FLEX – Fluorescence Explorer

By capturing the faint glow of plant photosynthesis, FLEX is the next level of vegetation detection. Monitoring Earth’s vegetation has huge implications for Earth’s ecosystems and climate processes. This mission is more than plant exploration, but a crucial step towards sustainable Earth monitoring from space.

Mission Objective

FLEX is a fluorescence imaging satellite. It joins the orbit of Sentinel-3, and together, they will map global photosynthetic activity. Its mission is to collect data from land and provide data about vegetation, such as photosynthetic efficiency, health, and stress.

Mission Significance

This information is helpful to develop deeper insight into most topics in vegetation, such as:

• Carbon cycle
• Agriculture management
• Food security

Concept of FLEX (Source: ESA)

Engineering Challenges

FLEX needs to detect extremely faint chlorophyll fluorescence signals. Therefore, it has high-standard technical requirements:

• Exceptional radiometric sensitivity and stability
• High spectral resolution, while keeping stray light extremely low
• Thermal stability

Moreover, because FLEX flies in tight coordination with Sentinel-3, precise temporal and geometric synchronization between the two satellites is required.

Instrument Characteristics

• The main data collector is FLORIS, the single instrument that is carried by FLEX.
• FLORIS – FLuORescence Imaging Spectrometer – is a high-resolution imaging spectrometer that detects the amount of fluorescence from the planet.
• FLORIS collects data in conjunction with Sentinel-3’s Ocean and Land Color Instrument (OLCI) and Sea and Land Surface Temperature Radiometer (SLSTR).
• This combined effort enables the retrieval of the fluorescent signal emitted by plants during photosynthesis. The amount of fluorescent will provide all the vital information about the plant.
• FLEX consists of a single three-axis stabilized satellite flying one after another with Sentinel-3 to make the most effective use of other observation tools that already exist. This framework allows the system to provide supplementary measurements that are acquired within 6-15 seconds of each other to minimize the effects of moving clouds.

Concept of the FLEX (Source: ESA)

Acktar’s Solution

Acktar coated the spectrometer, FLORIS, with Fractal Black and Magic Black to suppress stray light that might distort incoming signals and also to maintain thermal stability. Acktar enabled FLEX to accurately capture fluorescence emissions and provide high-quality environmental data.

Impact

The photosynthetic process enables the existence of life on our planet by converting carbon dioxide and sunlight into energy. Until now, it wasn’t possible to measure the efficiency of photosynthesis on large spatial scales. When photosynthesis occurs, the planets emit a fluorescent glow. It can’t be seen with the naked eye, but it can be measured from space – this is the core of the FLEX mission. The data from FLEX may help our understanding of the movement of carbon in the atmosphere and the effects of photosynthesis on carbon and water cycles. Rapid population growth is threatening global food security in the future. The data about plant health and stress may be useful in creating a sustainable program for the necessary food production.

Methodology Overview of the HyPlant

One of the purposes of the mission is to measure the fluorescence from space with a passive system using only sunlight. For that, HyPlant was developed. It is a susceptible instrument that can span the scales from single leaves.

• Within plants and algae cells, two distinct solar power systems operate sequentially. These systems collect energy from sunlight and generate energy for the photosynthesis process.
• During the process, the system emits heat and a subtle luminosity known as fluorescence. The intensity and wavelength of this glow vary depending on environmental factors and the overall well-being of the plant. The efficacy of these systems determines the varying degrees of brightness displayed by each solar power system.
• The Hyplant is equipped with two imaging spectrometers, which perceive different wavelengths. The first spectrometer captures a range extending from red to NIR, carefully segmenting the wavelengths to detect the fluorescence signals.

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