WE PROPOSE TO DEVELOP A HIGH RESOLUTION TERAHERTZ (THZ) SOUNDER OPERATED AT AMBIENT TEMPERATURE FOR LOWER THERMOSPHERIC NEUTRALWINDS TEMPERATURE AND DENSITY MEASUREMENTS BETWEEN 100 AND 150 KM FROM A LOW-EARTH ORBIT. THE INSTRUMENT TERAHERTZ LIMB SOUNDER (TLS) IS DESIGNED SPECIFICALLY TO MEASURE THE DOPPLER SHIFT AND WIDTH OF ATOMIC OXYGEN FINE STRUCTURE EMISSION LINE AT 2.0 THZ (145 M). IT WILL PROVIDE PROFILES OF GLOBAL VECTOR WIND TEMPERATURE AND ATOMIC OXYGEN DENSITY FOR BOTH DAY AND NIGHT IN SUCH A CRITICAL REGION WHERE THERE ARE STRONGEST INTERACTIONS BETWEEN THE NEUTRAL AND IONOSPHERIC ATMOSPHERES. AS STATED IN THE 2009 HELIOPHYSICS RECOMMENDED ROADMAP FOR SCIENCE AND TECHNOLOGY MEASUREMENTS OF NEUTRAL WINDS ARE CRUCIAL FOR UNDERSTANDING IONOSPHERIC VARIABILITY AND THE PAUCITY OF SUCH MEASUREMENTS REPRESENTS THE GREATEST EXPERIMENTAL IMPEDIMENT TO PROGRESS. THE ION-NEUTRAL COUPLING IN THE ATMOSPHERE (INCA) WHOSE GOAL IS TO UNDERSTAND HOW NEUTRAL WINDS CONTROL THE IONOSPHERIC VARIABILITY HAS BEEN IDENTIFIED AS ONE OF THE ROADMAP RECOMMENDED NEW SCIENCE TARGETS FOR FUTURE SOLAR TERRESTRIAL PROGRAM AND THE TWO HIGH-PRIORITY AREAS IN THE GEOSPACE SCIENCE PROGRAM. TLS UNEQUIVOCALLY SUPPORTS FUTURE GEOPHYSICS MISSION SCIENCE AND DIRECTLY BENEFITS THE FUTURE INCA MISSION PLANNING AND IMPLEMENTATION. DURING THE PROPOSED 36-MONTH PERIOD (2/1/13 TO 1/31/16) WE WILL DEVELOP A COMPACT LOW-NOISE AND LOW-MASS RECEIVER ARRAY CONCEPT FOR THE TLS INSTRUMENT AND A CONCEPTUAL DESIGN FOR TLS OPERATION ON A LEO PLATFORM.