Mortimer directs his own research and has developed his own miniaturized spectrometer for the use in Earth based observation. This is to be used specifically for space based and in-situ monitoring of atmospheric trace gases. Mortimer is also part of a team responsible for the calibration of a future Climate Change monitoring instrument; the Sea and Land Surface Temperature Radiometer (SLSTR) based on the satellite Sentinel 3. This is to be launched in 2012.