Chautauqua Courses

Interferometry in Radio Astronomy: The VLA and VLBA

Held in Socorro, New Mexico on July 11 through Jul7 13, 2007 at the NRAO headquarters.

South Baldy Peak (10,783 feet), which is to the west of Socorro. The local golf course is in the foreground.

Observatory operations center in Socorro where the VLBA (Very Large Baseline Array) is managed.


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Wednesday noon NRAO staff meeting where staff members discussed eMerlin, an interferometer being built in the UK, in cooperation with NRAO. They discussed how budget shortfalls were impairing the project, laying of optical fibers between radio dishes, above ground along rail lines (perhaps not a good idea), artificial deadlines, and how one poor programmer was going to rewrite all of the antenna control software. Sounds similar to what I face in the corporate world.

The presentation on the progress of eMerlin.


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The project manager for the ALMA electronics explains the workings of the analog to digital converter units that will be fitted into the base of each of the ALMA dishes in Chili.

One of the analog to digital converters.


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One of the VLBA correlator cabinets. The correlator combines the signals from the different dishes on the array to make a single image.

A VLBA correlator board.


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Disk packs for the VLBA sitting on shelves.

Disk packs for the VLBA being read.


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The VLA test racks where repaired components are tested prior to installing out at the array.

Cross section of one of the wave guides used to transmit data from the antennas to the main building where the signals are processed. These wave guides are being replaced with fiber optic cables as part of the upgrade that will boost the array's sensitivity.


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Feed horn electronics being tested. The insulated lines going into and out of the assembly are helium lines, which are used to cool the electronics. The electronics are housed in the aluminum chamber, which is evacuated to prevent condensation.

A couple of repaired receivers. Note the feed horns and the vacuum chambers. The electronics in the receivers are cooled with helium gas and kept in a vacuum to reduce noise. The vacuum is necessary to prevent condensation.


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One of the receiver electronics packages that sets behind a feed horn showing the components that split the signal into right and left circularly polarized signals.

The same unit with the piece that holds the feed horn and channels the signal to the electronics via millimeter sized wave guides..


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Here I am in front of the antenna hanger. When an antenna is brought to the hanger the dish is removed from the base if the azimuth bearing shows excessive wear and a new bearing can be installed. This dish was being retrofitted for an upgrade to the array.

One of the antennas of the array in for repairs next to the antenna hanger. This dish was just refitted as part of an upgrade project to boost the array sensitivity.


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Dave Finley explaining some of the features of the radio dish before taking our class up onto the antenna.

On the surface of the dish listening to Dave Finley explain about the workings of the dish surface and the secondary reflector.


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Inside the antenna looking up at the feed horns.

The feed horns.


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The fiber-optics inside the dish.

Climbing out onto the surface of the dish.


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The five horsepower motors that move the dish in altitude.

The adjustment bolts that are used to fine tune the parabolic shape of the dish.


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The secondary reflector dish.

The feed horns as seen from the dish.


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One of the antenna transporters.

The track splices used when a dish is moved from one of the stations onto the main track. The antenna transporter uses hydraulic jacks to lift itself off the track and then rotates the wheels onto the main track.


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Wheel assemblies of the antenna transporter.

Close-up of the rotary hydraulic motor on one of the wheel assemblies.


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Antenna control room at the VLA.

View of the computer control screens.


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Two of the prototype ALMA antennas for the new sub-millimeter array being built in the Atacama desert of Chili.

The two ALMA dishes seen from behind.


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Backup tapes of the all of the processed data collected at the VLA from 1976 to present.

A pronghorn antelope walking through the observatory grounds.


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One row of analog to digital converters for one branch of the array. There are nine converters in each row (one for each of the nine dishes that makes up a branch).

The fiber-optic cables going to the correlators.


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Having lunch at the Eagle Guest Ranch in Datil New Mexico .

Listening to Dave Finley tell stories about the filming of the movie "Contact" over lunch.


