Author Topic: Starlink : General Discussion - Thread 2  (Read 1095800 times)

Offline vsatman

Re: Starlink : General Discussion - Thread 2
« Reply #3420 on: 12/28/2021 08:23 pm »

1) They have limited spectrum for the uplink, but (unlike at the user terminal receiver) there are no arbitrary limits on flux density or aperture size at the satellite receiver. So the SNR can be arbitrarily high as needed, and the power flux and aperture can be sized to make the uplink data throughput match the downlink. It doesn't seem to me that uplink spectrum is a limiting issue at the moment.

2)Or, since each antenna array is really thousands of small antennas, they could subdivide the arrays into 2 or more smaller or sparser arrays and transmit multiple beams simultaneously in different directions. This assumes they have the necessary margins on power and beam angle, since the small or sparse array will perform worse on one or more of those factors.

1) for Uplink User Terrminal has 62 MHz bandwidth and has very god modcod  64QAM is possible..
2) Yes . but limitation is Link from GW to Satellite  - this  is max 4000 MHz -  2000 MHz in each polarisation
If it is possible to convert on satellite board   left  Ka band in right Ku band  we will have total 16 beams per sat... But not more...

Offline su27k

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Re: Starlink : General Discussion - Thread 2
« Reply #3421 on: 12/30/2021 03:51 am »
Elon Musk rejects claims his satellites are squeezing out rivals in space

Quote from: ft.com
Elon Musk has hit back at criticism that his company’s Starlink satellites are hogging too much room in space, and has instead argued there could be room for “tens of billions” of spacecraft in orbits close to Earth.

“Space is just extremely enormous, and satellites are very tiny,” Musk said. “This is not some situation where we’re effectively blocking others in any way. We’ve not blocked anyone from doing anything, nor do we expect to.”

His comments, made in an interview with the Financial Times, came in response to a claim from Josef Aschbacher, head of the European Space Agency, that Musk was “making the rules” for the new commercial space economy. Speaking to the FT earlier this month, Aschbacher warned Musk’s rush to launch thousands of communications satellites would leave fewer radio frequencies and orbital slots available for everyone else.
« Last Edit: 12/30/2021 03:51 am by su27k »

Offline su27k

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Re: Starlink : General Discussion - Thread 2
« Reply #3422 on: 12/31/2021 05:28 am »
U.S. Didn't ID Near Crash Between SpaceX and Chinese Space Station, Despite Complaint

Quote from: newsweek.com
A U.S. Department of State spokesperson said in a statement that the government agreed with an assessment by the Space Force that America "did not estimate a significant probability of collision between the CSS and any Starlink spacecraft."

"The U.S. Government has reaffirmed that assessment, is reviewing the details of the (People's Republic of China's) note verbale to the UN Secretary General of December 3, 2021, and looks forward to following up bilaterally with the PRC," the spokesperson wrote. "The United States is committed to sustainable, rules-based activities in outer space, whether those activities are performed by governments or the private sector."

The State Department noted that the U.S. has offered spaceflight safety information to China since 2010. That information includes notifications "of potentially hazardous close approaches" between Chinese spacecraft and other objects. If an object appears on course to strike a Chinese ship, the U.S. will provide a notification to a "designated point of contact."

Offline Tomness

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Re: Starlink : General Discussion - Thread 2
« Reply #3423 on: 12/31/2021 05:41 am »
U.S. Didn't ID Near Crash Between SpaceX and Chinese Space Station, Despite Complaint

Quote from: newsweek.com
A U.S. Department of State spokesperson said in a statement that the government agreed with an assessment by the Space Force that America "did not estimate a significant probability of collision between the CSS and any Starlink spacecraft."

"The U.S. Government has reaffirmed that assessment, is reviewing the details of the (People's Republic of China's) note verbale to the UN Secretary General of December 3, 2021, and looks forward to following up bilaterally with the PRC," the spokesperson wrote. "The United States is committed to sustainable, rules-based activities in outer space, whether those activities are performed by governments or the private sector."

The State Department noted that the U.S. has offered spaceflight safety information to China since 2010. That information includes notifications "of potentially hazardous close approaches" between Chinese spacecraft and other objects. If an object appears on course to strike a Chinese ship, the U.S. will provide a notification to a "designated point of contact."

So in other words. There was no probility. Just trying slow down their progress or block it from their country. You can't block the signal but you can jam it. Press is all over it because it has Musk's name on it.

