On the evening of April 27, 2020, a new celestial image excited some enthusiasts. In the Beijing area, a group of “Starlink” satellites rose from the north-west at around 8:37 p.m., passed the moon, and then darkened and disappeared a few minutes later.
这些Starlink卫星是SpaceX公司“Starlink计划（Starlink）”所发射的通讯卫星之中的一部分，它们通常会由22个卫星连成一串，在某个特定轨道平面上运行。当它们划过天空之时，因反射太阳光而发亮，在天空形成一串光点，形为夜空中的一道壮观景象，有人比喻它们为天空中的“The Three-Body Problem舰队”。
SpaceX will launch 12,000 satellites into low-Earth orbit in about a decade, according to the Federal Communications Commission(FCC) in April 2019, and in October, SpaceX announced that it would add 30,000 “Starlink” stars, although Musk initially promised that the satellites would be barely noticed, but they were frequently displayed in telescopes and camera lenses around the world, but they had to cause concern and worry among astronomers.
What exactly is SpaceX’s Starlink program? What impact will it have on scientific research and human life? Is there a way to avoid or resolve the problems it may cause?
Global Network Coverage – “Starlink Program”
The Starlink program, proposed by space service company SpaceX in 2015, provides high-speed Internet access to the world through a constellation of near-Earth orbit satellites. Elon Musk, the Iron Man prototype, plans to rely on Starlink to extend high-speed broadband internet to hard-to-build ground-based or inaccessible areas, making it cheap and stable for people in almost any part of the planet.
Since the satellite network has no problems brought about by the construction of ground communication base stations, and the communication delay of signal transmission between satellites is lower than that of using optical fiber to spread between base stations, it can be said that the “Starlink Plan” is fully capable of fighting the “fifth generation mobile communication technology (5G)”.
Figure 1: 60 Starlink satellitestacks loaded into rocket rectifiers.Source:SpaceX
According to the earliest plan, SpaceX would launch about 12,000 Starlink satellites into near-Earth orbit, a three-layer network of satellites located in orbits 340 kilometers (7,500), 550 kilometers (1,584) and 1,150 kilometers (2,825) from the ground. According to SpaceX’s filing with the FCC last October, they plan to build on that, launching an additional 30,000 satellites, bringing the total to 42,000.
With the help of a cost-effective rocket, the Falcon 9, which can be reused multiple times, the Starlink Program is currently able to launch satellites in batches and frequently. Under the 2019 plan, SpaceX will launch at least nine times in 2020, possibly 24 times, or about every half-month. However, from the current status of the first four months of the launch, it completed six successful launches, followed by one in May and one in June.
The Falcon 9 launches 60 satellites at a time, so of course the ability to launch more frequently will require SpaceX to be able to produce enough satellites in a short time, and their production base could generate six Starlink satellites a day, according to SpaceX’s march report. Enough to satisfy the Falcon’s frequent future launches. In the future, of course, SpaceX expects to launch satellites using a star-ship rocket that is still under development, and its ability to launch will be greatly enhanced by then, reaching 400 satellites at a time.
Each satellite launched was able to successfully enter orbit as required, with some exceptions, of course. For example, of the 60 Starlink satellites first launched in April 2009, three lost contact. As of April 22, 2020, SpaceX has successfully launched eight times, including 422 Starlink satellites, with 417 Starlink satellites in operation. They are using these satellites in North America to conduct some private network testing services, and larger public testing will begin in November 2020.
Figure 2: In October 2019, Musk tweeted a successful test of starlink’s network. Source: twitter
Near-Earth rail traffic jam, who is responsible for space car accidents
Don’t look around for routers, don’t worry about the sea mountains no signal, it seems that the “Starlink plan” is really very convenient, why would anyone resist it?
First of all, near-Earth orbit is not a “clean land”, according to the United Nations satellite registration website (www.unoosa.org), as of today, a total of 9,449 man-made objects can be launched into the universe (including the launched Starlink satellite), there are still about 2,000 satellites in orbit, even under the current 12,000 “Starlink plan”, will increase this number to five or six times. By then, a large number of satellites and space junk will float in this area, leading to severe congestion in near-Earth space.
Figure 3: Earth wrapped in satellites
While SpaceX says each Starlink satellite will be “able to track in-orbit debris and automatically avoid collisions” and will automatically deorbit when it reaches its lifetime, it is stated that 100% of the components should be eliminated in the atmosphere (95% of the parts of the v0.9 satellite launched in May 2019 will disappear into the atmosphere), In the latest v1.0 release after November 2019, all parts will disappear), but if they are damaged in orbit or failed to disperse successfully, the satellites will still pose a serious problem.
