TerraSAR-X is an

imaging radar Imaging radar is an application of radar which is used to create two-dimensional images, typically of landscapes. Imaging radar provides its light to illuminate an area on the ground and take a picture at radio wavelengths. It uses an antenna and ...

Earth observation satellite An Earth observation satellite or Earth remote sensing satellite is a satellite used or designed for Earth observation (EO) from orbit, including spy satellites and similar ones intended for non-military uses such as environmental monitoring, me ...

, a joint venture being carried out under a public-private-partnership between the

German Aerospace Center The German Aerospace Center (, abbreviated DLR, literally ''German Center for Air- and Space-flight'') is the national center for aerospace, energy and transportation research of Germany, founded in 1969. It is headquartered in Cologne with 3 ...

(DLR) and EADS Astrium. The exclusive commercial exploitation rights are held by the geo-information service provider

Astrium Astrium was a European aerospace company and subsidiary of the European Aeronautic Defence and Space Company (EADS), headquartered in Paris. It designed, developed and manufactured civil and military space systems and provided related services ...

. TerraSAR-X was launched on 15 June 2007 and has been in operational service since January 2008. With its twin satellite

TanDEM-X TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurement) is a German twin satellite mission using interferometric synthetic aperture radar (InSAR). It is developed in a public-private partnership between the German Aerospace centre (DLR In ...

, launched 21 June 2010, TerraSAR-X acquires the data basis for the WorldDEM, the worldwide and homogeneous DEM available from 2014.

Satellite and mission

Using a

phased array In antenna (radio), antenna theory, a phased array usually means an electronically scanned array, a computer-controlled Antenna array, array of antennas which creates a radio beam, beam of radio waves that can be electronically steered to point ...

synthetic aperture radar Synthetic-aperture radar (SAR) is a form of radar that is used to create two-dimensional images or 3D reconstruction, three-dimensional reconstructions of objects, such as landscapes. SAR uses the motion of the radar antenna over a target regi ...

(SAR) antenna (

X-band The X band is the designation for a band of frequency, 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 set at approximately 7.0� ...

wavelength 31mm, frequency 9.65 GHz), TerraSAR-X provides radar images of the entire planet from an Earth

polar orbit A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It has an inclination of abo ...

of 514km altitude. This is selected so that the satellite follows a

Sun-synchronous orbit A Sun-synchronous orbit (SSO), also called a heliosynchronous orbit, is a nearly polar orbit around a planet, in which the satellite passes over any given point of the planet's surface at the same local mean solar time. More technically, it is ...

. This specific orbit means that the satellite moves along the day–night boundary of the Earth and allows it to present the same face to the Sun, thus providing the best solar incidence angles to its solar cells for power. TerraSAR-X was designed to carry out its task for five years, independent of weather conditions and illumination, and provides radar images with a resolution of up to 1 m.

TerraSAR-X imaging modes

TerraSAR-X acquires radar data in the following three main imaging modes: * SpotLight: up to 1 m resolution, scene size 10 km (width) × 5 km (length); * StripMap: up to 3 m resolution, scene size 30 km (width) × 50 km (length); * ScanSAR: up to 16 m resolution, scene size 100 km (width) × 150 km (length); In addition, the design of TerraSAR-X's SAR antenna allows a variety of polarimetric combinations: single or dual polarization, or full polarimetric data takes. Depending on the desired application, one of four different processing levels is selected: *Single Look Slant Range Complex (SSC) *Multi Look Ground Range Detected (MGD) *Geocoded Ellipsoid Corrected (GEC) *Enhanced Ellipsoid Corrected (EEC)

TanDEM-X and WorldDEM Akida

TanDEM-X (TerraSAR-X add-on for Digital Elevation Measurements) is a second, similar spacecraft launched on 21 June 2010 from

Baikonur Cosmodrome The Baikonur Cosmodrome is a spaceport operated by Russia within Kazakhstan. Located in the Kazakh city of Baikonur, it is the largest operational space launch facility in terms of area. All Russian Human spaceflight, crewed spaceflights are l ...

in Kazakhstan. Since October 2010, TerraSAR-X and TanDEM-X have orbited in close formation at distances of a few hundred metres and record data synchronously. This twin satellite constellation will allow the generation of WorldDEM, the global digital elevation models (DEMs). With higher accuracy, coverage and quality – WorldDEM is a consistent DEM of the Earth's land surface is envisaged to be acquired and generated within three years after launch. Available from 2014, WorldDEM is to feature a vertical accuracy of 2 m (relative) and 10 m (absolute), within a horizontal raster of approximately 12×12 square meters, slightly varying depending on the geographic latitude.

