Zhi DongXi (public number: zhidxcom)
Author | Yang Chang
Edit | Li Shuiqing
Zhidong January 18 news, last year had twice "touched porcelain" Chinese space station Starlink satellite (Starlink) satellite trouble, recently, some astronomers pointed out that the US space company SpaceX starlink project satellite has seriously affected astronomical observations.
Astronomers analyzed images taken by the Survey Telescope between 2019 and 2021 and found that the number of images affected by the starlink increased by 35 times, and as more starlink satellites were launched, they estimated that there would be starlink satellites in every future observation map, hindering normal scientific observations.
This is only the negative impact of the Starlink project after launching less than 5% of the number of targets, SpaceX began to implement the Starlink project as early as 2019, planning to launch 42,000 Starlink satellites, forming a Starlink network, providing satellite Internet services for the world, and has launched about 2,000 satellites, with more and more Starlink satellites successfully launched into near-Earth orbit, the various threats brought by Starlink will also increase, and the probability of threats to the safety of astronauts and spacecraft will also increase.
On December 28, 2021, at a regular press conference on the same day, Foreign Ministry spokesman Zhao Lijian confirmed that in July and October 2021, the US Starlink satellites approached the Chinese space station twice, during which Chinese astronauts were on missions inside the space station, and for safety reasons, the Chinese space station took emergency collision avoidance measures.
Zhao Lijian pointed out that the US side should respect the international order in outer space based on international law and take immediate measures to prevent the recurrence of such incidents. SpaceX founder Elon Musk did not respond.
Starlink satellites are not the first time to affect astronomical observations and astronauts, spacecraft safety, before, it has been pointed out many times that too many starlink satellites will interfere with astronomical observations, occupy the earth's low space orbit, increase the risk of spacecraft collisions, produce a large amount of space junk and so on. However, SpaceX did not stop its plan because of criticism from all sides, and at 8:04 Beijing time on January 19, the Starlink satellite will also carry out its second launch of the year, which is likely to exacerbate the threat to normal astronomical observation and human space security exploration.
For the problems pointed out by all parties, has the starlink improved, and is there a possible way to deal with the "barbaric growth" starlink, the Chinese space station, etc.?
First, in addition to affecting astronomical observations, starlink has twice threatened the security of the Chinese space station
Since SpaceX launched its first Starlink satellites in May 2019, the astronomical community has been concerned about the impact of the Starlink program on astronomical observations, interfering with astronomers' discovery of various natural objects.
In order to quantify the impact of the Starlink satellite on astronomical observations, astronomers from the United States and other countries analyzed astronomical observation images taken by the ZTF (Zwicky Transient Facility) Observatory of the Palomar Observatory in the United States.
ZTF scans the entire night sky every 2 days to capture image data of various types of stars, and astronomers have found that from November 2019 to September 2021, ZTF's images showed traces of 5301 star-chain satellites.
▲Orbital traces due to the operation of the star chain in astronomical observation images
As more and more starlink satellites enter orbit, dawn and dusk observations are most affected, with only 0.5% of such images affected by starlinks in 2019 and 18% of the affected images by 2021, with astronomers estimating that currently, there is a 0.04% probability that astronomers will fail to spot some rare astronomical event, such as missing a new asteroid.
Astronomers expect that if the number of satellites in orbit reaches 10,000, all dawn or evening astronomical observation images will show at least one trace of the orbit formed by the satellites.
For other more sensitive astronomical observation instruments, the images taken will be more affected by the star chain.
As the number of starlink satellites tracked by astronomers (red) increases, so does the number of affected astronomical observation images (blue).
In addition to influencing astronomical observations, starlink satellites have affected the exploration of space by other spacecraft, the most serious of which has threatened the safety of astronauts on the Chinese space station and the Chinese space station.
In order to fulfill its obligations under the Outer Space Treaty, an important international law in the field of outer space, and to safeguard the safety of astronauts' lives, the Chinese Government informed the UnPromissing Secretary-General of the above-mentioned dangerous situation and the measures taken by China through the Permanent Mission of China in Vienna on 3 December 2021, and requested the Secretary-General to inform the States parties.
China sent a note verbale to the United Nations
According to the United Nations note sent by China, Starlink left its prescribed orbit and approached the Chinese space station twice, and in order to ensure the safety of astronauts on the Chinese space station, the Chinese space station assembly implemented two preventive collision avoidance controls ("emergency collision avoidance").
▲ The note verbale detailed the situation of the Chinese space station's emergency avoidance of the starlink satellite twice
The Starlink satellites and the Chinese space station both have fixed orbits, orbiting different altitudes around the earth, about 555 kilometers and 390 kilometers, respectively, and originally there was no crossing or overlap.
