Solar occultation measurements from satellite have been very successful at sounding the upper atmosphere from cloud-top to well into the mesosphere (e.g. HALOE, ATMOS, SAGE, POAM). The HALOE instrument achieves transmission precision of 4 X10-6 at 2 arcminute resolution (1.6 Km at the Earth limb) with the differential gas correlation technique. With modern detectors, high precision tracking, better throughput and differential broadband radiometry, achievable precision should approach 10-7 (~10-9 km-1 extinction) or better. We show that this will allow accurate sounding of CO2, O3, H2O and NO mixing ratios simultaneously with temperature and pressure well into the lower thermosphere. In addition, such precision could provide the first mapping of the Earth's cosmic dust layer.