ROAA – Antenna Array for Measuring the Atmosphere

Fraunhofer IIS researchers developed a special antenna array as part of the ESA's (European Space Agendy) ROAA (Radio Occultation Antenna Array) project. The challenge involved finding a way to precisely measure the earth's atmosphere from space. One approach is through radio occultation, a process that uses radio signals to measure atmospheric properties such as pressure, temperature and water vapor content.

Thanks to its unique geometry, ROAA is capable of receiving satellite (GPS and Galileo) signals. The antenna array developed by Fraunhofer IIS boasts optimal directional properties, superior impedance matching and a compact, lightweight design.

Technical description

Miniaturization technology

The ROAA was built on the foundation of the Fraunhofer IIS GNSS-Antenna. The array consists of eight impedance-matched antenna elements.

High performance

Thanks to sophisticated miniaturization technology, the ROAA concept utilizes a complex energy supply network designed by Fraunhofer IIS to power the wideband radiators.

Technical data

  • Frequency range: L5/E5a (1156,45 MHz – 1196,45 MHz) and L1/E1bc (1571,42 MHz – 1579,42 MHz)
  • Polarization: right hand circular
  • In-band VSWR: < 1.1:1
  • Cross-polarization suppression: > 15 dB
  • Co-elevation angle of the main lobe: 27.6°
  • Group delay: < 0.33 ns per band
  • Phase center stability: < 2.5 mm per band
  • Compact power supply network thanks to special miniaturization technology
  • Two-layer construction

Atmosphere measurements

Drawing on the array of the satellites and spacecrafts at the time of measurement
© Fraunhofer IIS/Hans Adel
Array of the spacecrafts at the time of measurement (t1 and t2)

The ROAA was developed in order to measure the earth's atmosphere for the radio occultation experiment. Radio occultation exploits the planetary eclipse phenomenon.

The method involves two satellites in orbit around a planet. The satellite operating in the higher orbit transmits radio signals that are received by the second satellite, which then measures the phase, amplitude and polarization until it disappears behind the planet. The measurements are used to determine atmospheric properties such as pressure and temperature.


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Feasibility analyses

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Fraunhofer IIS – your development partner

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