First release of the PAZ polarimetric radio occultation data for precipitation characterization
The GPS polarimetric data obtained aboard the PAZ satellite have started its dissemination 

The data are suitable to study atmospheric precipitation from a different perspective

The 1st “ROHP-PAZ Users Workshop” will be held online with more than 50 participants from three continents

A team of researchers from the Institute for Institute of Space Studies of Catalonia (IEEC  — Institut d’Estudis Espacials de Catalunya) at the Institute of Space Science (ICE, CSIC) has released the data obtained by the experiment with GPS signals on board the Spanish Earth observation satellite PAZ, launched in February 2018. These data sets are the only GPS signals acquired at two polarizations from a spaceborne satellite, a new technique called polarimetric radio occultations (PRO). The researchers had previously confirmed that the recorded polarimetric signals are sensitive to heavy rainfall and other hydrometeors, a hypothesis tested in the GPS experiment aboard PAZ (read more about it here). 

The Radio Occultation is a technique to observe the atmosphere of a planet using two elements: one that transmits radio or microwave signals (in this case, the GPS satellites) and another element that receives them (here, a device installed aboard the PAZ satellite). The peculiarity of this technique is that, if the transistor and receiver elements are joined in a straight line, it crosses the Earth, i.e. the elements are hidden by the Earth. However, the signal continues to be received because the GPS beam bends. This bending of the rays can be measured and related to the vertical structure of the atmosphere. As a result, vertical profiles of temperature, pressure and moist are typically inferred from GPS radio occultation data.

The novelty of the Radio Occultation and Heavy Precipitation experiment aboard PAZ (ROHP-PAZ) is its capability to quantify the effects suffered by the signals induced by large rain droplets (intense rain) and frozen particles (cloud ice, snow, graupel…). These features are captured through the vertical and horizontal components of the GPS signal, the so-called ‘polarimetric observations’, measured for the first time from space. The other spaceborne sensors measuring rain and cloud ice look at the rainy scenarios from above, in the form of vertical ‘slices’, while the polarimetric radio occultation technique provides horizontal ‘slices’ of the precipitation at reasonable vertical intervals, a side-look that complements the rest of measurements. The experiment is also the only one able to jointly sense precipitation and its thermodynamic properties, important pieces of information to understand the conditions underlying intense precipitation. 

After a process of accurate data calibration, today 22 April 2020 the sets are being made publicly available.  The set will be regularly expanded as the PAZ satellite continues its data acquisition, at a rate of approximately 200 new vertical profiles per day. “Opening the data to other researchers is a major milestone of our activity: it is the only way our research can be verified and new ideas can be tested by other researchers'' explains Dr. Estel Cardellach, principal investigator of the experiment and IEEC researcher at ICE (CSIC). “We are positive that the polarimetric radio occultations have potential to contribute to a broad range of geophysical applications, but we can not do all by ourselves: scientists working on meteorology, weather forecast or climate have the expertise to apply these signals to new uses, so they need access to the data,” adds Cardellach.

Involving other research communities

To celebrate the data release and to boost the use of these data sets among the meteorology, weather forecast, climate and remote sensing research communities, the first ‘ROHP-PAZ Users Workshop’ is taking place on 23 April 2020. Because of the Coronavirus (Covid-19) pandemic outbreak, its format has been changed to become a fully online event. 

“Over 50 scientists from Europe, America and Asia have registered for the meeting, coming from different scientific backgrounds” reports Dr. Ramon Padullés, ROHP-PAZ and IEEC researcher at ICE (CSIC). “The interest towards this new technique is increasing, and we hope the online workshop will boost new collaborations and science return.”

One of the key questions to be discussed in the meeting is how to use this new type of data to improve the weather forecast and the climate projections as, currently, both of them have limited capabilities to conclude about extreme precipitation events. The workshop is organized together with researchers at NASA Jet Propulsion Laboratory (JPL), who also participated in the calibration phase of the mission and who plans to release their own ROHP-PAZ data sets later this year.

The data are accessible through the ROHP-PAZ website, which also contains outreach information.


The ROHP-PAZ experiment is an experiment funded by the Spanish Ministry of Science and Innovation, and led by ICE (IEEC-CSIC). In addition to NASA JPL, the experiment is possible through collaborations with the PAZ satellite owner, operator and exploiter, Hisdesat, the National Oceanic and Atmospheric Administration (NOAA) and the University Corporation for Atmospheric Research (UCAR). 



More information

The Institute of Space Studies of Catalonia (IEEC  — Institut d’Estudis Espacials de Catalunya) promotes and coordinates space research and technology development in Catalonia for the benefit of society. IEEC fosters collaborations both locally and worldwide and is an efficient agent of knowledge, innovation and technology transfer. As a result of over 20 years of high-quality research, done in collaboration with major international organisations, IEEC ranks among the best international research centers, focusing on areas such as: astrophysics, cosmology, planetary science, and Earth Observation. IEEC’s engineering division develops instrumentation for ground- and space-based projects, and has extensive experience in working with private or public organisations from the aerospace and other innovation sectors.  

IEEC is a private non-profit foundation, governed by a Board of Trustees composed of Generalitat de Catalunya and four other institutions that each have a research unit, which together constitute the core of IEEC R&D activity: the University of Barcelona (UB) with the research unit ICCUB — Institute of Cosmos Sciences; the Autonomous University of Barcelona (UAB) with the research unit CERES — Center of Space Studies and Research; the Polytechnic University of Catalonia (UPC) with the research unit CTE — Research Group in Space Sciences and Technologies; the Spanish Research Council (CSIC) with the research unit ICE — Institute of Space Sciences. IEEC is integrated in the CERCA network (Centres de Recerca de Catalunya).


IEEC Communication Office
Barcelona, Spain

Rosa Rodríguez Gasén

Institute of Space Science (ICE, CSIC)
Institute of Space Studies of Catalonia (IEEC)

Barcelona, Spain
Estel Cardellach
Distinguished researcher
Attached Documents
Generalitat de CatalunyaUniversitat de BarcelonaUniversitat Autònoma de BarcelonaUniversitat Politècnica de CatalunyaConsejo Superior de Investigaciones CientíficasCentres de Recerca de Catalunya