From space, it’s not our cities that stand out as a mark of human impact on our plan­et. It’s our farms. Farming has changed our plan­et, but farm­ing itself is chang­ing. By 2050, we need to be able to pro­duce 70% more food whilst also address­ing today’s glob­al chal­lenges: pop­u­la­tion growth, cli­mate change, and water scarci­ty.

Every plant is unique. Each has dif­fer­ent needs. What we call pre­ci­sion agri­cul­ture” starts with this sim­ple insight. The bet­ter you tar­get your use of water, fer­til­iz­er, her­bi­cides, even down to the lev­el of an indi­vid­ual plant, the less you waste and the small­er your resource foot­print.

The inter­est­ing thing is not just fig­ur­ing out what one plant needs, but doing it on the scale of a mil­lion plants. This is where imag­ing can help. Capturing the detail, but from a dis­tance. Some farm­ers already used drones or oth­er air­craft to do just that. But these are not tools avail­able to all. I want to ask what if pre­ci­sion agri­cul­ture could be a ser­vice acces­si­ble to any­one on the plan­et?

The sheer scale of farm­ing means that any imag­ing tech­nol­o­gy needs to be com­pact and robust enough to be placed on satel­lite, but also pow­er­ful enough to be able to zoom right in. This is the chal­lenge that we’ve tak­en on in our lab at Imperial College, and we’re try­ing to solve it using lasers.

Closeup photo of a leaf, showing a graph of its signature in the electromagnetic spectrum

All mat­ter has its own unique sig­na­ture that sits some­where on the elec­tro­mag­net­ic spec­trum. The green col­or of a leaf is a sig­na­ture of the light-harvesting chem­istry it con­tains. But the col­ors of vis­i­ble light are only a small part of the elec­tro­mag­net­ic spec­trum. There are use­ful sig­na­tures spread all across it from the ultra­vi­o­let, to the infrared, and beyond.

Closeup photos of leaves fresh and in two other states of death/decay, showing how their spectra don't match that of the fresh one

For crop farm­ers, these sig­na­tures can help iden­ti­fy water stress, the ear­li­est signs of a pest out­break. And cru­cial­ly, whether each plant is active­ly grow­ing towards matu­ri­ty. This infor­ma­tion can be used to act ear­li­er and smarter to opti­mize yields. All you need to do is to be able to tune in reg­u­lar­ly to read the right parts of the spec­trum.

Today, we have satel­lites that use this approach to mon­i­tor plant health. But the major­i­ty of today’s satellite-based imag­ing tech­nol­o­gy is pas­sive. It can only col­lect reflect­ed sun­light that escapes back into space. This lim­its the res­o­lu­tion obtain­able, and means it can only be used in the day­time. This leaves data vul­ner­a­ble to error, min­i­mizes what you can see, and means you can’t zoom in to the lev­el of indi­vid­ual plants. And this is where lasers come in.

By active­ly send­ing a beam of light back to the Earth, we can get 24-hour cov­er­age and cre­ate 3D images from the canopy down to a sin­gle plant on the ground. Because the beam is intense, we can cut through weath­er and atmos­pher­ic dis­tor­tion. And because the beam is care­ful­ly con­trolled, we get the accu­ra­cy we need to pre­cise­ly map each plant to reveal plant pat­terns across each field.

The chal­lenge has been to find the right laser mate­r­i­al for the job. Our research is based on alexan­drite, a laser type which has been around since the 1970s. What makes it intrigu­ing is that it’s tun­able to pre­cise­ly read the indi­ca­tors of plant health.

Today, alexan­drite lasers are most often seen in the cos­met­ic indus­try. These are large, immo­bile machines which need bulky and inef­fi­cient lamps to work. This is hard­ly suit­able for space, where tech needs to be com­pact and robust enough to last for years. But in our lab, we’ve been able to re-engineer alexan­drite lasers. By tak­ing advan­tage of advances in com­mer­cial tech which has been designed for the laser dis­play mar­ket, we’ve been able to replace these lamps with a device that can be up to ten times more effi­cient. Our device is small enough to fit in your palm, but robust enough to go into space.

Placed on an orbit­ing satel­lite, our laser can not only deter­mine the extent of veg­e­ta­tion across the plan­et but also key health infor­ma­tion includ­ing dis­ease, drought, and defor­esta­tion. If we can make this wide­ly avail­able, this could be sig­nif­i­cant for areas of lim­it­ed resources, but valu­able for every­one from gov­ern­men­tal mon­i­tor­ing of defor­esta­tion to the loan farmer max­i­miz­ing his crop yield.

The col­ors of plants are ide­al for our laser, but it’s not the only sig­na­tures that it’s lim­it­ed to. It can also be used to mon­i­tor and also quan­ti­fy trace gas­es. Imagine being able to accu­rate­ly mon­i­tor pol­lu­tion, from pipeline leaks to nat­ur­al dis­as­ters, in real time. These devel­op­ments promise future space-based plat­forms that could not only help to opti­mize glob­al crop yields but also improve the accu­ra­cy of pol­lu­tion mon­i­tor­ing. We can bet­ter be able to man­age and under­stand our impact on the plan­et for the wel­fare of gen­er­a­tions to come. This could help us reach our tar­get of 70% more food by 2050.

Think about the way that high-resolution satel­lite maps like Google Earth have trans­formed nav­i­ga­tion and are open­ing up new busi­ness mod­els, for exam­ple Uber and self-driving cars. What if satellite-based laser imag­ing could do the same for farm­ing?


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