Satellite radar

Radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

stands for ''Radio Detection and Ranging'' and traditionally contains: * Range finding (EDM) by means of the time a reflected signal needs to return; * Direction measurement via the adjustment of the antenna, and; * Other analysis such as SAR, polarization and Interferometry. Satellite radar systems came into operation over fifteen years after the adoption of optical camera systems. The resolution is lower than optical imaging, but

radar Radar is a system that uses radio waves to determine the distance ('' ranging''), direction ( azimuth and elevation angles), and radial velocity of objects relative to the site. It is a radiodetermination method used to detect and track ...

can gather information at any time of the day or night and independent of

cloud cover Cloud cover (also known as cloudiness, cloudage, or cloud amount) refers to the fraction of the sky obscured by clouds on average when observed from a particular location. Okta is the usual unit for measurement of the cloud cover. The cloud c ...

. Early radar satellite techniques were altimetry (measuring height over sea level), NASA's SEASAT (launched in 1978), study of waves/wind or soil data. The military has used radar since the late 1930s and radar satellites at least since 1978.

Novel design features of TerraSAR X

TerraSAR X introduced some technical-industrial novelties. One of these innovations is a kind of zoom shot, with the resolution and scanning field vice versa changeable in a 1:10 relationship, either a larger area to grasp or a small area with the highest possible resolution. Furthermore, the antenna can be aligned by electronics within an angle range so that the point of view is adjustable. Earlier radar satellites could radiate the antenna only in one direction.

Scanning and trajectory

With the adjustable angle

sensor – along with other course refinements (

precession Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In o ...

by the earth flattening) – any place on earth can be observed preferentially within 1 to 3 days. For a specific point on the Earth's equator, TerraSAR X has a revisit cycle of 11 days. The revisit time decreases towards the poles, e.g. Northern Europe has a revisit time of typically 3–4 days.

Ground segment

The ground operating mechanism and controls for the TerraSAR X is developed by the DLR in Oberpfaffenhofen. It consists of Mission Operating Equipment, the Payload

ground segment A ground segment consists of all the ground-based elements of a spaceflight, space system used by operators and support personnel, as opposed to the Satellite space segment, space segment and user segment. The ground segment enables management of ...

and the Instrument Operation and Calibration Segment. At the base of the ground segment lies the German Space Operation Center (GSOC), the German Remote Sensing Datum Center (DFD) as well as Institutes for Methodology of Remote Sensing (MF) and the Institute for High-Frequency Engineering and Radar Systems (HR) which are all part of the DLR.

Applications

Applications of the high-resolution TerraSAR-X radar imagery include: *Topographic mapping: 2D and 3D, in scales down to 1:25,000, map updates *Surface movement: Based on time series acquired by TerraSAR-X over the same area surface displacements caused by subsurface mining, oil-/gas extraction, infrastructure construction, excavations, or underground engineering can be visualised. *Change detection: for the monitoring of large-scale construction projects, infrastructure networks, monitoring and documentation of changes and developments *Land cover and land use mapping: accurate and up-to-date land cover / land use informations, also from places, where it is difficult to get informations with using other technologies because of permanent cloud cover *Defence and security applications: Applications include effective mission planning, the quick assessment of natural or manmade disasters or border control through detection of paths (changes), fences and moving objects *Rapid emergency response: due to its rapid revisit time TerraSAR-X is a reliable source of information in case of natural or man-made disasters (e.g.

earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...

flood A flood is an overflow of water (list of non-water floods, or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are of significant con ...

s, military conflicts etc.) providing reliable information for disaster management and response allowing the recognition and assessment of damages to populated areas and traffic infrastructure, the identification of focus areas, and an efficient coordination of rescue actions. *Environmental applications: e.g. forest monitoring, flood monitoring, water quality applications *Further applications currently under evaluation: traffic monitoring, maritime applications, vegetation monitoring

Scientific use of TerraSAR-X data

The scientific use of the TerraSAR-X data will be coordinated through the TerraSAR-X Science Service System by the DLR.TerraSAR-X Science Service System
/ref> The new-quality data records, as provided by TerraSAR-X, will offer a vast amount of new research incentives, for instance in ecology, geology,

hydrology Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and drainage basin sustainability. A practitioner of hydrology is called a hydro ...

and

oceanography Oceanography (), also known as oceanology, sea science, ocean science, and marine science, is the scientific study of the ocean, including its physics, chemistry, biology, and geology. It is an Earth science, which covers a wide range of to ...

. The smallest movements of the Earth's surface (

plate tectonics Plate tectonics (, ) is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago. The model builds on the concept of , an idea developed durin ...

volcanism Volcanism, vulcanism, volcanicity, or volcanic activity is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon. It is caused by the presence of a he ...

, earthquake) are further scientific fields of application.

Commercial use of TerraSAR-X data

To ensure the commercial success of the mission, EADS Astrium founded its 100% subsidiary Infoterra in 2001; the company being responsible for establishing a commercial market for TerraSAR-X data as well as TerraSAR-X-based geo-information products and services.

References

External links

Astrium GeoTerraSAR-X
at DLR website.
TanDEM-X
at DLR website.
Science Home
at DLR website

at Astrium website {{DEFAULTSORT:Terrasar-X Satellites of Germany Spacecraft launched by Dnepr rockets Spacecraft launched in 2007 Synthetic aperture radar satellites Twin satellites