09/07/2026
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Thirty years after the European Area Company first demonstrated the facility of flying two satellites in very shut formation, the idea was just lately recreated. By briefly positioning two Copernicus Sentinel-1 radar satellites to copy the pioneering ERS-1–ERS-2 ‘tandem mission’, ESA achieved one-day repeat radar imaging of the identical Antarctic area.
The outcomes as soon as once more display how this strategy can be utilized to measure glacier movement and pinpoint the essential grounding line with distinctive precision.
ESA’s first Earth observing satellites, ERS-1 and ERS-2, have been launched in 1991 and 1995, respectively. On the time, these two satellites have been Europe’s most subtle Earth statement satellites ever developed and launched.
Shortly after ERS-2 had been positioned in orbit, ESA manoeuvred the 2 ERS satellites right into a novel tandem formation, permitting them to watch the identical space of Earth simply 24 hours aside.
This orbital association was maintained for 9 months. The tandem mission offered scientists with an unprecedented quantity of intently spaced observations and a singular alternative to trace adjustments occurring over very quick timescales.
Whereas an additional tandem marketing campaign was carried out in 2008 with ERS-2 and the Envisat satellite tv for pc, the latest repeat of the idea concerned the Copernicus Sentinel-1C and Sentinel-1D radar satellites.
Throughout Sentinel-1D’s commissioning part, it was positioned briefly in shut formation with Sentinel-1C, to attain a one-day repeat-pass interval for the constellation. Importantly, this tandem configuration supported cross-calibration of the 2 satellites and verified their interferometric artificial aperture radar efficiency.
In parallel, ESA maximised the scientific return from Sentinel-1A earlier than its current retirement by working it with Sentinel-1C in its commonplace six-day repeat-pass configuration.
ESA’s Sentinel-1 System Supervisor, Dirk Geudtner, mentioned, “The near-simultaneous observations from the three Sentinel-1 satellites offered a uncommon alternative to observe glacier and ice-sheet dynamics throughout totally different timescales.
“Specifically, by imaging the identical area of Antarctica simply sooner or later aside, the Sentinel-1C and Sentinel-1D satellites recreated the statement time interval that made the unique ERS-1–ERS-2 tandem mission a breakthrough for measuring glacier movement and mapping grounding strains.”
A grounding line is the essential boundary the place a glacier or ice sheet stops resting on bedrock and begins to drift on the ocean, forming an ice shelf. It acts as an anchor level, controlling how shortly ice flows from the continent into the ocean.
Each the stream velocity of glaciers and ice streams, and adjustments within the place of the grounding line are key indicators of how ice sheets are responding to local weather warming. Collectively, these measurements assist scientists estimate adjustments in ice mass stability and quantify the quantity of ice being discharged into the ocean, bettering projections of future sea-level rise.
Comparisons between the measurements from the ERS tandem part and people from the Sentinel-1C–Sentinel-1D tandem configuration reveal how Antarctica has modified over the previous three a long time – because the side-by-side interferograms under present.
For instance, adjustments of ice velocity and floor deformation of the Scar Inlet Ice Shelf, the southern remnant of the previous Larsen-B Ice Shelf, and over the fast-flowing Evans Ice Stream in West Antarctica might be seen within the side-by-side interferograms.
The Sentinel-1C–Sentinel-1D interferogram on the fitting reveals main fractures and rifts within the ice shelf that weren’t current within the corresponding 1995 ERS-1–ERS-2 interferogram on the left.
The weakening of the ice shelf has contributed to the acceleration and thinning of tributary glaciers, rising ice discharge and driving the inland migration of the grounding line. This modification is a key indicator of the dynamic response and stability of grounded ice plenty.
The graph under reveals the substantial enhance in Leppard Glacier’s ice-flow velocity between 1995 and 2026 utilizing one-day interferometric artificial aperture radar observations from each tandem phases.
Prof. Emeritus Helmut Rott, who having labored extensively with ERS-1–ERS-2 tandem interferometric artificial aperture radar information, mentioned, “Detailed observations of such options and their temporal change, as offered by the ERS-1–ERS-2 and Sentinel-1C–Sentinel-1D one-day repeat information, opens wonderful alternatives for improved understanding and predictions of processes of ice-shelf weakening and disintegration, grounding line migration and lack of grounded ice.”
The uncommon mixture of observations from all three Sentinel-1 satellites additionally highlights the ice-flow velocity over the Evans Ice Stream, in West Antarctica.
Evans Ice Stream, the principal ice stream draining the southern Antarctic Peninsula into the Ronne Ice Shelf, transports ice at speeds of round 3–4 metres per day.
Due to its quick stream and well-characterised dynamics, it has been proposed because the calibration and validation website for polar ice-sheet merchandise from the upcoming Copernicus ROSE-L mission.
The ice stream occupies a deep trough bounded by steep valley partitions, with pronounced shear margins that seem as tightly packed fringes within the radar interferograms. These options present worthwhile data on ice deformation and assist scientists assess how ice streams reply to local weather change.
As a result of the ice flows so quickly, the usual six-day Sentinel-1A–Sentinel-1C interferogram, acquired on 22 and 28 March 2026, accommodates extremely compressed fringes, making it tough to measure absolute ice-flow velocity precisely. In distinction, the one-day Sentinel-1C–Sentinel-1D interferogram from 22 and 23 March 2026 produces a way more extensively spaced fringe sample, enabling much more exact measurements of ice-flow velocity.
As well as, the ‘double-difference’ interferogram, derived from two Sentinel-1C–Sentinel-1D pairs, clearly reveals the tidal ice deformation and shear zones.
Thomas Nagler, CEO at ENVEO and member of ESA’s Mission Advisory Group for the Sentinel-1 Subsequent Era and the ROSE-L missions, mentioned, “Lowering the repeat-pass interval from six days to only sooner or later allows monitoring shear zones and fast-moving glaciers and ice stream by the use of interferometry with larger accuracy.”
ESA’s Sentinel-1 and Sentinel-1 Subsequent Era Mission Supervisor, Thibaut Decoopman, mentioned, “Sentinel-1 has established a benchmark for high-quality, end-to-end radar interferometric efficiency.
“Constructing on this success, Sentinel-1 Subsequent Era will safe the continuity of C-band observations whereas offering enhanced efficiency to deal with the evolving wants of customers and Copernicus providers.”
Notice: This analysis was supported by ESA SUPSAR-Ice Velocity and ESA’s Climate Change Initiative initiatives.
