ICESat-2 ATLAS

The ICESat-2, launched in 2018, uses lasers to measure ice sheets, glaciers, sea ice, land topography, vegetation, and clouds.

Jonathan Goodman

Background

Figure 1: An artist's rendition of of the ICESat-2 and ATLAS laser sensor

The Ice, Cloud, and Land Elevation Satellite-2, or ICESat-2, was launched by NASA on September 15, 2018. It continues the mission of the original ICESat, which operated 2003-10, to study the Mass Balance of the Cryosphere (the total change in sea and land ice worldwide).

The ICESat-2 carries a single sensor (LiDAR), the Advanced Topographic Laser Altimeter System, or ATLAS, which uses a visible green laser beam fired 10,000 times per second to record surface elevation of ice and land features.

Unique Features

Figure 2: Opto-Mechanical Engineer Tyler Evans explains how the ATLAS sensor transmits lasers to the ground. ATLAS is the primary instrument on board the ICESat-2 spacecraft.

  • Carries a single instrument - the Advanced Topographic Laser Altimeter System
  • Laser light is at 532 nanometers - visible green
  • 10,000 laser pulses/second (40/s on the first ICESat)
  • Takes a measurement every 2.3 feet
  • The on-board solid-state data recorder stores at least 580 gigabytes of data every day
  • It sends data back to two ground stations, in Svalbard, Norway, and Wallops Island, Virginia, every two orbits
  • The satellite flies at 4.3 miles per second
  • Solar panels on ICESat-2 generate 1320 Watts
  • Weighs 3483 lbs (1580 kg)

Orbit Information and Resolution

Orbit

Orbits the Earth at an altitude of 500 km in a sun-synchronous near-polar orbit (92 degree inclination)

Spectral Resolution

Single green laser at 532 nanometers at a pulse repetition frequency of 10 kHz

Spatial Resolution

Varies, down to 70 cm.

Temporal Resolution

91-day exact-repeat cycle

Radiometric Resolution

Since ICESat-2 uses a LiDAR sensor, it does not have a radiometric resolution equivalent to Multispectral/Hyperspectral systems.

Applications

ICESat-2 has four designated scientific objectives:

  • Measure melting ice sheets and investigate how this effects sea-level rise
  • Measure and investigate changes in the mass of ice sheets and glaciers
  • Estimate and study sea-ice thickness
  • Measure the height of vegetation in forests worldwide

Beyond these four designated objectives, ICESat-2's altimetric capabilities can be used to measure the elevation of land areas, oceans, clouds, and surface water. In this way, ICESat-2 compliments other missions such as Landsat by providing scientists with accurate elevation/height data.

Figure 3: NASA video "ICESat-2 Elevates Our View of Earth"

Case Study

The Tibetan Plateau is also known as “the third pole of the world” because of its high concentration of land glaciers, third to only Antarctica and Greenland. The Plateau’s glaciers are an important part of the global cryosphere, and are also linked to freshwater availability for communities locally.

The rapid melting and ice mass loss on the Tibetan Plateau puts local communities at risk of water shortages, while also exposing them to rapid and catastrophic morphological change in the form of landslides and ice bridge collapse, which can lead to infrastructure damage and loss of ecological balance. Studying these rapid changes to ice mass are important both for understanding global change and for protecting local communities from devastating natural disasters.

Data provided by ICESat-2 is crucial for understanding the extent and spatial dimensions of ice mass loss globally and on the Tibetan Plateau in particular. In a recent paper, Tong et al. (2024) use ICESat-2 data from 2018-2022 to measure glacier thickness changes in the Southeastern Tibetan Plateau and compare this data to the loss in overall land water storage in the region. Their study confirms that glaciers in the Southeastern Tibetan Plateau are rapidly melting, leading to an overall lower inventory of land water storage.

In their study, the researchers note the accuracy of the ICESat-2 data as compared to the original ICESat, due to its improved sensor technology. They also highlight the effective use of ICESat-2 data alongside other water-measurement remote sensing instruments. In this study they combine ICESat-2 data with data from another NASA Satellite, GRACE-FO.

Tong, Jinwei, Zhen Shi, Jiashuang Jiao, Bing Yang, and Zhen Tian. 2024. “Glacier Mass Balance and Its Impact on Land Water Storage in the Southeastern Tibetan Plateau Revealed by ICESat-2 and GRACE-FO.” Remote Sensing 16 (6). doi:10.3390/rs16061048.

References

Figure 1: An artist's rendition of of the ICESat-2 and ATLAS laser sensor