The successful launch of Sputnik in 1957 marked a milestone in human history as the first time an artificial object has ever orbited Earth. But we learned little about the space SNAFU, which we courted with the advent of satellite technology. In the 64 years, the night sky on our planet became increasingly congested. Today, more than 3,000 satellites orbit the Earth and are joined by millions of pieces of space debris – such as pieces of a broken satellite, ejected parts of rockets and spots from spacecraft. NASA estimates that there are about 6,000 tons of debris in low Earth orbit alone.
This orbital debris not only poses a danger to navigation for astronauts, but also reflects sunlight down to the surface, interfering with ground-based telescopic observations. A study recently adopted by Monthly Notices of the Royal Astronomical Society: Letters suggests that there is now nowhere on Earth free of light pollution produced by air debris and satellites. Even more worrying is that researchers expect the amount of debris in orbit to increase by an order of magnitude over the next decade, when mega-constellations of mini-satellites broadcasting the Internet, such as SpaceX’s Starlink program, take off.
“Astronomers – and casual viewers of the night sky – must expect a future in which the low-Earth orbit population includes tens of thousands of relatively large satellites,” warned Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics in a 2020 study. significant for certain types of observations, certain observatories and at certain times of the year. “
Until a few years ago, humanity had launched less than 10,000 objects into orbit since the beginning of the space age. With the advent of low-cost rocket launch technology – in which the price per kilogram of launch vehicle has dropped from $ 24,800 during the shuttle era to just $ 1,240 today – the speed at which we launch satellites into orbit must increase exponentially.
A total of more than 20,000 satellites are expected to be launched into LEO by 2025 – approximately ten times the total number of satellites active in 2018. Only SpaceX has permission from the US government to launch 12,000 Starlinks into orbit (with plans to there are as many as 42,000 of them), while the Amazon Kuiper project has the right to send 3,236 of its own satellites in the coming years. Both programs seek to create an orbital network in Low Earth Orbit capable of providing a high-bandwidth and low latency Internet connection accessible from anywhere on the planet. Although their intentions are noble, the unintended consequences of the gathering of many spaceships in our sky could radically change our view of the solar system around us.
“If 100,000 or more LEOsats, proposed by many companies and many governments, are deployed, no combination of mitigation measures can completely avoid the impact of satellite pathways on the scientific programs of current and planned terrestrial optical NIR astronomical facilities,” the 2020 U.S. report said. astronomical society.
When the first 360 star connections were released in May 2019, for example, their presence in the night sky was immediately noticeable. Their highly reflective design made each mini-satellite about 99 percent brighter than the surrounding sites during the five months it took them to reach their 550km altitude. This effect is especially pronounced at sunrise and sunset, when the sun’s rays are reflected by the solar panels of the satellites. SpaceX’s attempt to reduce this reflectivity with a “darkening treatment” in early 2020 was only partially successful.
“We find an approximately 55% reduction in DarkSat’s reflective brightness compared to other Starlink satellites,” said Jeremy Tregloan-Reed of the University of Chile at Antofagasta in a 2020 study.
The brightness of the celestial object is measured on the scale of stellar magnitude – ie. the brighter the object, the higher and more negative will be its corresponding rating. For example, the Sun is rated at -26.7 magnitude, while the North Star is rated at +2. Any object rated above +6 is virtually invisible to the human eye, although telescopes and other sensitive observation systems can detect objects with a color less than +8. According to a study by Treglon-Reed, the processed Starlink satellite shows a magnitude of +5.33 at its working height, compared to +6.21 for an unprocessed satellite.
