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Very Large Array (VLA)

From the early 1960s at NRAO, astronomers knew they needed an array
of radio dishes to complement the work of our giant, single-dish
telescopes. An array is a group of several radio antennas observing
together creating, in effect, a single telescope many miles across.

As a first step, NRAO built the Green Bank Interferometer to learn
and develop best communications, correlation, and atmospheric correction
practices. Throughout the 1960s and 1970s, this four-element array
helped NRAO prepare for a Very Large Array of 27 telescopes.

Each of the VLA’s 28 antennas (including the one that is a spare) is
an 82-foot dish with 8 receivers tucked inside. The dish moves on an
altitude-azimuth mount, what you’ve probably seen as a classic tripod
mount: it tilts up and down and spins around.

Atacama large millimeter/submillimeter array (alma)

The Atacama Large Millimeter/submillimeter Array is the
most complex astronomical observatory ever built on Earth. Teams from
North America, East Asia, and Europe merged projects to develop this
breakthrough scientific instrument in northern Chile.

ALMA has opened a new window on the Universe, capturing
never-before-seen details about the very first stars and galaxies,
probing the heart of our Milky Way Galaxy, and directly imaging the
formation of planets.

ALMA is a transformative radio telescope that can study cosmic light
that straddles the boundary between radio and infrared. Most objects in
the Universe emit this kind of energy, so the ability to detect it has
been a driver for astronomers for decades.

Millimeter and submillimeter light is easily absorbed by water vapor
in the atmosphere. The dry climate and extreme elevation (5000 meters or
16,500 feet) of the site in the Chilean Atacama Desert provide ALMA
with the right conditions for detecting these faint signals from space.

ALMA uses 66 high-precision dish antennas of two sizes: 54 of them
are 12 meters (39 feet) across and 12 of them are 7 meters (23 feet)
across. The total collecting area of this array is over 6,600 square
meters (71,000 square feet).

The 12-meter antennas can be moved to different locations by
custom-made Antenna Transporters in order to form arrays ranging from
very tightly packed configurations only 160 meters across to wide
configurations 16 kilometers across. More extended arrays give ALMA a
zoom lens for finer details, while more compact arrays give better
sensitivity in order to observe dimmer objects.

next generation very large array (ngvla)

In the 1970s the Very Large Array (VLA) was imagined as an array of
27 82-foot (25-meter) dishes arranged in a “Y” shape. More than 3,000
researchers from around the world have used the VLA for more than 11,000
different observing projects. The VLA has had a major impact on nearly
every branch of astronomy, and the results of the research it has made
possible are abundant in the pages of scientific journals and textbooks.
More than 200 Ph.D. degrees have been awarded on the basis of research
done with the VLA.

In the 21st century, astronomers are imagining the next generation
Very Large Array (ngVLA) with 244, 59-foot (18-meter) dishes spread over
5,505 miles (8,860 km). An additional 19 twenty foot (6m) dishes will
make up a short-spacing array at the heart of the telescope. These
choices are not arbitrary. By engaging the larger astronomical
community, a consensus has been arrived at. This is the observatory
needed to address some of the biggest science questions that radio
astronomy can help answer. Several of those are listed below, but
perhaps the most exciting are those we haven’t even thought of yet.

very long baseline array

The Very Long Baseline Array was designed and built by NRAO, beginning its first full observations in 1993. Using the VLBA as one of the world’s most powerful radio cameras, astronomers peer through the dark cores of glowing gas clouds and see the stars that make them tick. In time-lapse, the VLBA sees hearts of galaxies pulsing as their central supergiant black holes whip out quintillions of tons of charged gas every day.

Mapping the Universe

The VLBA is a critical tool for astronomy, where knowing distances is the basis for figuring out mass, makeup, and movement of cosmic objects.

Monitoring the Changing Earth

To determine their exact locations on Earth to within fractions of an inch, the VLBA telescopes observe very distant quasars.

With the support of the US Naval Observatory, the VLBA telescopes then act like pins tacked to the Earth’s crust; any movement of the crust shows up as a change in distances between the telescopes.

Tracking Near-Earth Asteroids

Radar facilities beam radio pulses on to nearby asteroids. The VLBA’s telescopes collect the beams as they return to Earth, pinpointing an asteroid’s location over time. The precise timing of reflections received by the VLBA telescopes reveals the asteroid’s spin rate and direction and allows prediction of changes in its orbit.

The Very Long Baseline Array is a network of ten observing stations located across the United States. Each station consists of a 25-meter radio antenna dish and a control building. Radio signals captured by each
antenna are amplified, digitized and recorded. The recorded data are then sent
to Socorro, NM to be processed by a powerful computer known as a correlator. By combining their data, the stations form one of the world’s most powerful radio
cameras.

Locations
The VLBA stations are located in areas with limited radio interference, and widely spread across the country. The distance between any two stations is known as their baseline. The longer the baseline, the better the angular resolution.

The most widely separated antennas are at Mauna Kea in Hawaii and St. Croix in the U.S. Virgin Islands, which are 8,611 km apart. While each VLBA antenna is identical, each location is unique.

St. Croix – U.S. Virgin Islands

Hancock – New Hampshire

North Liberty – Iowa

Fort Davis – Texas

Los Alamos – New Mexico

Pie Town – New Mexico

Kitt Peak – Arizona

Owens Valley – California

Brewster – Washington

Mauna Kea – Hawaii

Kitt Peak, Arizona

This antenna is one of 22 optical and 2 radio telescopes on Kitt Peak, making it one of the largest concentrations of astronomical instruments in the Northern Hemisphere.

Owens Valley, California

The site sits in the deepest graben in the United States, a deep rift valley between the Sierra Nevada and White Mountains, with mountains rising up to 14,000 feet and the valley floor at about 4,000 feet National Radio Astronomy Observatory. It’s in a rain shadow, making it one of the driest places in the U.S., which is ideal for radio astronomy

St. Croix, Virgin Islands

The St. Croix antenna, paired with the westernmost VLBA station in Hawaii, creates a baseline of nearly 5,000 miles. Enough to make the array behave like a single telescope with a diameter almost the size of the Earth. This setup gives the VLBA the highest resolution of any single radio observatory, allowing it to pinpoint distant quasars and measure Earth’s rotation and continental drift.

North Liberty, Iowa

It’s the only VLBA telescope in the Midwest, making it a unique link in the array that spans 5,351 miles from Hawaii to the Virgin Islands.

Mauna Kea, Hawaii

On Mauna Kea, the antenna sits atop an extinct volcano in Hawaii, one of the tallest mountains on Earth, offering a high, dry site with minimal radio interference

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