Radar astronomy

radarRadar observationsplanetary radarRadar imageradar detectionRadar imagingradar-rangingradars
Radar astronomy is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the reflections.wikipedia
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Radar

radar stationradarsradar system
The strength of the radar return signal is proportional to the inverse fourth-power of the distance.
The modern uses of radar are highly diverse, including air and terrestrial traffic control, radar astronomy, air-defense systems, antimissile systems, marine radars to locate landmarks and other ships, aircraft anticollision systems, ocean surveillance systems, outer space surveillance and rendezvous systems, meteorological precipitation monitoring, altimetry and flight control systems, guided missile target locating systems, ground-penetrating radar for geological observations, and range-controlled radar for public health surveillance.

99942 Apophis

Apophis(99942) Apophis99942 Apophis Mission Design Competition
This aids in forming long-term predictions of asteroid-Earth impacts, as illustrated by the object 99942 Apophis.
Radar astrometry in January 2005 further refined its orbit solution.

Arecibo Observatory

AreciboArecibo radio telescopeArecibo Planetary Radar
There are two radar astronomy facilities that are in regular use, the Arecibo Planetary Radar and the Goldstone Solar System Radar.
It is used in three major areas of research: radio astronomy, atmospheric science, and radar astronomy.

Radio astronomy

radio astronomerradioradioastronomy
Radar astronomy differs from radio astronomy in that the latter is a passive observation and the former an active one.
Radar astronomy

Imaging radar

radar imagingradar imageryimaging
Radar images provide information about the shapes and surface properties of solid bodies, which cannot be obtained by other ground-based techniques.
Radar astronomy

Venus

Morning Starevening starCytherocentric
The next easiest target is Venus.
Radar observations of Venus were first carried out in the 1960s, and provided the first measurements of the rotation period, which were close to the modern value.

Pluton (complex)

PlutonCenter for Deep Space CommunicationsComplex “Pluton-M”
Pluton
Pluton (at 1980ss – Pluton-M) is a system of deep space communications and planetary radar in Crimea.

NASA Deep Space Network

Deep Space NetworkDSNUSA
Deep Space Network
It also performs radio and radar astronomy observations for the exploration of the Solar System and the universe, and supports selected Earth-orbiting missions.

6489 Golevka

6489 Golevka
In 1995, Golevka was studied simultaneously by three radar observatories across the world: Goldstone in California, Yevpatoria RT-70 radio telescope in Ukraine (Yevpatoria is sometimes romanized as Evpatoria) and Kashima in Japan.

4179 Toutatis

4179: Toutatisfirst successful asteroid exploration mission
4179 Toutatis
Radar imagery shows that Toutatis is a highly irregular body consisting of two distinct lobes, with maximum widths of about 4.6 km and 2.4 km, respectively.

Five hundred meter Aperture Spherical Telescope

FASTFive-hundred-meter Aperture Spherical TelescopeFive Hundred Meter Aperture Spherical Telescope (FAST)
Five-hundred-meter Aperture Spherical Telescope
Fifth, Arecibo's larger secondary platform also houses several transmitters, making it one of only two instruments in the world capable of radar astronomy.

Microwave

microwavesmicrowave radiationmicrowave tube
Radar astronomy is a technique of observing nearby astronomical objects by reflecting microwaves off target objects and analyzing the reflections.

General relativity

general theory of relativityrelativitygeneral relativity theory
Radar techniques provide information unavailable by other means, such as testing general relativity by observing Mercury and providing a refined value for the astronomical unit.

Mercury (planet)

Mercuryplanet MercuryMercurio
Radar techniques provide information unavailable by other means, such as testing general relativity by observing Mercury and providing a refined value for the astronomical unit.

Astronomical unit

AUastronomical unitsAUs
Radar techniques provide information unavailable by other means, such as testing general relativity by observing Mercury and providing a refined value for the astronomical unit.

Astrometry

astrometricastrometricalastrometrist
Relying upon high powered terrestrial radars (of up to one MW ) radar astronomy is able to provide extremely accurate astrometric information on the structure, composition and movement of solar objects.

Impact event

impactasteroid impactmeteorite impact
This aids in forming long-term predictions of asteroid-Earth impacts, as illustrated by the object 99942 Apophis.

Parallax

trigonometric parallaxsolar parallaxmotion parallax
In particular, optical observations measure where an object appears in the sky, but cannot measure the distance with great accuracy (relying on Parallax becomes more difficult when objects are small or poorly illuminated).

Goldstone Solar System Radar

Goldstoneradar mapping
There are two radar astronomy facilities that are in regular use, the Arecibo Planetary Radar and the Goldstone Solar System Radar.

Solar System

outer Solar Systeminner Solar SystemSol system
The maximum range of astronomy by radar is very limited, and is confined to the Solar System.

Inverse-square law

inverse square lawinverse squareinverse-square
This is because the signal strength drops off very steeply with distance to the target, the small fraction of incident flux that is reflected by the target, and the limited strength of transmitters.

Ephemeris

ephemeridesAstronomical tablesorbital data
It is also necessary to have a relatively good ephemeris of the target before observing it.

Moon

lunarthe MoonLuna
The Moon is comparatively close and was detected by radar soon after the invention of the technique in 1946.

Public relations

PRpublic relationpublic affairs
In addition such technical prowess had great public relations value, and was an excellent demonstration to funding agencies.

Jet Propulsion Laboratory

JPLNASA Jet Propulsion LaboratoryJet Propulsion Laboratory (JPL)
The first unambiguous detection of Venus was made by the Jet Propulsion Laboratory on 10 March 1961.