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The following panoramas were created with Autostich, which is available from the author's (Matthew Brown) home page at the University of British Columbia Autostich Home Page

Panorama from the balcony of Baca Hall where we stayed. Full sized image. 1,613Kb


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Panorama of the VLA showing the operations center, the two ALMA prototype dishes, and one leg of the array. This image was taken from the antenna hanger. Full sized image. 1,151Kb


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Panorama of the VLA taken from the operations center. Full sized image. 1,915Kb


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New Mexico Tech University Mineral Museum. We visted this during our lunch break on Wednesday.

Example of gold mined in New Mexico.

More gold from New Mexico.


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Minerals from the southwestern states.

Calcite crystals from California.


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Native copper from New Mexico.

Cuprite from New Mexico.


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Gypsum crystal from Socorro County New Mexico.

Barite from New Mexico.


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Ultraviolet display showing fluorescent minerals.

More fluorescent minerals.


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A Radio View of the Universe and the New Green Bank Telescope

Held in Green Bank, West Virginia on May 30 through June 1, 2006

The Reber antenna at the entrance of the observatory. Reber was the first radio astronomer. He built this dish in his backyard during the 1930's and listened to radio emissions with head phones and recorded his observations in a notebook. The alt-azimuth design is basically the same as the giant 100 meter radio telescope.


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The first 21-cm horn on display next to the observatory lab building. Made from wood and sheet metal.


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The Drake equation. The small conference room in the astronomer quarters where we stayed had this plaque hanging over the fireplace. The Drake equation, which attempts to quantitatively estimate the number of advanced civilizations in our Milky Way Galaxy, was first proposed in this conference room.


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The 40 foot radio telescope used by our class. This telescope was the first to be used in the SETI program. It is now used for educational purposes. Its electronics were salvaged from the old 300 foot telescope that collapsed into a pile of twisted scrap metal in November 1988.


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At the controls of the 40 foot radio telescope. Three members of our class (Bill, Steve and John) learn to take 21-cm spectra of the Milky Way.


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The 45 foot radio telescope used for solar flare observations. Apparently, sunspots make a lot of radio noise before flares explode. This telescope tracks the Sun every day watching for possible flares.


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Early morning views of the observatory. In the center of the left picture is one of the dishes of the interferometer. In the distance on the are the 140 foot radio telescope and the 100 meter telescope. On the right is the US Navy radio telescope that was used for GPS work. Currently this radio telescope is idle.


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On the left is another view of the US Navy radio telescope. On the right are two more of the dishes that make up the interferometer as seen from the top of the 100 meter radio telescope.


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The 100 meter Robert C. Byrd radio telescope. This telescope is also simply known as the GBT. This telescope is the replacement for the 300 foot telescope that collapsed in 1988. Senator Byrd obtained the 100 million dollars for its construction from federal emergency funds. He called the 300 foot collapse a "great catastrophe".


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On the left is the elevator that took us up to the altitude bearings. From there we walked the cat walk to the elevator that took us up the receiver arm to to feed room. On the right is the platform at the level of the altitude bearings.


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On the left is another view from the altitude bearing platform. In the center is the head astronomer over the GBT pointing out the various features of the telescope. On the right is a view of the panels and actuators that make up the dish. There are over 2000 panels and the actuators are able to adjust the shape of the dish to within a fraction of a millimeter.


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On the left is a view from the top of the feed horn room showing the openings of the various feed horns. The large feed horn in the foreground is the 21-cm horn. The image on the right shows the 10 meter secondary dish and the primary focus feed.


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Inside the GBT feed room. Top row: the 21-cm detector. Bottom row: some of the other detectors. These detectors are cooled to 15 Kelvin with helium gas that is cooled through a multistage expansion process. The helium makes a loud chirping sound as it passes through the plumbing.


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Two views of the azimuth wheels that support the GBT. There are 16 wheels that support 1 million pounds each. While we were climbing the GBT, maintenance workers were replacing sections of the circular track. The track is covered by a sheet metal cover to prevent objects from falling under the wheels. The image on the right shows two of the workers taking a break beside the wheels. The sheet metal cover can be seen in the left hand image.


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Two animation sequences showing the GBT in operation. Animations are provided by the NRAO.


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