Wen 丨 Silicon Valley 101 (ID: svstyle), interview 丨 Hongjun, author 丨 Hu Shaoyang
"If one day the Earth is hit by an asteroid and astronomers don't provide enough warning time, don't blame them, you should go to the companies that send satellites." 」 Lu Jianwei, a doctor of astronomy and astrophysics at the University of Arizona, mentioned in an interview with the guest podcast "Silicon Valley 101".
The "company that sends satellites" here refers to the Starlink project launched by SpaceX created by Elon Musk. By launching many small satellites into low-Earth orbit, we will build a high-speed Internet in space. Astronomers have continued to report that Musk's Starlink program is having a devastating impact on astronomical observations on the ground, and some scientific research projects are completely impossible.
Coincidentally, at the end of December 2021, Netflix released a sci-fi satire called "Don't Look Up", which tells the story of a comet the size of Mount Everest that is about to crash into the earth, but humanity is still immersed in political struggles and entertainment to death.
Asteroid impact on Earth is not the imagination of science fiction movies, just two months ago, NASA also launched the world's first planetary defense test mission, if the future predicts that extraterrestrial objects are about to hit the earth, try to change the asteroid orbit.
Figure | DART mission schematic from NASA/Johns Hopkins Applied Physics Lab
Although StarLink can provide high-speed space Internet to remote areas, it also has many negative effects on human exploration of the universe. As of January 15, 2022, of the 1993 satellites launched by StarLink, 1469 are operating normally, and more than 200 satellites have lost contact, with a loss rate of up to 10%. These missing satellites become space junk, and when humans launch spacecraft or space telescopes into space, they first need to break through the interference of this layer of space junk.
In addition to affecting aviation safety, Starlink has a greater impact on astronomy. What specific impacts are starlinks having on astronomical observations, and is there a solution? The following is a selection of interviews with Hong Jun, host of the podcast "Silicon Valley 101", Lu Jianwei, Ph.D. in Astronomy and Astrophysics at the University of Arizona, and Long Feng, a postdoctoral fellow at the Harvard-Smithsonian Center for Astrophysics.
01 Four major effects of starlinks on ground-based observations
Lv Jianwei: Artificial celestial bodies or artificial debris around the Earth will have a negative impact on the launch of the Weber telescope, but at present, these effects are relatively limited, and within a few minutes after the launch of the Webb Space Telescope, it will fly to Lagrange L2 point. According to NASA's plan, the Weber Space Telescope is expected to reach Lagrange L2 on January 23. The site is located nearly 1.5 million kilometers from Earth, so there's no need to worry about the impact of Earth's man-made objects on it.
Figure | The flight progress of the Webb telescope From: NASA
But starlinks, including their wreckage, have had a big impact on some telescopes and common satellites in low-Earth orbit.
In order to avoid collisions with SpaceX's star chain, China's space stations had to adjust their orbit twice last year, so star chains are a challenge to the survival and safety of astronauts. In 2019, Europe's Aeolus satellite nearly collided with a star-chain satellite.
The number of small satellites in the Starlink is very large, and their orbits are not easy to predict. You ask the people at SpaceX, and they don't necessarily know where a moon in the starlink is at what point.
There are many companies in China, the United States, and Europe that plan to build a global Internet through their own "Starlink Project". So in the long run, if there are no restrictions on this industry, in the near future, there may be dozens to millions of small satellites in the sky at the same time. Over time, they will produce all sorts of debris that pose a big problem for near-Earth astronaut safety.
We astronomers don't hate Musk himself, but we hate this starlink program, and they really hate the impact on astronomy.
First, the reflected light from the Starlink satellites could burn out astronomical telescopes. Although the human eye looks like starlink moons are relatively dark, they are very, very bright for sensitive astronomical telescopes. Many astronomical telescope detectors are so sensitive that some stars that cannot be seen by the naked eye need to be avoided, otherwise the detectors of astronomical telescopes will be burned by the light emitted by those stars.
How bright is SpaceX's star chain for astronomers? Let's say you're reading in a quiet library, or holding your breath, looking for a small animal. SpaceX's star chain is like a person who suddenly rushes over to beat a gong and drum, with a big horn, and yells at you. He just left, and then came another person who beat the gong and drum, and kept looping, and helplessly, you don't know when these people will come and when they will leave. The orbit of the star chain can be guessed, but it cannot be completely avoided.
Figure | 39 starlink satellites that appeared in 20 minutes, composed of 202 photos From: SatTrackCam Leiden
Second, the passage of a small near-Earth satellite in the starlink may result in the complete inability of the data from previous observations for several hours. If astronomers want to observe a distant object, the usual practice is to point the telescope to the location of the object, make a long exposure, and stare at the area of the sky without stopping to look and take pictures. A little shorter and a half hours, a little longer, even for days to keep an eye on that direction. The strong signal generated by small satellites will contaminate the starlight signal of the observing star, so you are not sure whether the data you see comes from the observing star or the small satellite.
In the past, there was a sudden light change signal in a certain celestial area, and it was usually believed that there might be a supernova there, or that a new celestial body was suddenly born. But after SpaceX's star chain appeared, this light-changing signal was likely reflected by the sun from the remnants of a small satellite.
Third, there are some astronomical phenomena that occur once in a thousand years or even once in a thousand years that may be missed. Scientists who do exoplanet research are more concerned about the planets around the star. The classic method of detection is to stare at a star and make repeated observations, recording the light emitted by the star, and the curve of change over time, which requires a long period of stable monitoring of the celestial region. If a starlink satellite suddenly appears, it will cause the light curve to suddenly produce an abnormal signal, and you can't be sure if this is normal data.
