On the evening of January 6, SpaceX Falcon 9 took off from Cape Canaveral and deployed its payload one hour later: 60 Starlink satellites. These satellites joined the ranks of 120 other satellites launched in May and November last year, as SpaceX tried to accelerate the deployment of its initial broadband constellation, putting as many as 1,500 such satellites into orbit in 2020 alone. Approximately 36 hours after
was deployed, participants could see these satellites at the 235th meeting of the American Astronomical Society (AAS) in Honolulu before dawn on January 8. Although the city lights are bright, the satellite is easy to see through a hole in the cloud and dozens of bright objects line up in a line from west to east.
It is unclear how many attendees attempted to view the satellites, but later that morning, many people attended a special session of the conference to discuss the impact of the Starlink satellites and the general giant constellations on their fields. Since the launch of the first Starlink satellite in May, astronomers have complained that these satellites and other systems that may be launched in the next few years may make it difficult for astronomers to use ground-based telescopes to make observations. The interference of satellite
with astronomical observations is not a new phenomenon. “Any object in Earth’s orbit that reflects the sun, any object with an albedo greater than zero, can leave traces in the astronomical image,” said Pat Sezer, emeritus professor of astronomy at the University of Michigan.
He said that on any one night, the observatory can see hundreds of objects. “We really hope that there are no satellites,” he said, “but this battle has been lost a long time ago, starting in 1957.”
What makes Starlink unique is its number and brightness. When initially launched into the parking track at an altitude of about 300 kilometers, their visual magnitude was between 2 and 3: Bright enough to be easily seen with the naked eye, even in light-polluted cities. When they reach a 550-kilometer orbit, they will dim to about fifth level, and can only be seen with the naked eye in the darker sky far away from the city.
However, even at magnitude 5, satellites are bright enough to cause problems for professional astronomers, who need long exposures in large telescopes to observe faint celestial bodies. Seitzer said that before Starlink, there were only about 200 objects in Earth’s orbit that were so bright, but by the end of 2020, this number may increase ninefold due to Starlink. “So life becomes very interesting,” he said.
Although astronomers may have known SpaceX’s plan to launch Starlink satellites, they did not expect them to be so bright. Jeff Hall, director of the Lowell Observatory in Arizona and chair of the AAS committee dealing with light pollution and waste space issues, said: “The first thing that surprised everyone is that a’string of pearls’ shines in the sky.” .
Falcon 9 superiors launched about 60 Starlink satellites. 6 Over the ocean between Australia and Antarctica. Image source: Still from SpaceX
webcast video SpaceX said it was also shocked. SpaceX Vice President of Government Satellite Affairs Patricia Cooper (Patricia Cooper) said on behalf of the company at the AAS meeting: “Of course we know that this is a novel spacecraft with a novel architecture, but the level of brightness and visibility allows We are surprised.”.. SpaceX has not revealed many technical details about the Starlink satellite. Cooper said that these satellites are “products of a highly iterative design process,” designed to minimize the size of each spacecraft, thereby maximizing the number of satellites that a single Falcon 9 can launch. Each satellite weighs 260 kg, has four phase-ray antennas facing the earth and a solar array deployed on the satellite.
Cooper said the company spent several months to understand why the Starlink satellite looks so bright. He said that part of the reason has to do with the configuration of the solar array, especially when each satellite is increasing its orbit and the array is moving to a “low resistance” position, which increases its reflectivity as seen from the ground. The unique design of the
satellite also played a role. “The cause of brightness does not seem to be intuitive,” he said. “It turns out that we believe that surfaces that scatter or reflect light can also make a significant contribution.”
Now that SpaceX believes it understands what makes Starlink satellites so bright, it is testing ways to reduce their reflections. . Cooper said that one of the 60 satellites launched on January 6 was covered by “various dimming treatments” designed to reduce reflections. “The goal is to collaborate with the astronomy community to observe and measure the effectiveness of these coatings.”
However, it may take several months for astronomers to know how effective this “DarkSat” is. Seitzer said that at least until the end of February, the earliest date the satellite can reach its final orbit, can astronomers compare it with other Starlink satellites. At the same time, SpaceX must also understand how these coatings affect the satellite’s thermal performance.
Therefore, it may take several months for SpaceX to decide whether to apply these coatings to all future Starlink satellites or to fly other experimental DarkSats. At the same time, the company plans to launch more unmodified satellites, and the next batch of 60 is scheduled to be launched on January 20. “We tend to work very fast. We tend to quickly test, learn and iterate, “Cooper said, but declined to say how long the company thinks it will take to find a permanent solution.
The company has been in contact with the AAS working group that was formed shortly after. On the launch of Starlink in May 2019, Hall, who leads the task force, said this includes monthly conference calls and face-to-face meetings during the AAS meeting.