SAR

Principles

Small satellites with synthetic aperture radar (SAR) payloads are a growing trend in the satellite industry. The long pathlength traveled by the satellite in orbit acts as a large virtual antenna enabling meter and even sub-meter resolution imaging. Spaceborne SAR is an active system that yields high-resolution images of Earth's surface. SAR takes advantage of properties of EM waves to penetrate clouds, foliage and even upper layers of Earth's surface.The technique is based on constructive coherent processing of the EM wave echoes reflected back from Earth's surface.

Features

EOS SAR satellites will operate in Stripmap, Spotlight, and ScanSAR modes that will support wide range of applications. Interferometric operation is also supported.

The satellites are designed to achieve high operational efficiency and allow for rapid deployment of single and dual-band SAR constellations. Dual-band operation ( X- and S-band) increases versatility for all weather conditions and improves object-ground contrast. Special configuration of the radar front end allows for imaging of selected areas in both bands in a single orbit.

EOS is building a SAR satellite payload suitable for constellations enabling high revisit rates.

A constellation of 12 satellites will enable 2–3 hours revisit time for a given area.

Formation flying with optical satellites is under development for more efficient utilization of satellite resources. In addition, the combination of SAR and optical images enriches the informational content of satellite products.

Modes of operation

  • Stripmap

    Main imaging mode, provides good resolution and large coverage

  • Spotlight

    Provides best resolution for selected area

  • Interferometry

    Enables recording time-series data, change detection, ground subsidence, etc.

Deployed
Stowed

Light-weight deployable reflector antenna

Benefits of reflector antenna

  • less complex wrt phased array
  • polarization invariant
  • multifrequency operation
  • larger aperture => better SNR or lower Tx power
  • low weight
  • simpler signal processing (fewer signals to process) => power savings
  • long lifetime

SAR payload

Technical characteristics

  • light-weight deployable reflector antenna
  • multibeam operation enabling wide swath
  • high resolution (as low as 25 cm)
  • single or dual-band operation (X- and/or S-bands)
  • Linear (X-band), Quad-pol (S-band)
  • 50 kg SAR payload weight
  • Stripmap, Spotlight and ScanSAR modes

Dual band performance

X- and S-band

  • dual band operation allows for any weather imaging
  • diversifies image acquisition
  • special antenna feed design allows dual band imaging of selected areas in a single orbit
  • provides better image contrast

X-Band

  • high resolution imaging
  • target identification
  • object classification
  • DEM and topography

S-Band

  • higher penetration capabilities (foliage, ground)
  • lower rain attenuation
  • soil moisture and crop classification
  • higher contrast for reflective objects

Vision for project stages

Parameter
Operating band
Resolution, m
Antenna type
Swath width, km
Polarization
Max imaging time per orbit, min
Modes
Bandwidth, MHz
Number of beams / feeds
Weight, kg
Launch year
1st satellite
X
1x1.5 / 0.5x0.25/ 2x3
Mesh reflector
25/25/50
Linear
20
Stripmap/ Spotlight/ ScanSAR
600
4
200
2023
2nd generation satellite
X S
1x1.5 / 0.25x0.25/ 2x3 1.5x1.5/1.5x0.5
Mesh reflector Mesh reflector
25/25/50 25/25
Dual polarization Full-polarimetric
10 10
Stripmap / Spotlight / ScanSAR Stripmap / Spotlight
1200 200
4 2
250
2024
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