You can essentially steer the telescope by choosing where to receive radio waves above the dish, allowing you to focus on various objects and track them as the earth rotates.įocusing those waves to a narrow area above the dish doesn’t do much good unless you have a receiver up there to collect and measure them. The beauty of a spherical reflector is that, by changing the position at which you measure the reflected waves above the dish, you’re measuring those waves from different parts of the sky. That might sound like a bad thing since you want to gather and focus as much signal as possible across the entire dish. Spherical reflectors don’t perfectly focus all the incoming rays. Rather than using a parabolic shape for the dish that would focus everything to a single point, they chose a spherical curve. The designers of Arecibo had a pretty clever solution to the problem. Radio telescopes can be used during the day and night - so there’s more sky to look at over the course of a day or year - but a telescope that can’t steer is still pretty useless. Because the dish was fixed to the earth, it was constrained to point at whatever part of the sky happened to be overhead. Although it looks solid from a distance, the reflector was a series of aluminum panels carefully suspended on steel cables. The telescope’s dish was constructed inside an enormous circular sinkhole. Arecibo facilitated some of the most exciting astronomical discoveries of our age, including the Nobel-prize winning observation of binary pulsars providing the first evidence of gravitational waves. It could send out radio signals and measure the returning echoes from nearby objects in space, including planets and asteroids. Not only could it receive the faintest of radio signals, it could transmit them as well, allowing Arecibo to work as a celestial radar. The most iconic part of the observatory was the massive radio telescope. If you grew up in Puerto Rico, you almost certainly visited this incredible facility on a field trip or two or three. A big part of Arecibo’s mission is education and outreach programs to engage the public’s interest in astronomy and atmospheric sciences. The National Science Foundation took over the facility in 1969 to use it for more peaceful endeavors, with help from a few managing partners over the years. Located on the Caribbean island of Puerto Rico, the Arecibo Observatory was designed and constructed in the 1950s and 60s as a department of defense project to detect nuclear warheads in the upper atmosphere. Arecibo took that strategy to the extreme with it’s 305-meter (or 1,000-foot) diameter dish - the largest in the world until China’s half-kilometer FAST scope took the title in 2016. To speed up observations, you can also gather radio waves from a larger area and focus them into a clearer signal. The longer you focus on an object, the more resolution you get. You essentially have two options to get high-quality radio astronomy data: more time or more space. These radio waves can be quite faint, complicating the task of separating them from the background noise. A radio telescope is basically an antenna that can tune in to some frequencies of electromagnetic radiation that emanate from celestial objects. Most of the gamma rays, x-rays, ultraviolet, and infrared portions of the spectrum are blocked out by the atmosphere. The same way we observe visible light from celestial objects using our eyes and optical telescopes, we can also take advantage of the other parts of the electromagnetic spectrum in astronomy. Today, we’re discussing the Arecibo telescope collapse. Why was this telescope so important, how did it work, and why did it fail? I’m Grady, and this is Practical Engineering. The National Science Foundation, who owns the observatory, recently released their report to congress on the cause of the failure and the events leading up to it. This 57-year-old megastructure not only made many incredible scientific discoveries over its lifetime, it was also an emblem of humanity’s interest and curiosity about our place in the universe. In December of 2020, the Arecibo telescope - one of the largest and most iconic astronomical instruments in the world - collapsed.
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