One Centimetre Radio Array (OCRA)

JBO aims to construct a one hundred beam receiver some time in the future, operating at a frequency band centred on 30 GHz (one centimetre wavelength). This will be installed on a 32 metre diameter radio telescope at Torun in Poland, shown in figure 1, which is ideal for high frequency multi-beam work as it has very accurate reflector panels and has paraboloid/hyperboloid (non-shaped) optics. Currently we are working on two projects, designated OCRAp and FARADAY, that are being used to develop the technology needed for the full OCRA system

Figure 1. Torun 32-metre Telescope in Poland.

OCRAp is a two-beam prototype receiver, based on the design for the 30 GHz Planck LFI radiometer. The radiometer block diagram is shown below. MIC low noise amplifiers and phase switches (bi-phase modulators), designed by Frank Winder and constructed by Eddie Blackhurst at JBO, are used together with commercially made magic T hybrids and detectors. The radiometer noise temperature is expected to be less than 15 kelvins.

Figure 2. Foxtrot Radiometer

Following tests at Jodrell Bank during the summer of 2002, the radiometer will be installed on the Torun radio telescope ready for extensive testing during the winter of 2002/2003. We are hoping for clear, cold weather conditions, which will give us a stable and low-loss atmosphere over the telescope.

The tests carried out in the laboratory were very successful and the reciever performs to a high engineering standard.

The receiver was shipped to Poland in December 2002. Two JBO engineers, a JBO astronomer and a PhD student met the receiver in Poland and performed some routine bench tests. The tests proved successful indicating the receiver had survived the journey.

At the beginning of the year the receiver was mounted on the Polish telescope.There is much work to be done on the telescope itself such as pointing. However the pictures below show some first order measurements taken of planets Jupiter and Saturn.

OCRA tests transit Jupiter

OCRA tests transit Saturn

ADDITIONAL PHOTOS

John Kitching, our mechanical engineer, has taken some recent photographs of the OCRA-p receiver.

OCRA cryostat

OCRA cryostat being assembled

OCRA cryostat with horns in place

Current Activities May 2005

The OCRA-p receiver has been successfully imported into Poland and is now in use.