Sputnik’s successful launch in 1957 marked a milestone in human history as the first time a man – made object had ever orbited the earth. But little did we understand of the space-based SNAFU we used to come up with satellite technology. During the 64 years since, the night sky has become increasingly congested. Today, more than 3,000 satellites orbit the earth, and they, along with millions of pieces of world debris – such as pieces of broken satellite, discarded rocket parts and spots of space paint. NASA estimates that there is around 6,000 tons of debris in low-Earth orbit alone.
This orbital waste not only creates a navigational hazard for astronauts, it also reflects sunlight down to the surface and disrupts terrestrial telescopic observations. A study recently accepted by Monthly notes from the Royal Astronomical Society: Letters suggests that there is now no place on earth that is free from light pollution produced by air debris and satellites. Even more worryingly, scientists expect that the amount of debris in orbit will increase by an order of magnitude over the next decade as mega-constellations of internet-radiating mini-satellites, such as SpaceX̵
“Astronomers – and random viewers in the night sky – must 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 will be important for certain types observations, certain observatories and at certain times of the year. “
Until a couple of years ago, humanity had launched fewer than 10,000 objects in space since space time. But with the advent of low-cost commercial rocket launch technology – which has seen the price per pound of launch cargo drop from $ 24,800 during the shuttle period to just $ 1,240 today – the speed we put satellites into orbit is set to increase exponentially. .
In total, more than 18,000 satellites are expected to be launched in LEO by 2025 – about ten times the total number of satellites active in 2018. SpaceX alone has permission from the US government to launch 12,000 Starlinks (with plans to have as many as 42,000 of them), while Amazon’s Kuiper project has permission to launch 3,236 satellites in the coming years. Both of these applications seek to create an orbital network in Low Earth Orbit that is capable of providing high bandwidth, low latency Internet access available from anywhere on the planet. Although their intentions are noble, the unintended consequences of packing many spacecraft into our skies can fundamentally change our view of the surrounding solar system.
“If 100,000 or more LEO rates proposed by many companies and many governments are deployed, no combination of mitigations can fully avoid the impact of satellite paths on the science programs of current and planned terrestrial optical NIR astronomy facilities,” a 2020 report from the American Astronomical Society noted.
When the first 360 Starlinks were launched in May 2019, their presence in the night sky became immediately noticeable. Their highly reflective design made each mini-satellite about 99 percent brighter than surrounding objects during the five months it took them to toughen up to 550 km altitude. This effect was especially pronounced at sunrise and sunset when the sun’s rays reflected from the satellites’ solar panels. SpaceX’s attempts to reduce reflectivity using a “darker treatment” in early 2020 proved only partially successful.
“We are seeing about a 55 percent reduction in the reflective brightness of DarkSat compared to other Starlink satellites,” noted Jeremy Tregloan-Reed of the University of Chile in Antofagasta in a 2020 study.
The brightness of a celestial object is measured along the scale of star 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, while the North Star is rated at +2. Any object rated above +6 is effectively invisible to the human eye, although telescopes and other sensitive observation systems can detect objects as weak as +8. According to Treglon-Reed’s study, the treated Starlink satellite showed a strength of +5.33 in altitude, compared to +6.21 for an untreated satellite.
It’s better, but not good enough, said Treglon-Reed Forbes March last year. “It’s still too bright,” he said. “More needs to be done. The idea is to get these numbers out to the decision makers [and astronomical societies] who is in talks with SpaceX [and mega constellation companies] and try to improve this further. ”
The overall impact these satellites will have depends on a number of factors, including the type of telescope used, the time of day and the season the observations are made, and the height of the satellite constellation. Studies of large areas in both the visible and infrared spectra (such as those carried out by the Vera C. Rubin Observatory in Chile) are particularly vulnerable to this disturbance, as are those carried out at dusk. And while constellations orbiting in LEO generally go dark when they first enter the Earth’s shadow, those in a geosynchronous orbit of 750 miles and beyond – like the short-lived OneWeb program – “will be visible all night long in summer and significant fractions of during the winter, autumn and spring, and will have a negative impact on almost all observation programs, “according to AAS.
“Higher altitude satellites must inherently be less reflective than lower altitude satellites to give a similar stripe [in professional detectors]. This is due to two factors: orbital speed (lower altitude satellites move faster, so spend less time on each pixel) and focus (lower altitude satellites are less in focus, so the line is wider but has lower brightness, “University of Washington astronomer Dr. Meredith Rawls recounted Forbes.
In response to the 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. These include limiting constellations to a maximum altitude of 550 – 600 km, which requires some satellites to have a star size of +7 or higher, and sharing orbital information about these constellations with the research community so that astronomers can avoid these areas in the sky.
“SpaceX has shown that operators can reduce reflected sunlight through satellite bodies, sun protection and dark surfaces,” found the SATCON-1 workshop. “A joint effort to obtain public data with higher accuracy about expected locations for individual satellites (or refugees) may allow for some point avoidance and closure of mid-exposure during satellite passage.” Alternatively, operators can design their satellites to actively deorbit when they reach the end of their life – as Starlink’s satellites do – or they can just launch fewer constellations in general. Whether national or international regulators will actually adopt these recommendations remains to be seen.
But even though satellite operators manage to turn down the brightness of their constellations, we are still facing an increasingly dense orbital “cemetery” of destroyed satellites and air debris. NASA’s Orbital Space Debris Office estimates that half a million pieces of marble are zipping around LEO at 22,300 km / h – fast enough to blow even the ISS ‘powerfully reinforced windows at impact – and as many as 100 million pieces measuring one millimeter or less. .
NASA became the first national space agency to develop a comprehensive plan for mitigation waste in 1995. These guidelines were later adapted by the 10-nation Inter-Agency Space Debris Coordination Committee (IADC) and eventually adopted by the UN General Assembly in 2007. The US government established also its Orbital Debris Mitigation Standard Practices (ODMSP) in 2001, in a renewed effort to “limit the generation of new, long-lived debris by controlling debris released during normal operations, and minimize debris generated by accidental explosions, selection of safe flight profile and operational configuration to minimize accidental collisions, and deposition of space structures on assignment. “In addition, the Ministry of Defense operates the Space Surveillance Network, which is charged with cataloging and tracking objects between 0.12 and 4 inches in diameter using a combination of ground-based visual telescopes and radar arrays.
Tracking this debris is just the first step. A number of space agencies are in the process of developing systems for actively capturing and disposing of orbital waste. For example, JAXA is considering a 2,300-foot-long “electrodynamic tether” that, when deployed, will crush passing debris back toward the planet where it will burn up during atmospheric re-entry. In 2018, a consortium led by the UK’s Surrey Space Center demonstrated its Remote Debris unit – actually a large space network designed to capture dead satellites and rogue space junk up to 10 meters in length.
Come 2025, ESA hopes to launch its ClearSpace-1 mission where a four-stage capture device will attempt to snatch space debris as an oversized claw-game prize, and then dispose of itself and its abandoned wealth in the Earth’s atmosphere.
“Space debris is a global problem, as 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 orbital debris is not addressed explicitly in current international law. An international effort must be made to demand ownership of debris and help finance safe removal. ”