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Goodbye THEA

Submitter: Jan Geralt Bij de Vaate
Description: As has been reported before, one of the promising new technologies for the giant Square Km Array (SKA) radio telescope is the use of Aperture Arrays. These could replace the cumbersome 3D structures of the familiar dish telescopes with elegant 2D arrays of dipoles. Since such arrays are steered electronically, they do not have any moving parts, which makes them much cheaper to operate. But their biggest advantage is that they can "look" in several different directions at the same time, just like the phased array radars on modern navy ships. This allows the frigates to track multiple targets at once, while it greatly increases the survey speed of radio telescopes.

In some ways, the radar problem is relatively easy: It only uses narrow frequency bands, and deals with signals with a known modulation. Radio astronomers have to detect faint unmodulated noise in very wide bands, with little protection. Therefore, it is not surprising that lots of research is needed to develop this attractive new technology. ASTRON has been playing a leading role in this since the dawn of SKA in 1990.

The ASTRON research program has produced a range of prototypes of increasing complexity: from AAD, to OSMA, to THEA, to EMBRACE. The aptly named THEA (which stands for THousand Element Array as well as Two Hundred Element Array) made a big impact in the radio astronomy community with the 'Worlds first full-sky dynamic 24 hour HI survey' (see inset). This success was one of the triggers for the SKADS program, funded by the EU, in which more than 30 European institutes participate, and which has produced a beehive of exemplary international collaboration.

Now that the first series of tiles for the much larger EMBRACE demonstrator are filling up our lab space, it is time to say goodbye to THEA. In good ASTRON tradition, we have studied her every detail, and have learned a lot. Before being overpowered by the embrace of the future, the original THEA designers are gratefully salvaging her goodies.
Copyright: ASTRON
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