The International Space Station. Copyright: ESA.
The European Space Agency (ESA) has proposed a new concept that involves mounting an instrument on the International Space Station (ISS) and interpreting signals from navigation satellites reflected off ocean surfaces to provide measurements of sea-surface height, ocean currents and waves.
In 2011 ESA called for proposals to explore how the Space Station could be used to make scientifically valid observations of Earth. After reviewing and assessing numerous proposals, the decision came to further develop the GEROS-ISS mission concept. GEROS-ISS stands for Global Navigation Satellite Systems (GNSS) reflectometry, radio occultation and scatterometry on board the ISS.
The mission involves installing an instrument with an antenna on the Space Station that would capture signals directly from navigation satellites as well as signals that are reflected or scattered from Earth. This process could be used to calculate the height of the sea surface, and to measure waves – or ‘roughness’ – that can then be used to work out the speed of surface winds.
The mission will be supported by measurements from altimeter satellites such as CryoSat and Sentinel-3, and satellites carrying wind scatterometers such as MetOp.
It is the first concept to assess the potential of spaceborne GNSS reflectometry to determine and map ocean height at scales of 10–100 km or longer in less than four days. Current satellite altimeters, in comparison, offer global maps at scales of around 80 km, which are produced from multiple datasets every 10 days.
In addition, GEROS-ISS can be used to generate vertical profiles of atmospheric humidity, pressure and temperature using radio occultation to analyse signal refraction.
