ASI - Agenzia Spaziale Italiana - Mission and Projects ASI - Agenzia Spaziale Italiana - Mission and Projects


Radio Occultation Sounder for Atmosphere

ROSA is a mission mainly dedicated to a better knowledge of the Climate Change. The mission takes its name from the name of the instrument ROSA (Radio Occultation Sounder for Atmosphere), that is the core of this program. The instrument uses the Radio Occultation technique and it is able to perform the vertical profile of atmospheric temperature, pressure and humidity as well as the profiles of the electron content in the ionosphere. ROSA can be considered as a very precise “global thermometer”.


The Radio Occultation technique is based on the effects of interactions between the electromagnetic signals, emitted by the navigation satellite, i.e. the GPS satellites, and the atmospheric layers crossed. An “occultation” occurs when a GPS satellite, rising or setting behind the Earth’s limb, is viewed by a LEO (Low Earth Orbit) satellite. The signal crossing the Earth’s atmosphere is refracted and deviated; this effect is function of the atmospheric physical parameters in the crossing point. Due to the relative motion between the LEO and the GPS satellites, the electromagnetic waves perform a sampling of always deeper and denser atmospheric layers, permitting in this way the vertical profiles of the physical characteristics of the atmosphere.


The ROSA instrument is able to measure the atmospheric vertical profiles with very high resolution (~200 m in the troposphere and ~1000 m in the stratosphere) and high thermal accuracy (<1K). For a global characterization of the atmosphere it is necessary to have in the space, at the same time, many of this kind of instruments. The ROSA mission is a “mission of opportunity”. The main steps of this mission are:

  • Development and manufacturing of the ROSA instrument
  • Installation of similar ROSA instrument on several Earth Observation Missions
  • Development of a G/S based on the ASI Multi Mission G/S
  • Development of advanced RO data processors.

ASI is in collaboration with other Space Agencies working in this field for an exchange of the Radio Occultation data. Up to now, ASI has accepted three flight opportunities for the ROSA instrument. ROSA will be embarked on the Indian satellite OCEANSAT-2 (launch date for the middle of 2008), on the Argentinean satellite Aquarius/SAC-D (launch date 2010) and on the Italian ASI satellite SABRINA (launch date 2011).