Starlink : General Discussion - Thread 2

[Twark_Main]

Design OneWEB & StarLink Gen1  is very  similar, you can say Musk in 2016 copied the first version of StarLink from OneWEB

Let's just say there's a lot of history between SpaceX/Musk and OneWeb/Wyler.

https://en.wikipedia.org/wiki/OneWeb_satellite_constellation#History


(also it's stylized "OneWeb" and "Starlink," per their respective websites)

[dondar]

No. Handoffs take about a second. They're not going to keep half their ground capability shut down waiting for one.

Design OneWEB & StarLink Gen1  is very  similar, you can say Musk in 2016 copied the first version of StarLink from OneWEB. And OneWEB described everything in detail and unambiguously in its application for the FSS from 2016.

//Each OneWeb satellite will have 16 nominally identical user beams, operating in Ku-band, each
consisting of a non-steerable highly-elliptical spot beam. There are also two identical steerable
gateway beam antennas, operating in Ka-band, on each OneWeb satellite, and each of these
antennas creates an independently steerable circular spot beam. The 16 Ka-band uplink channels
in one gateway receive beam (the one tracking the servicing gateway) are converted to 16 Kuband downlink channels, each one routed to one of the 16 user beams (“forward links”),
nominally at 250 MHz bandwidth. Additionally, 16 different Ku-band uplink channels from the
same 16 user beams are converted to 16 Ka-band downlink channels and sent back to the same
gateway transmit beam (“return links”), each having a nominal channel bandwidth of 125 MHz.
The second gateway beam is tracking the next gateway earth station for handover procedures

No operator in their right mind will interrupt the service for a while while the antenna is slowly tuned to another gateway. strange to talk about this in 2022

we can say that Wyler copied (borderline with stolen) the design he was doing for Google. The design(patents and everything) which were transferred later to SpaceX.
P.S. there is number of fundamental design differences between Starlink and OneWeb.
P.P.S. You have no slightest idea  what are you talking about: "slowly tuned to" is perfect example of many.

[vsatman]

No. Handoffs take about a second. They're not going to keep half their ground capability shut down waiting for one.

P.P.S. You have no slightest idea  what are you talking about: "slowly tuned to" is perfect example of many.
[/quote]
Are you saying that setting up to another gateway takes less than 1 second?? And where can you read about it?

[Nomadd]

No. Handoffs take about a second. They're not going to keep half their ground capability shut down waiting for one.

P.P.S. You have no slightest idea  what are you talking about: "slowly tuned to" is perfect example of many.
Are you saying that setting up to another gateway takes less than 1 second?? And where can you read about it?

I certainly don't get my information by claiming Starlinks are the same as OneWebs or any other of the utter nonsense you continually post in here. Most of your knowledge of how anything works was outdated twenty years ago.

[vsatman]

Most of your knowledge of how anything works was outdated twenty years ago.

//I cited data from the OneWEB application to FCC from 2016, can you at least somehow refute these calculations ??
so show me your calculations of the linkbudget for this case, I will be happy to look at them..

[SpaceCadet1980]

Most of your knowledge of how anything works was outdated twenty years ago.

//I cited data from the OneWEB application to FCC from 2016, can you at least somehow refute these calculations ??
so show me your calculations of the linkbudget for this case, I will be happy to look at them..

What OneWeb does and is capable of has nothing to do with what what Starlink satellites do. There is no need to refute something that is irrelevant to the topic.

Nomadd's point about your knowledge being out of date doesn't need anything as much as even a link budget to support it. It just needs simple facts like that a phased array antenna can transmit (or receive) different data in 2 (or more) different directions at the same frequency and polarization. There is some hardware complexity cost, and ultimately on-board processing capability may be the limiting factor, but this is something that you have repeatedly ignored or denied.

To answer a related question:

However, it's not clear what the minimum angular separation is needed to reuse downlink channels, or that each antenna can use each channel exactly once per polarization.

This is going to be on the order of the beamwidth. Most likely the beams should be separated by the angle between the first nulls, known as the first null beamwidth. As a reasonable approximation, this is probably around double the more commonly discussed half power beamwidth. Various practical concerns such as processing throughput and RF architecture will determine how many beams can be actually handled at a time. We simply do not have the information required to make reasonable guesses about how many times each frequency/polarization combination can be reused on each satellite. The best we could do is work backwards from the throughput per satellite, but I think there is a possibility that has changed with the most recent satellites, as it has been a while since I have seen a number quoted by SpaceX for that.

