SpaceX будет разрабатывать спутники в Сиэтле

[кукушка]

Elon 420 Time :f09f9bb0:
Viv:
— Спутников Starlink на орбите: 360
Сегодня запущено: 60
... aka 420 спутников Starlink
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anime. radio:
— У Илона было всего 2 дня на то, чтобы поставить 420 спутников на 4/20 ... он сам это выбрал
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Elon Musk:
— Если этот запуск пройдет успешно, мы выведем 422 спутника... [ред. - запуск - успешный! ]
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Viv:
— Сведите 2 из них. Сделай это для мемов
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Elon Musk:
— Они на самом деле сойдут хаха
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Owen Sparks:
— Это вы про испытательные Тинтины?
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Elon Musk:
— Да

Everyday Astronaut
— Есть ли причина, по которой спутники стали ярче и заметнее в последнее время?
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Elon Musk:
— Угол солнечной панели во время подъема орбиты и парковочной орбиты. Мы исправляем это сейчас.
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TesLatino :f09f9a80: P3.0.12.5 Rafael:
— Есть ли на cпутниках "козырёк" типа солнцезащитного козырька, например, козырьки на старых / традиционных скафандров астронавтов?
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Elon Musk:
— Он сделан из специальной темной пены, которая чрезвычайно радиопрозрачна, чтобы не влиять на антенны с фазированной решеткой. Очень похоже на автомобильный солнцезащитный козырек.

[кукушка]

https://spacenews.com/spacex-launches-second-batch-of-starlink-broadband-satellites/


SpaceX включил несколько обновлений для своего второго набора спутников Starlink. Лорен Лайонс, инженер из команды StarX компании SpaceX, сказала во время запуска веб-трансляции, что спутники имеют пропускную способность на 400% больше, могут генерировать вдвое больше широкополосных лучей с фазированной антенной решеткой и оснащены новой антенной системой Ka-диапазона.

SpaceX сказал, что один из новых 60 спутников может не завершить подъем орбиты после отделения от ракеты, и в этом случае один спутник сгорит в атмосфере Земли. Компания заявляет, что компоненты Starlink «на 100% разборные», что означает, что ни один из них не должен достичь поверхности Земли.  

SpaceX запустил вторую партию спутников Starlink на высоте 160 километров ниже, чем в своем запуске в мае, что означает, что несуществующие спутники будут десорбироваться быстрее. На спутниках Starlink электрические двигатели на криптоновом топливе достигают целевой орбиты после выхода из ракеты.

«У нас все еще есть способы перейти от твитов к видео 4K о кошках, но мы уже в пути», - сказал Лайонс.

SpaceX конкурирует с рядом других компаний, в частности, Amazon, OneWeb и Telesat, которые также стремятся развернуть сотни или тысячи спутников для обеспечения глобального доступа в Интернет из космоса.

[Max Andriyahov]

кукушка написал:
anime. radio:— У Илона было всего 2 дня на то, чтобы поставить 420 спутников на 4/20 ... он сам это выбрал

наркоманы)))

[Магадан Магадан]

В 4 раза это 17х4=68 Гбит/с на спутник в около 250 кг, ВанВэб обошли на порядок, молодцы.

[lev_g]

кукушка написал:
 https://spacenews.com/spacex-launches-second-batch-of-starlink-broadband-satellites/

Это статья о втором, ноябрьском запуске старлинка, не очень актуально на сегодня.

[tnt22]

https://spaceflightnow.com/2020/04/22/spacexs-starlink-network-surpasses-400-satellite-mark-after-successful-launch/

SpaceX's Starlink network surpasses 400-satellite mark after successful launch
April 22, 2020 | Stephen Clark


A Falcon 9 rocket streaks into the sky over Cape Canaveral in this long exposure photo. Credit: SpaceX

SpaceX launched 60 more spacecraft Wednesday to join the Starlink fleet beaming broadband signals around the world, while the company's engineers move closer to debuting a sunshade that could reduce the satellites' impacts on ground-based astronomy.

Спойлер

Riding 1.7 million pounds of thrust fr om nine Merlin main engines, a Falcon 9 rocket took off at 3:30:30 p.m. EDT (1930:30 GMT) Wednesday fr om pad 39A at NASA's Kennedy Space Center in Florida.

The Falcon 9 launcher, standing 229 feet (70 meters) tall, tilted on a track northeast from Florida's Space Coast and rocketed through a thin layer of high clouds on the way to orbit.

Two-and-a-half minutes after liftoff, the Falcon 9's first stage booster shut down and separated to begin a controlled descent back into the atmosphere. The rocket's single-engine upper stage ignited seconds later, and the Falcon 9 released its clamshell-like payload fairing more than three minutes into the mission.

Flying into space for the fourth time, the reusable first stage nailed a pinpoint landing on SpaceX's drone ship in the Atlantic Ocean east of Charleston, South Carolina. Two recovery ships were stationed in the Atlantic to retrieve the rocket's two-piece payload shroud, which was also recycled from a previous flight.