Offline thirtyone

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Re: Starlink : General Discussion - Thread 2
« Reply #3424 on: 12/31/2021 11:13 am »
I suspect this is still a general problem of country-to-country coordination for space conjunctions. The US does actually have more space assets than most countries (China included), and I'm sure China didn't want to trust US space radar to protect its own shiny new space station (which of course the US government is not particularly happy about). They don't have nearly as well developed space radar systems either, so they could only take the conservative approach. I'm also fairly certain that SpaceX does not (and probably is expected to not by the US Government) have any direct contact with any Chinese space agencies to coordinate in these encounters.

Not much SpaceX could do (I think they're really doing their best at this point), SF's extensive radar network didn't flag an issue, and China quite likely genuinely wasn't sure if a conjunction was going to happen, so they took it safe. There is good reason for a neutral party to be a clearinghouse for global collision data. Think it's in everyone's interest. I really doubt this is anything about Musk or SpaceX or whatever, just the issue in general. China is definitely quite proud of their space station, and the US is definitely worried about their space ambitions and any potentially aggressive moves.

Online TrevorMonty

Re: Starlink : General Discussion - Thread 2
« Reply #3425 on: 01/01/2022 04:01 pm »
Does dish come with five cat rating?

https://twitter.com/Tippen22/status/1476985855981993984?t=QLvwImR6pcg3SP90KqKx1Q&s=19

Sent from my SM-G570Y using Tapatalk


Offline vsatman

Re: Starlink : General Discussion - Thread 2
« Reply #3426 on: 01/01/2022 07:10 pm »
There is good reason for a neutral party to be a clearinghouse for global collision data. Think it's in everyone's interest. I really doubt this is anything about Musk or SpaceX or whatever, just the issue in general. China is definitely quite proud of their space station, and the US is definitely worried about their space ambitions and any potentially aggressive moves.

The main thing is that this neutral monitoring center has data on all satellites.
But now most countries, including the United States, consider the orbits of their military satellites to be secret and do not report them to anyone ....

Offline OTV Booster

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Re: Starlink : General Discussion - Thread 2
« Reply #3427 on: 01/01/2022 11:13 pm »
There is good reason for a neutral party to be a clearinghouse for global collision data. Think it's in everyone's interest. I really doubt this is anything about Musk or SpaceX or whatever, just the issue in general. China is definitely quite proud of their space station, and the US is definitely worried about their space ambitions and any potentially aggressive moves.

The main thing is that this neutral monitoring center has data on all satellites.
But now most countries, including the United States, consider the orbits of their military satellites to be secret and do not report them to anyone ....
Military sats are a very small percentage especially with constellations coming on line. The onus would be on the launching party to dodge, IMO. The danger would be secret sats unintentionally hitting each other. Low probability.


What are the chances of an orbit staying secret for very long? Even a stealthed sat with an unknown amount of maneuvering capability has limits on what it can do. With known launch rocket capability and the normal amount of military interest in what the other guy is doing, ISTM the major players will have a good idea of what is where within a few weeks or less.
We are on the cusp of revolutionary access to space. One hallmark of a revolution is that there is a disjuncture through which projections do not work. The thread must be picked up anew and the tapestry of history woven with a fresh pattern.

Offline JayWee

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Re: Starlink : General Discussion - Thread 2
« Reply #3428 on: 01/01/2022 11:33 pm »
There is good reason for a neutral party to be a clearinghouse for global collision data. Think it's in everyone's interest. I really doubt this is anything about Musk or SpaceX or whatever, just the issue in general. China is definitely quite proud of their space station, and the US is definitely worried about their space ambitions and any potentially aggressive moves.

The main thing is that this neutral monitoring center has data on all satellites.
But now most countries, including the United States, consider the orbits of their military satellites to be secret and do not report them to anyone ....
Hypothethically, if there was a military megaconstellation, would it be also secret or it'd be simply unbearable?

Offline su27k

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Re: Starlink : General Discussion - Thread 2
« Reply #3429 on: 01/03/2022 09:30 am »
Semi-annual report to FCC: https://licensing.fcc.gov/myibfs/download.do?attachment_key=14325486

Nothing really interesting jumps out, 3,333 collision avoidance maneuvers, in 10 occasions they were asked to forgo maneuver so that the other satellite can move instead. They deorbited ~110 satellites, Russia ASAT test gets a mention, no word on the Chinese claim.

