Initial Validation Results from the Integrated Use of Permanent GNSS Stations and SAR Corner Reflectors in Cyprus by means of the CyCLOPS Strategic Research Infrastructure

Kurzfassung

The Cyprus Continuously Operating Natural Hazards Monitoring and Prevention System, abbreviated CyCLOPS, is a national strategic research infrastructure unit, with main objective the systematic study of geohazards in Cyprus and the broader EMMENA region. The project was coordinated by Cyprus University of Technology in collaboration with the German Aerospace Center (DLR), and holds the support of the critical national stakeholders, such as the Geological Survey Department and the Department of Lands and Surveys. CyCLOPS is comprised of two main components; (a) a multi-parametric network of sensors (MPN) established throughout the government-controlled areas of Cyprus and (b) an Operation Centre (OC). The MPN is comprised by a permanent and a mobile segment, which is deployed at areas of interest. The permanent segment includes six permanent sites, each of which contains a Tier-1 GNSS reference station co-located with two calibration-grade triangular trihedral corner reflectors of 1.5m inner length to account for both the ascending and descending tracks of SAR satellite missions, such as ESA’s Sentinel-1. Furthermore, the GNSS equipment is co-located with precise weather stations and tiltmeters. The mounting considerations for the permanent segment are aligned with the most stringent specifications, as outlined by UNAVCO, IGS and EPN. Therefore, besides its zero-order geodetic nature, the unit aims to become a calibration and validation (Cal/Val) infrastructure for current and future SAR satellites constellations. The mobile segment is comprised by the same grade of GNSS equipment, hosted on a specifically designed mobile configuration, which enables flexibility in the deployment of the stations, even at harsh environments, to monitor dynamic phenomena, such as landslides. Furthermore, the mobile segment includes electronic corner reflectors (ECRs), which are, again, co-located with the GNSS sensors, weather stations and tiltmeters. CyCLOPS achieved full operational capacity in June 2021. Since then, it continuously monitors the geodynamic regime of the southeastern Mediterranean area along with several active landslides occurring at the western part of the island. Consequently, the objective of this research is to deliver a brief presentation of the infrastructure, the first experience after 1.5 years of system operation, and outline results from the analysis of SAR products using our Corner Reflectors. The latter can be carried out, for instance, by means of the SAR Calibration Tool (SCT), developed by Aresys Srl, to estimate accurate geometric and radiometric calibration for Sentinel-1 products over Cyprus. Radiometric calibration will be assessed by means of a Point-Target-Analysis (PTA) on the SLCs to estimate parameters such as peak signal power, clutter power and RCS. The now almost 2 year long dataset will be analysed in full in order to verify the temporal stability of the network and to identify, for instance, drops in accuracy due to collection of precipitation in the CRs. The geometric or geolocation accuracy will be assessed, taking into account the effects of propagation delay of the SAR signal through the troposphere and ionosphere, and geodynamical effects which influence the previously determined, e.g. through surveying, CR position such as the coordinate reference frame and solid earth tides.