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In December 2020, astronomers documented a burst of highly energetic light in one of the most distant galaxies ever observed. But less than a year later, the paper\u2019s claims lay in limbo. Other scientists said it had merely been a passing satellite.<\/p>\n
\u201cI was a bit sad that the gamma ray burst turned out to be just an artificial satellite,\u201d said Krzysztof Kami\u0144ski, an astronomer at the Astronomical Observatory Institute in Poland who said he matched the position, time and brightness of the discovery to an orbiting spacecraft.<\/p>\n
Linhua Jiang, an astronomer at Peking University in Beijing who led the original finding, said his team stood by their work, adding that the probability of a satellite passing directly in front of the distant galaxy at exactly the right moment was minuscule at best.<\/p>\n
The dispute likely will not be the last time that scientists argue over whether a passing satellite is being mistaken for an astronomical discovery.<\/p>\n<\/div>\n<\/div>\n
Earth\u2019s orbits are filling with satellites at an astounding pace. Already there are more than 9,000 satellites orbiting the planet, and more than 5,000 of them belong to Starlink, the constellation built by SpaceX to beam internet service down to Earth. They are to be joined by thousands of satellites from other companies and countries in the decades ahead.<\/p>\n
The more of them there are, the greater the satellites\u2019 interference with ground astronomy\u2019s ability to answer questions about the cosmos \u2014 and humanity\u2019s place in it.<\/p>\n<\/div>\n<\/div>\n
SpaceX did not reply to requests for comment. But astronomers on the ground said they are not ready to give up the night skies to trains of freshly deployed satellites. They are combining new and old technologies with ingenuity to deal with the proliferating obstacles to their observations. They are also working with the industry to find fixes to darken satellites. And they are trying to persuade regulators to pay more attention to the mushrooming satellite industry.<\/p>\n
The strategies are paying off \u2014 for now. But researchers\u2019 quest to preserve the power of astronomy faces fundamental disadvantages. It can take decades to build new telescopes, while dozens of new satellites may be added to the night skies every week.<\/p>\n<\/div>\n<\/div>\n
\u201cThe time scales are very mismatched,\u201d said Meredith Rawls, a research scientist at the Vera C. Rubin Observatory, a powerful U.S.-funded telescope in Chile that is to come online in 2025. \u201cThe speed at which the satellite industry is designing and launching their hardware is just lightning fast compared to astronomy.\u201d<\/p>\n
To photograph the night sky, telescope operators for more than a century captured images on glass plates.<\/p>\n
That began to change with the emergence of charge-coupled device detectors. First invented in 1969, CCDs are digital, snapping images around 100 times faster than film cameras.<\/p>\n
In the 1980s, some of the first telescopes emerged with electronic CCD \u201ceyes.\u201d Today, telescopes around the world continue to rely on this Nobel Prize-winning technology. While CCDs are not the fastest camera technology now available, they are the most common. It also takes decades to build the most powerful ground observatories, and many were designed with 20th century levels of imaging techniques in mind.<\/p>\n
That includes the Vera Rubin Observatory, named after an astronomer who played a central role in discovering dark matter. Its mission includes spotting planet-killing asteroids and studying the relationship between dark matter and dark energy.<\/p>\n<\/div>\n<\/div>\n
The telescope relies on a behemoth CCD detector that is around the same size as the average car, but several thousands of pounds heavier. It is the largest astronomical digital camera ever constructed. Capturing a wide field of the sky, it is supposed to peer into the mysteries of objects 20 million times fainter than the human eye can see.<\/p>\n
But as satellites fill the skies, astronomers who planned to rely on the Rubin telescope for scientific discovery are concerned.<\/p>\n
\u201cThe whole point of Rubin is to open up this new window into the universe to find things that we didn\u2019t even know to look for,\u201d Dr. Rawls said. \u201cAnd if instead we\u2019re going to look through the equivalent of a windshield of bugs, you don\u2019t know what you\u2019re not going to see.\u201d<\/p>\n<\/div>\n<\/div>\n
