“When you think back to the mid-1960s, the space race was on, the American public was passionate regarding what was happening, the idea of using this technology not only for military action, but also to film these cameras and looking at what is happening on the surface of the Earth, was unique,” says Sohl. “People really didn’t know what to expect. »
Since 1972, nine Landsat satellites have populated the Earth’s skies, although one of them, Landsat 6, did not reach orbit. Today, three of them circle the planet in polar orbits, observing strips of land 185 kilometers wide and making very detailed measurements. Every sixteen days, the same places are once more observed by the same satellites. Thus, in five decades of observation, Landsat has compiled the most detailed record ever made of the evolution of our blue planet.
“It’s a great discovery program”, rejoices James Irons from NASA, which ran the Landsat program for decades. “At the time Landsat 1 was launched, the whole of the Earth was not yet well mapped – the data was rather thin. »
Thus cartographer and pilot Elizabeth Fleming was able to use Landsat data to leave an unusual trace in history.
THE PIXEL THAT ENLARGED CANADA
In 1973, those in charge of a Canadian coastal study decided to use Landsat data to better map the country’s northern coasts, which were then poorly documented. While inspecting the data from the satellite, Fleming spotted a telltale signature in the spectrum of light reflecting off the Earth’s surface. She concluded that it came from an island, not an iceberg.
Measuring just 25 meters wide by 45 meters long, the rocky atoll reflected infrared light instead of absorbing it like the surrounding seawater. The island was too small to be seen properly, but it significantly changed the average reflectivity of the pixel it occupied.
“For this pixel, it’s a mixture of water and earth,” Sohl describes. “So you see a marked contrast to the surrounding area. »
In 1976, a team from the Canadian Hydrographic Service flew into the skies of northern Labrador to confirm the existence of the island, and fix its position on the map; following all, she had only been seen in a single pixel of satellite data. About 12 miles offshore, the chunk of rock emerged from the surf in a perilous array of reefs, shoals and underwater rocks, an area that was avoided by sailors. Fleming’s discovery was confirmed: the island did exist.
According to the story reported to the Canadian Parliamentwhen hydrographer Frank Hall descended on the ice-covered island from a helicopter, he narrowly escaped a deadly attack from a well-hidden polar bear.
“I can still see myself listening to the radio when I was little and hearing regarding, with a certain excitement because I dreamed of being an explorer when I grew up, regarding the discovery of the new island off the east coast of Canada” , told Scott ReidMember of Parliament, in 2001.
“It was a discovery of practical importance to Canada, as it allowed it to expand its territorial waters. »
THE LANDSAT LEGACY
The equipment that makes up the new Landsat fleet, called Landsat 9 and launched in September 2021, are more advanced versions of Landsat 1. These scan our planet with more wavelengths of light, their eyes are sharper and they are equipped with thermal imagers.
From their orbit, these satellites measure the retreat of the coasts, characterize the urban heat islands, watch a gold rush in the Amazon and even track the amount of water consumed on 8,000 hectares of California wine country.
“The uses of remote sensing, whether it’s vineyards, agriculture, or helping to fight fires in the West… It’s just great to be involved,” Sohl said.
Today, Landsat is joined by hundreds of Earth observation satellites, both government and commercial. This constellation makes crucial observations that help guide decisions regarding managing our planet’s increasingly limited resources.
“In all of our Earth observations, we see the impact of a growing population,” Irons says. When Landsat 1 was launched, less than 4 billion people lived on Earth, a number that has since doubled.
“It is becoming more and more difficult for the Earth’s resources to support us in these conditions. But I try to be optimistic, and my hope is that with accurate information, people will be in a better position to make sound decisions. »