That’s better, but it’s not enough, Treglon-Reed said Forbes last March. “It’s still too bright,” he said. “More needs to be done. The idea is to provide these figures to politicians [and astronomical societies] who are negotiating with SpaceX [and mega constellation companies] and then try to improve this further. “
The overall impact of these satellites will depend on a number of factors, including the type of telescope used, the time of day and season of observations, and the height of the satellite constellation. Studies in wide areas in both the visible and infrared spectra (such as those conducted by the Vera C. Rubin Observatory in Chile) are particularly vulnerable to this intervention, as are those conducted at dusk. And while the constellations orbiting LEO usually darken after passing into the Earth’s shadow, those in geosynchronous orbit at 750 miles and beyond – like the short-lived OneWeb program – will be “visible all summer long and significant parts of the night in winter, autumn and spring and will have a negative impact on almost all monitoring programs “, according to AAS.
“Satellites at higher altitudes must be inherently less reflective than satellites at higher altitudes in order to leave a comparable band [in professional detectors]. This is due to two factors: orbital speed (lower altitude satellites move faster, so they spend less time on each pixel) and focus (lower altitude satellites are less focused, so the band is wider but has a lower peak brightness, ”University of Washington Astronomer Dr. Meredith Rawls said Forbes.
In response to the growing problem, astronomers around the world, as part of the SATCON-1 National Science Foundation’s seminar last July, compiled a list of potential corrective actions and policies. These include limiting constellations to a maximum altitude of 550-600 km, requiring individual satellites to have a magnitude of +7 or higher, and sharing information about the orbits of these constellations with the research community so that astronomers can avoid these areas of the sky.
“SpaceX has shown that operators can reduce reflected sunlight through satellite body orientation, sun protection and surface darkening,” said the SATCON-1 workshop. “Joint efforts to obtain more accurate public data on the predicted locations of individual satellites (or ephemeris) could avoid directing and formwork at medium exposure during satellite transit.” Alternatively, operators could design their satellites to actively deactivate when they reach the end of their service life – as Starlink satellites do – or they could simply launch fewer constellations altogether. Whether national or international regulators will actually accept these recommendations remains to be seen.
But even if satellite operators manage to reduce the brightness of their constellations, we still face an increasingly dense orbital “graveyard” of broken satellites and space debris. NASA’s Orbital Space Waste Service estimates that there are about half a million pieces of marble debris chipping around LEO at 22,300 miles per hour – fast enough to chip even heavily reinforced ISS windows on impact – and up to 100 million pieces with dimensions millimeter or less.
NASA became the first national space agency to develop a comprehensive space debris mitigation plan in 1995. These guidelines were later adapted by the 10-member Interdepartmental Committee for the Coordination of Space Waste (IADC) and eventually adopted by the UN General Assembly. in 2007, the U.S. government also established its standard practices for mitigating orbital debris (ODMSP) in 2001, renewing its efforts to “limit the generation of new, durable debris by controlling waste generated during normal operations, minimizing the waste generated by accidental explosions, the selection of a safe flight profile and the operational configuration to minimize accidental collisions and the ejection of space structures after the mission. “In addition, the Department of Defense operates a space surveillance network that is tasked with cataloging and tracking objects between 0.12 and 4 inches in diameter using a combination of ground-based visual telescopes and radar grids.
Tracing these debris is only the first step. A number of space agencies are in the process of developing systems for the active capture and destruction of orbital debris. JAXA, for example, is considering a 2,300-yard-long “electrodynamic bond” that, when deployed, would smash passing debris back to the planet, where it would burn up as it re-enters the atmosphere. In 2018, a consortium led by the British space center Surrey successfully demonstrated its RemoveDebris device – essentially a huge space network designed to capture dead satellites and crooks up to 10 meters long.
Coming in 2025, ESA hopes to launch its ClearSpace-1 mission, in which a quad capture device will try to grab space debris as a huge reward for playing nails, and then get rid of itself and its abandoned generosity. in the Earth’s atmosphere.
“Space debris is a global problem as it affects all nations,” said Airbus missionary systems engineer Xander Hall. CNN in 2018. “Any garbage in space is the property of the original operators, and orbital debris is not explicitly addressed in current international law. International efforts must be made to claim ownership of the debris and to help fund its safe removal. “