The Falcon 9 rocket released retention rods holding the Starlink satellites to the upper stage around 15 minutes after launch. Video from camera on the rocket showed the 60 flat-panel satellites — each with mass of about a quarter-ton — receding into space over the North Atlantic Ocean.

The satellites were each expected to extend their power-generating solar panel wing go through an activation sequence. Krypton ion thrusters on the spacecraft will boost them from their preliminary elliptical transfer orbit to an operational altitude of 341 miles (550 kilometers) over the coming weeks and months.

The successful launch Wednesday marked the 84th flight of a Falcon 9 rocket since June 2010. That makes SpaceX's Falcon 9 the most-flown orbital-class U.S. launcher currently in operation, exceeding the 83 missions performed by the Atlas 5 rocket built by rival United Launch Alliance.

Wednesday's launch was SpaceX's seventh Falcon 9 mission of the year.

[свернуть]

It was the first Falcon 9 launch since March 18, when one of the Falcon 9's nine Merlin booster engines shut down prematurely. The rocket was able to recover from the engine failure, and still placed its payload of 60 Starlink satellites into the planned orbit.

Elon Musk, SpaceX's founder and CEO, said Wednesday the engine problem was caused by a "small amount of isopropyl alcohol (cleaning fluid)" that was trapped in a "sensor dead leg," or an area wh ere it couldn't flow through. The fluid ignited in flight, causing the engine to automatically shut down.

Lauren Lyons, a SpaceX engineer hosting the company's launch webcast, said ground crews did not perform that particular cleaning procedure on the Falcon 9 rocket used Wednesday.

With Wednesday's launch, SpaceX has delivered 422 Starlink satellites to space, including two prototypes that are now being deorbited. Since last May, SpaceX has orbited 420 Starlink spacecraft. Three of those relay stations are no longer in orbit, according to publicly-available U.S. military tracking data.

SpaceX's next Starlink launch after Wednesday could happen as soon as early May on another Falcon 9 rocket mission from Cape Canaveral.

That will be followed by SpaceX's first launch with astronauts on-board — scheduled for May 27 — to begin a test flight of the company's Crew Dragon spaceship to the International Space Station.

SpaceX seeks to modify Starlink regulatory license

SpaceX has regulatory approval from the Federal Communications Commission to eventually field a fleet of up to 12,000 small Starlink broadband stations.

Officials say 24 launches are needed to provide global broadband service through the Starlink service. But the company could provide an interim level of service over parts of the Earth — such as Canada and northern parts of the United States — later this year, once SpaceX has launched around 720 satellites on 12 Falcon 9 flights.

SpaceX has modified the architecture of the Starlink network several times. Most recently, SpaceX submitted an application to the Federal Communication Commission on Friday proposing to operate more satellites in lower orbits than the FCC previously authorized.

The first phase of the Starlink network will include 1,584 satellites orbiting 341 miles (550 kilometers) above Earth in planes inclined 53 degrees to the equator. That part of the constellation, which SpaceX intends to launch through the end of the year, remains unchanged in SpaceX's application.

SpaceX previously had regulatory approval from the FCC to operate another 2,825 satellites in higher orbits between 690 miles (1,110 kilometers) and 823 miles (1,325 kilometers) in altitude, in orbital planes inclined 53.8, 70, 74 and 81 degrees to the equator.


Artist's illustration of the distribution of satellites in SpaceX's Starlink network. Credit: SpaceX

The modified plan submitted to the FCC by SpaceX foresees Ku-band and Ka-band satellites in the next phase of the Starlink network all operated at altitudes between 335 miles (540 kilometers) and 354 miles (570 kilometers) at inclinations of 53.2, 70 and 97.6 degrees.

The application covers 4,408 Starlink satellites, one fewer than SpaceX envisioned under the previous architecture.

In documentation submitted Friday to the FCC, SpaceX said lower altitude will put the satellites closer to Starlink consumers and allow the network "to provide low-latency broadband to unserved and underserved Americans that is on par with service previously only available in urban areas."

The change will also improve Starlink service for U.S. government users in polar regions and allow for more rapid deployment of the network, SpaceX said.

Flying Starlink satellites in lower orbits will help ensure they re-enter the atmosphere a shorter time in case of failure. And the spacecraft will broadcast signals at reduced power levels because they are closer to Earth, which SpaceX said will allow the Starlink fleet to be compliant with limits to reduce radio interference with other satellite and terrestrial wireless networks.

Last week's application to modify SpaceX's FCC license is the latest in a series of adjustments to the Starlink architecture. Before the first launch of 60 Starlink satellites last year, SpaceX received FCC approval to migrate the positions of the fleet's first 1,584 satellites from 714 miles (1,150 kilometers) to 341 miles (550 kilometers).

