BGS monitored surface ground motion (subsidence, uplift or stability) in the Vale of Pickering using line-of-slight (LOS) interferometric synthetic aperture radar (InSAR). This is an ideal technique for ground motion monitoring because archive radar data (acquired by satellites since 1992) can be used to ascertain a baseline of motion or lack of motion prior to any gas exploration or production. The analysis also produces data over a region rather than at a point location.
Satellite data
The archive radar data was acquired by the ERS–1/2 and ENVISAT satellites for the periods 1992 to 2000 and 2002 to 2009 respectively. There is no satellite coverage in the region between 2009 and 2014 due to the orbital decay of ENVISAT. Nonetheless, the period 1992 to 2009 was sufficient to provide a meaningful baseline assessment of ground motion prior to unconventional gas operations.
For the Vale of Pickering, the European Space Agency (ESA)’s archives include two data stacks of ERS–1/2 and ENVISAT scenes that cover a standard satellite frame extending 100 × 100 km. 75 ERS–1/2 SAR scenes for 1992 to 2000 and 25 ENVISAT ASAR scenes for 2002 to 2009 are available. This data (1992 to 2000 and 2002 to 2009) was provided by ESA under grant ID 31573 and analysed by BGS.
The ESA radar satellite Sentinel–1A was launched in April 2014. However, at the time of analysis, a sufficient stack of data had not been acquired by the satellite to carry out high-precision InSAR analysis.