The Ultra-Fine resolution mode, available on RADARSAT-2, acquires images at a spatial resolution of three metres. In this mode, the radar operates with the highest sampling rate, therefore the ground coverage is limited (10 to 30 km) to keep the acquisition within the recording limits. The Ultra-Fine imaging mode provides the one of the best resolution available commercially with a spaceborne SAR system. This better detect targets that are closely spaced and provide enhanced definition of other targets, thereby reducing ambiguities and increasing confidence in the data.
RADARSAT-1 provided horizontal-transmit and horizontal-receive (HH) data only. RADARSAT-2 can transmit horizontal (H) and vertical (V) polarizations and, depending on the selected mode, the sensor receives either H or V signals or both of the signals simultaneously. Therefore, in addition to providing complete RADARSAT-1 continuity, RADARSAT-2 generates products with VV polarization, cross-polarization (HV or VH), dual-polarization (HH+HV or VV+VH) or quad-polarization (HH+VV+HV+VH) over a range of spatial resolutions. This allows the end-user to select the combination that is best for the specific application.
Each scattering element (HH, VV, HV and VH) has varying sensitivities to different surface characteristics and properties, helping to improve the discrimination between features. Moreover, polarimetric data can be used to characterize the polarimetric signature of various surface features, which is very useful in the study of scattering mechanisms and in resolving ambiguities about the observed area.
RADARSAT-1 has wide area coverage with its large accessibility swath. However, the revisit time for some latitudes can be a limiting factor in some applications. Left- and right-looking modes on RADARSAT-2 reduce the revisit time by one half and the accessibility swath is doubled. In effect, the market for SAR images expands as applications that were not previously feasible will be given an opportunity to develop. Moreover, in emergency situations, the choice of beam mode and position can be set to ensure the greatest repeat coverage of the region of interest. Nominally, 10 minutes are required to switch from one side to the other. The flexibility of RADARSAT-2 makes it a powerful tool to support world mapping and disaster management activities.
Fine Beam modes are intended for applications which require higher spatial resolution and lower swath coverage. Fine Resolution Beams cover the incidence angle range from 30° to 50°. This imaging mode is available in co-polarization, cross-polarization, dual-polarization and quad-polarization.
In addition, several new Fine Resolution products is available on RADARSAT-2, and the list of enhanced imaging modes follows.
The Multi-Look Fine Resolution Beam mode is the four-look version of the Fine Resolution mode, therefore providing the same spatial resolution with improved radiometric resolution. The four looks are made possible by the higher sampling rate of the RADARSAT-2 SAR. The Multi-Look Fine imaging mode is available in selective single polarization (HH or VV).
Ultra-Fine Beam modes of three-metre resolution is intended for applications which require very high spatial resolution. The Ultra-Fine Beam imaging mode is available in selective single polarization (HH or VV)
Standard Beams allow imaging over a wide range of incidence angles acquired in seven different modes referred to as S1 to S7. The incidence angles range from 20° at the inner edge of S1, to 49° at the outer edge of S7. Experience with RADARSAT-1 has demonstrated that the Standard Beam Mode generates image quality characteristics which provide a good compromise between spatial resolution, radiometric resolution and image coverage. On RADARSAT-2 this imaging mode is available in copolarization, cross-polarization, dual-polarization and quad-polarization.
An Extended Low Incidence Beam will cover the incidence angle range from 10° to 23° with a swath coverage of 170 km. At these incidence angles, the antenna operates beyond its optimum range, therefore some minor degradation of the image can be expected. The spatial resolution is the same as Standard Beams. This imaging mode is available in copolarization, cross-polarization and dual-polarization.
The incidence angle range beyond 49° is covered with the High Incidence Beams up to 60°. As with the Low Incidence Beams, minor degradation of the image can be expected due the operation of the antenna outside its optimal range. The spatial resolution is the same as Standard Beams. This imaging mode is available in co-polarization, cross-polarization and dual-polarization.
Wide Swath Beams allow the coverage of a larger region than the Standard Beam at the expense of a slightly coarser spatial resolution. Three Wide Swath Beams cover a range on incidence angles from 20° to 45°. This imaging mode is available in copolarization, cross-polarization and dual-polarization.
ScanSAR imagery is generated with a combination of single beams covering adjoining swaths. This provides the largest swath coverage available in RADARSAT-2 products. However, the increased coverage is obtained at the expense of spatial resolution. ScanSAR imaging mode is available in copolarization, cross-polarization and dual-polarization.