Scientists are using the impressive capabilities of the SAOCOM constellation to investigate how creeping masses of frozen debris move across mountainous periglacial landscapes.

Known as rock glaciers, these landforms consist of a mixture of ice and debris that travel very slowly across the land; unlike ‘true’ glaciers, however, they are typically covered with a layer of rocks or other debris.

Research has established that rock glaciers are highly sensitive to variations in the climate and, as a result, they are important indicators of the long-term environmental changes impacting the planet. The spatial distribution and behaviour of these landforms can also influence the availability of water resources and impact the likelihood of geohazards in periglacial regions.

For decades, rock glaciers have been inventoried worldwide but these datasets typically do not consider kinematic information, which is used to characterise how quickly the frozen masses travel across the landscape. 

To address this challenge, researchers from nine institutes aimed to develop a common methodology for estimating the motion of rock glaciers using spaceborne interferometric synthetic aperture radar (inSAR) measurements. Several missions contributed to the analysis, including ALOS-2, Copernicus Sentinel-1 and SAOCOM. 

The study formed part of a joint effort from the International Permafrost Association (IPA) Action Group and ESA’s Climate Change Initiative (CCI) to define standard guidelines for the inclusion of kinematic information in rock glacier inventories.

A three-phase systematic procedure was created to implement kinematic data into existing inventories and it was applied to some 5,000 moving areas of more than 3,600 rock glaciers worldwide.

Using data from ALOS-2, which operates in L-band, and data from Copernicus Sentinel-1, which operates at the shorter C-band wavelength, it was established that the methodology was able to successfully achieve its objective. 

The team then tested out the capabilities of the L-band SAR constellation SAOCOM, which is owned by Argentina's space agency (CONAE). Part of ESA’s Third Party Missions programme, SAOCOM is one of only a small number of L-band satellite systems in orbit and, of these missions, it offers the quickest revisit rate and therefore the highest temporal resolution.

SAOCOM’s unique attributes enabled it to provide kinematic information that the other SAR missions used in the analysis were not able to observe.

Thanks to its fast revisit rate and its L-band capabilities, the mission was found to be more effective in measuring large displacement rates of several mm per day when compared to Sentinel-1 C-band data.

In addition, the L-band observations of SAOCOM preserved the coherence of information collected over one or more years more effectively than C-band observations, meaning that small movements in the order of a few cm per year could be better interpreted. This is particularly relevant in regions that are affected by surface runoff or where there is little vegetation, as is the case for many rock glaciers that have become inactive due to environmental conditions, known as relict glaciers.

The team also capitalised on SAOCOM’s high temporal resolution compared to other L-band missions to investigate rock glaciers in South America and Europe with a greater level of detail. The mission typically offered revisit rates of 16 or 32 days in these regions.

Tazio Strozzi, remote sensing scientist at Gamma Remote Sensing and lead author of the study, concluded, "Here we have demonstrated the benefits of L-band data in the monitoring of rock glaciers, which could have implications for future research in this area of study. The planned Copernicus Sentinel Expansion Mission ROSE-L, for instance, is expected to provide L-band data on an open basis and our findings highlight the potential of these data to investigate rock glacier creep worldwide."