The successful launch of Sputnik in 1957 was a milestone in human history as the first man-made object to orbit the earth. But little did we understand about the space-based SNAFU we were pursuing with the advent of satellite technology. In the 64 years since, our planet’s night sky has become increasingly crowded. Today, more than 3,000 satellites orbit the earth and are joined together by millions of pieces of space debris – such as pieces of broken satellite, discarded vehicle parts and stains of spacecraft paint. NASA estimates that there are about 6,000 tons of debris in the Low Earth orbit alone.
i
This orbit not only creates navigational hazards for astronauts, but also reflects sunlight to the surface, and it obstructs telescope observations on the ground. A recent study by Monthly notices from the Royal Astronomical Society: Letters suggests that nowhere on earth is there light pollution caused by overhead debris and satellites. Even more worrying: researchers expect the amount of debris in orbit to increase by an order over the next decade as mega-constellations of Internet-radiating mini-satellites, such as SpaceX’s Starlink program, take off.
“Astronomers – and casual viewers of the night sky – should expect a future in which the low-Earth population includes tens of thousands of relatively large satellites,” warned Jonathan McDowell of the Harvard-Smithsonian Center for Astrophysics in a 2020 study. “The consequences are significant for certain types of observation, certain observatories and at certain times of the year.”
Until a few years ago, since the beginning of the space age, mankind has launched less than 10,000 objects into orbit. With the advent of cheap commercial missile launch technology – which dropped the price per pound of launch cargo from $ 24,800 during the Shuttle era to just $ 1,240 today, the pace at which we put satellites into orbit will increase exponentially. .
In total, more than 18,000 satellites are expected to be launched into LEO by 2025 – about ten times the total number of satellites active in 2018. SpaceX alone has permission from the U.S. government to send 12,000 Starlinks into orbit (with plans to have as many) 42,000 of them), while Amazon’s Kuiper project is authorized to launch 3,236 satellites in the coming years. . Both of these programs aim to create a low-bandwidth orbital network network that can provide a high-bandwidth, low-latency Internet connection available anywhere. Although their intentions are noble, the unintended consequences of packing many spacecraft into our air can fundamentally change the view of the surrounding solar system.
NOIRlab
“If the 100,000 or more LEOsats proposed by many companies and many governments are used, no combination of mitigations can completely avoid the impact of satellite paths on the scientific programs of current and planned ground-based optical NIR astronomy facilities,” a 2020 report of the American Astronomical Society noted.
When 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 surrounding objects during the five months it took to revamp their 550 km altitude. This effect was especially pronounced with sunrise and sunset when the sun’s rays reflected from the solar panels of the satellites. SpaceX’s attempt to reduce reflectivity using a “darkening treatment” in early 2020 was only partially successful.
“We detect about 55 percent in the reflective brightness of DarkSat compared to other Starlink satellites,” Jeremy Tregloan-Reed of the University of Antofagasta in Chile noted in a 2020 study.
The brightness of a celestial object is measured by the scale of steroid size – that is, the brighter an object, the larger and more negative its corresponding rating will be. For example, the Sun is rated at -26.7 strength while the North Star is rated at +2. Any object higher than +6 is effectively invisible to the human eye, although telescopes and other sensitive observation systems can spot objects as dull as +8. According to Treglon-Reed’s study, the treated Starlink satellite shows a strength of +5.33 at its operating altitude, compared to +6.21 for an untreated satellite.
i
It’s better, but not good enough, Treglon-Reed said Forbes last March. “It’s still way too bright,” he said. More needs to be done. The idea is to pass these numbers on to the policymakers [and astronomical societies] talking to SpaceX [and mega constellation companies] and then try to improve it further. ”
The total impact that these satellites will have depends on a number of factors, including the type of telescope used, the time of day and the season in which the observations are made, and the height of the satellite constellation. Wide area recordings in the visible and infrared spectra (such as those done by the Vera C. Rubin Observatory in Chile) are particularly vulnerable to this disturbance, as are those done during twilight hours. And while constellations orbiting in LEO generally darken as soon as they move in the Earth’s shadow, those in a geosynchronous orbit will travel about 700 kilometers – like the short-lived OneWeb program – all night long during the summer and significant fractures of the night be visible. during the winter, autumn and spring, and will have a negative effect on almost all observation programs, “according to the AAS.
