astronomy

Leighton Radio Telescopes

Leighton Radio Telescopes 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 Leighton Radio Telescopes rather than just read about it. In short: The Leighton Radio Telescopes are 10.4 meter parabolic dish antennas designed by Robert B. Leighton in the 1970s, which were fabricated on the Caltech campus during the 1970s and 1980s.

Key takeaways

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

Reference excerpt

The Leighton Radio Telescopes are 10.4 meter parabolic dish antennas designed by Robert B. Leighton in the 1970s, which were fabricated on the Caltech campus during the 1970s and 1980s. The telescope surfaces reached an accuracy of 10 microns RMS, allowing observations throughout the millimeter and submillimeter bands. In all, eight of these telescopes were made. They were used as the six elements of the Owens Valley Radio Observatory (OVRO) millimeter interferometer in California, and as single telescopes at the Caltech Submillimeter Observatory in Hawaii and the Raman Research Institute (RRI) at Bangalore, India. In the spring of 2005, the six Leighton telescopes in Owens Valley were moved to a high mountain site in the White Mountains to form the core of the CARMA array of 25 telescopes. The CARMA array was decommissioned in 2015 at which time the Leighton telescopes were moved back to OVRO, where they are now being repurposed for different projects including the CO Mapping Array Pathfinder (COMAP) (a 19 pixel imaging array), the Event Horizon Telescope (EHT), and various transient detection projects.

Origins In 1973 Robert Leighton proposed to the NSF to build four 10.4 meter diameter parabolic dish radio antennas. Three of the antennas were to be used as a millimeter-wave interferometer to be sited at OVRO, and the fourth was to be used as a single submillimeter telescope at a high mountain site. The proposal was approved (AST 73–04908), and total funding was $477,700.

The Mount The telescopes have an altazimuth fork mount. The azimuth axis is an inverted circular cone, the apex of which is supported by a thrust bearing. Cam-follower roller bearings mounted around the top of the base push against the top of the inverted cone to complete the azimuth axis constraint. There is a cable wrap for signal and power wiring which rides atop the azimuth thrust bearing. On the top of the cone is the azimuth platform, which supports two elevation bearings. The elevation tipping platform that supports the primary reflector is driven in elevation by a rotating ball-screw. The azimuth platform is large enough to allow several people to work on it. It also houses a small sidecab room to the right of the right elevation bearing, which houses the Nasmyth focus radio receivers (typically SIS receivers). The sidecab also houses electronics for the axis encoders, LO & IF systems and tiltmeters along with the antenna control computer. Three motors drive the telescope, two in azimuth and one in elevation. An offset in the drive voltage is maintained between the azimuth motors, in order to prevent backlash when driving the 1.74 meter diameter bull gear. The telescopes can slew at a rate of 40 degrees per minute.

Optics The 10.4 meter primary mirror has a 0.4 focal ratio. The hyperboloid secondary mirror is 0.606 meters in diameter, and directs the light to either a Cassegrain focus or a Nasmyth focus, depending upon whether or not a tertiary mirror is present. The telescope has an effective focal ratio of 12.4 at the Cassegrain focus, which is located at the point of intersection of the azimuth and elevations axes.

The Dish

The primary mirror, usually called the dish, is composed of 84 panels which are hexagonal when projected onto the aperture plane (the RRI dish had 81 panels). Each panel is approximately 1.15 meters across. The panel that would have tiled the center of the dish is absent, providing the hole required for Cassegrain and Nasmyth foci. Panels near the edge of the dish are irregularly shaped, and in some cases larger than the nominal size, in order to tile the circular aperture without needing any very small panels. The mirror is 92% homologous, maintaining a nearly parabolic shape with only the focal point changing when the mirror deforms due to gravity as the telescope elevation changes. Deviations from homology are less than 17 microns RMS over the telescope's entire elevation range. These focus changes are compensated for by moving the secondary mirror laterally and along the optical axis.

A unique feature of the Leighton telescopes is that the primary is fabricated as a single 10.4 m diameter precision surface, rather than individually machined panels. The dish panels are made of a lightweight (15 kg/m3) aluminum honeycomb material with vertical channels. To produce the reflector's parabolic shape, the panels were assembled atop the same steel tube space frame that will support the panels on the deployed telescope. The space frame was mounted on an air bearing surrounding a central mast. An arm extended from the central mast, which had a parabolic track on the bottom side. The parabolic track was shaped by a laser metrology system that made use of the fact that a parabola is the locus of points equidistant from the focal point and a directrix line. The directrix in this case was the upper side of the arm. After the parabolic track was created, a cutting tool moved along the track, and cut the honeycomb panels as the dish rotated on the air bearing. After the honeycomb panels were cut to the proper parabolic shape, an aluminum skin was applied to each panel, to provide the dish's reflecting surface.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Leighton Radio Telescopes

Start with the simplest possible case. Write down what Leighton Radio Telescopes 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 Leighton Radio Telescopes 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 Leighton Radio Telescopes 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 Leighton Radio Telescopes

In research: Leighton Radio Telescopes 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 Leighton Radio Telescopes 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: Leighton Radio Telescopes is common in secondary-school and first-year university syllabi. It links to neighbouring topics California Institute of Technology, Owens Valley, Radio telescopes, so understanding it makes those chapters shorter.
In everyday life: Look for Leighton Radio Telescopes 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 Leighton Radio Telescopes in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Leighton Radio Telescopes 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 Leighton Radio Telescopes out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Leighton Radio Telescopes in simple terms?

The Leighton Radio Telescopes are 10.4 meter parabolic dish antennas designed by Robert B. Leighton in the 1970s, which were fabricated on the Caltech campus during the 1970s and 1980s.

Why does Leighton Radio Telescopes 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 Leighton Radio Telescopes?

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 Leighton Radio Telescopes.