In December, the FCC granted a SpaceX request to reconfigure the distribution of the Starlink satellites in different orbital planes. SpaceX said that request was intended to expand Starlink coverage faster around the United States without the need for more satellites.

SpaceX working on sunshade for future Starlink satellites

At lower altitudes, the Starlink satellites will fly in a region with busier space traffic. SpaceX says its Starlink spacecraft can maneuver to avoid collisions with other objects in orbit, and it releases orbital data on the Starlink satellites so other operators can also perform evasive maneuvers.

Astronomers have also raised concerns about the brightness of the Starlink satellites, which could interfere with ground-based telescope images, particularly around sunrise and sunset.

The Starlink satellites reflect more sunlight than SpaceX or astronomers anticipated before the first dedicated Starlink launch last year. The American Astronomical Society and other groups are working with SpaceX to try and lim it the satellites' impacts on astronomy.

One of the ground-based facilities most at risk of interference from the Starlink satellites is the U.S. government-funded Vera Rubin Observatory, formerly known as the Large Synoptic Survey Telescope. The observatory under construction in Chile will capture deep, wide-field images of the entire southern sky, allowing astronomers to learn more about dark energy and dark matter, and detect potentially hazardous asteroids with orbits near Earth, among other objectives.

Steve Kahn, director of the Vera Rubin Observatory, said Wednesday that SpaceX is responsive to astronomers' concerns.

"They've been quite cooperative in working with us," Kahn told Spaceflight Now in an interview.

"SpaceX is committed to promoting all forms of space exploration, which is why it has already taken a number of proactive steps to ensure it does not materially impact optical astronomy," the company wrote in Friday's application to the FCC, which does not have regulatory authority over the brightness of satellites. "SpaceX is working with U.S. and international astronomy organizations and observatories to measure scientifically the actual impact of its satellites."

Flying more Starlink satellites at lower altitudes could make the relay nodes appear brighter from the ground, but there will be fewer Starlink satellites visible in the sky at one time. The spacecraft at lower altitudes will also spend less time illuminated by sunlight.

"In some respects, that's good for astronomy because the Earth's shadow is a cone," said Pat Seitzer, an astronomer and orbital debris expert at the University of Michigan. "So the satellites at higher altitude will be visible longer into the darkest part of the night, but because they're closer now, they'll be brighter. So we'll just have to sort out and see how that works."

Seitzer agreed with SpaceX that the lower operating altitude for the Starlink satellites "really helps them for space safety, in terms of space debris or orbital debris considerations."


An astronaut on the International Space Station captured this view of a string of Starlink satellites April 13. Credit: NASA

One of 60 Starlink satellites launched Jan. 6 carried a new darker coating intended to reduce the spacecraft's reflectivity. SpaceX said last month that preliminary data indicated a "notable reduction" in the brightness of that satellite, which has been dubbed "DarkSat."

"The darkening that they did on DarkSat is about a factor of two-and-a-half fainter — so about 1 magnitude in astronomical units — and it's still visible to the unaided eye under excellent conditions," Seitzer said. "That is you're a person with great vision sitting on top of a mountaintop faraway from the city lights."

Kahn agreed, adding that the darker coating was a step in the right direction for astronomers.

"Beyond this (darkening) treatment, SpaceX is developing new mitigation efforts that it plans to test in the coming months," SpaceX wrote in Friday's FCC filing. "Additionally, SpaceX will make satellite tracking data available so astronomers can better coordinate their observations with our satellites."

One change SpaceX is studying is the addition of a sunshade, or visor, to unfurl like an umbrella on Starlink satellites to reduce the amount of sunlight glinting off the spacecraft.

Musk tweeted Wednesday that SpaceX is taking "key steps to reduce satellite brightness." He wrote that the satellites "should be much less noticeable" when they're flying at lower altitudes soon after launch.

He said SpaceX is changing the angle of each satellite's solar panel, and all of the Starlink satellites will have sunshades beginning with the fleet's ninth launch. That launch is expected in a couple of months.

Beyond the 4,400 Ku-band and Ka-band satellites covered in Friday's application for a modified FCC license, SpaceX plans to launch another 7,500 V-band data relay stations into orbits around 214 miles (345.6 kilometers) in altitude. The FCC has already approved SpaceX to operate the V-band network.

[tnt22]

Jonathan McDowell ✔@planet4589 4:27 AM - Apr 23, 2020

I estimate there are now 412 operational Starlink sats with 3 reentered, 2 Tintin prototypes retired, and 5 apparently dead in orbit

[tnt22]

Michael Baylor @nextspaceflight 3:30 AM - Apr 23, 2020

NASASpaceflight forum member internetftw put together this neat visual of how the Starlink satellites orbit raise and plane change using data from the previous six missions.
https://forum.nasaspaceflight.com/index.php?topic=49936.msg2071372#msg2071372 ...

