Protecting the RF environment at the Cerro Chascón Science Preserve Guillermo Delgado European Southern Observatory.

Protecting the RF environment at the Cerro Chascón Science Preserve

Guillermo DelgadoEuropean Southern Observatory

La Serena 07/03/02 [email protected]

Millimeter astronomy


Guglielmo Marconi (1874-1937)


ITU and the international frequency spectrum regulation

The International Telecommunication Union (ITU) was created in 1865 and today is an specialized agency of the UN

ITU issue treaties after WARCs or can issue recommendations. As all cases of International Law, the countries have sovereign privileges within their borders

ITU recommends, the local administrations can accept or not. The good-will of the local administrations is fundamental


Radio astronomy as a radiocommunication service

Recognised as a radiocommunication service by ITU at the WARC of 1959

Represented at ITU by the Inter-Union Commission for the Allocation of Frequencies for Radio Astronomy and Space Science –IUCAF – (IAU, URSI, COSPAR), has no voting rights

Passive service


ITU recommendations

Interfering signal are all those unwanted signals exceeding in 10% the sensitivity of the system (ITU-R RA.769-1)

The local authorities are reminded that it is very difficult for the radio astronomy service to share frequencies with other services (ITU-R RA.769-1)

It is suggested to create “coordination zones” for transmitters (ITU-R RA.1031-1)


International protection of radio astronomy

There are some frequency bands assigned internationally for the radio astronomy service:

Assigned as primary service shared with other passive services

Assigned as primary service shared with other active services

Assigned as secondary service


Telecommunication authority in Chile

Jaime EtcheberrySecretary of Infrastructure, transport and telecommunications

Ricardo LagosPresident of Chile

Christian NicolaiSub-secretary of Telecommunications

Patricio TomboliniSub-secretary of Transport

Juan Carlos LatorreSub-secretary of Infrastructure


Atacama Large Millimeter Array (ALMA)

Scientific Preserve of Cerro Chascón, 5000 m altitude, 60 km NE of San Pedro de Atacama

64 antennas 12 m diameter Collecting area ~ 7.200 m2

Surface accuracy < 25 m Baselines 18 to 14.000 m Resolution comparable to the

Hubble Space Telescope Operating frequency 30 to 950

GHz Bandwidth 4 GHz


ALMA sensitivity

Using ITU criteria (Handbook on Radio Astronomy, ITU-R RA.769-1) and ALMA parameters (Antenna diameter 12 m, frequency 230 GHz, bandwidth 8 GHz, integration time 2000 s, Tsys 80 K) we obtain a sensitivity at the antenna aperture of 600 Jy

1 Jansky (Jy) = 10-26 W m-2 Hz-1


ALMA location


Llano de Chajnantor


Frequency bands required by ALMA

Band No. Frequency range

[GHz]

1 31,3 – 45

2 67 – 90

3 84 – 116

4 125 – 163

5 163 – 211

6 211 – 275

7 275 – 370

8 385 – 500

9 602 – 720

10 787 - 950


What have been done internationally to protect against radio interference at the radio astronomy stations

Local assignment of frequency bands attributed to other services

Radio quite zone around the radio astronomy stations (small geographic area)

Coordination zone around the radio astronomy stations (large geographic area)


Our proposal to achieve protection against radio interference at Chajnantor

Local assignment of the ALMA required frequency bands (small geographical area) SUBTEL

Creation of a coordination zone around Chajnantor (larger geographical area) SUBTEL

Radio quite zone around the radio astronomy stations (small geographical area) ¿CONAMA?, ¿SUBTEL?,


What we have done

Made a presentation at SUBTEL of the ALMA project and our protection request to the Subsecretario and other technical managers

Obtained a compromise of collaboration from SUBTEL and created a joint working group

Produced a 52 pages document about the need of RFI protection, including legal background and protection precedence in other countries. This document was used in our presentation at SUBTEL


What we still need to do

Complete technical data requested by SUBTEL to define the size of the coordination zone

Obtain a formal recognition from SUBTEL to avoid future policy changes

Educate the general public (and the politicians) about radio astronomy and the need to protect the observing environment


Other astronomical projects at the Chajnantor area

Cosmic Background Imager (CBI), Caltech Mobile Anisotropy Telescope (MAT), Princeton Millimeter Interferometer (MINT), Princeton Atacama Pathfinder Experiment (APEX), MPIfR, ESO,

NSF Atacama Submillimeter Telescope (ASTE), NAOJ Infrared telescopes

– University of Tokyo Atacama Observatory (TAO)– Cornell Atacama Telescope (CAT)


End of the talk

Sorry for talking so much! Questions?

Protecting the RF environment at the Cerro Chascón Science Preserve Guillermo Delgado European Southern Observatory.

Documents

radio astronomy service

radio interference

fundamentalradio astronomy

transmitters itur

services itur

system itur

frequency rangeghz131

primary service