Sites watched from orbit

What these readings can say. A thermal anomaly means NASA's FIRMS satellites saw more heat at the site than it usually shows, at the moment they passed. It does not say why: flaring, a process upset, maintenance and a fire read alike. What they cannot. A fire put out between two passes is never seen, cloud and smoke hide heat, and a site that flares gas every day reads hot on its own, which is why each site is measured against its own normal. A quiet site is no reading at all, never a statement that nothing happened. A site view is a dated Sentinel-2 image: context for a reading, never proof of damage. The SWIR view shows heat and burn scars that true colour cannot. Port occupancy counts large vessels inside the port's box from Sentinel-1 radar, as a weekly median against the port's own trailing eight weeks. It cannot see ships at a quay or outside the box, and small craft do not register.