Of the first Starlink launched in May 2019, three lost contact and were unable to take active control, creating space junk, although SpaceX said the three satellites would be pulled by gravity to burn up in the Earth’s atmosphere.
But SpaceX isn’t the only company to have such a plan, with Amazon in the U.S. and OneWeb in the U.S. seeing opportunities for space networks and plans to launch satellite networks. And Amazon’s Blue Origin Rockets is also a company with mature rocket technology, so near-Earth space is likely to become extremely crowded soon.
12,000 False Starlight – All-Round “Lock down” Ground Astronomical Observations
In addition to space accidents, the Starlink satellite poses a greater challenge for global astronomical observations.
The idea of satellite communications was put forward and put into practice as early as the 1990s. From 1997 to 1998, the United States launched 66 mobile global communications satellites (originally planned to launch 77, hence the name of element 77), but due to the lack of market demand at that time, “Star Plan” in 1999 went bankrupt and restructured.
But the star’s ascent has brought a “flash” this rather alarming artificial celestial phenomenon, because Motorola company in the design of the star when it equipped it with three aluminum antennas, as the satellite spins these mirror-like antenna will reflect the sun’s light to the ground, in the ground to form a few kilometers wide light belt, in the light belt area of people can see the star quickly from the dark light, flash.
Figure 4: The luminometers of a star can rise from 5-6 to -8 or more when the flash occurs, and then darken again in a few seconds until disappear.Source:http://www.astrocn.com/beta/tags/%E9% 93% B1% E9% 97% AA
And the number of stars far higher than the Starlink satellite has also been some star enthusiasts have been filmed in turn “flash” phenomenon, brightness can even exceed the weaving actress, if this flash filled all day, the resulting light pollution will be unimaginable.
Figure 5: Astronomy enthusiasts captured a row of Starlink satellites flashing in turn, source youtube.com/watch? v-cycLZQtM8HU
Not only that, but even if Starlink satellites did not flash, their impact on deep space observations was immeasurable. “The latest report shows that starlink satellites stay around 5 for most of the time,” said Jonathan McDowell, an astronomer at the Harvard-Smithsonian Center for Astrophysics. “
Although it is almost invisible to the naked eye, these satellites are still too bright for the stars, both for the stars and for researchers with professional astronomical observations (dark stars with the main target of 10-20 stars, etc.). Because the number of Starlink satellites is so large, the resulting enthusiasts and professional astronomical observations have resulted in a large number of waste films due to the entry of the Starlink satellites into the mirror.
“Look, Leonardo, I’ve got the Mona Lisa for you Starlink! Source: twitter/SuperASASSN
Because the circumference is much faster than the astronomical target, the Starlink satellite entering the telescope’s field of view leaves a narrow trajectory in the images taken by the telescope. And because the Starlink satellite appears so frequently in photographs that it becomes a separate term as a verb in English. The new definition is: “To ‘starlink’ a photo – to add satellite-like trails to a photo, for added pizzazz” (“Starlink photo – add a satellite-like trace to the photo”). “)。 How would you feel as a fan of famous paintings if you saw the Mona Lisa’s famous paintings being unprovoked and added to a few Starlink tracks? It must have been felt that Starlink had ruined the beauty of the whole painting. The same is true of the destruction of Starlink satellites for star photography.
Starlink satellite captured by a star photographer. Credit: REIDAR HAHN/FERMILAB
Figure 6: Starlink satellite runs diagonally through the telescope’s entire field of view while shooting NGC 5353/4 at the Lowell Observatory in Arizona, USA.Source:Victoria Girgis/Lowell Observatory
Figure 7: The second batch of Starlink satellites captured by Cerro Tolo Inter-Observatory (CTIO) in Chile. Source: NSF’s National Optical-Infrared Astronomy Research Laboratory/CTIO/AURA/DELVE
Figure 8: On 22 November 2019, the Alpha meteor shower in the constellation of Kirin was observed at the Farah Observatory in Italy.
It is clear that for both amateur star enthusiasts and professional astronomers, the data on celestial bodies that are obscured and exposed by the trajectory is all forsaby. In professional data processing, specialized algorithms are used to identify these satellite tracks and then smear this information.
Figure 9: Using algorithms to identify and eliminate the impact of satellite trajectories.Source:Desai et al.2016
But beneath the starlink satellite, perhaps this is the way the telescope is left.
