After Starlink's crazy expansion, Elon Musk's SpaceX announced the largest satellite de-orbiting operation in history.

In recent years, with the rapid growth of the number of low Earth orbit satellites, the Earth's orbit is becoming increasingly congested, and space security issues are becoming more prominent. In the early hours of today Beijing time, SpaceX, a company owned by Musk, announced that it will lower the orbit height of thousands of "Starlink" satellites to reduce collision risks. Michael Nichols, vice president of the "Starlink" project, stated that the company is initiating a major restructuring plan of the satellite constellation, lowering all satellites currently operating at an altitude of about 550 kilometers (342 miles) to an orbit of about 480 kilometers (298 miles). This move aims to transfer satellites to less congested orbit layers, reduce collision risks, and allow satellites to quickly leave orbit and burn up in the atmosphere in case of anomalies or malfunctions, thus reducing the generation of space debris. According to Nichols, about 4,400 Starlink satellites will participate in this altitude reduction within the year. In addition to creating a relatively safer and more controllable space for satellite operations, Nichols pointed out that this adjustment is also closely related to the solar activity cycle. The sun's activity cycle lasts about 11 years, and the strength of the activity directly affects the density of the Earth's upper atmosphere. The next period of minimal solar activity is expected to occur in the early 2030s. As this period approaches, the density of the upper atmosphere will decrease, meaning that the natural orbital decay time at the same altitude for satellites will increase. By lowering the orbit height, the decay time, which could originally be over four years, can be reduced to a few months during the minimal solar activity period, increasing the decay rate by over 80%. Lowering the orbit height of satellites theoretically can also reduce latency, but as not all delays are due to satellite distance, the improvement in delay due to a 70-kilometer orbit height change is very limited. It is worth noting that the background of this altitude reduction is not calm. According to CCTV International News, on December 29th local time, a Chinese representative at the UN Security Council's Aria Mode meeting on low Earth orbit satellite issues stated that some countries' commercial satellite constellations are expanding recklessly, lacking effective regulation and posing significant security challenges. For example, the "Starlink" project under Musk's company has over 10,000 satellites in orbit, which have approached the Chinese space station twice, causing emergency evasions. Recently, a satellite disintegrated, producing over 100 debris pieces, posing a serious threat to developing countries' spacecrafts without orbit control capabilities. Earlier, SpaceX confirmed that one of its Starlink satellites experienced an anomaly, possibly due to a small internal explosion, which led to a leaking propellant tank and a rapid decay of the semi-major axis by about 4 kilometers (2.5 miles), releasing fragments. Looking at the overall data, low Earth orbit is becoming increasingly congested. Last year, SpaceX added over 3,000 satellites through 121 launch missions, almost one new satellite launched every three days on average. According to the World Economic Forum's report for 2024, the number of low Earth orbit satellites is expected to increase by 190% in the next decade. Once a satellite collides or explodes, a large number of debris will spread throughout the orbit. This space debris increases the risk of future collisions, threatening active satellites, future space missions, and may even trigger the "Kessler Syndrome." The "Kessler Syndrome" is a theory proposed by a scientist at NASA, suggesting that once space debris reaches a critical point, collisions could trigger a chain reaction, generating more debris, causing some orbits to become unusable. This article is from "Cai Liang She", author: Zhu Ling, GMTEight Editor: Li Cheng.