been proved to be useful, but still have some limitations: the airborne sensors mainly in availability, coverage and cost. Space-borne instruments still need some improvements for this particular application, mainly in the spectral resolution to have sufficient spectral detail to be able to detect stress with greater accuracy.