THE OBJECTIVES OF THIS INVESTIGATION ARE (1) TO USE THE INSIGHT CAMERAS TO MONITOR ATMOSPHERIC OPACITY (TAU) THROUGH THE MISSION; (2) TO CHARACTERIZE THE ATMOSPHERIC DUST AT THE LANDING SITE AND PLACE IT INTO CONTEXT WITH OTHER MEASUREMENTS; (3) TO CHARACTERIZE THE ROLE OF DUST IN BOUNDARY-LAYER METEOROLOGY; (4) TO IDENTIFY AND CHARACTERIZE ICE CLOUDS AND HAZES AND CONSTRAIN THE WINDS THAT TRANSPORT THEM; AND (5) MEASURE NIGHT OPACITY AND CONSTRAIN THE RATE OF MICRO-METEORITE IMPACTS. THE PROPOSED WORK REQUIRES IMAGES FROM THE INSTRUMENT DEPLOYMENT CAMERA (IDC) WITH THE INSTRUMENT CONTEXT CAMERA (ICC) AS A BACKUP. ARM MOTIONS ARE NOT PLANNED AFTER THE DEPLOYMENT PHASE; THUS THE PROPOSED WORK IS BASED AROUND A SINGLE AIM NEAR THE SOUTHERN HORIZON CONSISTENT WITH ICC AND IDC CAPABILITIES. TO MEASURE OPACITY SKY IMAGES TAKEN EARLY OR LATE IN THE DAY WILL PROVIDE SKY RADIANCE OVER A RANGE OF ELEVATION AND SCATTERING ANGLES. VARIATION OF RADIANCE ALONG CONSTANT SCATTERING ANGLE DETERMINES ATMOSPHERIC OPACITY; GIVEN WELL-CALIBRATED ACCURATE DATA A RADIATIVE TRANSFER MODEL (DISORT) RETRIEVAL OF OPACITY IS STRAIGHTFORWARD. FOR REAL DATA OBTAINED WITH A CAMERA EXPOSED TO A DUSTY MARTIAN ENVIRONMENT FOR AN EXTENDED TIME USE OF RELATIVE RADIANCE VARIATION (WITH ELEVATION ANGLE AT CONSTANT SCATTERING ANGLE) LARGELY REMOVES THE EFFECT OF A DUST COATING THAT MAY VARY IN TIME AND REDUCES SENSITIVITY TO CALIBRATION UNCERTAINTIES. THE PROPOSED METHOD WAS TESTED WITH SKY IMAGING DATA ACQUIRED OVER ONE MARS YEAR USING OPPORTUNITY'S NAVCAM. THE OPPORTUNITY IMAGES WERE TAKEN IN INSIGHT-ANALOG MODE WITH A FIXED AIM ACROSS MARTIAN SEASONS AND INCLUDED TIMES OF DUST STORMS SEASONALLY HIGH AND LOW DUST AND DUST MIXED WITH ICE HAZES. COMPARISONS TO DIRECTLY MEASURED (PANCAM) OPACITY DETERMINED THAT THE INTRINSIC ERROR OF THE NAVCAM METHOD WAS<0.1. THE PROPOSED (FOR TAU) IDC AIM ALLOWS IMAGING OF THE SKY AND GROUND NEAR THE HORIZON. THIS ENABLES SEVERAL RELEVANT IMAGING CAMPAIGNS: SKY IMAGING AT DIFFERENT TIMES OF DAY ALLOWS THE SCATTERING ANGLE COVERAGE THAT WILL BE USED TO DETERMINE SCATTERING PHASE FUNCTION; HORIZON IMAGES WILL BE USED TO DETERMINE BOUNDARY LAYER DUST CONTENT; SHORT-PERIOD TIME-LAPSE IMAGES WILL BE USED TO SEARCH FOR AND CHARACTERIZE DUST DEVILS AND CLOUDS AND THEIR MOTIONS; IMAGES AT NIGHT WILL BE USED TO IMAGE STARS AND VALIDATE THE OPACITY MEASUREMENT WHILE SIMULTANEOUSLY ALLOWING METEORS TO BE DETECTED. NOTE THAT WHILE THE PROPOSAL IS BASED ON IMAGING DURING AND BEYOND THE DEPLOYMENT PHASE THE IMAGING IS DESIGNED TO BE CONSISTENT WITH THE REQUIREMENTS OF THE TAU MEASUREMENT AND DOES NOT REQUIRE USE OF THE ARM AFTER THE DEPLOYMENT PHASE. THE PROPOSED INVESTIGATION FULLY SATISFIES THE REQUIREMENTS OF THE FIRST 'SPECIAL INVESTIGATION' OF THE NRA: ATMOSPHERIC OPACITY (TAU) WILL BE MEASURED AND REPORTED ON AN OPERATIONS-RELEVANT TIMESCALE USING ALGORITHMS THAT WILL BE PROVIDED FOR USE IN AUTOMATED PROCESSING OF IDC AND ICC IMAGES. THE METHOD HAS BEEN VALIDATED BY ANALYSIS OF ONE MARS YEAR OF OPPORTUNITY DATA THAT WERE TAKEN TO MIMIC POSSIBLE INSIGHT MEASUREMENTS. THE METHOD HAS BEEN DESIGNED AND TESTED FOR AUTOMATED PERFORMANCE. THE INVESTIGATION IS ALSO RELEVANT TO 'SPECIAL INVESTIGATION' 6 ATMOSPHERIC PHENOMENA: THE OPACITY MEASUREMENT IS PART OF A LARGER INVESTIGATION OF THE DUST CYCLE AT THE INSIGHT LANDING SITE THAT FOCUSES ON THE ROLE OF DUST IN LOCAL METEOROLOGY. IN ADDITION IMAGES WILL ALSO BE USED TO INVESTIGATE ICE CLOUDS AND HAZE ABUNDANCE AND VARIATION AND TO CONSTRAIN HIGH-LEVEL WINDS. THE PROPOSED WORK WILL ALSO IMPACT OTHER MISSION AND PARTICIPATING SCIENTIST OBJECTIVES: OPACITY VARIATIONS ARE RELEVANT TO THE SUBSURFACE THERMAL ENVIRONMENT; POSSIBLE NIGHT-TIME IMAGES MAY BE RELEVANT TO THE MICRO-METEORITE FLUX.