Europe has launched satellites to watch plants glow

Plants are stubbornly good at looking well, so a field of wheat can be in trouble for weeks before anybody notices. By the time the leaves start to turn, the damage is done, and the harvest suffers.

ESA satellites can spot a faint red light plants give off while they are feeding on sunshine, and that light reveals whether a plant is growing or merely surviving. That glow only appears during photosynthesis. No glow, no grow. So, when drought, disease or exhausted soil start shutting a plant down, the light fades weeks before the leaves do.

Existing satellites measure greenness, which tells you what a field looks like, but Flex measures the glow, which tells you what a field is actually doing. And while Flex is doing the detective work, Sentinel-3C measures the cloud, heat and ground conditions that would otherwise throw its readings off.

Reading light from 500 miles up

The difficulty is the glow makes up a tiny fraction of the light coming off a field, and Flex has to find it through the entire depth of the atmosphere while travelling at thousands of miles an hour.

It does this with a spectrometer, an instrument splitting light into extremely narrow bands of colour. The glow sits at a wavelength the Sun itself barely produces, so when that band comes back brighter than it ought to be, something down there is busy turning sunlight into food.

Nobody has managed it from orbit before. ESA selected the mission back in 2015, which gives you a fair sense of how hard it has been to get to lift-off.

The unfashionable side of space

There is a version of the space industry that gets all the attention. Billionaires, Mars, asteroid mining, and the held notion we might one day need somewhere else to live.

Flex and Sentinel-3C are the other version. Satellites living in low orbit, collecting the sort of unglamorous data that tells us whether the rainforests are coping and fields of wheat will hold.

Pointing a camera at Earth shouldn’t be seen as a lesser ambition than pointing one at Mars. The most complicated system humans have to understand right now is not the lunar surface, it’s the one we’re standing on, and it’s behaving rather oddly.

FOS Future Lab presented by Randox has always kept a foot in orbit. Our ambassador is astronaut Sir Tim Peake, and recent exhibits have ranged from Space Forge's reusable satellites and Pulsar Fusion’s world-beating space propulsion systems to ESA's Euclid mission mapping billions of galaxies.

Flex follows the same instinct — a voyage of discovery — only the focus is on Earth, not outer space.

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