North stars
Some of the current and future top radio observatories in the Northern Hemisphere
FAST
(Five-hundred-meter Aperture Spherical Telescope) A huge radio dish, built in a natural bowl-shaped valley in Pingtang County, Guizhou, southwest China. With a surface area of 0.2km2, FAST is currently the most sensitive radio telescope in the world. (The 300-metre Arecibo radio telescope in Puerto Rico collapsed in late 2020; the Green Bank Telescope in West Virginia and the German Effelsberg Telescope have diameters of approximately 100 metres.)
ngVLA
(Next Generation Very Large Array)
This future facility will be more than 10 times as sensitive as the current VLA observatory in New Mexico. The plan is for 244 radio dishes with diameters of 18 metres, supplemented with 19 smaller 6-metre dishes, distributed across large parts of the USA. ngVLA will fill the gap between observations by SKA (at relatively long wavelengths) and by the ALMA observatory in Chile, which studies cosmic microwave radiation.
LOFAR
(Low-Frequency Array)
An array of some 20,000 dipole antennas, spread over seven European countries, with the core in the northeast of the Netherlands. Thanks to its long baselines of more than 1,000km, LOFAR has a larger angular resolution than SKA-Low, which will operate at comparable low radio frequencies. However, SKA-Low will be much more sensitive. “LOFAR was a real pioneer,” says former LOFAR director Michiel van Haarlem.
DSA-2000
(Deep Synoptic Array)
A future array of no less than 2,000 small, simple antennas with diameters of 5 metres, in the remote Hot Creek Valley in Nevada. A 110-antenna prototype is under construction in California. DSA-2000 will be able to quickly map the whole visible radio sky. By carrying out such surveys on a regular basis, astronomers hope to discover many short-lived transient phenomena, such as fast radio bursts.