The successful launch of Sputnik in 1957 marked a turning point in human history as the first time that an artificial object had ever orbited the Earth. But we understood little about the space SNAFU we were courting with the advent of satellite technology. In the 64 years since then, the night sky of our planet has become increasingly crowded. 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, discarded rocket parts and spacecraft-colored stains. NASA estimates that there are about 6,000 tons of waste in Low Earth orbit alone.
This orbital debris not only poses a danger to astronauts, but also reflects sunlight to the surface, interfering with the Earth’s observations of the telescope. A study he recently accepted Monthly Notices of the Royal Astronomical Society: Letters suggests that there is nowhere on Earth now free from light pollution produced by aboveground waste and satellites. Worryingly, researchers expect the amount of debris in orbit to increase by an order of magnitude over the next decade as mega-constellations of mini-satellites that radiate the Internet, such as SpaceX’s Starlink program, take off.
“Astronomers – and occasional night sky viewers – must expect a future in which the population of low Earth orbit includes tens of thousands of relatively large satellites,” warned Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics in a 2020 study. “Impacts will be 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. However, with the advent of cheap commercial rocket launch technology – which has seen the price per pound of launched cargo fall from $ 24,800 during the Shuttle era to just $ 1,240 today – the rate at which we put satellites into orbit is set at exponential growth.
In total, more than 18,000 satellites are expected to be launched into LEO by 2025 – roughly ten times the total number of satellites active in 2018. The SpaceX alone has US government permission to launch 12,000 Starlinks into orbit (with plans to have as many as 42,000 ), while Amazon’s Kuiper project is authorized to send 3,236 of its own satellites in the coming years. Both of these programs seek to create an orbital network in Low Earth Orbit capable of providing a broadband Internet connection and low latency available from anywhere on the planet. Although their intentions are noble, the unintended consequences of packing many spacecraft into our skies could fundamentally change our view of the surrounding solar system.
“If 100,000 or more LEOs proposed by many companies and many governments are deployed, no combination of mitigation can completely avoid the impact of satellite tracks on the scientific programs of current and planned terrestrial optical-NIR astronomical objects,” the 2020 U.S. Astronomy report said. society.
When, for example, the first 360 Starlinks were launched in May 2019, their presence in the night sky was immediately noticeable. Their highly reflective design made each mini-satellite about 99 percent brighter than the surrounding objects over the five months it took them to dig at its 550km working height. This effect was especially pronounced at sunrise and sunset when the sun’s rays bounced off the satellite’s solar panels. SpaceX’s attempt to reduce that reflectivity through “dimming treatments” in early 2020 proved to be only partially successful.
“We detect an approximately 55 percent reduction in DarkSat’s reflective brightness compared to other Starlink satellites,” noted Jeremy Tregloan-Reed of Chile’s Antofagasta University in a 2020 study.
The brightness of a celestial object is measured on a scale of stellar magnitude – that is, the brighter the object, the corresponding its rating will be higher and more negative. For example, the Sun is rated at -26.7 magnitude, while the North is rated at +2. Any object with a rating above +6 is actually invisible to the human eye, although measuring telescopes and other sensitive observation systems can detect objects dimmed by +8. According to a Treglon-Reed study, the treated Starlink satellite showed a magnitude of +5.33 at its working altitude, compared to +6.21 for the raw satellite.
That’s better, but not good enough, Treglon-Reed said Forbes last March. “It’s still too bright,” he said. “Much remains to be done. The idea is to pass these numbers on to policy makers [and astronomical societies] who are negotiating with SpaceX [and mega constellation companies] and then try to improve this further. “
The overall impact that these satellites will have depends on a number of factors, including the type of telescope used, the time of day and the observation season, and the height of the satellite constellation. Broad-area and both infrared and infrared surveys (such as those conducted by the Vera C. Rubin Observatory in Chile) are particularly vulnerable to these disturbances, as are those conducted during twilight. And while the constellations orbiting LEO mostly darken when they pass into Earth’s shadow, those in geosynchronous orbit at 750 miles and beyond – like the short-lived OneWeb program – would be “visible all night during summer and significant parts of the night during winter, fall and spring. , and will have negative impacts on almost all observation programs, ”states AAS.
“Satellites at higher altitudes must be substantially less reflective than satellites at lower altitudes to leave a similar sequence [in professional detectors]. This is due to two factors: orbital speeds (satellites at lower altitudes move faster and spend less time on each pixel) and focus (satellites at lower altitudes are less focused, so the range is wider but has a lower peak brightness “, University to Washington astronomer Dr. Meredith Rawls told Forbes.
In response to a growing problem, astronomers from around the world, as part of the National Science Foundation’s SATCON-1 workshop last July, compiled a list of potential corrective actions and policies. This includes limiting the constellations to a maximum altitude of 550-600 km, requiring individual satellites to have a stellar magnitude of +7 or greater, and sharing information about orbitals related to those constellations with the research community so astronomers can avoid those areas in the sky.
“SpaceX has shown that operators can reduce reflected sunlight through satellite body orientation, sun protection, and surface darkening,” the SATCON-1 workshop revealed. “A joint effort to obtain more accurate public data on the predicted locations of individual satellites (or ephemeris) could make it possible to avoid pointing and triggering medium exposure during satellite transitions.” Alternatively, operators could design their satellites so that they actively fall out of use when they reach the end of their lifespan – as Starlink satellites do – or they could just launch fewer constellations at all. Whether national or international regulators really adopt these recommendations remains to be seen.
But even if satellite operators manage to reduce the brightness of their constellations, we are still faced with an increasingly dense orbital “graveyard” of broken satellites and space debris. NASA’s orbital space debris estimates that around LEO at speeds of 22,300 km / h it squeezes pieces of marble-sized debris – fast enough to withstand even heavily reinforced ISS windows on impact – and as many as 100 million pieces a millimeter or less in size.
NASA became the first national space agency to develop a comprehensive space debris mitigation plan in 1995. These guidelines were later adapted by the Interdepartmental Committee on Space Waste Coordination (IADC) and eventually adopted by the UN General Assembly in 2007. The U.S. government also established its standard orbital waste mitigation (ODMSP) practice in 2001, in a renewed effort to “limit the generation of new, long-lived waste by controlling waste released during normal operations, minimizing remnants of accidental explosions, and selecting a safe flight profile. and operational configurations to minimize accidental collisions and postponement of space structures after a mission. “In addition, the Department of Defense operates a Space Surveillance Network that is in charge of cataloging and tracking objects between 0.12 and 4 inches in diameter using a combination of ground-based visual telescopes and radar arrays.
Monitoring this waste is only the first step. Numerous space agencies are in the process of developing a system for the active capture and disposal of orbital debris. JAXA, for example, is considering a 2,300-meter-long “electrodynamic bond” that, if deployed, would break up debris back toward the planet where it would burn up when it re-enters the atmosphere. In 2018, a consortium led by the British Space Center Surrey successfully demonstrated its RemoveDebris device – basically a huge space network designed to capture dead satellites and naughty space debris up to 10 meters long.
Coming in 2025, ESA hopes to launch its ClearSpace-1 mission in which a four-legged capture device will try to snatch space debris like a grand claw reward, and then remove itself and its neglected grace into Earth’s atmosphere.
“Space debris is a global problem because it affects all countries,” said Airbus mission engineer Xander Hall. CNN in 2018. “Every piece of garbage in space is owned by the original operators, and the orbital remains have not been explicitly dealt with in applicable international law. International efforts must be made to claim ownership of the waste and to help fund its safe disposal. “