Figure 10: The results of the Farra Observatory’s Global Meteor Network (GMN) camera captured the aftermath of the Constellation meteor shower stack, with a large number of Starlink tracks filled with the entire picture.Source:Farra Observatory (GMN)
It’s clear that throwing away the data directly seems more like the right thing to do than a satellite’s trajectory, and the Starlink project is forcing astronomers to throw away more data that should have been useful.
The effects of the future 42,000 Starlink satellites on observations were simulated according to the Large Integrated Sky Survey Telescope (LSST). The results show that up to 30% of the images will contain at least one satellite trajectory, and the brightness measurements of these satellites also indicate that they will be oversaturated in LSST images, 20 million times brighter than the typical galaxy, and in extreme cases, because these observations will be invalidated, for which LSST will have to add four years to the 10-year observation plan to compensate for these losses.
LSST proposes two ways to alleviate this problem, one is to increase the number of exposures, by breaking down the standard exposure time of 30 seconds into two 15 seconds, if only one of the satellite tracks is included, then the impact of another exposure to complement the trajectory; But there is no doubt that either solution is premised on extended observation programs.
Window from the “fog”, radio band is also a hard-hit area
Not only in the visible light band, but even in the radio band, starlink satellites still cause serious observational interference.
Take the 500-meter spherical radio telescope (FAST) in Guizhou, China, for example, with a center radius of 5 kilometers in the core area to maintain radio silence, any mobile phones, digital cameras, smart wearable devices in the region are strictly prohibited, and even so FAST still can not avoid interference from the sky, only to arrange observations to avoid satellite transit time.
Figure 11: FAST, located in the hinterland of Guizhou’s deep mountains, can only rely on geographical conditions to shield interference from the ground
“Radio astronomy facilities are highly susceptible to satellite transmission signals, after all, radio telescopes are unable to use geographical barriers to mask interference from the sky. Liese van Zee, chairman of the Us Radio Frequency Commission (CORF), said. Radio waves generated by the work of the Starlink satellite may directly affect the observation of high-frequency signals by radio telescopes.
Since the scientific targets detected by radio telescopes are mostly very weak electromagnetic signals in the universe, and it is clear that Starlink satellites emit much stronger than them, they can cause intense radio interference to cosmic lines of the same frequency, not only flooding the required information with large amounts of satellite data, but also potentially damaging highly sensitive radio observation equipment. In order to avoid the adverse effects of Starlink satellites, radio telescopes on the ground must avoid the time period of satellite transit for observation, and if the Starlink satellites are fully in low-Earth orbit, perhaps we will have to abandon some of the observations in the band, which is undoubtedly a loss for radio astronomy.
In general, these sky-filled satellites will increase the burden of astronomical observations on the ground, either in early observation planning or in the processing of later data, due to the involvement of Starlink satellites resulting in a doubling of the workload. Didier Queloz, a professor at the University of Cambridge and a 2019 Nobel Prize-winning physicist, said in a recent interview, “I like the idea of global coverage of wireless networks, but it’s not at no cost.” Some people are using the sky to do business, as a result we are about to lose the sky! “
Can SpaceX’s remedy be the best of both worlds?
Musk has been claiming that starlink will have no effect on astronomical observations until the official Starlink satellite launches in May 2019, but after all, Musk is not a scientist and underestimates the satellite’s impact on astronomical observations. Soon after the satellite launch, scientists estimated the impact of a large number of satellites to astronomical observations, and did find that the impact on astronomical observations was considerable. Musk also responded positively to the results. So in the course of the American Astronomical Society (AAS) and the International Astronomical Union (IAU) to assist astronomers and SpaceX in their dialogue, it is true that the SpaceX team is also preparing to take a number of ways to reduce the impact of satellites on astronomical observations.
SpaceX will launch a “Starlink-1130” in a planned launch on January 6, 2020, to test the effect of reducing brightness by blackening the satellite’s surface. According to observations on March 6, the brightness of the blacked-out Starlink satellite was about twice as low as that of the non-blacked-out Starlink satellite, and the star and so on decreased from 6.7 to 7.6. Although this blackening approach is difficult for the naked eye to see, it is still insufficient to meet the needs of professional observatories, especially those that conduct large field observations.
In general, however, no one wants to blackout satellites in particular. First of all, because of the blackened satellite material first of all need to have high requirements, such as can not and the atmosphere of oxygen atoms oxidation, otherwise will lead to layer drop, the production of space junk, the harm is also great. In 1983, on its way back, the space shuttle Challenger was hit by a falling piece of paint that had caused a very visible trace. Fortunately, the glass windows are four floors. In addition, when blacked out, will lead to the face of the sun, the temperature rise, and into the Earth’s shadow without sun exposure, the temperature drops, so it will lead to excessive changes in satellite temperature, greatly reducing the life of the satellite.
