The Need for Extra Images

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Polar regions are changing rapidly with rising global temperatures. Landsat’s temporal and spatial resolutions are good for observing ice shelves, glaciers, sea ice, glacier fronts, glacier calving, icebergs, surface roughness across the ice sheet, and cracks and crevasses indicative of ice movement and flow. Landsat can even detect warm pools of water upwelling from the deep ocean called polynyas.

The Thermal Infrared Sensors (TIRS) on Landsats 8 and 9 are exceptional imagers. “The thermal infrared really allows us to be able to separate out polar temperatures. Liquid water is obviously above the melting point, so we can clearly discriminate between what’s frozen and what’s liquid water and then what the temperature of the water is,” Crawford explained.

TIRS can also see in the dark. The extra satellite images acquired for the LEAP project are collected in polar regions during the darkness of winter, which in the past was considered to be too dark to get useful imagery. But with the extra acquisitions now possible with Landsats 8 and 9, these changes can be studied in more detail, even in darkness or polar twilight.

Daily Workload

Landsats 8 and 9 each already collect about 750 images per day. Can they handle the extra workload? 

It’s more about the ground station capability than the sensors getting tired or overworked. In the past, the Landsat ground station network was designed to handle up to 500 images per day based on the Landsat 7 acquisition strategy. But during development of Landsat 8, it was realized that the satellite could acquire more images. “So after launch, the USGS quickly found out that Landsat 8 could image much more of the globe and thus started the capability to incrementally expand imaging of the polar regions,” Crawford said.

“Landsat 8 and Landsat 9 are not really working overtime. They’re just acquiring more data because it’s clear that the data is useful and beneficial to polar science.”

Petermann Glacier

The American Geophysical Union (AGU) science news magazine Eos recently published an article about the LEAP project. The article uses Petermann Glacier in northwestern Greenland as an example. Crawford expanded on this example, saying that the low sun angle in these images is actually a benefit to revealing more detail about such glaciers: 

“There’s a nice illustration of a time series of the Petermann Glacier showing that when the sun is either at the horizon or slightly below the horizon, we can actually see a lot more. And, you know, that makes a lot of sense because snow and ice are still really bright mediums on the surface, and so even if the illumination is low, you can still see a lot of detail because of the high reflectivity, and a lot of useful information that could have been hidden as a result, in this example would have been topographic shadowing.”

For more information and images about Landsat capturing changes at Petermann Glacier, see EROS’ Earthshots page.

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Data Acquisition Requests

LEAP is not the only special acquisition campaign. Landsats 8 and 9 also collect nighttime imagery of active volcanoes, forest fires across the Western U.S., and geothermal and urban heat island hotspots. “LEAP is just one part of [Landsat’s] special request capability,” Crawford said.

Crawford suggests looking for special request data that might already be available in EarthExplorer. “I advise users to see if the data is there, and if it’s not there, then you can use the acquisition request process to acquire the data. And it’s important to remember that we acquire this data as a best attempt. It’s not guaranteed that the special request is going to be acquired.”

Listen to the LEAP podcast with EROS’ Chris Crawford on the USGS EROS website. Find more than 100 podcasts in our Eyes on Earth podcast library.