A new dataset has been released for the SEASTARex campaign, which took place in the Iroise Sea in 2022 to support scientific demonstration and validation of the SEASTAR mission.

ESA conducts airborne and ground-based campaigns to support the development of new instruments, and calibration and validation of existing instruments. These campaigns simulate satellite-based instruments and are conducted all over the world in support of a wide range of applications.

The goal of the SEASTARex 2022 campaign was to support the SEASTAR mission, which was one of four candidates for ESA’s 11th Earth Explorer. Though SEASTAR was not selected to proceed, the campaign provided valuable insight into the mission concept that will help develop future advances in the field of Doppler oceanography.

The concept for SEASTAR was to monitor fast-evolving, small-scale ocean dynamics in coastal seas, shelf seas and marginal ice zones. Using a 1 km resolution along-track interferometric Synthetic Aperture Radar (SAR), the satellite would have studied the exchange of heat, carbon, and nutrients between land, cryosphere, atmosphere, and oceans.

SEASTAR was intended to measure 2D Total Surface Current Vectors (TSCV) and Ocean Surface Vectors Wind (OSVW) fields, and Direction Ocean Wave Spectra (DOWS) using an innovative approach on a single satellite. The goal was to use two orthogonal squinted along-track interferometry and SAR beams, with a third beam performing scatterometry.

SEASTARex tested this concept with a Ku-band airborne instrument called OSCAR (Ocean Surface Current Airborne Radar), which was developed for the purposes of this the campaign to simulate the capability of the SEASTAR instrument. The SEASTARex objectives were to:

• Acquire OSCAR measurements with ground truth data over a well-characterised ocean site
• Develop a Level-2 processing chain to retrieve TSCV and OSVW from Level-1 OSCAR Doppler and Normalised Radar Cross Section (NRCS) data
• Evaluate TSCV data from OSCAR in comparison to ground truth measurements
• Assess OSVW data from OSCAR in comparison to spaceborne scatterometers

The campaign involved four flights over the Iroise Sea, an area of the Atlantic Ocean with strong currents and often violent storms. Flights took place over the following locations between 17 and 26 May 2022:

• Morlaix airport – Which was used as a calibration site over land
• The ocean near Ouessant island – Ground truth was provided with a X-band marine radar and stereo-video in a nearby lighthouse and a high frequency radar on the mainland of France
• The open ocean - Presenting a homogeneous area with uniform bathymetry and environmental conditions. The aircraft flew in star and circular patterns to acquire data in different azimuth directions.
• An off-shore site in the Bay of Biscay – The aircraft performed underflights with the Advanced Scatterometer (ASCAT) onboard two MetOp satellites, to calibrate OSCAR and validate OSVW observations.

SEASTARex successfully validated the concept of the SEASTAR satellite mission, highlighting unparalleled potential to collect critical data on ocean currents and winds in challenging coastal regions where alternative measurements are expensive and difficult to implement.

The SEASTARex dataset consists of Single Look Complex (SLC) SAR images from OSCAR, which are processed as NetCDF products.

The dataset is openly available for download following submission of a data access request.

Learn more about the SEASTARex 2022 campaign and how to request the data.