The study of bodies in the Solar System by bouncing radio pulses off them. Radar work requires very large (and hence sensitive) telescopes, such as the 305-m radio dish at Arecibo Observatory. Radar astronomy can be used to determine the accurate distances of the planets (by measuring the time delay of the reflected signal), rotation rates (by Doppler broadening of the signal), and to map surface features (by detailed analysis of the echoes). Notable achievements in radar astronomy include the accurate measurement of the astronomical unit; determination of the rotation periods of Mercury and Venus; and the mapping of the cloud-covered surface of Venus. Earth-based radar has also been used to study the surface of Mars, the larger moons of Jupiter and Saturn, the rings of Saturn, asteroids, comets, and meteor trails. Several spacecraft sent to Venus have carried radar mapping equipment, notably Pioneer Venus Orbiter, Veneras 15 and 16, and Magellan. In addition, the Cassini spacecraft has mapped Saturn’s moon Titan by radar.
https://www.jpl.nasa.gov/news/news.php?release=2011-011
The bouncing of radio waves off objects in the Solar System, with reception and analysis of the ‘echoes’. Radar contact with the Moon was first made in 1945 and with Venus in 1961. The travel time for radio reflections allows the distances of objects to be determined accurately. Analysis of the reflected beam reveals the rotation period and allows the object's surface to be mapped topographically. The rotation periods of Venus and Mercury were first determined by radar. Radar maps of Venus were obtained first by Earth-based radar and subsequently by orbiting space probes.
- response function
- response surface
- response time
- response variable
- responsibility
- responsive Web design
- ressentiment
- restart
- rest energy
- rest frame
- resting potential
- restitution coefficient
- rest mass
- Restoration (1660)
- restore
- restraining bend
- restraint of trade
- restricted file system
- restricted law of specification
- restricted least squares estimator
- restricted three-body problem
- restriction
- restriction enzyme
- restriction fragment length polymorphism
- restriction mapping