Offline jpo234

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You want to be inspired by things. You want to wake up in the morning and think the future is going to be great. That's what being a spacefaring civilization is all about. It's about believing in the future and believing the future will be better than the past. And I can't think of anything more exciting than being out there among the stars.

Offline Reynold

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Re: Starlink : General Discussion - Thread 2
« Reply #3431 on: 01/04/2022 07:30 pm »
Per this SpaceNews article, the head of the India division also resigned, effective December 31, 2021.

https://spacenews.com/starlinks-head-of-india-resigns-as-spacex-refunds-preorders/

From talking to people who have tried to do business there, India is not particularly welcoming to outside companies coming in and selling products without "local partners" owning majority shares and greasing the right palms in the process, so I do not predict that license will be forthcoming any time sooon. 

Offline jpo234

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Re: Starlink : General Discussion - Thread 2
« Reply #3432 on: 01/04/2022 09:47 pm »
Per this SpaceNews article, the head of the India division also resigned, effective December 31, 2021.

https://spacenews.com/starlinks-head-of-india-resigns-as-spacex-refunds-preorders/

From talking to people who have tried to do business there, India is not particularly welcoming to outside companies coming in and selling products without "local partners" owning majority shares and greasing the right palms in the process, so I do not predict that license will be forthcoming any time sooon.

https://en.m.wikipedia.org/wiki/Licence_Raj
You want to be inspired by things. You want to wake up in the morning and think the future is going to be great. That's what being a spacefaring civilization is all about. It's about believing in the future and believing the future will be better than the past. And I can't think of anything more exciting than being out there among the stars.

Offline su27k

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Re: Starlink : General Discussion - Thread 2
« Reply #3433 on: 01/05/2022 03:56 am »
Interesting paper from the 18th Space Control Squadron about the work they did to support mega-constellations, namely Starlink and OneWeb: Report on 2020 Mega-Constellation Deployments and Impacts to Space Domain Awareness

Quote from: Abstract
The rapid proliferation of low-Earth orbit satellite constellations came into full-force in 2020. The primary difference in these launches compared to historical launches involved the number of simultaneous deployments, the frequency of deployments, and the scaled use of electronic propulsion for orbit-raising. We examine the impacts of this emerging methodology on the space surveillance mission and the improvements made to date to meet the challenges of this new environment. Starting with pre-launch conjunction assessment, new techniques have been adopted to blend risk mitigation practices, system capabilities, and screening responsiveness. During the launch phase, existing sensor management and tasking processes have evolved to ensure custody of all newly launched objects as well as the existing space catalog. This also drove changes during the object separation phase which required new orbital modeling techniques and analyst expertise to distinguish the clustered objects in a short period of time. Novel approaches towards satellite operator-provided ephemerides, in addition to rapid software upgrades, enabled a new field of orbital analysis which will soon dominate the efforts of resident space object custody. The increase of payloads and data also increased the volume of orbital conjunction assessment data, which drove the need for increased collaboration between data providers and satellite operators to ensure safety of operations in the space domain. Finally, the increase in satellites has resulted in an increase in reporting as satellites re-enter the atmosphere prompting a more efficient approach on how these events are managed and reported.
« Last Edit: 01/05/2022 03:57 am by su27k »

Offline su27k

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Re: Starlink : General Discussion - Thread 2
« Reply #3434 on: 01/08/2022 07:25 am »
Space debris expert warns U.S. ‘woefully behind’ in efforts to clean up junk in orbit

Quote from: SpaceNews
McKnight said commercial mega-constellations like SpaceX’s Starlink or OneWeb are criticized for compounding the congestion in LEO but these companies should be seen as victims that are increasingly at risk. “Old abandoned massive objects pose greater risk than smaller, more agile constellations,” he added. “Many of these satellite operators are working with mitigation guidelines and operational procedures that are much more stringent than any government guidelines. They’re being safer than what the government’s asking them to do. But they are going to likely have some difficult times in the near future because of debris objects.”

Offline su27k

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Re: Starlink : General Discussion - Thread 2
« Reply #3435 on: 01/14/2022 04:23 am »
Tim Farrar is at it again: Starlink's reach won’t be enough to solve rural broadband dilemma — Farrar

Quote from: fiercewireless.com
Because there is only a finite amount of spectrum available to LEO broadband systems such as Starlink (which must be shared with other LEO systems within the U.S., according to FCC rules), only a limited amount of capacity can be delivered to users in a given area, regardless of the number of Starlink satellites in the sky.

