Ryle Telescope

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The Ryle Telescope was re-arranged to form the long baseline array of AMI after this photo was taken.

The Ryle Telescope (also known as the '5 km telescope') is a linear east-west radio telescope array at the Mullard Radio Astronomy Observatory. In 2004 three of the telescopes were moved, creating a compact two-dimensional array of telescopes at the east end of the interferometer. This cluster of telescopes is now operated as the long baseline array of the Arcminute Microkelvin Imager. The telescope is named after Martin Ryle.

The telescope is an 8-element interferometer operating at 15 GHz (2cm wavelength). The elements are equatorially mounted 13 m Cassegrain antennas, on an (almost) east-west baseline. Four aerials are mounted on a 1.2 km rail track, and the others are fixed at 1.2 km intervals. Baselines between 18 m and 4.8 km are therefore available, in a variety of configurations. For high-resolution imaging, the mobile aerials are arranged along the track, to give uniform baseline coverage to 4.8 km; for low-brightness astronomy (e.g. the Sunyaev-Zel'dovich effect) the mobile aerials are arranged in a 'compact array', with a maximum baseline of about 100 m. All aerial pairs are correlated, so some long baseline data are always available, even in the 'compact array' configuration.

As the telescope is an east-west instrument, most imaging observations involve 12-hour observations in order to fill the synthesised aperture (calibration observations are routinely interleaved). Another consequence of the geometry is that it is not practical to image sources near the equator, or in the south.

Although the telescope is not designed as a common user instrument, the operators are happy to accept proposals for observing time on the instrument from outside observers, provided that they do not overlap substantially with existing observing programmes, on a 'best efforts' basis. Monitoring variable sources is possible using short observations which can often be inserted between longer 'standard' observations.

The telescope has three main scientific programs: study of the Sunyaev-Zel'dovich effect in galaxy clusters, particularly in determining the Hubble constant; surveying for radio sources that would contaminate degree-scale observations of the cosmic microwave background made with the Very Small Array, and flux monitoring of galactic variable sources.