Northeastern Space Radio Observatory - ROEN

The Rádio-Observatório Espacial do Nordeste - ROEN (Northeastern Space Radio Observatory) project is located at Eusébio, near by Fortaleza, CE, Brazil. It is the result of a cooperation between the National Geological Survey (NGS) (changed to Geoscience Laboratory, National Ocean Services), which belongs to NOAA (National Oceanic Atmospheric Administration), Escola Politécnica da Universidade de São Paulo (EPUSP) signed during 1988 and 1989) and the participation of  CRAAE (Centro de Rádio-Astronomia e  Aplicações Espaciais - Radio Astronomy and Spatial Applications Center / Cooperation between Mackenzie, INPE, USP and Unicamp) and INPE. This project also received support from FINEP/MCT and NOAA. The implementation of  Radio-Observatory in the Eusébio station, that belongs to INPE, was performed by CRAAE. ROEN began operations in 1993. Geodetic VLBI and GPS observations are carried out regularly, as contributions to international programs and networks. ROEN is currently coordinated by CRAAM, Center of Radio Astronomy and Astrophysics, Mackenzie Presbyterian University, São Paulo, in agreement with the Brazilian National Space Research Institute, INPE. A new contract has been signed in May 2004 between NASA and CRAAM, Mackenzie Presbyterian Institute and University to support partially the activities at ROEN until 2009, under the auspices of an Agreement of Cooperation recently signed between NASA- representing research interests of NOAA and USNO, from USA - and the Brazilian Space Agency, AEB. Part of the operational cost, staff and part of infra-structure is provided by INPE and by Mackenzie.

The system is composed by a big antenna (14.2 m diameter) which includes the most complete electronic instrumentation available to operate space geodetic programs. This is the first one located in Brazil.

It uses the radio-astronomy technology. The reference bases are the quasars that are located at billions of light years far from the Earth. Observations from two of the radio-telescopes allows one to get the interference at radio waves. The simultaneous observations of these quasars performed by a set of observatories located around the world gives the absolute positions on the Earth surface. Those positions are determined with precision of millimeters. Due to the large separation between the radio-observatories in the network, this methodology is known as VLBI (Very Long Base Interferometry).

The Space Radio Observatory uses several sofisticated equipments. For time base, it is used a atomic hydrogen maser that is the most advanced technology to time standard. The receivers are cryogenic and operate at very low temperatures to have more sensibility. The data acquisition system is the MARK III with processing capability higher than 100 Mbit/s).



Fortaleza's VLBI geodetic terminal is part of an international network. It is the most important one as becomes the geodetic link between north-American, European, African and Antarctic continents. The Space Geodetic Global Programs uses VLBI and constitutes of essential importance on modern cartography, navigation and precise geodesy, as for research on earth rotation irregularities, geodynamics, seismology and tectonics plates movement, and quantitative evaluations on global changes.

As example of results from geodetic VLBI applications is the support to Cartography, Geodesy and Navigation (which makes use of GPS satellites constellation) services. Spatial navigation, artificial satellite orbitography and dissemination of absolute timing are also applications of this service.

The monitoring performed from geodetic VLBI intends to investigate the plastic motions of the planet, tectonic plates derives and its relationship to earthquake predictions. The earth rotation motion irregularities are measured by VLBI with precision a hundred times better than traditional optical methods. This technique allows the study of the influence of global meteorological variations (such as the "El Niño" phenomena) on the Earth rotation, which is part of researches in global change. As one application of geodetic VLBI is the study of the oceanic tide throught measuring sea level for a very long period. This will allow the detection of any possible variation on sea level (for instance, its increase due to green house effect on earth polar ice fusion).


The Rádio-Observatório Espacial do Nordeste (ROEN) is now part of the international network of geodesic VLBI and contributes to IERS (International Earth Rotation Service), supporting Brazilian programs on geodesy, cartography and navigation, using special methodologies such as GPS and absolute timing services. ROEN has regularly participated on the following international programs on geophysics and geodesy: IRIS-S, SOUTH TRF, GLOBAL TRF, NEOS-A, RDSAT, CRF, NAVSAT and CORE-B.


IVS-R4 Determination of space earth orientation.
IVS-T2 Determination of earth rotation parameters.
RDSAT Best characterization of South American plate motion.
NVSAT Improvement of NAVSTAR satellite constellation orbit model.
SOUTH TRF Upgrade on South Hemisphere terrestrial reference system.
CRF Celestial reference system determination.
CORE-B Determination of earth orientation, on a smaller time scale for geodynamic studies.


Some important results from geodetic VLBI experiments are listed below:

Determination of the earth reference system with few millimeters precision;

Determination of the celestial reference system with a fraction of milliarcsecond.

Detection of earth tectonic plate relative motion. As an example, Fortaleza city is moving 12 mm/year to north , 5 mm/year to east and 2 mm/year up.

Discrepancy between the geophysical model and VLBI measures. Those measures have shown that the Earth's core is more elliptical than we came to know before.

Evidences on correlation between variation on length of day and large scale meteorological phenomena were found.

Improved earth orientation and earth plates movement models.


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