(0:48)

[tnt22]

https://ria.ru/20200423/1570465916.html

Маск защитит спутники Starlink "зонтиками", чтобы не мешать астрономам
14:35 23.04.2020

МОСКВА, 23 апр - РИА Новости. Спутники связи Starlink разработки американской компании SpaceX в ближайшие месяцы начнут защищать "зонтиками от Солнца", чтобы те не мешали проводить астрономические наблюдения, заявил основатель компании Илон Маск.

Ранее сообщалось, что в 2019 году с началом запусков Starlink астрономы стали жаловаться на то, что яркость спутников мешает им наблюдать звёзды. В качестве одной из мер SpaceX покрыло светопоглощающим материалом один из космических аппаратов, улетевших в январе.

В феврале из данных, приведенных научным сотрудником Института астрономии РАН Николаем Самусем, следовало, что 30-40% астрономических снимков будут испорчены следами от "светящихся" отраженным от Солнца светом спутников Starlink.

"Мы предпринимаем ключевые шаги для уменьшения яркости спутников. (Они) должны быть намного менее заметными во время подъема высоты орбиты путем изменения положения панели солнечной батареи", - написал Маск в Twitter.

"И все спутники получат "солнцезащитные зонтики", начиная с девятого запуска", - добавил он.

Спойлер

Накануне SpaceX запустила очередные 60 спутников Starlink ракетой-носителем Falcon-9 с космодрома на мысе Канаверал (штат Флорида). Это был седьмой запуск по программе Starlink, в результате которого количество выведенных на орбиту спутников достигло 420. Девятый пуск по программе намечается в июне.

Спутниковая система связи Starlink предназначена для обеспечения жителей Земли глобальным широкополосным доступом в интернет. В октябре 2019 года стало известно, что SpaceX планирует вывести на околоземную орбиту 42 тысячи спутников Starlink - это в 5 раз больше, чем было запущено космических аппаратов всеми странами мира с 1957 года.

[свернуть]

[lev_g]

Маск: через три месяца мы начнем закрытое тестирование сервисов StarLink, а публичное - через 6 месяцев.

https://www.teslarati.com/spacex-starlink-internet-service-beta-program/

[тавот]

Магадан написал:
ВанВэб обошли на порядок

Что теперь вспоминать о покойнике то ? Кстати, а какая судьба ждёт их уже запущенные 74 спутника ? Будут болтаться мёртвым грузом ?

[lev_g]

тавот написал:
 

Магадан написал:
ВанВэб обошли на порядок

Что теперь вспоминать о покойнике то ? Кстати, а какая судьба ждёт их уже запущенные 74 спутника ? Будут болтаться мёртвым грузом ?

Не факт, что уже точно покойник. Если будет ликвидация - скорее всего сведут. 

[tnt22]

https://spacenews.com/spacex-to-test-starlink-sun-visor-to-reduce-brightness/

SpaceX to test Starlink "sun visor" to reduce brightness
by Jeff Foust — April 27, 2020


SpaceX's VisorSat will use sunshades modeled on sun visors in a car windshield to keep sunlight fr om reflecting off the satellite's antennas, reducing its brightness as seen from the ground. Credit: SpaceX

WASHINGTON — SpaceX Chief Executive Elon Musk said April 27 that he hopes to test a new way to reduce the brightness of the company's Starlink satellites on the next launch for the broadband megaconstellation.

In a briefing to a committee working on the next astrophysics decadal survey, Musk said the experimental "VisorSat," along with a new approach for orienting Starlink satellites as they raise their orbits, should address concerns raised by astronomers that the Starlink constellation could interfere with their observations.

"Our objectives, generally, are to make the satellites invisible to the naked eye within a week, and to minimize the impact on astronomy, especially so that we do not saturate observatory detectors and inhibit discoveries," Musk said.

SpaceX first attempted to address the brightness problem with an experimental "DarkSat" included in a batch of Starlink satellites launched in January. The satellite used what the company described as experimental darkening treatments over reflective surfaces, like its antennas, in an effort to reduce the amount of sunlight it reflects and thus make it darker.

While DarkSat has shown some promise, appearing about one magnitude darker than untreated Starlink satellites, the company is moving in a different direction. "We found an option that is even better than that, which is basically to give the satellites shades," he said.

Musk and others at SpaceX have previously discussed a sunshade that they compared to a patio umbrella that would deploy from a satellite, keeping the antennas in shadow. Musk, at the committee meeting, described a concept called VisorSat that would deploy panels, like sun visors mounted on a car windshield, to block the sun.

"We have a radio-transparent foam that will deploy nearly upon the satellite being released, and it blocks the sun from reaching the antennas," he said. "They're sun visors, essentially: they flip out and block the sun and prevent reflections." He predicted that the visors would have a "massive effect" on the brightness of the satellites.

