Arecibo has a special characteristic that makes it unique among all the great radio telescopes in the world. It can do things that even the much more modern Chinese FAST can't do - it has the ability to transmit, while others only serve as receivers. This allows Arecibo to conduct radar astronomy, transmitting microwaves and observing how they are reflected off distant objects.
There is no replacement for the Arecibo Observatory, nor is there likely to be any in the near future. The 500-meter Aperture Spherical Telescope (FAST) in China is larger than Arecibo, but it does not have the crucial transmission capacity. The Goldstone Deep Space Communications Complex in California can transmit, but since it is primarily concerned with communicating with spacecraft, there is little free time for scientific observations. Even when available for research, the largest dish in the Goldstone array is only 1/4 the diameter of the reflector at Arecibo.
The 1993 Nobel Prize in Physics was awarded to Russell Hulse and Joseph Taylor for their work with Arecibo in monitoring a binary pulsar, providing a strict test of Einstein's theory of general relativity and the first evidence for the existence of waves. gravitational.
Arecibo also helps NASA characterize asteroids that could pose a threat to Earth through the agency's Near-Earth Object Observation Program at the Planetary Defense Coordination Office.
Normally, the transmission is not something that you would expect a radio telescope to do. No more than an optical telescope would be expected to project light into the sky.
In 1974, researchers spread what has come to be called the Arecibo Message to star cluster M13. This 210-byte burst of digital information included simple images of the human form and of the radio telescope itself. It represents the first concerted attempt, and to date only, to communicate directly with potential extraterrestrial life.
Since 1989, Arecibo has been able to capture direct images of an asteroid in space. Usually, asteroids are too far away and too small to be more than a specification of light through an optical telescope, but when viewed by radar, the shape and rotation of Castalia (the first-ever captured image of an asteroid) it was easily observed.
To this day, the Arecibo Observatory remains the largest and most powerful deep-space transmitter in the world. The radar imagery you can generate of distant objects is absolutely unmatched.
It is the most powerful and sensitive planetary radar system. According to the University of Central Florida, the observatory has collected more than 12 petabytes of data in its 50-year history, that is, 1.2 x 1010 megabytes, more than 10 billion megabytes. In 2019, UCF expanded its agreement with Microsoft, resulting in the observatory gaining access to a variety of services, from analytics to artificial intelligence, to develop a new platform that will help facilitate the access and storage of all 12 petabytes of data. which observatory has collected in its 50 years of history. Fully implemented, the new platform is expected to make robust information on planets, pulsars, asteroids, and comets easily accessible to scientists working in Arecibo and around the world.
More than simply satisfying our curiosity about the cosmos, this capability is the most important part of NASA's Planetary Defense program. We already rely heavily on antiquated orbital assets to help identify and track potentially dangerous asteroids as they approach Earth, losing Arecibo's unique radar capabilities makes the situation worse.
The Arecibo Observatory is regularly used to track near-Earth asteroids, investigate radio sources, and occasionally relay messages to those who are listening.
The University of Arizona is proud of the Osiris Rex mission of taking a sample from an asteroid. When Osiris Rex approached the asteroid called Bennu and took a sample, part of what made it possible was working years before on the huge radar telescope in Puerto Rico. Michael Nolan leads the Osiris Rex science team but was previously director of Arecibo. “We were able to model the shape, measure the orientation of the turnover rate measurements. Look at its surface and use it in planning the Osiris Rex mission. "
Dr. Nolan says Arecibo is the most powerful part of the program to find asteroids that could hit Earth.
Beyond its impressive history and being Puerto Rico's greatest scientific legacy, there are powerful reasons to demand the reconstruction of the Arecibo Radio Telescope. Of immediate interest is the role of the Arecibo Radio Telescope in the tracking and characterization of asteroids. The Arecibo planetary radar was until recently the most powerful asteroid detection and survey instrument in the world, observing approximately 100 near-Earth asteroids per year. Half of them were newly discovered objects whose orbits were not precisely known. The Arecibo observations helped scientists determine whether asteroids would hit our planet and ensured that their trajectories were cataloged for future observations.
