CRS-15 carried an instrument to measure the temperature of plants. ECOSTRESS observes thermal infrared from the station, and because a plant under water stress closes its stomata and stops cooling itself by evaporation, its temperature rises — making heat a direct proxy for drought stress in vegetation.
The station's orbit was well suited to it. Unlike a Sun-synchronous satellite that always passes at the same local time, the station drifts through the day, allowing plant stress to be observed at different hours — which matters because stress peaks in the afternoon.
The flight also delivered an experimental robotic assistant, a spherical device with a screen and a voice interface intended to test whether an autonomous helper could reduce crew workload. It was received with amusement and mixed practical reviews.
Around 2,700 kilograms of cargo was delivered in total, including experiments on the germination of seeds, the behaviour of bacteria in microgravity, and hardware for the station's cooling system.
Both the booster and the capsule were on their second flights. The mission passed without incident, and its instrument continues to produce drought and heat-stress maps used by agricultural and water agencies.
