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DE Optical Turbulence Collection Sensor

Description:

TECHNOLOGY AREA(S): Info Systems 

OBJECTIVE: Develop an Optical Turbulence Collection Sensor to support the development of Directed Energy (DE) decision aids. 

DESCRIPTION: DoD is spending billions of dollars developing laser weapon technology. There are a number of programs in development in the USAF and US Army designed to create lethal and non-lethal capabilities that are expected to be fielded in the next 5-15 years [1]. Currently, there are no persistent optical turbulence collection sources in the DoD or US gov’t. Historically, measurements of optical turbulence have been made at point locations using indirect methods such as thermosondes with thin-wire microthermal sensor and onboard electronics convert the temperature difference to a voltage signal, which can be translated into refractive index structure parameter, Cn2. This instrument is commonly used balloon-born to measure turbulence profiles of the atmosphere, but when used at a stationary location, its fragile construct means that it breaks under tough meteorological conditions. Additionally, point measurement have been made using sonic-anemometers, which built to handle any conditions due to its metal frame and its lack of moving parts. More direct optical measurement can be made using system such as generalized scidar or scintillometer for example. Scintillometers measure the turbulence over a given path instead of at a specific location [2, 3] and can lack range correlated turbulence. Additionally, they also required an optical source or target at the far end of the path (transmit and receive geometry) in order to make measurements. AF Weather will likely need a mechanism to collect optical turbulence data that overcomes the limitations of historical systems in order to support the various Directed Energy Weapons being developed and ultimately fielded. In order to properly account for atmospheric conditions a three dimensional, volumetric scan of the atmosphere may be required to support laser weapons. This type of scan will provide not only real-time conditions, but begin to build a worldwide climatology of this atmospheric parameter of interest. 

PHASE I: Research the existing and near-term optical turbulence collection sensors. Analyze which ones, if any, can operate 24/7 and can collect data in a volumetric scan, similar to a weather radar over distances ranging from approximately 1-10 km. Determine the optimized location and placement of the sensor to acquire uncontaminated data. Design a solution while adhering to security & IA doctrine. 

PHASE II: Using the results from Phase I, develop a prototype optical turbulence collection sensor. Determine how this system would plug into the existing AF Weather observing network and how the data would be disseminated. Verify product usefulness by engaging in collection efforts with comparisons to other validated optical turbulence sensors. Operate the system under persistent, dissimilar weather conditions and make data comparisons. 

PHASE III: Produce production quality collection sensors. 

REFERENCES: 

1: United States Air Force Directed Energy Weapon Flight Plan, 2017

2:  Jumper, G., Et al., "Comparison of Recent Measurements of Atmospheric Optical Turbulence," AIAA-2005-4778, AFRL-VS-HA-TR-2005-1124, 2005.

3:  Travouillon, T., et al., "Accurate measurements of Optical Turbulence with Sonic-anemometers," Journal of Physics: Conference Series 595, 2015.

KEYWORDS: Atmospheric Propagation, Atmospheric Characterization, Optical Turbulence, Volumetric Wavefront Sensing, Adaptive Optics, Phase-front Distortion, Decision Aid 

CONTACT(S): 

Dr Nicholas Morley (AFRL/RDLA) 

(505) 846-0805 

nicholas.morley@us.af.mil 

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