Contributors: Megan Kanaga Creutzburg

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Canadian Space Agency http://www.asc-csa.gc.ca/eng/default.asp

RADARSAT-2 was launched in 2007 by the Canadian Space Agency following the launch of RADARSAT-1. It carries a Synthetic Aperture Radar (SAR) sensor, which is a powerful microwave instrument that can transmit and receive signals to obtain detailed images of the Earth.

SAR sensors are a form of active remote sensing where, instead of recording the amount of sunlight reflected from a surface or radiation emitted from a surface (e.g., thermal imaging), radar pulses are emitted from the sensor and then the reflected responses are recorded. Radar sensors operate in the microwave region of the electromagnetic spectrum. RADARSAT-1 and RADARSAT-2 operate in the C-band frequency range of the electromagnetic spectrum at a wavelength of 5.6 cm.

Radar is a ranging sensor - meaning that it detects the distance to objects by timing how long it takes for emitted pulses to return to the sensor (LIDAR operates on the same principle using pulses of a different wavelength). This information is converted to elevation by processing the radar signal. By examining other properties of the radar responses (e.g., the amount of the signal that is returned), other properties of the surface (and in some cases even sub-surface properties like sub-canopy or sub-soil information) can be determined. For example, areas with high vegetative cover scatter much of the radar signal and will show up darker in a radar image than those with lots of bare ground that reflect more of the radar signal. The microwaves emitted by a radar sensor can be directed to oscillate in one particular direction. This is known as polarization. Some surfaces, especially vegetation, can cause changes in the polarization of microwaves, and measuring the amount of the signal returned in horizontal versus vertical polarization can also provide information on the type of surface. The SAR sensor has the ability to emit or detect microwaves in any combination of horizontal or vertical polarizations. Also, because radar sensors emit their own radiation, they can function day or night and can often image through clouds or smoke, making them very versatile.

RADARSAT-2 offers all of the capabilities of RADARSAT-1 plus some additional features. RADARSAT-2 has selective single-polarization, selective dual-polarization, and quad-polarization, allowing the radar pulses to better detect target shape. It also carries sensors at ultra-fine spatial resolution (3 m), a selective look direction, and improved orbit control compared to RADARSAT-1.

• RADARSAT-1
• ENVISAT-ASAR

RADARSAT-2 emits microwaves in the C-band, at a wavelength of 5.6 cm. It also has a fully-polarimetric mode that can detect VV, HH, HV, and VH polarized data. V stands for vertical polarization and H stands for horizontal polarization, and the first letter refers to the polarization emitted by the antenna and the second letter refers to the polarization detected by the receiving antenna.

(source: RADARSAT-2: Innovation in Earth Observation http://www.radarsat2.info/about/rs2_overview_05.pdf)

RADARSAT-2 has the same orbit as RADARSAT-1. It circles the Earth 14 times a day and has an orbital period of 100.7 minutes. The same orbit path is repeated every 24 days, so the satellite can take the same image, with the same beam mode and beam position, every 24 days.

2008 to present.

RADARSAT-2 products can be purchased through the RADARSAT-2 website. See http://www.radarsat2.info/product/index.asp for products and pricing information.

RADARSAT-2 images are available in GeoTIFF format.

RADARSAT-2 data were not available until 2008, and thus there are few studies currently in the literature detailing its use. However, RADARSAT-2 data are expected to be used for many of the same applications as RADARSAT-1 but will produce higher quality data for most applications. Some examples include:

• Vegetation mapping
• Mapping elevation profiles
• Detecting soil moisture and texture
• Texture analysis
• Target detection

Processing of RADARSAT data will require remote sensing software and may require statistical/mathematical modeling software, depending on the application.

RADARSAT-2 image showing variation in contrast levels with different polarization modes (HH, VV or HV) and a composite image. In this example, HV polarization provides the best contrast for detecting the feature shown with the yellow arrows. Multiple polarization modes aid in target detection and other applications. (source: Radarsat-2: Innovation in Earth Observation, available at http://www.radarsat2.info/about/rs2_overview_05.pdf)

• RADARSAT-2 website http://www.RADARSAT2.info/
• NASA provides some general information on Imaging Radar at http://southport.jpl.nasa.gov/desc/imagingradarv3.html

• Jiao, X., H. McNairn, J. Shang, E. Pattey, J. Liu, and C. Champagne. 2009. The sensitivity of RADARSAT-2 quad-polarization SAR data to crop LAI. Proc. SPIE 7454: 74540O. doi:10.1117/12.825701.
• van der Sanden, J.J. 2004. Anticipated applications potential of RADARSAT-2 data. Canadian Journal of Remote Sensing 30: 369-379.
• van der Sanden, J.J. and S.J. Thomas. 2004. Applications Potential of RADARSAT-2: Supplement One. Natural Resources Canada. Available at http://www.RADARSAT2.info/sartrek/2005/jun/RSAT2_APPS_2004_PDF_Final.pdf