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In February 2009, two space satellites orbiting at a speed of nearly 17,000 km / h hit an altitude of 482 miles above Siberia.
One of them was an operational American communications satellite, Iridium-33. The other was an obsolete, heavier Russian military satellite called Cosmos-2251. For space scientists, the collision awakened suddenly a new type of disturbing calculation.
The very high-speed collision propelled two space orbits into a debris cloud containing 2,300 objects. This made other scientists – climatologists – aware that changes in the upper atmosphere could increase the risk of collision in space. There are currently 21,000 traceable space debris, ranging in size from the upper floors of old rockets to metal pieces the size of a dime.
As recently described Martin Mlynczak, principal investigator at the NASA Research Center at Langley in Hampton, Va., The accumulation of carbon dioxide emissions at altitude is progressively cooling a layer of high atmosphere where satellites orbit frequently. The good news is that cooling will make air less dense and could extend the life of existing satellites. The bad news is that it will preserve the rapid accumulation of space wastes that could otherwise sink into the lower atmosphere and burn.
A study by the European Space Agency (ESA) describes the problem more bluntly: "A scenario" as if nothing had happened "would lead to a gradual and uncontrolled increase in the number of objects in the world. Low orbit (LEO), collisions becoming the main debris. source."
The agency proposes to start avoiding this problem in 2023 by removing potential debris from its space vehicles.
"The [upper] the atmosphere is refreshing. We know it, "explained Mlynczak in an interview. "We need to know the evolution of density over the next 50 to 100 years to make space habitable for people and satellites."
The United States has become highly dependent on space satellites for communications, Earth observations, military needs, navigation, weather forecasts and a host of other uses. This is why satellite launches, especially those carrying recent groups of "cubesat" vehicles, about the size of half a gallon milk cartons, are proliferating every year.
An Indian-made rocket, called PSLV-C37, launched 104 of these satellites in February 2017, quickly spitting out vents on both sides. It was a world record for India and a milestone for US companies and institutions, which built 96 orbiters (ClimateWireJanuary 29).
More destructive collisions that paralyze satellites could result in a loss of information for science and the military. It would also result in higher costs for commercial satellite users, which would affect consumers, satellite owners and companies that provide expensive satellites, Mlynczak told a group of scientists at the National Center for Atmospheric Research in Boulder, in Colorado.
In space, the speed of even tiny objects in orbit can cause considerable damage. According to ESA, the impact of a debris 10 cm in diameter, about the size of a softball, "will most likely result in a catastrophic disintegration of the target".
ESA said that in 2016, the solar panel of one of the major European satellites, Sentinel-1A, was almost destroyed, which paralyzed its power supply. The object that touched it had a diameter of 1 centimeter, a piece of bazaar the size of a tenth.
In total, according to ESA, there have been about 5,400 rocket launches since the beginning of the space era in 1957. They have placed about 8,650 satellites in orbit. Of these, about 4,700 are still in space, but only about 1,800 are still functioning. The space surveillance networks operated by the United States, Europe and other countries currently estimate at 29,000 the number of debris of 10 centimeters or more in orbit diameter. All are not followed.
Until now, ESA estimates that there have been more than 500 ruptures, collisions or "abnormal events leading to fragmentation". The total weight of all objects currently in orbit is approximately 8,100 metric tons. With the increase in the number of launches, currently estimated between 70 and 90 each year, it is stated that "the probability of catastrophic collisions will also increase gradually".
NASA and space agencies in some other countries have approved rules that try to limit projected damage by forcing new vehicles in orbit to last up to 25 years. After that, they must have orbits or thrusters that tilt them into what are called "cemetery disposal orbits," where most of them will burn.
Until now, according to ESA, statistics show that there has been "poor results" and that a long-term proliferation of space wastes is still likely, even if the rule is respected around the world. NASA and ESA have studied how they could proceed each year to "active debris removal" through space missions guiding five to ten of the most dangerous debris in orbit in the "cemetery".
ESA plans to launch its "CleanSpace initiative" by removing one of its objects in orbit in 2023. She believes there is a risk that a large space debris will not burn completely in the lower atmosphere, but it is "several orders of magnitude lower than the risks commonly accepted in everyday life. Up to now, no human casualties have been reported.
According to Mlynczak, solar storms complicate the location and physical removal of objects in orbit. They can cause variations in the Earth's magnetic field and make it difficult to track objects in intervals of two or three days.
It seems however that the Earth is heading towards a period of weakening of solar activity and that, according to Mlynczak, "could give you the opportunity to do something here". The new satellite systems could help track objects in orbit and provide better estimates of long-term density reductions due to increased carbon dioxide accumulation in the upper atmosphere.
"But the development of small, low-cost sensors that can routinely be orbited over long periods of time to provide the accurate record needed to reliably predict long-term density changes is a technological challenge. This should be an active area of investment in technology and research, "said Mlynczak.
The most critical measure needed, he said, will be a precise data flow that will allow space agencies to project the decreasing density of the upper atmosphere, where satellites and debris will orbit in the next 50 to 100 years. This is another dimension of the overall costs of rising CO2 levels.
Reproduced from Climatewire with the permission of E & E News. E & E provides daily coverage of essential information on energy and the environment on www.eenews.net.
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