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NASSP Student Practical 2003/08/28

The National Astrophysics and Space Science Programme (NASSP) began in 2003. It is being hosted by the University of Cape Town. From August 25 to 29 the Honours students in the programme visited HartRAO for their Radio Astronomy practical. They were joined by two Hons. students from the Department of Physics and Electronics at Rhodes University.

The students were soon introduced to the the radio telescope:

climbing the telescope
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Here the first group of students begins the long climb up the telescope.

in the telescope
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The students get accustomed to the size of the radio telescope, twenty six metres in diameter.

in the cone
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In the centre of the telescope is the 'Cassegrain Cone", which houses all but one of the microwave feeds and receivers. The receivers (again excepting one) are all cooled to 16 degrees above absolute Zero, to improve their sensitivity. Here the students get a close look at the hardware needed for modern radio astronomy.

going down
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Its a long way down. The first group of students leave the telescope.

group 2
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The long white "icecream cone" in the foreground is the microwave feed horn operating in the 18 centimetre wavelength band. Beyond it, with the second group of students, is HartRAO Director Prof. Justin Jonas, who is pointing up at the secondary reflector above his head. You cannot see the hyperbolic subreflector in the picture above, but it is at the top of the picture below.

group 2
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The second group of students get together in the telescope.

radiometers 1
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The signals from the receivers are carried down to radiometers in the control room, which are used to measure the intensity of the signals[B. Here Prof. Jonas explains how this all occurs.

radiometers 2
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The students take a closer look at the radiometers.

control computer system
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The telescope is controlled by PC's using locally developed software running on Debian Linux. Here the students see how Prof. Jonas carries out a drift scan - a simple form of continuum flux measurement - on the radio galaxy Virgo A. Virgo A is a calibrator source - a "standard candle", against which other radio sources can be compared.

microwave lab 1
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The students also get "hands on" experience in the microwave laboratory, where receivers are built and tested. Here a spare microwave amplifier has been set up to measure its performance and noise figure. Prof. Jonas explains how the test setup works.

microwave lab 2
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The students are left on their own to measure the noise figure of the amplifier using hot and cold loads. First they make notes on the test configuration.

microwave lab 2
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What do we do now? The students figure out how to start taking measurements for the noise figure, using liquid nitrogen as the cold load.

Sun map

The scans used to contruct this map of the radio emission from the Sun at a wavelength of 2.5 cm were made during the practical. The Sun is 30 minutes of arc in diameter, while the beamwidth is 4 minutes of arc. Hence nearly 7.5 beamwidths fit across the Sun, enabling us to detect detail on its surface - usually enhanced radio emssion associated with sunspots. The scanning software was written by Jonathan Quick and the image shown here was created by Sarah Buchner.

NASSP student group
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The practical is almost over, and the students gather for a group photo in front of the radio telescope. They are flanked by Director Prof. Justin Jonas on the left, and Dr. Mike Gaylard on the right, who led the spectroscopy part of the practical.