In recent years, with the rapid increase in the number of low-Earth orbit satellites, Earth's orbit has become increasingly crowded, highlighting space safety issues. Early this morning Beijing time, SpaceX, Elon Musk's American space exploration company, announced that it will lower the orbital altitude of thousands of Starlink satellites to reduce the risk of collisions.
Michael Nichols, vice president of Starlink engineering, stated that the company is "launching a major reorganization of its satellite constellation," lowering all satellites currently operating at an altitude of approximately 550 kilometers (342 miles) to an orbit of approximately 480 kilometers (298 miles). This move aims to relocate satellites to less crowded orbital layers, reducing the risk of collisions and allowing them to deorbit and burn up in the atmosphere more quickly in the event of an anomaly or failure, thereby reducing space debris.
According to Nichols, approximately 4,400 Starlink satellites will participate in this orbital altitude reduction this year.
Besides creating a relatively safer and more controllable space for satellite operation, Nichols pointed out that this adjustment is also closely related to the solar activity cycle. Solar activity has a cycle of approximately 11 years, and the intensity of activity directly affects the density of Earth's upper atmosphere. The next solar minimum is expected to occur in the early 2030s. As the solar minimum approaches, the density of the upper atmosphere will decrease, meaning that the natural orbital decay time for satellites at the same altitude will be prolonged. By lowering the orbital altitude, the orbital decay time, which could originally last more than four years, can be shortened to several months during the solar minimum, increasing the orbital decay rate by more than 80%.
In addition, lowering the satellite's orbital altitude can theoretically reduce latency, but since not all latency is due to satellite distance, the latency improvement from a 70-kilometer change in orbital altitude is very limited.
It is worth noting that the background to this orbital altitude reduction is not peaceful. According to CCTV International News, on December 29th local time, the Chinese representative, speaking at the Security Council Arria-format meeting on low-Earth orbit satellites, stated that the rampant expansion of commercial satellite constellations by certain countries, lacking effective regulation, poses significant security challenges. Taking Elon Musk's Starlink project as an example, Starlink has over 10,000 satellites in orbit and has twice approached the Chinese space station, requiring emergency collision avoidance. Recently, one satellite disintegrated, producing over 100 fragments, seriously threatening spacecraft from developing countries lacking orbit control capabilities.
Previously, SpaceX confirmed that one of its Starlink satellites experienced an anomaly, possibly caused by a small internal explosion that led to a propellant tank leak, causing the semi-major axis to rapidly decay by about 4 kilometers (2.5 miles) and release debris.
Overall, low Earth orbit is becoming more crowded than ever before. Last year, SpaceX added more than 3,000 satellites through 121 launches, averaging almost one rocket launch every three days. According to a 2024 report by the World Economic Forum, the number of low Earth orbit satellites is projected to grow by 190% over the next decade.
If a satellite collides or explodes, the resulting debris will be scattered throughout its orbit. This space junk increases the risk of subsequent collisions, threatening existing satellites and future space missions, and could even trigger Kessler syndrome.
The "Kessler Syndrome" is a theory proposed by a NASA scientist who believes that once space debris reaches a critical point, collisions could trigger a chain reaction, producing more debris and rendering some orbits unusable.
(Source: Science and Technology Innovation Board Daily)
