OBJECTIVE: Develop a standalone, downrange crosswind sensor component capable of measuring the average crosswind velocity for distances of up to 800 m [(T)hreshold)], [1500 m (O)bjective] in order to increase first round hit probability. DESCRIPTION: Accurate wind speed measurements are crucial to military operations, especially long range small arms engagements. Crosswind is one of three major sources of error responsible for reducing the probability of hit, P(h) of a shooter, and deflection caused by crosswind is the most dominant factor affecting the flight of a bullet. Moderate crosswind velocity as low as 5 m/s will deviate a bullet off-course by as much as 1 mil for long range firing (800 meters and above) requiring a second attempt, which provides the target with the opportunity to reach defilade and increases the sniper"s own probability of detection. Local changes in the refractive index of air caused by atmospheric turbulence are quantifiable by remote sensing techniques which allow measurements of the crosswind velocity. Both active and passive methods have been demonstrated and experimentally verified in the field, with crosswind measurements determined accurately with an error on the order of the standard deviation of reference measurements. Snipers currently have the ability to measure wind at their present location with handheld anemometers. Additionally, snipers are trained to"read the wind"by observing the movements of blades of grass, swaying tree branches or mirage to estimate the wind mid range and at the target and then calculate an average wind speed. Such methods require a great deal of time practicing in order to master. Further, the practice of using swaying objects, such as swaying tree branches, lacks accuracy and often results in a"best guess"on windage correction. Fire control systems are currently under development that provide wind correction methods into a single fire control system, such as those by US-Israeli (FOCUS) and DARPA (One Shot) initiatives. There are currently no efforts to develop stand-alone wind sensing capability, which is capable of both independent operation and interfacing with the next generation of fire control systems. The objective of this effort is to develop a downrange crosswind measurement system which is significantly miniaturized (relative to aforementioned current programs), is capable of independent operation, and has an open architecture to facilitate integration into future fire control systems should the need arise. Further, this effort opens the door to exploration of both active and passive wind sensing capabilities, whereas prior efforts have been focused all but exclusively on active solutions. PHASE I: Identify a method, components and develop system architecture for a remote sensing device for downrange crosswind measurement in both day and night operation. Selected method shall be modeled and simulated to demonstrate improved crosswind velocity measurements over conventional methods at ranges of 800m (T) [1500m (O)], in crosswinds of 0 m/s to 20 m/s (gale force wind, per the Beaufort Scale), with a crosswind measurement error of no more than 1.5 m/s. Outlined performance shall be achieved in all ambient light conditions (day, night, dawn/dusk). A report shall be delivered documenting the research, modeling and components for a laboratory scale device. Active illumination methods must assess eye safety requirements. Expected maturity level at completion of Phase I is TRL 3. PHASE II: Develop a proof of concept breadboard prototype to demonstrate the technologies and capabilities identified and explored in Phase I. Upon completion and demonstration of proof of concept device, further develop the system to reduce the size, weight and power (SWAP) of the crosswind sensor such that it weighs no more than 1.5 lbs (T) [1 lb (O)], does not occupy a volume larger than 0.7 L (T) [0.5 L (O)], and operates on common U.S. Army inventory batteries (T), [AA or CR123 batteries (O)]. Developed prototype analysis shall include average crosswind velocity measurements in a relevant environment compared to measurements made by conventional wind estimation methods, for example, sniper wind estimation techniques or hand held local wind speed sensors. Expected maturity level at completion of Phase II is TRL 5. PHASE III: Upon successful completion of the research and development in Phase I and Phase II, the new system will be capable to be fielded as a clip-on or weapon mountable device (MIL-STD-1913, Picatinny Rail) and provide a known interface in order to be integrated into fire control systems under development. Dual use applications include use in wind energy generation, determining crosswind at airports, free space optical communications and monitoring the drift of chemical, biological and radioactive agents. Expected maturity level at completion of Phase III is TRL 7.