In 2015, ICEYE, a Finnish radar satellite company, with support by ExxonMobil Upstream Research Company, executed a series of field tests to assess the technical feasibility of using ICEYE's newly-designed Synthetic Aperture Radar (SAR) instrument for small ice feature detection in open water and pack ice imaging. The project consisted of three separate flight campaigns. The first campaign included calibration flights flown in Helsinki in March. The second campaign was performed in April, over sea ice in the Gulf of Bothnia. The third flight campaign, conducted in November, measured the performance of the instrument in weather.
In addition to validation of the designed SAR system, the main objective of the project was to obtain imagery of small ice features with the ICEYE prototype instrument. The analysis focused on the capability of the proposed SAR to detect small but potentially hazardous ice features. Two instrument configurations were used: a linear polarized antenna in VV configuration, and a circular cross-polarized antenna configuration. The reason for using a circular cross-polarized configuration in the SAR is that potential rain clutter can be reduced by suppressing odd-numbered reflections.
Test results from the ice measurement campaign showed that the linear VV configuration is sufficient for detecting features as small as 10 meters in waterline extension. On the other hand, small ice feature detection performance of the circular cross-polarized configuration was poor at transmitted power levels scaled to match the satellite case. Results also showed that sea state and target feature roughness play a significant role in detecting small features.
The third campaign was performed to understand whether rain clutter would affect the image quality with VV configuration, and whether such effects can be mitigated by a circular cross-polarized configuration. However, during the test period, only light to moderate rain conditions were encountered. In these conditions, the VV configuration suffered no rain clutter in levels affecting ice detection performance. A theoretical study concluded that in order for the rain clutter to interfere with imaging, the rain event must exceed levels that are extremely rare in arctic areas.
The flight test demonstrates that the ICEYE SAR data is valuable for ice management use. Once deployed in a constellation of small satellites, the resulting near-real time service can provide better situational awareness for potential operations in the Arctic.