Scientists are of the opinion that the Chinese FAST will not be able to completely replace the Arecibo because it was unique due to its location and technical equipment.
"The Arecibo had a more powerful radio transmitter up to 900 kW, which made it the most sensitive radio locator in the world. Also, the Arecibo was 7.5 degrees closer to the equator, which made most of the sky was visible when the Earth rotated. The Arecibo also had a wider operating range, to be able to work as part of international networks ", commented the member of the International Astronomical Union and principal investigator of the Institute of applied astronomy of the Russian Academy of Sciences. , Yuri Bondarenko.
As a fundamental contrast, Chinese facilities do not have a transmitter.
We just didn't know is just not good enough: as close as August 6, 2020, Earth scientists confirmed they had one less asteroid to worry about thanks to research by an international team of scientists at the Arecibo Observatory in Puerto Rico.
What? A potato-shaped asteroid elongated about 1 km (0.6 miles) along the longest axis.
Asteroid 2020 NK1 was discovered in early July by the University of Hawaii's Asteroid Land Impact Last Warning System (ATLAS) inspection team. Little was known about the asteroid, making it difficult to predict exactly where the asteroid would travel in the future. It was estimated to be 500 meters in diameter, roughly the length of five football fields.
Prior to the Arecibo observations, 2020 NK1 was calculated to be one of the greatest threats of all known asteroids on NASA's list of possible impactors, with about a one in 70,000 chance of impacting Earth between 2086 and 2101.
The Arecibo Planetary Radar Group made it a priority to observe the 2020 NK1 when it was within range, within 5 million miles, of the facility's powerful instruments. In this case, the time period was brief, from July 30 to July 31, around the same time that Tropical Storm Isaías was expected to hit the island. The observatory was closed to prepare for the storm, and as soon as it passed, it was put into action to detect and study the asteroid. Even when parts of the island lost power and the damage was assessed, Arecibo's team was able to determine the shape, orbit, and motion of the asteroid. The team of scientists and telescope operators were able to observe the asteroid for two and a half hours, collecting precise measurements of the asteroid's speed and distance from Earth, as well as high-resolution images of the asteroid. "These measurements greatly improve our knowledge of the 2020 NK1 orbit and allow predictions of its future whereabouts for decades to come," says Patrick Taylor, a Texas scientist at the Lunar and Planetary Institute, part of the Space Research Association of Universities, who participated in the observation remotely.
The observations showed that the asteroid is not expected to get close enough to Earth to pose a danger in the future, and its closest approach will come in 2043 when it will pass about 2.25 million miles from Earth, or more than 9. times farther than the Moon, the science team concluded.
Arecibo faces extinction, perhaps, just as we humans could be if we don't know what is about to hit us.
It is a problem of civilization. Perhaps the COVID-19 pandemic should force us to insist on science, in the case of the current pandemic, previous studies on the effects of biodiversity loss before its appearance could have prepared us for what has been a global disaster. The truth is that previous studies were neglected even when there were the first of the initial outbreak.
Lesson: neglecting science can produce tragedies.
Only two facilities in the world do serious planetary radar work. Arecibo, obviously, and the Goldstone Deep Space Communications Complex in the Mojave Desert. But Goldstone's priority is communicating with spacecraft, and its many nearby military installations mean that operators must ask permission before turning on their transmitter.
Arecibo is also much larger: it is 20 times more sensitive and its transmitters emit twice as many kilowatts of radio waves.
Losing their capabilities would have a huge impact, pun intended, on scientists' ability to predict and avoid asteroid threats. Species also don't have to go extinct for an asteroid crash to be significant. Rocks of about 100 meters hit here every few thousand years. "These objects cannot cause global destruction," says SETI Institute astronomer Michael Busch, "but they can cause damage on the scale of a small country or a large US state."