SpaceX is planning test VisorSat on the company's next Starlink launch. "It's a bit of a challenge, but that's our goal," he said. He didn't say how many satellites would be equipped with visors, or when the launch was scheduled. SpaceX has been performing Starlink launches at the rate of at least one a month so far this year, most recently April 22.

A second effort involves the brightness of the satellites as they raise their orbits after launch. Musk said the satellites appear bright because of the orientation of the solar panels, which are aligned differently during orbit raising than once at their operational orbit.

As soon as this week, Musk said SpaceX will try an "orientation roll" to change the alignment of the solar panels relative to the Earth, reducing the amount of sunlight they reflect to the ground. "Early indications are this will have a significant effect on the brightness during orbit raise," he said. "The satellites will be significantly less visible from the ground."

The measures SpaceX has taken have come after months of discussions with astronomers, who have been worried about the effects a full constellation of Starlink satellites — about 12,000 according to current plans, with proposals for up to 30,000 more — would have on astronomy. The situation was of particular concern to those operating telescopes with wide fields of view, like the Vera Rubin Observatory under construction in Chile, wh ere Starlink satellites would be visible in a large fraction of images taken each night.

In a separate presentation to the committee earlier in the day, Tony Tyson, chief scientist for the Rubin Observatory, said the concern was that the brightness of unmodified Starlink satellites would cause "nonlinear crosstalk," or severe image artifacts, in the observatory's camera. "We would be left with all of these fake trails, fake galaxies, etc., in our data, damaging the science," he said.

SpaceX has already made progress darkening the satellites, with newer satellites about one magnitude darker than the original "v0.9" satellites launched in May 2019 even without the darkening treatments used on DarkSat. If the satellites can be made about a factor of two darker than DarkSat, Tyson said a technique to correct for the nonlinear crosstalk can work, although it is computer intensive and won't correct for the original streak left in the images by passing satellites.

The new approaches won't address the issue of brightness of existing Starlink satellites, but Musk said their lifetime is limited. He estimated the initial generation of satellites will be deorbited in about three to four years to make way for improved satellites. "We'll just have far greater throughput capability with version two" of the Starlink satellites, he said.

While the focus of the committee presentation and subsequent discussion, which lasted for more than an hour, was on Starlink, there was some talk about the role SpaceX could play in supporting space-based astronomy, which is not affected by Starlink or other megaconstellations.

"I'm very excited about the future of space-based telescopes that could be very large," he said. He mentioned Starship, the company's next-generation large reusable launch system, which will begin regular flights "I think within a couple of years," he promised. "It allows for space telescopes to be transported to orbit at probably an order of magnitude lower cost than in the past."

"I'm pretty interested in trying to figure out how to help launch and possibly build a big observatory in space," he said, offering to meet with astronomers to discuss mission concepts. "Like a planet imager or something like that."

[tnt22]

https://www.spacex.com/news/2020/04/28/starlink-update

APRIL 28, 2020
STARLINK DISCUSSION NATIONAL ACADEMY OF SCIENCES

SpaceX is launching Starlink to provide high-speed, low-latency broadband connectivity across the globe, including to locations where internet has traditionally been too expensive, unreliable, or entirely unavailable. We also firmly believe in the importance of a natural night sky for all of us to enjoy, which is why we have been working with leading astronomers around the world to better understand the specifics of their observations and engineering changes we can make to reduce satellite brightness. Our goals include:

Making the satellites generally invisible to the naked eye within a week of launch. We're doing this by changing the way the satellites fly to their operational altitude, so that they fly with the satellite knife-edge to the Sun. We are working on implementing this as soon as possible for all satellites since it is a software change.

Minimizing Starlink's impact on astronomy by darkening satellites so they do not saturate observatory detectors. We're accomplishing this by adding a deployable visor to the satellite to block sunlight fr om hitting the brightest parts of the spacecraft. The first unit is flying on the next launch, and by flight 9 in June all future Starlink satellites will have sun visors. Additionally, information about our satellites' orbits are located on space-track.org to facilitate observation scheduling for astronomers. We are interested in feedback on ways to improve the utility and timeliness of this information.

To better explain the details of brightness mitigation efforts, we need to explain more about how the Starlink satellites work.

Starlink Orbits

Starlink has three phases of flight: (1) orbit raise, (2) parking orbit (380 km above Earth), and (3) on-station (550 km above Earth). During orbit raise the satellites use their thrusters to raise altitude over the course of a few weeks. Some of the satellites go directly to station while others pause in the parking orbit to allow the satellites to precess to a different orbital plane. Once satellites are on-station they reconfigure so the antennas face Earth and the solar array goes vertical so that it can track the Sun to maximize power generation. As a result of this maneuver, the satellites become much darker because the solar array visibility fr om the ground is greatly reduced.

Currently, about half of the over 400 satellites are on-station and the other half are orbit raising or in the parking orbit. Satellites spend a small fraction of their lives orbit raising or parking and spend the vast majority of their lives on-station. It's important to note that at any given time, only about 300 satellites will be orbit raising or parking. The rest of the satellites will be in the operational orbit on-station.