Some telescopes that use CCD detectors study such a narrow slice of the sky that satellites may not interfere with them. But the Rubin telescope\u2019s wide view poses unique problems. One study showed that, during certain times of night, almost every image taken from the telescope will be marred by at least one, if not many, satellites, searing a trail hundreds of pixels wide.<\/p>\n<\/div>\n<\/div>\n
Dr. Rawls laid out two strategies for dealing with this threat to the telescope: dodging and correcting.<\/p>\n
If astronomers know satellite paths in advance, the technology can anticipate and \u201cdodge\u201d the satellites by temporarily repointing the telescope.<\/p>\n
\u201cWe use an algorithm to determine where the telescope points,\u201d Dr. Rawls said. \u201cThe algorithm is brilliant, it can take into account lots of different weightings,\u201d she added, including avoiding swarms of satellites.<\/p>\n
Dr. Rawls said that dodging should remove about half of the streaks from Vera Rubin\u2019s telescope, depending on how many satellites are in orbit.<\/p>\n
For the correcting strategy, Dr. Rawls said that scientists are developing algorithms to scrub the satellites from data \u2014 a far more challenging task \u2014 but one that is less disruptive to observations.<\/p>\n<\/div>\n<\/div>\n
But given that the software solutions are all imperfect and challenging, some experts have suggested that telescope builders think about changing their hardware.<\/p>\n
Darren DePoy, an astronomer at Texas A&M University, was involved with some of the first telescopes in the 1980s to use CCDs. In 2018, he began testing and eventually using a much more ubiquitous detector: CMOS, for complementary metal oxide semiconductor, the same kind that is probably in your smartphone camera.<\/p>\n
\u201cAlthough the physics is very similar for CCD and CMOS detectors, how you get the signal out is a little different,\u201d Dr. DePoy said. \u201cFor CMOS, you can read all the pixels simultaneously, while you have to wait to read each pixel sequentially on a CCD detector.\u201d<\/p>\n
As an example, Dr. DePoy said that while a modern CCD might require about 10 seconds to photograph a faint galaxy, the equivalent CMOS detector would take closer to 10 milliseconds \u2014 1,000 times faster. By taking numerous rapid exposures, astronomers can excise the frames smeared by satellites or airplanes, then average the rest to create a pristine final image.<\/p>\n
Dr. DePoy said that small CMOS detectors are already popular among amateur astronomers who own hobby telescopes. He finds it hard to imagine that CMOS isn\u2019t the future. But, for now, he estimated that fewer than 10 larger telescopes use the technology.<\/p>\n<\/div>\n<\/div>\n
Part of the sluggish embrace is because inertia is cheaper.<\/p>\n<\/div>\n<\/div>\n
Buying and integrating large CMOS detectors is still expensive compared with using existing CCD detectors, said Richard Green, an astronomer at the University of Arizona and an interim director at the Center for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference, an organization that sponsors research around the topic.<\/p>\n
That problem was noted by Dr. Rawls when she was asked if the Rubin telescope could use CMOS technology.<\/p>\n
\u201cThe concept of changing it now is just laughable,\u201d she said. \u201cBecause that\u2019s like you\u2019re building a house and they\u2019re about to put the windows in and someone\u2019s like, \u2018Hey, should we use a different foundation?\u2019\u201d<\/p>\n
The United States government is both championing the commercialization of space and sponsoring telescopes like the Rubin Observatory. For that reason, Dr. Green said it was up to the government to deal with the effects on astronomy, perhaps by charging companies to pay for telescope upgrades.<\/p>\n<\/div>\n<\/div>\n
\u201cIf the government says we\u2019ll do that by assigning a fee to satellite operators, well that\u2019s great,\u201d he said. \u201cSomebody in the government ought to help us deal with the fallout.\u201d<\/p>\n
The government so far has not moved to compel satellite operators to help pay for telescope upgrades. But some companies are attempting to address aspects of the problem.<\/p>\n
SpaceX declined to comment when asked about the company\u2019s work to lessen the effects of its satellites on science. But astronomers familiar with its efforts described some of the work.<\/p>\n