“Satellites with higher altitude must inherently be less reflective than satellites with lower altitude, to leave a similar line [in professional detectors]. This is due to two factors: rotation speed (lower altitude satellites move faster, so spend less time on each pixel) and focus (lower altitude satellites are less focused, so the bar is wider but has a lower peak brightness, “University of Dr. Meredith Rawls, astronomer in Washington, tells Forbes.
In response to the growing problem, astronomers from around the world, as part of the National Science Foundation’s SATCON-1 workshop in July last year, compiled a list of possible affirmative actions and policies. This includes limiting constellations to a maximum altitude of 550 – 600 km, which requires individual satellites to have a star size of +7 or higher, and sharing information about these constellations with the research community, allowing astronomers to explore those areas. heaven can avoid.
“SpaceX has shown that operators can reduce reflected sunlight through satellite body orientation, sun protection and surface darkening,” the SATCON-1 workshop found. ” A joint effort to obtain public data with higher accuracy about the predicted locations of individual satellites (or short-lived satellites) may allow for some avoidance and medium exposure during satellite transit. ‘ Alternatively, operators can design their satellites to orbit actively when they reach the end of their lifespan – as Starlink’s satellites do – or they can just launch fewer constellations in general. Whether national or international regulators will actually accept these recommendations remains to be seen.
But even if satellite operators manage to lower the brightness of their constellations, we are still confronted with an increasingly dense orbital “graveyard” of broken satellites and spatial debris. NASA’s Orbital Space Debris Office estimates that there are half a million pieces of debris around LEO at 22,300 km / h – fast enough to chip even the ISS ‘heavily reinforced windows after impact – and as many as 100 million pieces of a millimeter or less. .
In 1995, NASA became the first national space agency to develop a comprehensive plan to reduce space debris. These guidelines were later amended by the 10-nation Inter-Agency Space Debris Coordination Committee (IADC) and finally adopted in 2007 by the UN General Assembly. The US government also introduced its Orbital Debris Mitigation Standard Practices (ODMSP) in 2001, in a renewed effort to ‘limit the generation of new, long-lived litter by controlling debris released during normal operations, and thus the debris minimized by accidental explosions. choosing safe flight profile and operational configuration to accidentally reduce collisions, and disposing of space structures after the mission. In addition, the Department of Defense operates the Space Surveillance Network, which is responsible for cataloging and locating objects with a diameter of 0.12 to 4 centimeters using a combination of visual telescopes on the ground and radar arrays.
Detecting this debris is only the first step. A number of space agencies are developing systems to actively capture and dispose of orbital debris. JAXA, for example, is considering a 2,300-meter electrodynamic chain that, when deployed, will crush the debris that falls back to the planet, where it will burn during atmospheric re-entry. In 2018, a consortium led by the Surrey Space Center in the UK successfully demonstrated its RemoveDebris device – essentially a large space network designed to capture dead satellites and rogue spaces up to 10 meters long.
ESA
Come 2025, the ESA hopes to launch its ClearSpace-1 mission, in which a square capture device will attempt to snatch spatial debris like a large claw game prize, and then remove itself and its desolate abundance into Earth’s atmosphere. .
“Space debris is a global problem because it affects all nations,” said Airbus mission systems engineer Xander Hall CNN in 2018. “Every piece of rubbish in space is owned by the original operators and remnants of revolution are not explicitly addressed in current international law. An international effort must be made to claim ownership of the rubble and help remove it safely. ‘