Starlink Satellite

The Starlink satellite design was driven by the fact that they fly at a very low altitude compared to other communications satellites. We do this to prioritize space traffic safety and to minimize the latency of the signal between the satellite and the users who are getting internet service fr om it. Because of the low altitude, drag is a major factor in the design. During orbit raise, the satellites must minimize their cross-sectional area relative to the "wind," otherwise drag will cause them to fall out of orbit. High drag is a double-edged sword—it means that flying the satellites is tricky, but it also means that any satellites that are experiencing problems will de-orbit quickly and safely burn up in the atmosphere. This reduces the amount of orbital debris or "space junk" in orbit.

This low-drag and thrusting flight configuration resembles an open book, where the solar array is laid out flat in front of the vehicle. When Starlink satellites are orbit raising, they roll to a limited extent about the velocity vector for power generation, always keeping the cross sectional area minimized while keeping the antennas facing Earth enough to stay in contact with the ground stations.

When the satellites reach their operational orbit of 550 km, drag is still a factor—so any inoperable satellite will quickly decay—but the attitude control system is able to overcome this drag with the solar array raised above the satellite in a vertical orientation that we call "shark-fin." This is the orientation in which the satellite spends the majority of its operational life.



Satellite Visibility

Satellites are visible from the ground at sunrise or sunset. This happens because the satellites are illuminated by the Sun but people or telescopes on the ground are in the dark. These conditions only happen for a fraction of Starlink's 90-minute orbit.

This simple diagram highlights why satellites in orbit raise are so much brighter than the satellites that are on-station. During orbit raise, when the solar array is in open book, sunlight can reflect off of both the solar array and the body of the satellite and hit the ground. Once on-station, only certain parts of the chassis can reflect light to the ground.



Physics of Satellite Brightness

The apparent magnitude of an object is a measure of the brightness of a star or object observed from Earth. It is a reverse logarithmic scale, so higher numbers correspond to dimmer objects. A star of magnitude 3 is approximately 2.5 times brighter than a star of magnitude 4. Based on observations that have been taken by us and by members of the astronomical community, current Starlink satellites have an average apparent magnitude of 5.5 when on-station and brighter during orbit raise. Objects up to about magnitude 6.5-7 are visible to the naked eye (naked-eye visibility is closer to 4 in most suburbs), and our goal is for Starlink satellites to be magnitude 7 or better for almost all phases of their mission.

There are two types of reflections off of Starlink satellites: diffuse and specular. Diffuse reflections occur when light is scattered in many different directions. Imagine shining a flashlight at a white wall. Specular reflections happen when light is reflected in a particular direction. For example, the glint of sunlight off of a mirror. Diffuse reflections are the biggest contributor to observed brightness on the ground, because diffuse reflections go in all directions. You can see diffuse reflections as long as the satellite is visible. This is why Starlink satellites can create the "string of pearls" effect in the night sky. It's a little counter-intuitive, but the shiny components of the Starlink satellites are a much smaller problem. Whether diffuse or specular, having a high reflectance helps the satellites stay cool in space. When sunlight hits a specular surface of the spacecraft and reflects, the vast majority of light reflects in the specular (mirror reflection) direction, which is generally out toward space (not toward Earth). Occasionally when it does, the glint only lasts for a second or less. In fact, specular surfaces tend to be the dimmest part of the satellite unless you are at just the right geometry.

The biggest contributors to Starlink being bright are the white diffuse phased array antennas on the bottom of the satellite, the white diffuse parabolic antennas on the sides (not shown below), and the white diffuse back side of the solar array. These surfaces are all white to keep temperatures down so components do not overheat. The key to making Starlink darker is to prevent sunlight from illuminating these white surfaces and scattering via reflection toward observers on the ground. While in orbit raise and the parking orbit the solar array dominates due to the much larger surface area. However, once the satellites are at their operational altitude, the antennas dominate because the bright backside of the solar array is shadowed.

Solutions In-Work

We've taken an experimental and iterative approach to reducing the brightness of the Starlink satellites. Orbital brightness is an extremely difficult problem to tackle analytically, so we've been hard at work on both ground and on-orbit testing.

For example, earlier this year we launched DarkSat, which is an experimental satellite wh ere we darkened the phased array and parabolic antennas designed to tackle on-station brightness. This reduced the brightness of the satellite by about 55%, as was verified by differential optical measurements comparing DarkSat to other nearby Starlink satellites. This is nearly enough of a brightness reduction to make the satellite invisible to the naked eye while on-station. However, black surfaces in space get hot and reflect some light (including in the IR spectrum), so we are moving forward with a sun visor solution instead. This avoids thermal issues due to black paint, and is expected to be darker than DarkSat since it will block all light from reaching the white diffuse antennas.



