Glossary – R

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Research & Analysis

radar altimeters

Used to measure the distance between the platform (usually satellite or aircraft) and the ground surface. The radar altimeter is a short pulse, nadir viewing radar designed to measure precisely the distance from the satellite to the Earth surface. The instrument can also measure the shape of the returned pulse and the backscattering cross section. The latter two measurements permit inference of significant wave height and wind speed. The significant wave height can be inferred from the slope of the leading edge of the returned pulse and the wind speed can be inferred from the radar cross.


Radiating rays or reflecting beams of light


to send out rays or shine brightly


The process of emitting radiant energy in the form of waves or particles


Radiometers are meters used to detect and measure radiant energy that can be either electromagnetic or acoustic and measure radiated electromagnetic power. Types of radiometers include: infrared, multichannel filter, multiflyer and step frequency.


Rock Abrasion Tool

red giant

A star that has low surface temperature and a diameter that is large relative to the Sun.


Radio Frequency


Research Opportunities in the Space and Earth Sciences