With radar observations, scientists like Busch can pinpoint orbits and accurately advance them hundreds of years, warning civilization in advance. If rocket scientists deflect an asteroid, radar astronomers will grade their work, pinging the newly pushed asteroids and projecting their new, hopefully benign orbits.
“You cannot undo a hurricane; you can't undo a tornado, ”says puertorrican astronomer Rivera-Valentin. "You can undo the impact of an asteroid." But only if you know it's coming.
With more sensitive instruments and programs dedicated to detecting rocks, astronomers are discovering asteroids faster and faster, a pattern that will likely continue for a while. And without Arecibo? "We just won't be able to observe 75 to 80 percent of the objects that we were able to detect," says the puertorrican scientist.
And that means they won't have a precise idea of where 75 or 80 percent of those objects go, from car-sized ones to state crushers, now or in 2417. Now imagine the discovery rate will go down because we lose the Arecibo radar facility that has proven to be the best facility in the ideal location for such an instrument and such responsibility.
Was the erosion of Arecibo really inevitable and what does this mean for the scientific community? The real question is, what have we lost? Arecibo is not only a landmark in Puerto Rico. Are there successors to Arecibo who are capable of filling the huge void that the scientific community now faces? Looking at the aspects of the telescope that made it unique helps us find those answers.
Telescopes are essentially very sensitive instruments for observing remote sources of electromagnetic radiation. In the case of optical telescopes, this means the visible part of the EM spectrum. Radio telescopes work in a similar way, but they are tuned to receive radio frequencies. Arecibo was able to capture between 1-10 GHz with multiple receivers using 221 effective meters of its 304 meters in diameter. Much like how the primary mirror of an optical telescope largely determines how much light will eventually reach the sensor, so too does the size and shape of the primary mirror (dish) of a radio telescope.
If it is newer and physically larger, it would seem obvious that China's FAST telescope is superior to Arecibo, that is not entirely true. Arecibo dish reflectors are mounted more rigidly in place than FAST's. While the latter is more flexible with winches capable of adjusting the shape of the reflector mesh, this comes with offsets at these higher frequencies. Even with updates to FAST receivers similar to the updates Arecibo received in 1997, FAST could only cover frequencies up to about 5 GHz, only half the performance of Arecibo.
In addition to these properties, there is also the question of radar astronomy, which requires the transmission of powerful radar signals. Arecibo has four radar transmitters, 20 TW (continuous), 2.5 TW (pulsed), 300 MW, and 6 MW. These take up a significant amount of space and therefore cannot be mounted on the FAST secondary platform together with its receivers due to weight and space issues. Arecibo is just one of two telescopes that have been used regularly in radar astronomy, the other being the 70-meter Goldstone solar system radar, with a 500 kW transmitter.
Since the detection of asteroids and comets is an essential part of Arecibo's radar astronomy tasks (early warning and tracking system), this has left a significant blind spot. Without Arecibo, we have to rely primarily (limited we should point out, another pun) on optical telescopes to track these objects as they rush through the solar system, the biggest problem is that optical telescopes don't see hundreds of asteroids at least they don't. early enough.
So what happened? Everything seems to point to the lack of an adequate maintenance budget, which led to the situation where the many cables of the Arecibo Observatory were not regularly inspected, maintained, or replaced.
A major problem with scientific or research facilities like Arecibo is politics. When a politician is asked what he thinks of Arecibo, it is unlikely that many can sum up what the facility was used for and why its loss is felt far beyond the astronomical community.
In a world of the greed of billionaires and Wall Street marking progress in the billions for financial corporations with little commitment to the planet, the budget for a facility like Arecibo is microscopically small, even the idea of a total reconstruction is an efficient project compared to the world economy.
All we know for sure at this point is that despite its different geographic location and lack of radar transmission capability, the FAST telescope in conjunction with a number of smaller radio telescopes will NOT be able to replace most of the tasks left by Arecibo while asteroids by the hundreds (we hope) go unnoticed.
