All Topics  
Radar astronomy

 

 
   Email Print
   Bookmark   Link
 

 

Radar astronomy
 
 
  Topics Radar astronomy Topic Home

Radar astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
 is a technique of observing nearby astronomical objects by reflecting microwave
Microwave

Microwaves are electromagnetic radiation with wavelengths ranging from 1 mm to 1 m, or frequency between 0.3 hertz and 300 GHz....
s off target objects and analyzing the echoes. This research has been conducted for four decades. Radar astronomy differs from radio astronomy
Radio astronomy

Radio astronomy is a subfield of astronomy that studies Astronomical object at radio frequency. The initial detection of radio waves from an astronomical object was made in the 1930s, but subsequent advances have identified a number of different sources of radio emission....
 in that the latter is a passive observation and the former an active one.






Discussion
Ask a question about 'Radar astronomy'
Start a new discussion about 'Radar astronomy'
Answer questions from other users
Full Discussion Forum



Encyclopedia


1999jm8
Radar astronomy
Astronomy

Astronomy is the science of Astronomical object and Phenomenon that originate outside the Earth's atmosphere . It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the physical cosmology....
 is a technique of observing nearby astronomical objects by reflecting microwave
Microwave

Microwaves are electromagnetic radiation with wavelengths ranging from 1 mm to 1 m, or frequency between 0.3 hertz and 300 GHz....
s off target objects and analyzing the echoes. This research has been conducted for four decades. Radar astronomy differs from radio astronomy
Radio astronomy

Radio astronomy is a subfield of astronomy that studies Astronomical object at radio frequency. The initial detection of radio waves from an astronomical object was made in the 1930s, but subsequent advances have identified a number of different sources of radio emission....
 in that the latter is a passive observation and the former an active one. Radar systems have been used for a wide range of solar system studies. The radar transmission may either be pulsed and continuous.

The strength of the radar
Radar

Radar is a system that uses electromagnetic radiation waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain....
 return signal is proportional to the inverse fourth-power of the distance. Upgraded facilities, increased transceiver power, and improved apparatus have increased observational opportunities.

Radar techniques provide information unavailable by other means, such as testing general relativity
General relativity

General relativity or the general theory of relativity is the Geometry Theoretical physics of gravitation published by Albert Einstein in 1916....
 by observing Mercury
Mercury (planet)

Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 88 days. The orbit of Mercury has the highest Orbital eccentricity of all the Solar System planets, and it has the smallest axial tilt....
, and providing a refined value for the astronomical unit
Astronomical unit

An astronomical unit is a unit of length based on the mean distance from the Earth to the Sun. The precise value of the AU is currently accepted as 149,597,870,691 Plus-minus sign 6 metres ....
. Radar images provide information about the shapes and surface properties of solid bodies, which cannot be obtained by other ground-based techniques.

The extremely accurate astrometry
Astrometry

Astrometry is the branch of astronomy that relates to precise measurements and explanations of the positions and movements of stars and other celestial bodies....
 provided by radar is critical in long-term predictions of asteroid-Earth impacts, as illustrated by the object 99942 Apophis
99942 Apophis

99942 Apophis is a near-Earth asteroid that caused a brief period of concern in December 2004 because initial observations indicated a significant probability that it would strike the Earth in 2029....
. In particular, optical observations measure very accurately where an object appears on the sky, but cannot measure the distance accurately at all. Radar, on the other hand, directly measures the distance to the object (and how fast it is changing). The combination of optical and radar observations normally allows the prediction of orbits at least decades, and sometimes centuries, into the future.

Advantages


  • Control of attributes of the signal [i.e., the waveform's time/frequency modulation and polarization]
  • Resolve objects spatially;
  • Delay-Doppler measurement precision;
  • Optically opaque penetration;
  • Sensitive to high concentrations of metal or ice.


Disadvantages

  • Signal strength drops off very steeply with distance to the target.
  • Must have a relatively good ephemeris
    Ephemeris

    An ephemeris is a table of values that gives the positions of astronomical objects in the sky at a given time or times. Different kinds are used for astronomy and astrology....
     of the target before observing it.


