“When you think back to the mid-1960s, the space race was underway, the American public was passionate about what was happening, the idea of using this technology not only for military action, but also to film these cameras and looking at what’s 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 Earth’s skies, although one of them, Landsat 6, did not reach orbit. Today, three of them circle the planet in polar orbits, observing swaths of land 185 kilometers wide and making highly detailed measurements. Every sixteen days, the same places are observed again 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,” said NASA’s James Irons, who led the Landsat program for decades. “At the time Landsat 1 was launched, the entire Earth was not yet well mapped – the data was rather thin. »
In 1973, those responsible for 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 satellite data, Fleming spotted a telltale signature in the spectrum of light reflecting off the Earth’s surface. She concluded 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 see properly, but it significantly changed the average reflectivity of the pixel it occupied.
“For this pixel, it is a mixture of water and earth,” describes Sohl. “We therefore see a marked contrast with the surrounding area. »
In 1976, a team from the Canadian Hydrographic Service took to the skies over northern Labrador to confirm the existence of the island, and fix its position on the map; after all, it had only been seen in a single pixel of the satellite data. About 12 miles offshore, the chunk of rock jutted out of the foam into a perilous collection of reefs, shoals and underwater rocks, an area that was avoided by sailors. Fleming’s discovery was verified: the island did exist.
According to the story told in the Canadian Parliament, when 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 remember listening to the radio when I was little and hearing about, with a certain excitement because I dreamed of being an explorer when I grew up, the discovery of the new island off the east coast of Canada” , confided Scott Reid, Member of Parliament, in 2001.
“It was a discovery of practical importance for Canada, because it allowed it to expand its territorial waters. »
The equipment that makes up the new Landsat fleet, called Landsat 9 and launched in September 2021, is 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.
“The uses of remote sensing, whether it’s vineyards or agriculture or helping with firefighting 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 relating to the management of our planet’s increasingly limited resources.
“In all of our observations of Earth, we see the impact of a growing population,” says Irons. When Landsat 1 was launched, fewer than 4 billion humans 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 wise decisions. »
