The Goldstone Solar System Radar (GSSR) is a large

radar Radar is a detection system that uses radio waves to determine the distance (''ranging''), angle, and radial velocity of objects relative to the site. It can be used to detect aircraft, Marine radar, ships, spacecraft, guided missiles, motor v ...

system used for investigating objects in the

Solar System The Solar System Capitalization of the name varies. The International Astronomical Union, the authoritative body regarding astronomical nomenclature, specifies capitalizing the names of all individual astronomical objects but uses mixed "Solar ...

. Located in the desert near

Barstow, California Barstow is a city in San Bernardino County, California, in the Mojave Desert of Southern California. Located in the Inland Empire region of California, the population was 25,415 at the 2020 census. Barstow is an important crossroads for the In ...

, it comprises a 500-kW X-band (8500 MHz) transmitter and a low-noise receiver on the 70-m DSS 14 antenna at the

Goldstone Deep Space Communications Complex The Goldstone Deep Space Communications Complex (GDSCC), commonly called the Goldstone Observatory, is a satellite ground station located in Fort Irwin in the U.S. state of California. Operated by NASA's Jet Propulsion Laboratory (JPL), its m ...

. It has been used to investigate Mercury,

Venus Venus is the second planet from the Sun. It is sometimes called Earth's "sister" or "twin" planet as it is almost as large and has a similar composition. As an interior planet to Earth, Venus (like Mercury) appears in Earth's sky never f ...

Mars Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, only being larger than Mercury. In the English language, Mars is named for the Roman god of war. Mars is a terrestrial planet with a thin at ...

, the

asteroid An asteroid is a minor planet of the inner Solar System. Sizes and shapes of asteroids vary significantly, ranging from 1-meter rocks to a dwarf planet almost 1000 km in diameter; they are rocky, metallic or icy bodies with no atmosphere. ...

s, and moons of

Jupiter Jupiter is the fifth planet from the Sun and the largest in the Solar System. It is a gas giant with a mass more than two and a half times that of all the other planets in the Solar System combined, but slightly less than one-thousand ...

and

Saturn Saturn is the sixth planet from the Sun and the second-largest in the Solar System, after Jupiter. It is a gas giant with an average radius of about nine and a half times that of Earth. It has only one-eighth the average density of Earth; h ...

. The most comparable facility was the radar at

Arecibo Observatory The Arecibo Observatory, also known as the National Astronomy and Ionosphere Center (NAIC) and formerly known as the Arecibo Ionosphere Observatory, is an observatory in Barrio Esperanza, Arecibo, Puerto Rico owned by the US National Science ...

, until that facility collapsed. GSSR now stands alone.

Planetary observations

GSSR can work in two different modes. In the monostatic radar mode, GSSR both transmits and receives. In bistatic mode, GSSR transmits and other radio astronomy facilities receive. Although more difficult to schedule, this offers two advantages - the transmitter does not need to turn off to allow the receiver to listen, and it allows the use of

interferometry Interferometry is a technique which uses the '' interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber o ...

to extract more information from the reflected signal. Bodies that have been investigated using GSSR include: *Mercury: In particular, by watching specific reflected features of Mercury sweep across the Earth's surface (using spatially separated receivers), GSSR enables the pole position to be computed quite accurately. The measured

libration In lunar astronomy, libration is the wagging or wavering of the Moon perceived by Earth-bound observers and caused by changes in their perspective. It permits an observer to see slightly different hemispheres of the surface at different tim ...

s show Mercury has a liquid core. *Venus *Mars: GSSR was used extensively to characterize sites for Mars landers. *Asteroids: Small asteroids appear only as unresolved points of light in ground-based optical telescopes. Radar, however, can image near-Earth asteroids and comets with a resolution of several meters. For example, the asteroid 4179 Toutatis was imaged in 1992, 1996, 2000, 2004, 2008, and 2012. Although spacecraft such as

Dawn Dawn is the time that marks the beginning of twilight before sunrise. It is recognized by the appearance of indirect sunlight being scattered in Earth's atmosphere, when the centre of the Sun's disc has reached 18° below the observer's ...

can image particular asteroids in much finer detail, radar astronomy can investigate many more asteroids of different characteristics. For example, all existing images of binary asteroids were obtained through radar astronomy. *Moons of Jupiter *Rings and moons of Saturn Toutatis.jpg, 4179 Toutatis in 1996 Asteroid 1999 JM8.gif, (53319) 1999 JM8 in 1999 2005YU55-20111107.jpg, (308635) 2005 YU55 in 2011

Other scientific uses

*Recovery of the

Solar and Heliospheric Observatory The Solar and Heliospheric Observatory (SOHO) is a European Space Agency (ESA) spacecraft built by a European industrial consortium led by Matra Marconi Space (now Airbus Defence and Space) that was launched on a Lockheed Martin Atlas IIAS lau ...

after loss of attitude control. *Investigation of orbital debris around Earth.

References

{{Portal bar, California, Astronomy, Stars, Spaceflight, Outer space, Solar System, Education, Science Deep Space Network Space radars Mojave Desert Radio telescopes Astronomical observatories in California