I made up a joke myself, 10 to 20 years later, millions of starlink moons and other small moons were flying around the sky all night. Astronomers spent the night making astronomical observations, and the next day the two astronomers exchanged results. One said I counted hundreds of Starlink moons this evening. Another astronomer excitedly said, I've counted that much too. But the discovery that one of them seemed to collide became their biggest discovery, but it didn't reveal any new cosmic phenomena.
Long Feng: These near-Earth satellites, although they will not have much impact on the Webb Space Telescope, have a great impact on almost all ground-based telescopes.
To add to this, it affects not only optical telescopes, but also radio telescopes that are often used for nighttime observations. It is said that the communication frequency of the star chain is completely coincident with a certain frequency of our radio observation, which means that we can hardly receive the signal emitted by that frequency in the sky, and the signal is completely covered.
While we can use a space telescope as an alternative, it's too expensive and the success rate is too low. Therefore, for astronomical observations, these telescopes on the ground still mainly rely on equipment, so the impact of the star chain on us is actually quite large.
02 Legislation and blackening satellites do not solve the urgent need
Silicon Valley 101: Did SpaceX's Starlinks design the problem of astronomical observations, or did they have no way to solve it?
Lv Jianwei: Actually, I know a little bit of information, the astronomers on our side are also responsible for studying the star chain, the influence of such satellites on astronomy. At present, the Astronomical Society of the United States, including some international intergovernmental cooperation organizations, has gradually begun to carry out some preliminary exploration in this regard, and may promulgate some regulations in the future.
I don't think SpaceX thought that much when planning this project, and their main purpose was to realize business value. A very few people who do astronomy may realize that this is a problem, but he did not foresee the rapid development of the star chain system.
American astronomy does a plan every ten years. A plan for Decadal Survey on Astronomy and Astrophysics 2020 just came out this year, and ten years ago starlink satellites were completely non-existent, so no one cared about it. It wasn't until the last year or two that people finally realized that this was a very serious problem. Therefore, this year's plan has a lot of space to discuss the solutions in this regard, unfortunately the space is relatively limited.
Now that astronomers have communicated with SpaceX, SpaceX has taken temporary measures to paint the surface of the new batch of star chains, such as painting them black, reducing the brightness of the satellite after it is illuminated, but it is still very bright after coloring.
The other has a relationship with infrared, because the energy does not disappear, the energy of the optical band is reduced, and its infrared band energy will become stronger. So you've satisfied the optical astronomers a little bit, but the infrared astronomers are starting to get angry again. The final solution, I actually don't know very well, from the perspective of infrared scientists, you need to make the whole satellite very cold to solve the problem. But in fact, this approach can lead to costs that are so high that they are completely unattainable.
Silicon Valley 101: SpaceX is launching Starlink satellites very frequently. Will they reduce the frequency of satellite launches when they know the impact on astronomical observations?
Lv Jianwei: Not only SpaceX's StarLink, but also the governments of many countries, or some more far-sighted entrepreneurs, feel that this may be an important development direction in the future, so some governments and enterprises will promote similar projects. It is very likely that multiple constellation systems can be seen in the sky within two or three years, and I am personally very pessimistic about what impact that will have on astronomy.
Long Feng: It can be said that it is a subversive influence. The Continental Survey telescope, which now receives optical wavelengths, has been greatly affected, and even some scientific targets have no way to do it. I personally think it's actually quite ironic, access to the Internet through satellites, is a cool practice, it makes human life better through technological means. But in turn, this created a black field for the development of astronomy, but it locked the pace of human exploration of the universe from the ground.
Figure | Starlink Signal Receiver From: SpaceX
03 Asteroid impacts on Earth are becoming unpredictable
Silicon Valley 101: In The Light of Civilization or the Lock of Civilization? In this episode of Musk's Starlink Open Beta, the impact of the large amount of space junk generated by the Starlink on astronomical observations is explored, which is indeed a rather contradictory thing.
Lv Jianwei: A few years later, when ground-based astronomers watched SpaceX's star chain flying around in the sky, their mood was estimated to be the same as that of the peasant uncle seeing the locusts floating around in the sky.
Long Feng: I think these starlink moons will affect us humans to a certain extent, because astronomers need to observe some fast-moving small objects to judge the probability of them hitting the earth. But if there are always fast-moving satellites in the sky, it is almost impossible for us to make measurements of such objects. So we don't know which meteorite hit us one day.
Silicon Valley 101: Will it become a reality that recently featured a sci-fi satire film, Don't Look Up, about astronomers observing that comets are about to hit Earth and humans are still immersed in various political struggles?
Lv Jianwei: I personally think this movie is still a little optimistic, now there are many satellite programs like Starlink, and astronomers will not find celestial bodies that threaten the earth in the first step.
Long Feng: You have to find that moving celestial body among so many fast-moving satellites, which is very difficult.
Lv Jianwei : The search for this negotiable object requires very detailed observations of the whole day at sunset and sunrise. That was also the brightest time for low-orbit satellites like Starlink. Therefore, when there were no such starlink satellites, searching for NEAR-Earth objects was already a relatively hard job, like finding a needle in a haystack.
Now after the star chain goes to heaven, it is equivalent to throwing away many, many false targets in the case of finding a needle in a haystack. So if one day the Earth is hit by an asteroid and astronomers don't provide enough warning time, don't blame them, you should go to the companies that send satellites.