A method for correcting top-of-atmosphere reflectance data in high altitude imagery to a ground surface reflectance data. Transmission of light through Earth's atmosphere and its suspended load of aerosol particles degrades light within the visible through near infrared portion of the spectrum. This can severely affect the quality of the data recorded by orbiting Earth observation satellites. The method first measures the degree of atmospheric effects upon reflectance, then reverses these effects to deliver surface reflectance data and imagery cleaned of haze and thin clouds.

The present disclosure provides a Scheimpflug LIDAR apparatus for detecting a property of a gas comprising: a light source configured to emit a light along at least a first axis, a light detection arrangement, and an optical configuration fulfilling the Scheimpflug condition and Hinge rule. The light source comprises an expander aperture, and wherein the expander aperture and light detection arrangement are configured such that: a spot size of the emitted light along the first axis is matched to a pixel footprint of pixels configured to receive light from corresponding distances along the first axis, and an effective range resolution of at least one column of pixels or probe volume deteriorates linearly with respect to the range.

A visibility measurement device (10) comprising a camera (12) and a computing device (14) communicatively coupled to the camera and configured to: receive a first image from the camera; select a measurement feature in the first image, the measurement feature corresponding to a location within the field of view of the camera; measure an optical characteristic of the measurement feature to obtain a measured optical characteristic value for the location; and determine an ambient fog intensity value based on: the measured optical characteristic value; a reference optical characteristic value for the location; and a distance between the camera and the location, such that the ambient fog intensity value can be used to calculate the visibility in a direction between the camera and the location.

Methods and systems are provided for foreign object debris monitoring in an environment with a dynamic debris field, such as an environment for operating an aircraft. The debris monitoring technique includes generating a light beam and dispersing it to create a virtual witness plate, which is a two-dimensional sheet of light that covers a detection area. The technique also include detecting scattered light from the virtual witness plate caused by debris passing through it. A debris event may be generated based on the scattered light, indicating the presence of debris in the detection area.

A method for determining and transmitting slant visibility range information for a runway at a predetermined decision altitude, including a step of acquiring, by a first aircraft, an image of a surrounding scene located outside and ahead of the aircraft, a step of analyzing the image to detect visual runway references in the image and measure distance between the aircraft and each detected runway reference, a step of transmitting slant visibility range information to the ground station, implemented by the first aircraft, the information including a distance between a visual runway reference and the aircraft measured in the analysis step if at least one runway reference has been detected, or if not information according to which no visual runway reference was able to be detected, and a step of transmitting, by the ground station, slant visibility range information associated with the runway to at least one second aircraft in flight.

A method is provided for detecting a property of a gas comprising: emitting a light, comprising a plurality of wavelengths covering a plurality of absorption lines of the gas, along a first axis, the light being scattered by particles of the gas resulting in a scattered light, generating a sensor image using a detection arrangement configured to receive the scattered light and comprising: an optical arrangement having an optical plane and being configured to direct the scattered light on to a light sensor, the light sensor having at least one pixel columns, wherein the pixel columns are aligned to an image plane and configured to output a sensor image, wherein the first axis, the optical plane, and the image plane intersect such that a Scheimpflug condition is achieved, determining, from the sensor image, properties of the gas at a plurality of positions along the first axis.

A system comprises an optical air data system that measures aerosol and molecular scattering of light, and an optical instrument that measures aerosol and/or molecular scattering of light. A processor receives data from the air data system and from the optical instrument. The processor performs one or more signal analysis and data fusion methods comprising: (a) determining aerosol and/or molecular concentration from the received data, modifying a data analysis algorithm to optimize any remaining unknown parameters, and outputting enhanced air data parameters; (b) determining aerosol concentration from the received data, dynamically optimizing hardware settings in the air data system to enhance a signal level and avoid system saturation, and outputting enhanced air data parameters; or (c) determining aerosol and/or molecular concentration from the received data, estimating a confidence level of an air data algorithm, verifying optical health of the air data system, and reporting the optical health to a user.

A transmissometer and method for determining a transmissivity of an atmosphere within a chamber. A chamber contains the atmosphere. A light source generates a test beam and a light detector detects the test beam. A periscope is movable between a first position which allows the test beam to pass through the atmosphere in the chamber and into the light detector and a second position in which the test beam is deflected to pass into the light detector without passing through the atmosphere in the chamber. A processor determines the transmissivity of the atmosphere from a transmissivity measurement for the test beam obtained by the light detector when the periscope is in the first position and a transfer standard obtained at the light detector when the periscope is in the second position.

A shared optics and telescope for transmitting a transmission beam and receiving a return signal is provided. The shared optics and telescope includes a pair of axicon lenses operable to shape the transmission beam into an annular beam having an outer diameter and an inner diameter, a secondary mirror operable to deflect the annular beam into a deflected annular transmission beam, and a primary mirror that includes an inner mirror portion and an outer mirror portion, the inner mirror portion operable to expand the deflected annular transmission beam, and the outer mirror portion operable to collect the return signal.

An optical system that obtains characteristics of a transmission path in atmosphere, when laser light propagates through this transmission path, at a place separated from this transmission path and before the propagation, and corrects wavefront of the laser light based on the obtained characteristics, is provided. The optical system is provided with an irradiation device and an atmospheric characteristics obtaining system. The irradiation device irradiates an external target with light via a first optical path. The atmospheric characteristics obtaining system is arranged in a second optical path separated from the first optical path and obtains characteristics of atmospheric environment in the first optical path with respect to the irradiated light. The irradiation device is provided with wavefront correction optics. The wavefront correction optics correct wavefront of the irradiated light based on the obtained characteristics.