Landsat, a small island in Canada discovered by a satellite

“When you think back to the mid-1960s, the space race was going on, the American public was excited about what was going on, this technology was not just for military action, but the idea of ​​having these cameras to film and watch. What was happening on the surface of the Earth was unique. ,” Sohal said. “People really didn’t know what to expect. »

Since 1972, nine Landsat satellites have graced Earth’s skies, although one of them, Landsat 6, never reached orbit. Today, three of them orbit the planet in polar orbit, observing 185 km wide strips of land and making very detailed measurements. Every sixteen days the same places are again observed by the same satellite. Thus, in five decades of observations, Landsat has produced the most detailed record of the evolution of our blue planet.

“This is 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 still not well mapped – the data was rather thin. »

This is how cartographer and pilot Elizabeth Fleming was able to use Landsat data to leave an unusual mark on history.

The pixel that made Canada great

In 1973, those in charge of the Canadian Coastal Survey decided to use Landsat data to better map the country’s northern coasts, which were then poorly documented. While inspecting data from satellites, Fleming noticed a telltale signature in the spectrum of light from Earth’s surface. He concluded that it came from an island, not an iceberg.

Just 25 meters wide by 45 meters long, the rocky coral reflects infrared light instead of absorbing it like the surrounding seawater. The island was too small to be seen accurately, but it significantly changed the average reflectance of the pixels it occupied.

“For this pixel, it’s a mixture of water and earth,” Sohal describes. “So you see a marked contrast to the surrounding area. »

In 1976, a team from the Canadian Hydrographic Service flew over northern Labrador to confirm the island’s existence and fix its position on maps; After all, he only saw a single pixel of satellite data. About 12 miles offshore, the boulders jut out from the falls in a dangerous array of reefs, shoals and underwater rocks, an area to be avoided by mariners. Fleming’s discovery was confirmed: the island did exist.

According to the story told in the Canadian Parliament, when hydrographer Frank Hall descended from a helicopter onto the ice-covered island, he narrowly escaped a deadly attack by a well-hidden polar bear.

Regarding the search for new islands off the east coast of Canada, “I still find myself listening to the radio when I was a kid and listening with a certain excitement because I dreamed of being an explorer when I grew up.” Scott Reid, Member of Parliament, in 2001.

“This was a discovery of practical importance for Canada, as it allowed it to expand its territorial waters. »

Landsat legacy

The instruments that make up the new Landsat fleet, called Landsat 9 and launched in September 2021, are improved versions of Landsat 1. They scan our planet with longer wavelengths of light, their eyes are sharper and they are equipped with thermal imagers.

From orbit, these satellites measure coastal retreat, identify urban heat islands, monitor the Amazon gold rush, and even track the amount of water consumed by 8,000 hectares of California wine country.

“The use of remote sensing, whether it’s in vineyards, agriculture or helping to fight fires in the West… it’s great to be involved,” Sohl said.

Today, Landsat is joined by hundreds of Earth observation satellites, both governmental and commercial. This constellation provides important observations that help guide decisions about how to manage our planet’s increasingly limited resources.

“In all of our Earth observations, we see the effects of a growing population,” Irons said. When Landsat 1 was launched, less than 4 billion people lived on Earth, which has doubled since then.

“It is becoming more and more difficult for Earth’s resources to support us in this situation. But I try to be optimistic, and my hope is that with the right information, people will be in a better position to make the right decisions. »

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