Leighton Radio Telescopes facts for kids
The Leighton Radio Telescopes are special telescopes shaped like big dishes. They were designed by Robert B. Leighton in the 1970s. These 10.4-meter wide dishes were built at Caltech in the 1970s and 1980s. They were made very precisely, allowing them to study tiny radio waves.
Eight of these amazing telescopes were built. Six of them worked together as part of the Owens Valley Radio Observatory (OVRO) in California. Others were used alone at the Caltech Submillimeter Observatory in Hawaii and the Raman Research Institute in Bangalore, India.
In 2005, the six OVRO telescopes moved to the White Mountains. There, they became part of a bigger group of 25 telescopes called CARMA. CARMA stopped working in 2015. The Leighton telescopes then returned to OVRO. Today, they are being used for new projects. These include the CO Mapping Array Pathfinder (COMAP) and the Event Horizon Telescope (EHT). They also help find quick, sudden radio signals from space.
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How the Telescopes Started
In 1973, Robert Leighton suggested building four large radio dish antennas. He wanted three of them to work together at OVRO. The fourth would be a single telescope on a tall mountain. His idea was approved, and he received funding to build them.
The Telescope Mount
The Leighton telescopes sit on a special stand called an altazimuth mount. This mount lets the telescope move up and down, and spin around. The bottom part of the mount is shaped like an upside-down cone. It spins smoothly on a special bearing.
This part of the mount is big enough for people to work on it. It also has a small room called a sidecab. This room holds important equipment. This equipment helps the telescope receive radio signals. It also controls how the telescope moves.
Three motors help the telescope move. Two motors control the spinning motion. One motor controls the up and down movement. The telescopes can move quite fast, about 40 degrees every minute.
Telescope Optics
The main mirror, or dish, of the telescope is 10.4 meters wide. It has a special curve that helps focus radio waves. A smaller, secondary mirror helps direct these radio waves.
The waves can go to two different focus points. One is called the Cassegrain focus. The other is the Nasmyth focus. This design helps scientists use different tools to study the radio waves.
The Dish: How It's Made
The main mirror, or "dish," is made of 84 separate panels. Most of these panels are shaped like hexagons. The dish for the Raman Research Institute telescope had 81 panels. Each panel is about 1.15 meters wide.
The very center panel is missing, creating a hole. This hole is needed for the Cassegrain and Nasmyth focus points. Panels near the edge of the dish are shaped differently. This helps them fit perfectly into the round shape of the dish.
The dish is designed to keep its shape very well. Even when it moves, it stays almost perfectly curved. This is important for clear observations. Small changes in its shape are corrected by moving the secondary mirror.
A special thing about these telescopes is how the dish was made. The entire 10.4-meter surface was shaped as one piece. It was not made from many separate, pre-shaped panels.
The panels are made from a light aluminum material. To create the perfect curve, the panels were put together on a steel frame. This frame is the same one that supports the panels on the finished telescope. A special cutting tool then shaped the panels precisely. After shaping, an aluminum skin was added to each panel. This skin created the reflecting surface of the dish.
The steel frame is made of short tubes. These tubes connect with very precise pins. One person could put the frame together in just a few days. This design was even studied for building large telescopes in space.
This special design also allowed the dish to be taken apart. It could be moved in large sections to the observatory site. This was done without harming its optical quality. This method was very helpful when moving the telescopes to the CARMA site and back.
Most of the dishes were built at Caltech. They were made in a building once used to polish the huge Hale Telescope mirror. The dish for the Raman Research Institute telescope was built in India.
Where the Telescopes Were Used
The first three telescopes were set up at OVRO for testing. This was to see how well they worked together. After they were officially opened in 1985, three more antennas were added. This made a six-telescope array. The last of these six was finished in 1996.
In 2005, these six telescopes moved to the Inyo Mountains in California. They joined the CARMA array. CARMA stopped working in 2015. The six Leighton telescopes then moved back to OVRO for storage. One of them is now being used as the CO Mapping Array Pathfinder telescope.
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The Leighton telescope with the most accurate surface was sent to Mauna Kea, Hawaii. It became the Caltech Submillimeter Observatory. This telescope was named the "Leighton Telescope" after Robert Leighton passed away in 1997. It was special because it could actively control its surface.
Another Leighton telescope was in India at the Raman Research Institute. It followed the Leighton design closely. However, it was built entirely in India. It was also the only Leighton telescope that used special receivers at its main focus point.
This telescope was placed on top of a building. This building housed its electronics. It began working in 1988. It observed maser emissions from Mira-type stars. By 2009, its surface had changed a bit. But it could still observe high-frequency radio waves. The telescope stopped working around 2012.