In addition, there are some potential problems with this coating, which may lead to some false observations. When these blackened moons pass through a star, they cause the star’s brightness to decrease, which is known in astronomy as the occultation effect. This method is used in the search for exoplanets, and if a large number of satellites are launched, it can lead to many of these false signals, making data processing more difficult.
In addition to the satellites, spaceX engineers at the Satellite Conference in March 2020 suggested that each satellite could be equipped with an umbrella that would prevent the reflection of sunlight. But it’s just an idea, and how the umbrella device is designed and how it’s launched is a big question.
On April 27, 2020, the American Academy of Sciences organized a special session on astronomy 2020 for the 10-year plan for astronomy and astrophysics, inviting the astronomical community and Musk to talk. During the dialogue, SpaceX further suggested that the flash brightness is related to satellite posture, which will adjust the satellite posture, and that some blacked-out high-performance satellites will be launched to replace the old ones as soon as possible.
But SpaceX’s measures have limited improvements to the sky’s environment. One of Musk’s advices to astronomers is to make space observations and recommend his starship to astronomers at the conference. While launching space telescopes for observation is also one of the solutions, and rocket technology is already mature, the high budget for space equipment has deterred most astronomers. For example, the James Webb Space Station telescope alone has a budget of nearly $10 billion, while its main mirror is only 6.5 meters. The budget spent on sending earth-based telescope-sized behemoths (such as the 39-meter-diameter European Giant Telescope E-ELT) into space may also be astronomical.
Figure 12: THE James Webb telescope, which NASA has invested in.Source:NASA
In general, if SpaceX can’t come up with a better solution, I’m afraid the difficulties the Starlink project will bring to astronomy research are disaster. You know, there are about 5,000 stars visible to the naked eye on the ground, and for Starlink, even without the 30,000 of the follow-up plan, at the current launch rate, it will soon exceed the number of stars visible to the naked eye.
Although the FCC has approved that SapceX could launch 12,000 satellites, there have also been questions about the continued launch of SpaceX, which has actually damaged the sky environment by launching so many satellites into the near-Earth environment.
For now, however, more satellite launches are inevitable, so astronomers are also actively proposing strategies for responding to them from the perspective of observations and post-processing software, as mentioned above, as The LSST mentioned above, reduces the time of each observation.
In radio bands, CORF is also in talks with SpaceX to develop an agreement that balances the interests of science and telecommunications companies. Although the radio window of the Earth’s atmosphere is very wide, it is really unable to withstand too much division, leaving radio astronomy bandwidth has become more and more narrow.
The launch continues, and the discussion on this topic will continue for a long time. “Should the sky be free, or will it be the next market?” Didier Queloz said in an interview, “I’d be happy to see the debate about it, because we’re going to go to them every day (Starlink satellite), and I want the whole world to be part of the discussion, and is the Starlink satellite really what we want?” “
“Let future generations see the stars, see the green mountains and smell the flowers,” General Secretary Xi Jinping said at the opening of the 2019 World Horticultural Expo in Beijing, China. Looking up at the stars can not only satisfy the interests and hobbies of the people, but also an indispensable and important component of scientific development. If we look at the long history of scientific development, astronomy plays an irreplaceable role in the development of science and even in the progress of human civilization and society. We should cherish the stars above us together.
Thank you: Thanks to The Micro-Blogging Harper and Dr. Skinhead for their summary of the discussions on Starlink’s plan for the 10-year U.S. program.
Gou Lijun, Researcher of the National Observatory of the Chinese Academy of Sciences and Professor of Astronomy, University of the Chinese Academy of Sciences
Liu Ziming Master’s degree in the National Observatory of the Chinese Academy of Sciences
Tregloan-Reed J, Otarola A, Ortiz E, et al. First observations and magnitude sand sylweds of Starlink’s Darksat.
2: Vera C. Rubin Observatory – Impact of Satellite Constellations, https://www.lsst.org/content/lsst-statement-regarding-increased-deployment-satellite-constellations
3: https://www.youtube.com/watch? v-dA4FUFgXtKQ
4: Nadia Drake. Will Elon Musk’s Starlink satellites harm astronomy? Here’s what we know.https://www.nationalgeographic.com/science/2019/05/elon-musk-starlink-internet-satellites-for-astronomy-light-pollution/#close
: Desai S, Mohr J J, Bertin E, et al. Detection and removal of artifacts in-cono images. Astronomy and computing, 2016, 16: 67-78.