It is therefore far from clear that Starlink will be capable of serving a comparable number of customers to Viasat and Hughes (i.e. in excess of 500K subscribers), let alone a significant proportion of the millions of homes in the U.S. that currently lack terrestrial broadband, in the medium term.

Overall, while Starlink represents an admirable first attempt to develop a LEO broadband system and bring more choices to rural U.S. consumers, it cannot and will not become the only option for satellite broadband in the U.S. or around the world, because in many areas at least some potential customers will be unable to access Starlink, due to capacity limitations and/or the difficulty of securing a reliable line-of-sight to the constellation.

Starlink will have less than 500K subscribers? We'll see...

Offline DigitalMan

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Re: Starlink : General Discussion - Thread 2
« Reply #3436 on: 01/14/2022 06:08 am »
Tim Farrar is at it again: Starlink's reach won’t be enough to solve rural broadband dilemma — Farrar

Quote from: fiercewireless.com
Because there is only a finite amount of spectrum available to LEO broadband systems such as Starlink (which must be shared with other LEO systems within the U.S., according to FCC rules), only a limited amount of capacity can be delivered to users in a given area, regardless of the number of Starlink satellites in the sky.

It is therefore far from clear that Starlink will be capable of serving a comparable number of customers to Viasat and Hughes (i.e. in excess of 500K subscribers), let alone a significant proportion of the millions of homes in the U.S. that currently lack terrestrial broadband, in the medium term.

Overall, while Starlink represents an admirable first attempt to develop a LEO broadband system and bring more choices to rural U.S. consumers, it cannot and will not become the only option for satellite broadband in the U.S. or around the world, because in many areas at least some potential customers will be unable to access Starlink, due to capacity limitations and/or the difficulty of securing a reliable line-of-sight to the constellation.

Starlink will have less than 500K subscribers? We'll see...

It will be interesting to see what kind of response he will have if Starlink gets anywhere close to their long term goal of 10gb connections to its users.

Online DanClemmensen

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Re: Starlink : General Discussion - Thread 2
« Reply #3437 on: 01/14/2022 06:58 am »
Tim Farrar is at it again: Starlink's reach won’t be enough to solve rural broadband dilemma — Farrar

Quote from: fiercewireless.com
Because there is only a finite amount of spectrum available to LEO broadband systems such as Starlink (which must be shared with other LEO systems within the U.S., according to FCC rules), only a limited amount of capacity can be delivered to users in a given area, regardless of the number of Starlink satellites in the sky.

It is therefore far from clear that Starlink will be capable of serving a comparable number of customers to Viasat and Hughes (i.e. in excess of 500K subscribers), let alone a significant proportion of the millions of homes in the U.S. that currently lack terrestrial broadband, in the medium term.

Overall, while Starlink represents an admirable first attempt to develop a LEO broadband system and bring more choices to rural U.S. consumers, it cannot and will not become the only option for satellite broadband in the U.S. or around the world, because in many areas at least some potential customers will be unable to access Starlink, due to capacity limitations and/or the difficulty of securing a reliable line-of-sight to the constellation.

Starlink will have less than 500K subscribers? We'll see...

It will be interesting to see what kind of response he will have if Starlink gets anywhere close to their long term goal of 10gb connections to its users.
"Finite amount of spectrum" is very nearly meaningless, due to spectral reuse. When transmitters are in different locations and the receivers use sufficiently narrow beams, the same frequencies can be reused. Simple example: GEO satellites are at 2-degree longitude separation. Two GEO satellites in adjacent slots can use the same frequencies. The receiver chooses a satellite to use by pointing at it. Same thing happens with the LEO constellations, but it's more complicated because the satellites move with respect to the receivers. At the limit, the number of satellites that can transmit to one spot on the earth depends on how well the receiver can discriminate (how tightly the receiver can focus on the satellite) which is a function of the receiver's antenna size. The GEO arc is fairly full, but we are nowhere near saturating LEO. The earliest LEO constellations concentrated on making sure each spot on the Earth's surface could see at least one satellite, but the laws of physics would let a spot on Earth discriminate more than 100 satellites. As a practical matter there is a huge amount of complexity involved if you try to reach this level, but it's feasible.

