The Sentinel-1 Constellation - A new era of operational InSAR

The launch of Sentinel-1A on 3 April 2014 by the European Space Agency will transform our ability to monitor our restless planet with InSAR. For the first time, radar data will be acquired systematically and frequently (every 6 days once Sentinel-1B is launched in 2016) over all the tectonic and volcanic areas of the planet; the data will be freely available to the whole community; the mission has a long duration, with future launches planned to extend the time series to at least 20 years. In this presentation, I will discuss some the processing challenges, present preliminary differential interferograms and time series, and speculatively look back from 2034 on what the mission has achieved. Sentinel-1 acquires radar data in a novel mode, known as Interferometric Wide Swath or TOPS (Terrain Observation with Progressive Scans in azimuth) mode. TOPS mode has some advantages, the most significant of which is that a 250 km wide image can be acquired without the scalloping effect that is seen in conventional ScanSAR amplitude images. However, because the Doppler centroid varies in azimuth, phase artefacts are introduced in TOPS-mode interferograms unless the images are co-registered with an azimuth accuracy of ~5 cm. This, and the bursted nature of TOPS data, introduces new challenges and opportunities to InSAR processing. We show how the required coregistration accuracy can be achieved with an end-to-end geometric approach, and by exploitation of the view angle diversity in burst and swath overlap regions. We also discuss different strategies for when and how to stitch the bursts, which depend on the application domain and processing methodology. The systematic acquisitions and free and open data policy provide new opportunities for routine analysis and operational applications of InSAR. COMET (* http://comet.nerc.ac.uk) aims to provide processed results for all the tectonic and volcanic regions of the planet, and we will present preliminary results of our processing system from test regions in Turkey and Mexico. By 2034, there will be a 20 year archive of systematic radar acquisitions from the Sentinel-1 program. We will end this presentation with a speculative view from 2034 on the main achievements of the program. *COMET is the UK NERC's Centre for the Observation and Modelling of Earthquakes, Volcanoes and Tectonics.