astronomy

Very Long Baseline Array

Very Long Baseline Array is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Very Long Baseline Array rather than just read about it. In short: The Very Long Baseline Array (VLBA) is a system of ten radio telescopes which are operated remotely from their Array Operations Center located in Socorro, New Mexico, as a part of the National Radio Astronomy Observatory (NRAO). These ten radio antennas work together as an array that forms the longest system in the world that uses very long baseline interferometry.

Key takeaways

Very Long Baseline Array belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Very Long Baseline Array to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Very Long Baseline Array from memory before moving on to harder problems.

Reference excerpt

The Very Long Baseline Array (VLBA) is a system of ten radio telescopes which are operated remotely from their Array Operations Center located in Socorro, New Mexico, as a part of the National Radio Astronomy Observatory (NRAO). These ten radio antennas work together as an array that forms the longest system in the world that uses very long baseline interferometry. The longest baseline available in this interferometer is about 8,611 kilometers (5,351 mi). The construction of the VLBA began in February 1986 and it was completed in May 1993. The first astrometrical observation using all ten antennas was carried out on May 29, 1993. The total cost of building the VLBA was about $85 million. The array is funded by the National Science Foundation, and costs about $10 million a year to operate. Each receiver in the VLBA consists of a parabolic dish antenna 25 meters (82 feet) in diameter, along with its adjacent control building. This contains the supporting electronics and machinery for the receiver, including low-noise electronics, digital computers, data storage units, and the antenna-pointing machinery. Each of the antennas is about as tall as a ten-story building when the antenna is pointed straight up, and each antenna weighs about 218 metric tons (240 short tons).

The signals from each antenna are recorded on a bank of approximately one-terabyte hard disc drives, and the information is time-stamped using atomic clocks. Once the disc drives are loaded with information, they are carried to the Pete V. Domenici Science Operations Center at the NRAO in Socorro. There, the information undergoes signal processing in a powerful set of digital computers that carry out the interferometry. These computers also make corrections for the rotation of the Earth, the slight shifts in the crust of the Earth over time, and other small measurement errors.

Observations by the VLBA The Very Long Baseline Array usually makes radio observations at wavelengths from three millimeters to 90 centimeters, or in other words, at frequencies from 0.3 gigahertz to 96 gigahertz. Within this frequency range, the VLBA observes in eight different frequency bands that are useful for radio astronomy. The VLBA also makes observations in two narrow radio bands below one gigahertz that include spectral lines produced by bright maser emissions. The VLBA radio telescopes are located at:

High-Sensitivity Array The use of the VLBA can be scheduled dynamically, and its sensitivity can be improved by a factor of five by including other radio telescopes such as the Green Bank Telescope in West Virginia, the Very Large Array (VLA) in New Mexico and the Effelsberg radio telescope in Germany. These three additional sites are brought online for as much as 100 hours per four-month trimester. In this configuration, the entire array is known as the High-Sensitivity Array (HSA). The Arecibo radio telescope in Puerto Rico was also used, before it collapsed.

Baseline distance and angular resolution

Distance between each VLBA baseline (km):

The longest baseline in the array is 8,611 kilometres (5,351 mi).

Illustrations

Worked examples

Example 1 — a first encounter with Very Long Baseline Array

Start with the simplest possible case. Write down what Very Long Baseline Array claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Very Long Baseline Array before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Very Long Baseline Array ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Very Long Baseline Array

In research: Very Long Baseline Array appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Very Long Baseline Array in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Very Long Baseline Array is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1993 establishments in New Mexico, Interferometric telescopes, Kitt Peak National Observatory, so understanding it makes those chapters shorter.
In everyday life: Look for Very Long Baseline Array outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Very Long Baseline Array in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Very Long Baseline Array means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Very Long Baseline Array out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Very Long Baseline Array in simple terms?

Why does Very Long Baseline Array matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Very Long Baseline Array?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Very Long Baseline Array.