The first time the Chinese space station took emergency collision avoidance was on July 1, 2021. Starlink-1095 satellite in the period from May 16, 2021 to June 24, 2021, after continuous de-orbit to an average orbital altitude of 382 kilometers, to maintain the orbital altitude of operation, because the satellite orbiting the ground is perigee and apogee, the two spacecraft operating altitude range is close, prone to approach and collision risk, July 1, Starlink-1095 satellite and The Chinese space station appeared close to the time, for safety considerations, the Chinese space station took the initiative to avoid collision that night.
Less than four months after this dangerous situation, the Chinese space station took the second emergency encounter on October 21, 2021, this time because of the close proximity incident between Starlink-2305 and the Chinese space station. And the satellite is still in a continuous orbit maneuver.
In the face of China's notification, Musk did not make a targeted response, but on December 29, 2021 local time, Musk replied to the criticism of the director general of the European Space Agency for Musk's satellites occupying too many orbits.
Josef Aschbacher, the new director-general of the European Space Agency, has warned musk that the lack of coordination in implementing the Starlink program means the billionaire is setting his own space "rules," with one person owning half the world's active satellite data that will affect space radio frequencies and orbital space conditions.
Musk believes that the earth's low orbit can accommodate tens of billions of spacecraft, thousands of satellites are nothing, just like the appearance of thousands of cars on the earth, do not worry too much.
For Musk's statement, the American astrophysicist Jonathan McDowell questioned that spacecraft can fly at speeds of up to 27,000 kilometers per hour, requiring greater intervals than the distance required for cars on Earth to operate safely, and possible collisions between spacecraft can only be detected when the distance is relatively close, and space is already crowded.
Second, the Starlink target launched 42,000 satellites, what is the emergency avoidance function?
Musk's Starlink program has been in place for several years, as early as 2015, when SpaceX announced plans to build a satellite network in space to provide satellite Internet services for the ground, broadband Internet services to areas that lack fiber optic and physical Internet links, and expand the boundaries of people's use of the Internet.
According to the information released by Musk on Social Media on January 16, 2022 local time, at present, a total of 1469 Satellites are in operation, 272 are in orbit, and the laser link communication of the satellite will soon be activated.
Each Starchain satellite features a compact flat panel design that minimizes volume, features automatic collision avoidance, and is equipped with custom navigation sensors, optical space lasers, 4 phased array antennas and 2 parabolic antennas, as well as high-efficiency ion thrusters and a single solar array.
Starlink's autonomous collision avoidance device needs to be combined with the U.S. Department of Defense's debris tracking system to achieve autonomous maneuvering and avoid impact risks, and SpaceX said its automatic collision avoidance device is an order of magnitude higher than industry standards.
The specific autonomous collision avoidance process is achieved in this way, the ground system combines the starlink satellite orbit forecast information and space target database data, screens out the potential collision target, calculates the probability, and then transmits the high-probability collision information to the satellite end, the starlink satellite uses 4 mutually perpendicular momentum wheels to adjust the posture, use the ion propulsion engine to transform the orbit, complete the avoidance, this process is all automatically completed by the computer.
▲ Automatic collision avoidance device and customized navigation sensor of Starlink satellite
The main function of Starlink Satellite's custom navigation sensors is to determine the position, altitude and orientation of each satellite, so as to achieve precise placement of broadband throughput.
Optical space lasers are devices that SpaceX is testing that enables spacecraft to transmit data without a local ground station, enabling true global coverage.
Optical space lasers and antennas for Starlink satellites
The high-efficiency ion thruster is powered by the krypton element, which is mainly used to help the satellites maneuver and de-orbit at the end of the life of the starlink satellites, and to burn in the atmosphere near the Earth.
▲High-efficiency ion thrusters and solar cell arrays of Starlink satellites
In addition, in the face of astronomers' concerns, SpaceX redesigned the sun visor of the starlink satellite to reduce its brightness, thereby reducing the interference with astronomical observations.
Starlink initially aimed at 12,000 Starlink satellites, and later added 30,000 more.
At present, SpaceX has carried out 35 launch missions, launching a total of 1991 Starlink satellites, but some of the launched Starlink satellites have proved to be unresponsive and no longer maneuver in orbit, which is about 3% in 2020, and these "space junk" will endanger the safety of other operating spacecraft.
In 1978, NASA scientist Donald J. Kessler proposed the threat of a large number of spacecraft or space junk that could not function properly, and the collision of 2 spacecraft produced a lot of debris, which in turn would hit other spacecraft, forming more debris, and the earth may be slowly surrounded by layers of space junk.
In addition to the control failure, the starlink satellite orbit planning may also have problems, the starlink satellite not only posed a threat to the Chinese space station, but also almost collided with the European Space Agency's "Fengshen" meteorological satellite, on September 2, 2019, the "Fengshen" satellite and the Starlink-44 almost collided, the European Space Agency emergency change orbit to avoid accidents.
In April 2021, Starlink was almost colliding with oneWeb's satellite Internet satellite at a distance of 57.9 meters, and OneWeb mentioned that SpaceX turned off the anti-collision system on the satellite.
