Beam Modes

RADARSAT-1 had seven beam modes that offered resolution from 10m to 100m at swath widths from 50 km to
500 km.

RADARSAT-1 Beam Mode

RADARSAT-1 Processing Levels


RADARSAT-1 data (including archive data) can be processed in a number of ways to deliver products with different characteristics, for different applications.

Beam Mode Signal Data Single Look Complex (SLC) Path Image (SGF) Path Image Plus (SGX) Map Image (SSG) Precision Map Image (SPG) Ortho-Image
Fine check
check
check
check
check check check
Standard check
check
check
check
check check check
Wide check
check
check
check
check check check
ScanSAR Narrow check
NA check
NA NA NA check
ScanSAR Wide check
NA check
NA NA NA check
Extended High check
check check check check check check
Extended Low check check check check
check check check
More information is available on RADARSAT image processing.

RADARSAT-1 Single Beam Operational Modes


In Single Mode operation, the beam elevation and profile were maintained constant throughout the data collection period. A beam is characterized by its:

  • Nominal incidence angle
  • Nominal swath width
  • Nominal spatial resolution
 
​Fine Beam
The Fine mode is intended for applications which require the best spatial resolution available from the RADARSAT system. The azimuth resolution is 8.4 m, with range resolution 9.1 m to 7.8 m from F1 to F5. Since the radar operates with a higher sampling rate in this mode than in any of the other beam modes, the ground swath coverage has to be reduced to a nominal 50 km in order to keep the downlink signal within its allocated bandwidth. Originally, five Fine beam positions, F1 to F5, were available to cover the far range of the swath, the incidence angle range from 37 to 47 degrees. By modifying timing parameters, 10 new positions have been added with offset ground coverage. Each original Fine beam position can either be shifted closer to or further away from Nadir. The resulting positions are denoted by either an N (Near) or F (Far). For example, F1 is now complemented by F1N and F1F.
 

Standard Beam

Standard mode operates with any one of seven beam positions, referred to as S1 to S7. The nominal incidence angle range covered by the full set of Standard beam is from 20 degrees (at the inner edge of S1) to 49 degrees (at the outer edge of S7). The spatial resolution is 27 m in azimuth and 26 m (near) to 20 m (far) in range direction. Each individual beam covers a minimum ground swath of 100 km within the total 500 km accessibility swath of the full set of Standard beams. The nominal spatial resolution in the range direction is 26 m for S1 at near range to 20 m for S7 at far range. The azimuth resolution is the same, 27 m, for all beam positions. Standard modes allow imaging over a wide range of incidence angles with optimum system image quality.
 

Wide Beam

Wide beams are similar to the Standard beams except that the swath width achieved by this beam is 150 km rather than 100 km. As a result, only three Wide beams, W1, W2 and W3 are necessary to provide coverage of almost all of the 500 km swath range. They provide the comparable resolution as the standard beam mode although the increased ground swath coverage is obtained at the expense of a slight reduction in overall image quality. W1 and W2 are available for single beam products. W3 is used as one of the beams to form a SWA product but not recommended for a individual image because it contains a nadir ambiguity (narrow white vertical strip in the image).
 

Extended High Beam

Six Extended High beam positions, EH1 to EH6, are available for collection of data in the 49 to 60 degree incidence angle range. Since this mode operates outside the optimum scan angle range of the SAR antenna, some minor degradation of image quality can be expected when compared with the Standard mode. Swath widths are restricted to a nominal 80 km for the inner three positions, and 70 km for the outer three positions. The operational beam positions on the satellite are EH3, EH4 and EH6, which can cover the complete Extended High beam swath.
 

Extended Low Beam

A single Extended Low beam position, EL1, is provided for imaging in the incidence angle range 10 to 23 degrees with a nominal ground swath coverage of 170 km. As with the Extended High mode, some minor degradation of image quality can be expected due to operation of the antenna beyond its optimum elevation angle range.
RADARSAT-1 ScanSAR Operational Modes

There were two ScanSAR modes on RADARSAT-1: ScanSAR Narrow and ScanSAR Wide.

In ScanSAR operations, two, three or four single beams were used during data collection. Each beam was selected sequentially so that data was collected from a wider swath than was possible with a single beam. The beam switching rates were chosen to ensure at least one "look" at the Earth's surface for each beam within the along track illumination time or dwell time of the antenna beam. In practice, the radar beam switching was adjusted to provide two looks per beam.

The beam multiplexing inherent in ScanSAR operation reduced the effective sampling rate within each of the component beams. As a result, the increased swath coverage was obtained at the expense of spatial resolution.

For technical details on the RADARSAT-1 beam modes, refer to the Product Definition.