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a b a b Omnidirectional antenna Spectrum Analyzer GPIB interface Controlling computer NATIONAL INSTITUTE FOR SPACE RESEARCH – INPE/MCT SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/CIE/INPE - MCT SOUTHERN SPACE OBSERVATORY – SSO/CRS/CIE/INPE – MCT

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a

b

a

b

Omnidirectional antenna

Spectrum Analyzer

GPIB interface

Controlling computer

NATIONAL INSTITUTE FOR SPACE RESEARCH – INPE/MCT

SOUTHERN REGIONAL SPACE RESEARCH CENTER – CRS/CIE/INPE - MCT

SOUTHERN SPACE OBSERVATORY– SSO/CRS/CIE/INPE – MCT

FEDERAL UNIVERSITY OF SANTA MARIA – UFSM

TECHNOLOGY CENTER – CT/UFSM

SPACE SCIENCE LABORATORY OF SANTA MARIA – LACESM /CT/ UFSM

RADIO QUITE SITE QUALIFICATION FOR THE BRAZILIAN SOUTHERN SPACE OBSERVATORY BY MONITORING THE LOW FREQUENCY 10–240 MHZ ELETROCMAGNETIC SPECTRUM

Guilherme S. Rosa(1), Nelson J. Schuch(1), Casio E. Antunes(1), Natanael R. Gomes(2)

(1) Southern Regional Space Research Center – CRS/CIE/INPE – MCT, in collaboration with the Santa Maria Space Science Laboratory – LACESM/CT – UFSM, Santa Maria, RS, Brazil.

(2) Electronic and Computing Department and Space Science Laboratory of Santa Maria – Center for Technology – (DELC/CT - LACESM/CT) -UFSM, Santa Maria, RS, Brazil

[email protected]/ Fax: +55-55-3301-2213

ABSTRACT

The 2006 RF Spectrum monitoring at SSO in the frequency range of 20 – 230 MHz is presented in Fig. 5. The observations is for a day of data acquisition, February 4-5, 2006 which are presented in two different formats as diagrams (a) and (b) of Fig. 6. It is observe that the electromagnetic spectrum at the SSO remained free of radio interference in most of the observed frequency range. Basically they are the same signals observed in the past, such as signals from FM transmissions, TV and radio amateur.

METHODOLOGY

It was used a radio interference data acquisition system installed at INPE’s Southern Space Observatory, which is located at São Martinho da Serra, in South of Brazil, subunit of the Southern Regional Space Research Center – CRS/CIE/INPE–MCT, as Fig 1.

A radio interference (RF) data acquisition system kit was installed and operated at the Southern Space Observatory. The RF system kit consisted of: antenna, spectrum analyzer, GPIB board and controlling PC, as presented in Fig. 2.

Characterization of electromagnetic interference originated from natural or anthropogenic radio frequency sources is essential information to evaluate the radio noise level and the site quality in order to study the possibility for installation of sensitive radio astronomic instrumentation at the Southern Space Observatory – SSO/CRS/INPE-MCT (29°S, 53ºW), in São Martinho da Serra, RS, Brazil. The monitoring of the Electromagnetic Spectrum in the frequency range of 10 – 240 MHz has been carried out at the SSO - Observatory since 1992. The radio interference data acquisition is carried out by an integrated system of: omnidirectional antenna, amplifier, spectrum analyzer and controlling computer, which is used to control the spectrum analyzer and for data storage. The omnidirectional antenna is installed outside at the Observatory and the detected radio signals are transmitted via coaxial cable to the amplifier system. After the amplification procedure, the signals are processed and digitalized by the spectrum analyzer. The data communication between the spectrum analyzer and the computer is made by a GPIB interface. For a remote controlling of the data flux, reduction and analysis, the data are sent via TCP/IP Protocol (Internet) to the Southern Regional Space Research Center – CRS/INPE – MCT, in Santa Maria, RS, Brazil. The today’s observed data is analyzed and is compared with the results and analysis of the observed local electromagnetic spectrum at the SSO – Observatory since 1992. The results indicate no significant variations of the site noise quality and of the interference level on the local electromagnetic spectrum for the last 16 years. From the observations of the systematic monitoring of radio interference one may say that in southern Brazil there is a very good radio-quiet site potential for installation of sophisticated and sensitive passive radio instrumentation for data acquisition for space science or for radio astronomy, similar to LOFAR stations, at the Southern Space Observatory – SSO/CRS/INPE-MCT, in São Martinho da Serra, Brazil, RS.

Fig. 5 – RF Spectrum in the frequency range of 20 – 230 MHz observed at SSO, in 2006.

Fig. 2 – Radio interference data acquisition system

The RF Spectrum in the frequency range of 20 - 200 MHz observed at SSO, in 1992, is illustrated in Fig. 3.

Fig. 6 – a) Composition between all the resulting observations for one day of data acquisition, February 4-5, 2006; b) Different diagram presenting the same results as presented in (a)

SOUTHERN SPACE OBSERVATORY A RF PASSIVE SITE FOR INSTRUMENTATION SYSTEMS

CONCLUSIONS

The majority of the RF Electromagnetic Spectrum (HF and VHF) at the Southern Space Observatory – SSO/CRS/CIE/INPE-MCT, in São Martinho da Serra, Brazil, RS, is free of intense radio interference and may be used for data acquisition with sophisticated and sensitive passive radio instrumentation and for Radio Astronomy, such as the LOFAR.

Fig. 3 – RF Spectrum in the frequency range of 20 – 200 MHz observed at SSO, in 1992

REFERENCES

The 2003 data of the RF Spectrum monitoring at the SSO is presented in Fig. 4, which shows that most of the RF Spectrum is free of electromagnetic radio interference.

● Boonstra, A. J.; Bregman, J. D.; Mohamoud, A. A. LOFAR spectrum monitoring: dynamic range and spectral occupancy issues, SKA workshop, Agosto de 2000, Jodrell Bank, UK.

● Ellingson, S. W. Antennas for the Next Generation of Low Frequency Radio Telescopes, IEEE Trans. Antennas and Propagation, Vol. 53, No. 8, Agosto de 2005, p. 2480-2489.

Fig. 1 – Southern Regional Space Research Center

CRS/CIE/INPE - MCT

Santa Maria, RS – Brazil

ACKNOWLEDGMENTS

The authors would like to acknowledge the Program PIBIC/INPE – CNPq/MCT for fellowship and COSPAR for grant.

Geographic Coordination:

Latitude: 29º 26´ 24” S

Longitude: 53º 48´ 38” W

Ellipsoidal Altitude : 488 m

Geomagnetic Coordination:

Latitude: 19º 13´ 48” S

Longitude: 16º 30´ E

Inclination or “dip”: 33º S

Total Geomagnetic Field: 22,800 nT

Fig. 4 – a) RF Spectrum in the frequency range of 100 – 110 MHz observed at SSO, in 2003;

b) RF Spectrum in the frequency range of 110 – 180 MHz observed at SSO, in 2003

Main gate and buildings

1, 2, 3, 5 and 6 at

São Martinho da Serra, RS, Brazil

37TH COSPAR, Montreal, Canada, July 13 - 20, 2008


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