#EarthDayAtHome Plants from Space with Martha Anderson

I’m Martha Anderson I work for the US Department of Agriculture and I’m in the Agricultural Research Service. I work in Beltsville Maryland in a laboratory dedicated to hydrology and remote sensing so my job mostly focuses on using satellite remote sensing to monitor crops, crop health, and to monitor drought and drought impacts There’s a lot we can learn about the health of the planet, for example, by the heat that it’s emitting. We have found that we can get early signals of developing crop stress, like under a flash drought situation, from the thermal infrared light that that the surface emits. We can see thermal signals of stress before we can actually see in the field that the crops are getting stressed. So this early warning information can be really valuable to growers, gives them a little extra time to prepare for the oncoming drought, to mitigate the impacts of the drought.

So that can be very valuable 01:11 - for agricultural decision making. Thermal infrared radiation is a type of radiation It’s at a longer wavelength than we can see with our eyes. So we cannot see thermal infrared radiation, but there are special sensors and cameras that have been developed specifically to pick up and detect thermal radiation. This is really, really important. Any object, any body that has any temperature at all above absolute zero is emitting thermal radiation all the time. The hotter the body, the stronger the thermal emission.

01:54 - So with these thermal sensors in the thermal infrared wavelengths we can remotely tell how hot an object is from a remote standpoint. So when we’re using thermal cameras that are on satellite platforms we’re essentially mapping out the the variations in temperature across the land surface. We can detect relatively accurately how hot this crop field is compared to the adjacent crop field. So we have a demonstration of one of these thermal cameras that is going to show us how thermal infrared radiation can detect temperature differences from remote objects. from pens to people, everything gives off energy in the form of heat.

02:44 - And with special instruments that measure thermal wavelengths we can tell whether something is hot or cold. OK so as this demonstration showed these special thermal cameras are able to detect differences in temperature based on the thermal infrared radiation that the surfaces are emitting. So we’re using thermal sensors on satellites to essentially map out the temperature of the Earth’s surface. And this gives us a good indicator of how healthy, or unhealthy, the crops are. So much like the human body, when you’re starting to feel sick maybe one of the first things you do is go take your temperature.

03:33 - If it’s above normal, if it’s above ninety eight point six maybe something’s going on. The same thing holds for plants and crops as well. So when they’re starting to run out of soil moisture that’s available to them - maybe there’s a drought, if it’s a house plant maybe you haven’t watered your plant for a while - the plants start to get stressed. When there’s ample soil moisture they can take that that moisture up through the roots. It transpires out of little pores in the leaf surfaces and evaporates, and that evaporative cooling helps to regulate the plant temperature.

04:10 - So healthy well watered plants tend to be cooler. When the soil moisture starts to run out they don’t have enough water to evaporate, the leaf temperatures start to elevate and we can measure those elevated leaf temperatures and canopy temperatures from space with these thermal sensors. So essentially we’re using them as giant space thermometers to map out where the crops, where the forest, where the the grasslands are healthy, and where they’re more stressed and not doing so well. For those applications, we turn to the Landsat satellites most often. So Landsat satellites that have been operated by NASA and USGS back through the 1970s.

They collect routine, really high-quality, 05:05 - high resolution imagery including these thermal infrared images that we need for our work. And they allow us to see water use and stress at the scale of individual cropped fields. So we can distinguish corn from the neighboring soybean field and that’s really really important. Also, because Landsat has been operating for so long – thermal imaging has been enabled since the 1980s – we can study how patterns and water use have changed over the landscape over long periods of time as the climate has changed and as land-use patterns have changed. And so Landsat has been really a critical sensor for our work.

05:48 - But then more recently another thermal sensor was launched again by NASA and deployed on the International Space Station. And that sensor is called ECOSTRESS and it’s also been a really valuable tool for learning more about how crop stress impacts plants. So it was launched in 2018. It’s got about the same spatial resolution as Landsat but it passes over at different times of the day. Landsat is always going over at 10:30 in the morning. It’s on a sun-synchronous orbit so it passes over at the same time every day the same patch of land.

06:27 - Whereas ECOSTRESS may pass over at any time of the day so we can look at stress and water use in the morning and in the afternoon and see how things change during the day. So in combination, we really like to use all the thermal data that’s available to us. We combine Landsat data with ECOSTRESS data with this coarse resolution imagery from the geostationary satellites and merge them all into one really high-quality water use product. The ultimate goal is to map out crop water use and crop water requirements. And this has a lot of benefits both to water resource managers and also to the the growers themselves.

07:15 - If we can measure how much water different types of crops require under normal healthy conditions, we can make better decisions on how to allocate limited water resources between different types of uses. Well, I think this Earth Day, where we’ve kind of been more shut into our houses, we’re a little more isolated. It’s a really good time to think about how important nature is, how it sustains us. And how we can better take care of the planet that we’ve been given so that we can enjoy it into the future and keep ourselves and our environment healthy. So I think this 50th anniversary of Earth Day, it is is very unique for a lot of reasons.

08:14 - And one way to really monitor and to maintain the health of our planet is to support these ongoing Earth observing missions that are collecting such critical data about the health of our planet. .