Design of a Plant Health Monitoring System for Enhancing Food Safety of Space Crop Production Systems

The deployment of fresh crop production systems on spacecraft will require that plant health and food safety is determined without crew intervention. Currently, detecting the occurrence of poor growth in spaceborne plant growth chambers can be accomplished via nondestructive measurements of plant growth rates obtained from photographic analysis of daily increments in leaf area. However, this approach detects changes that may have taken place days earlier before a visible change in leaf area is observed. A prototype hyperspectral and chlorophyll fluorescence imaging system was designed for early symptom detection of plant stress in crop production systems. This prototype imaging system composed of a hyperspectral camera, two LED light banks and a translational arm was designed and constructed. The translational arm moves the camera and the LED light banks over plants growing below. The lighting system uses white LEDs to generate a reflectance signal and UV-A LEDs to induce a chlorophyll fluorescence signal. Plant images obtained with theis prototype plant health monitoring system (PHM) were used to evaluate image processing functions: calculating reflectance images, removing non-plant background pixels, and calculating vegetation indices from hyperspectral reflectance images. Future work will characterize the chlorophyll fluorescence imaging system and identify suitable vegetation indices for detecting common plant stresses (e.g. drought, overwatering, nutrient deficiencies, etc.) encountered in space crop production systems.