WE PROPOSE A THREE-YEAR CUBESAT MISSION DAILI TO STUDY DYNAMICAL CHANGES IN THE EARTH'S ATMOSPHERIC COMPOSITION IN THE APPROXIMATE 140 TO 290 KM ALTITUDE REGION. DAILI IMPLEMENTS A NEWLY DEVELOPED TECHNIQUE RECENTLY PUBLISHED IN GRL TO MEASURE THE ABSOLUTE O2 DENSITY AT MID AND LOW LATITUDES. THE TECHNIQUE UTILIZES THE RATIO OF TWO BRIGHT DAYGLOW EMISSIONS A PORTION OF THE O2A (0 0) BAND AT 765 NM AND THE OI REDLINE AT 630 NM. THIS WILL ALLOW THE FIRST COMPREHENSIVE MEASUREMENT OF O2 DENSITY IN THE 140 TO 200 KM ALTITUDE REGIME (THE THERMOSPHERE GAP REGION) WHERE ATMOSPHERIC NEUTRAL DENSITY MEASUREMENTS ARE SCARCE. THE REDLINE IS ALSO SENSITIVE TO IONOSPHERIC DENSITY AT ALTITUDES ABOVE 200 KM SO THIS TECHNIQUE WILL ALSO PROVIDE DAYTIME/NIGHTTIME IONOSPHERIC DATA FOR COMPARISON TO MODELS. VARIATIONS OF THE ALTITUDE PROFILES OF O2 AND THE REDLINE CAN BE USED TO STUDY TIDAL AND PLANETARY WAVE VARIABILITY THROUGHOUT THE MEASUREMENT REGIME AS WELL AS TRANSPORT OF NEUTRAL O2 FROM HIGH TO LOW LATITUDES DUE TO GEOMAGNETIC ACTIVITY. THE DATA WILL BE COMPARED TO STATE-OF-THE ART MODELS TO HELP IN THEIR EVALUATION. DAILI WILL ADDRESS THE FOLLOWING SCIENCE OBJECTIVES. (1) DETERMINE THE O2 DENSITY FROM 140 TO 180 KM AT MID AND LOW LATITUDES ON A DAILY BASIS AND COMPARE WITH MODELS SUCH AS MSIS AND TIME-GCM. (2) MEASURE THE ALTITUDE VARIABILITY OF TIDES AND PLANETARY WAVES FROM 140 TO 180 KM WHERE MEASUREMENTS BY OTHER MEANS ARE SCARCE. (3) DETERMINE THE LATITUDINAL AND ALTITUDINAL EXTENT OF THE TRANSPORT OF NEUTRAL O2 DURING GEOMAGNETICALLY ACTIVE PERIODS. (4) DETERMINE VARIATIONS IN THE F-REGION ELECTRON DENSITY PROFILE IN RESPONSE TO TIDES AND PLANETARY WAVES ABOVE 200 KM. THE 6U DAILI PAYLOAD CONSISTS OF A TWO-CHANNEL PHOTOMETER OCCUPYING ABOUT 2 U THAT IMAGES THE EARTH'S LIMB OVER A 6 DEGREE FOV ONTO DIFFERENT REGIONS OF A SINGLE CCD EACH COLOR CHANNEL OCCUPYING ABOUT 180 X 180 PIXELS. AT A NOMINAL LIMB DISTANCE OF 2300 KM THE FOV IS NOMINALLY FROM 140 TO 290 KM IN ALTITUDE OVER A 150 KM HORIZONTAL SPAN. A SUNSHADE WHICH OCCUPIES ABOUT 3U EXTERIOR TO THE OPTICS EXCLUDES SCATTERED LIGHT FROM THE SUN THE HARD EARTH AND LOW ALTITUDE CLOUDS. THE AEROSPACE CUBESAT BUS TAKES UP THE REMAINING SPACE. THE BUS SATISFIES ALL POWER THERMAL AND POINTING REQUIREMENTS FOR CAMERA OPERATION INCLUDING A STAR SENSOR AND ATTITUDE CONTROL SYSTEM CAPABLE OF PAYLOAD POINTING TO BETTER THAN 0.1 DEGREE. THIS POINTING SYSTEM WILL ALLOW HIGHER OR LOWER ALTITUDES THAN THE NOMINAL RANGE TO BE OBSERVED IF DESIRED. THE DAILI DATA RATE WILL BE ABOUT 5 MBYTES/DAY. IT IS PROPOSED THAT DAILI BE LAUNCHED FROM THE ISS USING THE NANORACKS CUBESAT DEPLOYER GIVING A NOMINAL 51-DEGREE INCLINATION ORBIT AT 400 KM ALTITUDE. THE DESIGN LIFE OF DAILI IS AT LEAST ONE YEAR. THE RECEIVED DATA WILL BE STORED AND PROCESSED AT AEROSPACE AND THEN COMPARED TO STATE-OF-THE ART MODELS INCLUDING AURIC TIMED GCM AND GLOW TO MEET THE OBJECTIVES. THE DAILI EXPERIMENT DIRECTLY ADDRESSES NASA S STRATEGIC GOAL 2.2 TO STUDY THE SUN AND ITS INTERACTIONS WITH THE EARTH AND THE SOLAR SYSTEM IN PARTICULAR THE GOAL OF ADVANCING UNDERSTANDING OF FUNDAMENTAL PHYSICAL PROCESSES OF THE SPACE ENVIRONMENT. THE COMPOSITION AND IONOSPHERIC DATA PROVIDED BY DAILI WILL FURTHER OUR UNDERSTANDING OF SUCH PROCESSES IN THE LOWER THERMOSPHERE WHERE MEASUREMENTS ARE SCARCE. THE WIDE SPATIAL AND TEMPORAL DISTRIBUTION OF THE DATA PROVIDED BY DAILI OVER THE COURSE OF ITS MISSION WILL IMPROVE THE ACCURACY OF OPERATIONAL MODELS OF BOTH THE NEUTRAL DENSITY AND THE IONOSPHERE.