Hugh Lewis, head of the astronautical research group at the University of Southampton in the United Kingdom, said that if two spacecraft pass by within a distance of 0.6 miles (1 kilometer) from each other, it is calculated that two spacecraft have a close contact and there is a risk of collision, and all Starlink satellites have about 1600 such cases every week, accounting for 50% of all such time, which can be said to easily threaten the safety of other spacecraft.
The close contact of spacecraft involving star-linked satellites, mapped by Hugh Lewis's team using data from the Socrates database to assess satellite threats, showed a continuous growth trend
In short, from the current various factual bases, the independent collision avoidance ability of StarLink seems to have little effect, and it is somewhat "overbearing".
Third, the competition for space exploration is becoming increasingly fierce, but the rules of space mainly rely on international law 50 years ago
Space is a resource belonging to all mankind, and how to regulate human space activities requires relevant international law to coordinate space actions between countries.
The subject of space law is the five international treaties promulgated by the United Nations Space Committee on the Peaceful Uses of Space, referred to as the Outer Space Treaty, the Rescue Agreement, the Liability Convention, the Registration Convention, and the Moon Agreement.
The most important of these is the Outer Space Treaty. The Outer Space Treaty was adopted in 1966 and entered into force on 10 October 1967, and the vast majority of United Nations Member States have signed and ratified this international space law.
In addition, the UNITED Nations General Assembly has adopted a series of principles, resolutions and declarations related to space activities, the latest of which may be the Guidelines for the Long-term Sustainability of Outer Space Activities adopted by the United Nations Committee on the Peaceful Uses of Outer Space in 2019, but this new guideline is not a soft space law and is not legally binding.
There are also some international organizations that have established relevant rules to regulate space exploration, such as the International Telecommunication Union (ITU), which is responsible for allocating satellite frequency and orbit resources, and countries are given priority access in the order of declaration.
For example, the United States passed the Outer Space Resources Exploration and Utilization Act in 2015, which stipulates that U.S. citizens enjoy the right to possess, own, transport, use and sell outer space resources; in 2016, Japan promulgated the Space Activities Act to regulate commercial space activities.
With the rise of commercial space business, some of the original regulations can no longer meet some of the current situations, and space sustainability and space debris issues are one of the key issues in the current space governance.
However, the satellite has a limited service life, and after abandonment, it loses control, and staying in space will become space junk, threatening other normal satellites. In 2009, the U.S. Iridium 33 satellite collided with the defunct Russian Cosmos-2251, which damaged iridium 33 and produced a large amount of debris.
Because of this, the United Nations Committee on the Peaceful Uses of Outer Space has issued a space debris mitigation guideline to reduce the impact of space debris on human space exploration, which provides for limiting the long-term presence of orbital stages of spacecraft and launch vehicles in low-Earth orbit after the end of mission.
Starlink plans to launch 42,000 satellites, each satellite life is only 5-7 years, in a 550 km orbit, the faulty satellites need 1-5 years to fall into the atmosphere and burn, once a large number of Starlink satellites fail, it will cause very serious consequences.
Spacecraft have fixed orbits, orbital height, orbit shape, orbit inclination are different, the current probability of satellite collision is not very large.
In addition, changes in orbit like Starlink satellites do not inform the behavior of nearby orbiting spacecraft, and can also threaten the safety of normally operating spacecraft.
In the face of possible collision accidents, many spacecraft have carried out advance planned deployment, such as the emergency collision avoidance function of The Chinese space station, in an emergency, the space station engine through the system control to lift the orbit, change the orbit height and inclination. In addition, experimental modules like Tiangong 1 and 2 have protective plates to deal with small space junk outside the module, and measures such as hiding and resisting are used to deal with the impact threats encountered.
In addition, the planning of space garbage recycling has also been put on the agenda, and the European Space Agency plans to go to space in 2025 to recycle space garbage, perhaps to avoid the threat that failed satellites pose to the functioning spacecraft.
But the more important and tricky issue is that as commercial space companies grow, more and more people are involved in space exploration, and there is a lack of regulation, and commercial space companies are making their own space rules, especially Musk's SpaceX. The boundaries between government space research and corporate space exploration are blurring, and people like SpaceX and NASA work very closely together, and how to set space rules that most of the world's countries can abide by may be more urgent.
Conclusion: Space exploration in the universe requires sustainable development
Space is an area that all countries are trying to compete in, just past 2021 commercial aviation continues to rise, a number of commercial space companies compete to carry people to space tourism, and many countries have launched their own satellites.
However, orbital resources are limited, who launches more satellites first, who can seize more orbits first, grasp more initiatives in space exploration, the rise of commercial space has intensified the situation of orbit competition, but the organizations or regions launched by various spacecraft should also consider sustainable issues to avoid various adverse effects caused by preemptive satellite launches, such as space junk and so on.