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The Greenbank Telescope

The Greenbank Telescope

The Greenbank site houses numerious telescopes, old and new. We will review a few of the smaller ones and then get to the GBT, for Greenbank Telescops - but sometimes called the Great Big Telescopse.

Jansky Telescope

This is a replica of the very first radio telescope, built by Karl Jansky.

Replica of Jansky telescope.

Another early radio telescope.

Old telescope at Greenbank

140ft Telescope

The 140ft telescope. Built in 1965.

The 140 foot Greenbank Telescope

VLA Prototype

These antennas were part of the basis for building the VLA.

VLA prototype antennas

300ft Greenbank Telescope

This is the old 300ft Greenbank Telescope. After working many years beyond its original design life it decided to retire. It decided to do so with a bang, instead of giveing prior notice. More information can be found here.

Old 300ft Greenbank Telescope

The 100m Greenbank Telescope

Some cars at the base of the telescope give some scale. There are also a few cables hanging from the dish. They are part of a temporary lift used when the dish is being repainted. The telescope in the background is the old 140ft telescope.

View of the Greenbank Telescope
Underneath the GBT, looking up.

The wheels

Standing next to the wheels starts to give an idea of the size of this telescope.

The large wheels on the Greenbank Telescope

The surface of the dish

View of the dish surface.

3D truss structure

The underside of the antenna is supported by a complicated looking three dimensional truss.

Complex truss in the Greenbank telescope.

Detail of truss joint.

One day before my steel design class I came in early and put this up on the projector. Students were discouraged when I told them it would be on the test. Then the professor came in, stared it with a startled look, and said "Now that's a complicated joint!"

Detail of a 3D truss joint on the Greenbank Telescope.

Feed horn defroster

Despite looking like a monster from a bad 70's sci-fi movie this is a useful peace of equipment. It defrosts the feed horns to prevent frost, snow, and ice from interfering with the signal.

Defroster for the Greenbank Telescope

The Receiver Cabin

In a room underneath the defroster is the receiver cabin. Seen here are a couple racks of support electronics.

Inside the receiver cabin.

Analog electronics

After arriving in the control building the receiver goes through a series of analog electronics prior to being digitized.

Rack of analog electronics.

The Control Room

The control room for the Greenbank Telescope

Anechoic chamber

The support labs at the Greenbank Telescope have an anechoic chamber for carefully examining what interference a device is generating. Remember that radio waves are electromagnetic, and are not the same thing as sound waves. The properties for making an anechoic chamber are very similar for both types of wave, with the result that the chambers look about the same. Both often use special foam, although the foam in this chamber has to be treated to have the correct radio properties. The wooden flooring used in parts of this chamber will produce audible echos but does not produce radio reflections.

GB anechoic chamber

Test antenna

This is a directional antenna used in the RF tests.

Directional antenna used for RF tests.

Detail of chamber wall

Detail of foam in anechoic chamber.

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© David C. Hunter, 2014
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