Early Mission (Orbit Raise and Parking Orbit) Roll Maneuver

Since the visor is intended to help with brightness while on-station, it does not shade the back of the solar array, which means that it will not prevent orbit raise and parking orbit brightness. For this, we are working on changing the way the satellite flies up from insertion to parking orbit and to station.

We're currently testing rolling the satellite so the vector of the Sun is in-plane with the satellite body, i.e. so the satellite is knife-edge to the Sun. This would reduce the light reflected onto Earth by reducing the surface area that receives light. This is possible when orbit raising and parking in the precession orbit because we don't have to constrain the antennas to be nadir facing to provide coverage to internet users. However, there are a couple of nuanced reasons why this is tricky to implement. First, rolling the solar array away from the Sun reduces the amount of power available to the satellite. Second, because the antennas will sometimes be rolled away from the ground, contact time with the satellites will be reduced. Third, the star tracker cameras are located on the sides of the chassis (the only place they can go and have adequate field of view). Rolling knife edge to the Sun can point one star tracker directly at the Earth and the other one directly at the Sun, which would cause the satellite to have degraded attitude knowledge.

There will be a small percentage of instances when the satellites cannot roll all the way to true knife edge to the Sun due to one of the aforementioned constraints. This could result in the occasional set of Starlink satellites in the orbit raise of flight that are temporarily visible for one part of an orbit.




On-Station Brightness

Satellites spend most of their lives on-station, wh ere they will always be in the shark-fin configuration during visible passes. We can adjust the solar array positioning in this configuration to reflect light from its largely specular solar cells away from Earth and to partially hide it behind the chassis. The main remaining goal is to block the phased arrays and antennae from direct view of the sun. The goal is to cover the white phased array antennas and the parabolic antennas on the sides of the satellite.

Using our low orbital altitude and flat satellite geometry to our advantage, we designed an RF-transparent deployable visor for the satellite that blocks the light from reaching most of the satellite body and all of the diffuse parts of the main body. This visor lays flat on the chassis during launch and deploys during satellite separation from Falcon 9. The visor prevents light from reflecting off of the diffuse antennas by blocking the light from reaching the antennas altogether. Not only does this approach avoid the thermal impacts from surface darkening the antennas, but it should also have a larger impact on brightness reduction. As previously noted, the first VisorSat prototype will launch in May and we will have these black, specular visors on all satellites by June. The parabolic antennas on the sides of the Starlink satellite also have visor-like coverings that darken them.



We have been working with leading astronomical groups in this effort—in particular the American Astronomical Society and the Vera C. Rubin Observatory—to better understand the methods and instruments employed by the astronomy community. With AAS, we have increased our understanding of the community as a whole through regular calls with a working group of astronomers during which we discuss technical details, provide updates, and work on how we can protect astronomical observations moving forward. A post on some of our sessions is here. One particularly useful presentation from a member of this working group is here.

While community understanding is critical to this problem, engineering problems are difficult to solve without specifics. The Vera C. Rubin Observatory was repeatedly flagged as the most difficult case to solve, so we've spent the last few months working very closely with a technical team there to do just that. Among other useful thoughts and discussions, the Vera Rubin team has provided a target brightness reduction that we are using to guide our engineering efforts as we iterate on brightness solutions.

These technical and community discussions are paired with our existing efforts to make the satellites easier for astronomers to avoid. Starlink trajectories are published through Space-track.org and celestrak.com, which many astronomers use in timing their observations to avoid satellite streaks. We've also started publishing predictive data prior to launch at the request of astronomers. These allow observatories to schedule around the satellites in the first few hours of deployment (as satellites de-tumble and enter the network).

Vera Rubin has been described as the limiting case for Starlink, due to its enormous aperture and wide field of view. These two characteristics work in concert to produce the perfect storm for satellite observations. Most astronomical systems look at an extremely small section of the sky (less than 1 degree), which makes it exceedingly unlikely that a satellite will cross in front of the imaging system in a given observation. On the other hand, systems with very large fields of view normally aren't extremely sensitive, meaning that, while streaks will occur, they will have a small impact on the overall data collection. This is why we've been working so closely with the team at the Rubin Observatory. In fact, despite its wide field of view, the Vera C. Rubin Observatory is sensitive enough to detect a sunlit golf ball as far away as the Moon.

So what can we do to mitigate our impact on these edge cases of wide, fast survey telescopes?

Minimizing the Impact on Astronomy

The huge collecting area of a larger telescopes like Vera C. Rubin Observatory leads to a sensitivity that will render even the darkest satellites visible.They are so sensitive that it won't be possible to build a satellite that will not produce streaks, in a typical long integration. There is much that can be done to reduce the impact of satellite streaks, and that starts with an understanding of how astronomical sensors work.

