NASA Distributed Active Archive Center (DAAC) at NSIDC

Supporting scientific study of the cryosphere

DAAC Data Projects: Active Microwave

Microwave sensing encompasses both active and passive forms of remote sensing. The microwave portion of the spectrum covers a wavelength range of approximately 1 cm to 1 m. Because of their long wavelengths, compared to the visible and infrared, microwaves have special properties that are important for remote sensing. Longer wavelength microwave radiation can penetrate through cloud cover, haze, dust, and rainfall as the longer wavelengths are not susceptible to atmospheric scattering, which does affect shorter optical wavelengths. This property allows detection of microwave energy under almost all weather and environmental conditions so that data can be collected day or night and in all kinds of weather.

Active microwave sensors provide their own illumination and do not depend upon ambient radiation like passive microwave sensors. Active microwave sensors are generally divided into two distinct categories: imaging and non-imaging. The most common form of imaging active microwave sensors is RADAR. Non-imaging microwave sensors include altimeters and scatterometers. In most cases, these are profiling devices which take measurements in one linear dimension, as opposed to the two-dimensional representation of imaging sensors. For specific details regarding the active microwave data at NSIDC, please refer to the instrument descriptions below.

RADARSAT-1: The data from this instrument offers the first high-resolution mapping of the entire continent of Antarctica. The RADARSAT Antarctic Mapping Project (RAMP) mosaics provide a detailed look at Antarctica's ice sheet morphology, rock outcrops, research infrastructure, coastline, and other features.

Scatterometry: The data collected from the scatterometer instruments have generated enhanced-resolution radar backscatter images on consistent, compatible grids. From this time series of radar images, derived products related to key climate-related parameters can be extracted for use in cryospheric and climate change studies.

Radar Altimetry: Radar altimeters provide measurements of the altitude of the Earth's surface to determine ice sheet topography, small-scale ocean roughness, and wind speed.