Galactic Emission Mapping
 The GEM telescope in Cachoeira Paulista, Brazil | |
| Alternative names | GEM |
|---|---|
| GEM Radio Telescope in Brasil | |
| Location(s) | Cachoeira Paulista, São Paulo, Brazil |
| Altitude | 570 m (1,870 ft) |
| Wavelength | 3 cm (10.0 GHz)–74 cm (410 MHz) |
| Telescope style | radio telescope  |
| Diameter | 5.5 m (18 ft 1 in) |
 Related media on Commons | |
| GEM Radio Telescope in Portugal | |
| Location(s) | Pampilhosa da Serra, Coimbra District, Portugal |
| Altitude | 800 m (2,600 ft) |
| Telescope style | radio telescope |
| Diameter | 9 m (29 ft 6 in) |
The Galactic Emission Mapping survey (GEM) is an international project with the goal of making a precise map of the electromagnetic spectrum of our galaxy at low frequencies (radio and microwaves).
Description of the project
The GEM Radio Telescope measures the radio emission of our
The telescope is in construction at
The telescope was projected and is operated by an international collaboration coordinated by the University of California, Berkeley and by the Lawrence Berkeley National Laboratory, under the guidance of George Smoot, awarded with the Nobel Prize in Physics in 2006.
In Brasil, the
GEM in Portugal
Scanning Process
In Portugal the radio telescope will perform scans by rotating on its base at a speed greater than one rotation per minute, therefore avoiding the error fluctuations caused by water vapour in the atmosphere. This scanning process will provide an important contribution to the data processing.
Telescope
A Ground Shield will be built to avoid signal contamination with thermal radiation that may come from below the horizon, to reflect side lobes to the sky and to reduce the noise originating from diffraction from the edges of the reflector to the receiver. This will be made possible by an aluminium grid surrounding the radio telescope, which is 10 meters wide but only 8 meters high because it will be inclined towards the exterior.
The edges will be curved with a radius larger than ¼ of the wavelength so that diffraction is reduced.
Localization
The antenna is located at Pampilhosa da Serra at an altitude of 800m above sea level. This location was chosen because it is surrounded by a mountain range which peaks at about 1000m above sea level, which give a natural "shielding" from the electromagnetic noise of the neighboring cities.
The same reason that made this location a good choice also created additional problems, since many of the necessary infrastructures had to be prepared and installed. The Telescope foundations were studied by the Département of Civil Engineering of the
A second telescope is planned on the same site, to study solar phenomena.
References
- ^ Fonseca, R. et al. Site evaluation and RFI spectrum measurements in Portugal at the frequency range 0.408–10 GHz for a GEM polarized galactic radio emission experiment. New Astronomy, 11(8):551-556, 2006.
- ISBN 85-7139-573-X.)
{{cite book}}: CS1 maint: multiple names: authors list (link - ^ Tello, C. et al. Spillover and diffraction sidelobe contamination in a double-shielded experiment for mapping Galactic synchrotron emission. Astronomy and Astrophysics Supplement Series, 145:495-508, 2000.
External links
- Página do Projeto GEM (in English)
- Radiotelescópio GEM no Brasil
- Radiotelescópio GEM em Portugal
- Instituto de Telecomunicações (in English)
- Movie about galactic emissions and GEM (in English)
