The Spaceborne Imaging Radar (SIR) – full name 'Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR)', is a

synthetic aperture radar Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or three-dimensional reconstructions of objects, such as landscapes. SAR uses the motion of the radar antenna over a target region to provide fine ...

which flew on two separate shuttle missions. Once from the

Space Shuttle Endeavour Space Shuttle ''Endeavour'' (Orbiter Vehicle Designation: OV-105) is a retired orbiter from NASA's Space Shuttle program and the fifth and final operational Shuttle built. It embarked on its first mission, STS-49, in May 1992 and its 25th and ...

in April 1994 on (

STS-59 STS-59 was a Space Shuttle program mission that took place in 1994. The launch was chronicled by the 1994 Discovery Channel special about the Space Shuttle program. Crew Mission highlights 9 April ''Endeavour'' began its sixth mission on ...

) and again in October 1994 on (

STS-68 STS-68 was a human spaceflight mission using that launched from Kennedy Space Center, Florida on 30 September 1994. Crew Launch Launch 30 September 1994 at 7:16:00.068 am EDT from Kennedy Space Center Launch Pad 39-A. The Launch windo ...

). The radar was run by NASA's Space Radar Laboratory. SIR utilizes 3 radar frequencies:

L band The L band is the Institute of Electrical and Electronics Engineers (IEEE) designation for the range of frequencies in the radio spectrum from 1 to 2 gigahertz (GHz). This is at the top end of the ultra high frequency (UHF) band, at the lower en ...

(24 cm

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

), C band (6 cm) and

X band The X band is the designation for a band of frequencies in the microwave radio region of the electromagnetic spectrum. In some cases, such as in communication engineering, the frequency range of the X band is rather indefinitely set at approxim ...

(3 cm), allowing for study of geology, hydrology, ecology and oceanography. Comparing radar images to data collected by teams of people on the ground as well as aircraft and ships using simultaneous measurements of vegetation, soil moisture, sea state, snow and weather conditions during each flight. The imaging radar was able to take images anytime regardless of clouds cover. The Radar-C system was built and operated by NASA's

Jet Propulsion Laboratory The Jet Propulsion Laboratory (JPL) is a federally funded research and development center and NASA field center in the City of La Cañada Flintridge, California, United States. Founded in the 1930s by Caltech researchers, JPL is owned by NASA an ...

(JPL). The mission was a joint work of NASA with the

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and

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space agencies. Each of the week long mission scanned about 50 million square kilometers of the Earth's surface, (19.3 million square miles). The SIR mission revealed hidden river channels in the

Sahara Desert , photo = Sahara real color.jpg , photo_caption = The Sahara taken by Apollo 17 astronauts, 1972 , map = , map_image = , location = , country = , country1 = , ...

indicating significant climate change in the past. SIR was also used for volcano research by keeping researchers a safe distance from hazardous and often inaccessible areas. The radar was also used to generate detailed three dimensional mappings of the Earth's surface. Radar also found temples in

Angkor Angkor ( km, អង្គរ , 'Capital city'), also known as Yasodharapura ( km, យសោធរបុរៈ; sa, यशोधरपुर),Headly, Robert K.; Chhor, Kylin; Lim, Lam Kheng; Kheang, Lim Hak; Chun, Chen. 1977. ''Cambodian-Engl ...

, and ancient segments of China's Great Wall.JPL, April 18, 1996, Space Radar Reveals Ancient Segments of China's Great Wall
/ref>

Specification

*Orbital altitude above earth = *The width of the imaged swath on the ground = *C-band beamwidth = 0.25 deg. × 5 deg. *L-band beamwidth = 1.1 deg. × 6 deg. *Scan angle range = ±23 deg. from boresight across narrow antenna direction only *Bandwidth = 10, 20 and 40 GHz *Pulse repetition rate = 1395–1736 pulses per second *Total science data = 50 hours per channel, per mission (two missions, total 100 hours) *Total instrument mass = *DC power consumption = 3000–9000 Watts *L-band data rate = 90 Mbit/s *C-band data rate = 90 Mbit/s *X-band data rate = 45 Mbit/s *L-band wavelength = 0.235 m *C-band Wavelength = 0.058 m *X-band wavelength = 0.031 m

References

{{Jet Propulsion Laboratory Spacecraft instruments 1994 in spaceflight Satellite meteorology Space synthetic aperture radar Satellite imaging sensors

Specification

See also

References