Improvements in and relating to remote sensing

A system 20 for remotely sensing light from a monitored environment. The system comprising: one or more retro-reflective optical elements 1A; a light source 22; a detector 38,39; a wavefront sensor 64 and control unit 41; and a deformable mirror 67 and controller 26. The elements bear a photo-luminescent material whose emission varies in response to an environmental parameter. The light source illuminates an element and the detector determines the parameter according to the emitted response. The wavefront sensor determines the wavefront of the emission and the control unit instructs the mirror to deform such that illuminating light is output with a modified wavefront. The illuminating light may be pulsed. The mirror may be continuous, may be deformed according to the conjugate of the detected wavefront and may update in time with the light pulses. The photo-luminescent material may be exposed to the environment, and may comprise Quantum Dots, PtTFPP or lucigenin and measure temperature, pressure or salinity.