“It does atmospheric science, it does solar system science, it does astronomy, it does astrophysics,” Rivera-Valentín says. “It’s important for science, and for the entire world.”
So the question is whether we will neglect science again and later regret not doing what we could and should have done.
Pachi Ortizfeliciano
#RebuildAreciboObservatory
#WhatAreciboMeansToMe
Postdata. Scientists talk Arecibo
Scientists around the world are holding their breath, waiting to see whether the Arecibo Observatory will survive. It's the rare instrument that has not just revolutionized the way experts see our solar system and our universe.
"We can prioritize science, we can decide that we want to make sure that Arecibo lasts into the future," Alessondra Springmann told Space.com.
Jill Tarter, a scientist famous for her work on the search for extraterrestrial intelligence (SETI) and the inspiration for the main character in "Contact," told Space.com. "But I think that in making that decision, they really do need to weigh the things that Arecibo can do that other places can't."
The particularly eye-catching item here is planetary radar, a rare capacity even among major radio facilities. Arecibo Observatory is the largest facility in the world that can blast a radar beam at near-Earth objects or even nearby planets, then wait for and analyze the echo as that beam bounces back.
In the case of asteroids, that echo gives scientists the information they need to determine whether the space rock could someday collide with Earth. Other facilities can do it less frequently and with less power, but nothing can match Arecibo, several scientists with ties to the facility emphasized.
Springmann's work focuses on planetary radar, and she's sympathetic to the observatory's current plight. Arecibo "really deserves to have a future not because of what it has done in the past, but because of what it can keep doing."
"It is really just a phenomenal, unique place — there's nothing like it on Earth," Springmann said. "There's very much an 'anything is possible' mentality there because it's designed to be so flexible; you're not necessarily locked in to only doing a handful of things with it."
Want to study the boundary between Earth's atmosphere and space? Want to map the surface of Venus or the distribution of nearby galaxies? Want to find a lost spacecraft or scientists' first exoplanet? Want to listen for gravitational waves rippling across space or send a message out to any aliens listening from afar? Want to determine the risk that a specific near-Earth asteroid will slam into Earth and determine whether it has a moon or two? Amid the lush greenery of Puerto Rico, Arecibo has done all of those.
In addition to its planetary radar work, Arecibo Observatory is also particularly noted for its observations of the fast-spinning neutron stars known as pulsars. Although the strange objects were discovered elsewhere, it was at Arecibo that scientists first identified a binary pulsar, work that won a Nobel Prize, and began the arduous process of trying to measure gravitational waves rippling out from the pair.
And Arecibo's threefold expertise has had a side effect on the scientists who have spent time at the observatory. "It's really brought a unique cross-section of scientists together," Springmann said. "Usually, planetary people, we don't interact with astronomers much, much less radio astronomers, and so I know all these radio astronomers I wouldn't have met otherwise. I've met aeronomers — I didn't even know aeronomy was a thing before I started there!" (Those are the atmospheric scientists.)
Abel Mendez, an astrobiologist at the University of Puerto Rico, is one of the exceptions, although he doesn't have as far to travel when he does choose to observe in person. He grew up in Puerto Rico and first visited the observatory as a 10-year-old for a personal tour with a scientist.
Mendez, Tarter, Springmann and countless other scientists are keeping their fingers crossed that the end is not imminent for Arecibo — that the venerable observatory can weather the current storm, as it has so many others, and continue probing the heavens for decades to come.
https://www.space.com/arecibo-observatory-science-impact-and-culture
Pdd: The news is headline throughout the world, reconstruction is the option that Puerto Rico and the scientific field acclaim
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1 comentario:
Submitted and under consideration: "The community overwhelmingly agrees that there is a need to build an improved next generation radio telescope at the AO (Arecibo) site.
From these discussions, we established the set of scientific requirements that the new facility should allow. "
Link in the article.
https://arxiv.org/abs/2103.01367
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