"line of sight" is another non-problem, given enough satellites. With a minimum constellation designed only to guarantee one satellite in view, then yes, a subscriber needs to see the whole sky. But with lots more satellites, a given user will have at least one satellite visible even if the whole sky is not visible. On average the users will end up seeing the whole sky, so it all works out.

Please note: this is a theoretical analysis. I do not know how it relates to today's Starlink constellation.

Offline envy887

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Re: Starlink : General Discussion - Thread 2
« Reply #3438 on: 01/14/2022 12:19 pm »
Tim Farrar is at it again: Starlink's reach won’t be enough to solve rural broadband dilemma — Farrar

Quote from: fiercewireless.com
Because there is only a finite amount of spectrum available to LEO broadband systems such as Starlink (which must be shared with other LEO systems within the U.S., according to FCC rules), only a limited amount of capacity can be delivered to users in a given area, regardless of the number of Starlink satellites in the sky.

It is therefore far from clear that Starlink will be capable of serving a comparable number of customers to Viasat and Hughes (i.e. in excess of 500K subscribers), let alone a significant proportion of the millions of homes in the U.S. that currently lack terrestrial broadband, in the medium term.

Overall, while Starlink represents an admirable first attempt to develop a LEO broadband system and bring more choices to rural U.S. consumers, it cannot and will not become the only option for satellite broadband in the U.S. or around the world, because in many areas at least some potential customers will be unable to access Starlink, due to capacity limitations and/or the difficulty of securing a reliable line-of-sight to the constellation.

Starlink will have less than 500K subscribers? We'll see...

It will be interesting to see what kind of response he will have if Starlink gets anywhere close to their long term goal of 10gb connections to its users.
"Finite amount of spectrum" is very nearly meaningless, due to spectral reuse. When transmitters are in different locations and the receivers use sufficiently narrow beams, the same frequencies can be reused. Simple example: GEO satellites are at 2-degree longitude separation. Two GEO satellites in adjacent slots can use the same frequencies. The receiver chooses a satellite to use by pointing at it. Same thing happens with the LEO constellations, but it's more complicated because the satellites move with respect to the receivers. At the limit, the number of satellites that can transmit to one spot on the earth depends on how well the receiver can discriminate (how tightly the receiver can focus on the satellite) which is a function of the receiver's antenna size. The GEO arc is fairly full, but we are nowhere near saturating LEO. The earliest LEO constellations concentrated on making sure each spot on the Earth's surface could see at least one satellite, but the laws of physics would let a spot on Earth discriminate more than 100 satellites. As a practical matter there is a huge amount of complexity involved if you try to reach this level, but it's feasible.

"line of sight" is another non-problem, given enough satellites. With a minimum constellation designed only to guarantee one satellite in view, then yes, a subscriber needs to see the whole sky. But with lots more satellites, a given user will have at least one satellite visible even if the whole sky is not visible. On average the users will end up seeing the whole sky, so it all works out.

Please note: this is a theoretical analysis. I do not know how it relates to today's Starlink constellation.

Spectrum reuse is limited by the allowable power flux at the Earth's surface.

Yes, making the receiver bigger helps. So does making it more efficient. But the biggest opportunity IMO is to make the spot beam tighter, by a combination of lower satellites and larger satellite-side transmitter antennas. This keeps the power flux constant, but means that the area that was formerly served by 1 beam is now served by 2, or 3 or more... each of which can reuse the same spectrum and thus serve 2x, or 3x, or more users.

The V-band VLEO constellation is already using smaller cell sizes than the Ka/Ku band constellation. So with the same efficiencies to can serve more customers per hertz of spectrum used.

Offline abaddon

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Re: Starlink : General Discussion - Thread 2
« Reply #3439 on: 01/14/2022 02:02 pm »
Quote from: fiercewireless.com
Overall, while Starlink represents an admirable first attempt to develop a LEO broadband system and bring more choices to rural U.S. consumers, it cannot and will not become the only option for satellite broadband in the U.S. or around the world, because in many areas at least some potential customers will be unable to access Starlink, due to capacity limitations and/or the difficulty of securing a reliable line-of-sight to the constellation.

If you strip out the rest of the BS, this is a reasonable statement that I think most people here would agree with.  Other than it's assuming the straw man (and anti-SpaceX/Elon fear-mongering) that Starlink is going to be some sort of Internet monopoly.

Tags: pole flip 
 

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