The astronomical community has done a great job of educating us on their imaging techniques. Optical systems use mirrors or lenses to focus light onto an imaging sensor. Most optical astronomy instruments use sensors called charge-coupled-devices (CCDs) as their detectors because astronomical targets, such as distant supernovae and galaxies, are generally dim–at the lim it of what can be detected by a sensor. For these applications, the lower noise level of CCDs allows for a higher signal-to-noise ratio for a given image, making it easier to see very faint features in the universe.

However, CCDs suffer from a key drawback: when compared to other common sensors, like the CMOS sensor in your cell phone. If you point your cell phone at a bright light, you'll see all the pixels saturate and turn white in the region of the bright source. If you look at the same target with an optical system that uses a CCD sensor, you'll notice that this bright spot extends to create vertical stripes on the image.

This difference is due to the way each sensor type reads the values for each pixel. While a CMOS sensor essentially has an amplifier at each pixel that turns the light collected into a digital value, a CCD sensor has a limited number of amplifiers and moves the collected light (in the form of electrons) across the sensor, to be digitized. This mechanism means that a saturated pixel on a CCD tends to wipe out data from an entire column of pixels.

This effect, commonly referred to as 'blooming,' is one example of how a very small but bright source of light can impact an astronomical observation. This principle is the core of our mitigation efforts. While it will not be possible to create satellites that are invisible to the most advanced optical equipment on Earth, by reducing the brightness of the satellites, we can make the existing strategies for dealing with similar issues, such as frame-stacking, dramatically more effective.

Future Satellites

SpaceX is committed to making future satellite designs as dark as possible. The next generation satellite, designed to take advantage of Starship's unique launch capabilities, will be specifically designed to minimize brightness while also increasing the number of consumers that it can serve with high-speed internet access.

While SpaceX is the first large constellation manufacturer and operator to address satellite brightness, we won't be the last. As launch costs continue to drop, more constellations will emerge and they too will need to ensure that the optical properties of their satellites don't create problems for observers on the ground. This is why we are working to make this problem easier for everyone to solve in the future.

[Apollo13]

https://twitter.com/Megaconstellati/status/1255181392964698113

Since February @SpaceX has asked the @FCC for authorization for 18 new @SpaceXStarlink earth stations bringing total to 23 gateways across US of which 5 are dual band (Ku+Ka). 6 Ku-band gateways with 4 antennas each = 24 22 Ka-band gateways with 8 Ka antennas each = 176 #Starlink

[Apollo13]

A Globalstar GW costed $2.9M each and they had four in the US (Clifton, TX, Sebring and FL), hope the cost is not that high now

A OneWeb ground station is far less than Globalstar or Iridium era since costs of fully articulating LEO antennas has come down through volume.  However, Starlink appear to be using COTS maritime antennas which cost ~$30,000.  It's all about the MTBF and management process.

200 антенн по 30 000 получается 6 млн на антенны. Сколько может стоить остальное оборудование гейтвеев?

Вообще расходы на гейтвеи похоже невелики в сравнении со спутниками и их запуском.

[STS]

эээ, я не понял, это такая низкая плотность наземного сегмента?

[VSATman]

Магадан написал:
В 4 раза это 17х4=68 Гбит/с на спутник в около 250 кг, ВанВэб обошли на порядок, молодцы.

Наоборот
первые 60 ИСЗ в 2019 имели   17/4= около 4. Причина у них Аплинк от Гейтвеев был в Ку диапазоне ( 500 Мгц доступно) , а не в Ка (2500 МГц доступно для связи)

[Магадан Магадан]

VSATman написал:
 

Магадан написал:
В 4 раза это 17х4=68 Гбит/с на спутник в около 250 кг, ВанВэб обошли на порядок, молодцы.

Наоборот
первые 60 ИСЗ в 2019 имели   17/4= около 4. Причина у них Аплинк от Гейтвеев был в Ку диапазоне ( 500 Мгц доступно) , а не в Ка (2500 МГц доступно для связи)

Любопытно. Цифра 17 Гбит/с называлась представителями СпейсХ где-то зимой, по памяти. Здесь в теме можно поискать.  К какой генерации спутников они относились конечно не ясно. Ясно что Маск на последнем пуске, как он сказал, увеличил количество лучей и следовательно общую полосу частот. Тогда пропускная способность спутника должна вырасти. Размер полосы при этом определяющий фактор.  Размер выделанной полосы частот не лимитирует общую рабочую полосу, в технологии есть возможность многократно ее повторять. Если у вас есть реальный частотный план с учетом повторения полосы частот, было бы очень интересно на него посмотреть.    

[Apollo13]

https://twitter.com/Megaconstellati/status/1257763348080480256?s=20

Since 27 April @SpaceX has filed for 3 more Ka-band gateways in the US including first site in Alaska increasing total to 31 gateways across 26 locations:
Los Angeles, CA (Triangular flag on post34.604028,-117.454361)
Prudhoe Bay, AK (Triangular flag on post70.246556,-148.569000)
Cass County, ND (Triangular flag on post47.151694,-97.408889)