absorption

A measure of the ability of a surface to absorb incident energy, often at specific wavelengths.

albedo

The ratio of the radiation reflected from an object to the total amount incident upon it, for a particular portion of the spectrum.

backscatter

In radar, the portion of the microwave energy scattered by the terrain surface directly back toward the antenna.

detector index

Index of the CCD detector (1 to 15).

irradiance

The density of the radiant flux that is incident on a surface per unit of wavelength.

luminance

The quantitative attribute of light that correlates with the sensation of brightness and is the evaluation of radiance by means of the standard luminosity function.

Mie Scatter

A form of atmospheric scatter that occurs when radiation interacts with atmospheric particles whose diameter is approximately equal to the wavelength of the radiation.

Monte-Carlo method

Probabilistic method allowing to trace the path of each photon knowing the inherent (scattering and absorption) characteristics of the medium.

optical density

The logarithm to base 10 of the inverse of the transmittance.

photon

A photon is a particle of light (or other electromagnetic radiation).

radiance

A measure of the energy radiated by the object together with the frequency distribution of that radiation.

radiative transfer equation

The equation which describes the radiation passage through a scattering and absorbing medium.

radiometer

An instrument for quantitatively measuring the intensity of electromagnetic radiation in some band of wavelengths in any part of the electromagnetic spectrum. Usually used with a modifier, such as an infrared radiometer or a microwave radiometer.

Raman Scatter

Raman scatter arises when the incident light excites molecules in the sample which subsequently scatters the light. While most of this scattered light is at the same wavelength as the incident light, some is scattered at a different wavelengths . This inelastically scattered light is called Raman scatter. It results from the molecule changing it's molecular motions.

Rayleigh scattering

A form of atmospheric scattering that is caused when radiation interacts with particles whose diameter is much smaller than its wavelength. It therefore affects shorter wavelengths.

reflectance

Ratio of the intensity of reflected radiation to that of the incident radiation on a surface.

scattering

The process in which a wave or beam of particles is diffused or deflected by collisions with particles of the medium which it traverses.

scattering phase function

The angular function which describes the directional scattering probability as a photon interacts with a scattering particle.

Snell's law

Gives the quantitative change of direction of a ray of light in passing from one medium to another. The product n sin z is the same on both sides of a plane interface between two media, where n is the local refractive index, and z is the local angle the ray makes with the normal to the interface.

spectrometer

A device used to measure radiant intensity or to determine the wavelengths of various radiations.