Planetary


The following are a list of planetary bodies that have been observed by this means:
Mars
MARS

In cryptography, MARS is a block cipher that was IBM's submission to the Advanced Encryption Standard process. MARS was selected as an AES finalist in August 1999, after the AES2 conference in March 1999, where it was voted as the fifth and last finalist algorithm....
 - Mapping of surface roughness from Arecibo Observatory
Arecibo Observatory

The Arecibo Observatory is a very sensitive radio telescope located approximately south-southwest from the city of Arecibo, Puerto Rico in Puerto Rico....
. The Mars Express
Mars Express

Mars Express is a space exploration mission being conducted by the European Space Agency . The Mars Express mission is exploring the planet Mars , and is the first planetary mission attempted by the agency....
 mission carries a ground-penetrating radar.
Mercury
Mercury (planet)

Mercury is the innermost and smallest planet in the Solar System, orbiting the Sun once every 88 days. The orbit of Mercury has the highest Orbital eccentricity of all the Solar System planets, and it has the smallest axial tilt....
 - Improved value for the distance from the earth observed (GR
General relativity

General relativity or the general theory of relativity is the Geometry Theoretical physics of gravitation published by Albert Einstein in 1916....
 test). Rotational period, libration
Libration

In astronomy libration refers to the various orbital conditions which make it possible to see more than 50% of the moon's surface over time, even though the front of the Moon is tidal locking to always face towards Earth....
, surface mapping, esp. of polar regions.
Venus
Venus

Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus , the Roman mythology goddess of love....
 - first radar detection in 1960. Rotation period, gross surface properties. The Magellan
Magellan probe

The Magellan spacecraft was a space probe sent to the planet Venus, the first unmanned spacecraft to be launched by NASA since its successful Voyager 1 spacecraft to Jupiter and Saturn in 1977....
 mission mapped the entire planet using a radar altimeter
Radar altimeter

A radar altimeter, radio altimeter, low range radio altimeter or simply RA measures altitude above the terrain presently beneath an aircraft or spacecraft....
.
Moon
Moon

The Moon is Earth's only natural satellite and the List of natural satellites by diameter satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is km, about thirty times the diameter of the Earth....
 - first detection in 1945 - Surface roughness, mapping of shadowed regions near the poles.
Jupiter
Jupiter

Jupiter is the fifth planet from the Sun and the Solar system by size planet within the Solar System. It is two and a half times as massive as all of the other planets in our Solar System combined....
 System - Galilean satellites
Saturn
Saturn

Saturn is the sixth planet from the Sun and the second largest planet in the Solar System, after Jupiter. Saturn, along with Jupiter, Uranus and Neptune, is classified as a gas giant....
 System - Rings and Titan from Arecibo Observatory
Arecibo Observatory

The Arecibo Observatory is a very sensitive radio telescope located approximately south-southwest from the city of Arecibo, Puerto Rico in Puerto Rico....
, mapping of Titan's surface and observations of other moons from the Cassini
Cassini-Huygens

Cassini?Huygens is a joint NASA/European Space Agency robotic spacecraft mission currently studying the planet Saturn and Saturn's natural satellites....
 spacecraft.
Earth
Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
 - numerous airborne and spacecraft radars have mapped the entire planet, for various purposes. One example is the Shuttle Radar Topography Mission
Shuttle Radar Topography Mission

The Shuttle Radar Topography Mission is an international research effort that obtained digital elevation models on a near-global scale from 56 ?S to 60 ?N, to generate the most complete high-resolution digital topographic database of Earth to date....
, which mapped the entire Earth at 30 m resolution.

Asteroid
Asteroid

Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, smaller than planets but larger than meteoroids....
s and comet
Comet

A comet is a Small Solar System body that orbits the Sun and, when close enough to the Sun, exhibits a visible coma or a tail?both primarily from the effects of solar radiation upon the Comet nucleus....
s


Radar provides the ability to study shape, size and spin state of asteroids and comets from the ground. Radar imaging has produced images with up to 7.5-m resolution. With sufficient data, the size, shape, spin and radar albedo of the target asteroids can be extracted.

Only a few comets have been studied by radar, including 73P/Schwassmann-Wachmann
73P/Schwassmann-Wachmann

73P/Schwassmann-Wachmann, also known as Schwassmann-Wachmann 3, is a periodic comet in our solar system which is in the process of disintegrating....
. There have been radar observations of more than 220 Near-Earth asteroids and over 100 Main belt asteroid
Asteroid belt

The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets....
s.

See also


  • Arecibo Observatory
    Arecibo Observatory

    The Arecibo Observatory is a very sensitive radio telescope located approximately south-southwest from the city of Arecibo, Puerto Rico in Puerto Rico....
  • Deep Space Network
    Deep Space Network

    The Deep Space Network, or DSN, is an international Wiktionary:network of communication facilities that supports interplanetary spacecraft missions, and radio astronomy and radar astronomy observations for the exploration of the solar system and the universe....
  • Radar
    Radar

    Radar is a system that uses electromagnetic radiation waves to identify the range, altitude, direction, or speed of both moving and fixed objects such as aircraft, ships, motor vehicles, weather formations, and terrain....
  • Radio astronomy
    Radio astronomy

    Radio astronomy is a subfield of astronomy that studies Astronomical object at radio frequency. The initial detection of radio waves from an astronomical object was made in the 1930s, but subsequent advances have identified a number of different sources of radio emission....


External links