[vsatman]

Nomadd's point about your knowledge being out of date doesn't need anything as much as even a link budget to support it. It just needs simple facts like that a phased array antenna can transmit (or receive) different data in 2 (or more) different directions at the same frequency and polarization. There is some hardware complexity cost, and ultimately on-board processing capability may be the limiting factor, but this is something that you have repeatedly ignored or denied.

again a lot of words about my "outdated" knowledge instead of just a short reference to an example of how a satellite with feeder lines of 4000 MHz was able to organize service channels with a total bandwidth of, for example, 8000 MHz. Why is there not a single example of this since 2016, when SpaceX submitted its application?? Although dozens of HTS satellites with frequency reuse are already operating in the world??

[SpaceCadet1980]

Nomadd's point about your knowledge being out of date doesn't need anything as much as even a link budget to support it. It just needs simple facts like that a phased array antenna can transmit (or receive) different data in 2 (or more) different directions at the same frequency and polarization. There is some hardware complexity cost, and ultimately on-board processing capability may be the limiting factor, but this is something that you have repeatedly ignored or denied.

again a lot of words about my "outdated" knowledge instead of just a short reference to an example of how a satellite with feeder lines of 4000 MHz was able to organize service channels with a total bandwidth of, for example, 8000 MHz. Why is there not a single example of this since 2016, when SpaceX submitted its application?? Although dozens of HTS satellites with frequency reuse are already operating in the world??

Feeder lines? What are you talking about? This is a phased array not a monolithic antenna and the way to describe its architecture is simply different, there is not some single "feeder line" but separate signals transmitted by many different elements in an array. Your question does not make sense, it is like asking how someone holding 2 buckets with 1 gallon each can possibly carry 2 gallons when the size of their buckets is only 1 gallon. Just like opposing polarizations are different buckets, so is angular separation. You are the one who has repeatedly made baseless assertions about Starlink based purely on ignoring the facts about how phased arrays work.

The simplest way I can think of to explain an architecture with multiple beams is to consider the receive case. You could put an ADC on every single element of an array. Then with enough time and/or processing power, you can add all of that digital data together with every combination of weights you want and independently distinguish signals from different directions (limited by beamwidth.) In practice there is you don't want/need to go that far and don't have infinite processing power so you would go with a different architecture. Same effect though. Like everything with antennas, transmit case is equivalent to receive, you add up the different signals per element and transmit them. Total power increases in proportion to the number of beams, but since this changes nothing about power density on the ground, it is not something that would explicitly come out in the FCC filings.

You are asking for a single example "since 2016" as if this is new magic people are claiming SpaceX invented. The physics has been around for a long time. Here is the first link I found from google searching for: phased array multiple simultaneous beams.
https://ieeexplore.ieee.org/document/6731900
"multiple simultaneous beams (at the same reference frequency) covering different pointing directions "
Please try to do the most minimal amount of research before posting, it really doesn't look good when you act like an expert but get basic facts wrong.

[Redclaws]

No. Handoffs take about a second. They're not going to keep half their ground capability shut down waiting for one.

P.P.S. You have no slightest idea  what are you talking about: "slowly tuned to" is perfect example of many.

Are you saying that setting up to another gateway takes less than 1 second?? And where can you read about it?
[/quote]

Sure, why not?  Location and frequency are already known and basic link latency is in the low tens of milliseconds.  There’s very little negotiation to do.

[vsatman]

Feeder lines? What are you talking about? This is a phased array not a monolithic antenna and the way to describe its architecture is simply different, there is not some single "feeder line" but separate signals transmitted by many different elements in an array. Your question does not make sense, it is like asking how someone holding 2 buckets with 1 gallon each can possibly carry 2 gallons
//
Please try to do the most minimal amount of research before posting, it really doesn't look good when you act like an expert but get basic facts wrong.

Oh my god, do you Google sometimes?? or not at all aware of elementary terms in the satcom industry??
Okay, let's start with the elementary:

A feeder link is – according to Article 1.115 of the International Telecommunication Union´s (ITU) ITU Radio Regulations (RR) – defined as: A radio link from an earth station at a given location to a space station, or vice versa, conveying information for a space radiocommunication service

Earth Station  in our case is parabolic Antenna +50 W tranceiver+modem  on GateWay ...  Space Station - StarLink satellite with parabolic antenna
And Link between  GW and Sats is feeder link.

For feeder link SpaceX can use 2000 MHz in Ka band in both polarisation divided in channels  500 MHz or
250 MHz or 125 MHz or 62,5 MHz.  Theoretically   one 500 MHz channel can transmit  up to 4000 Mbit (for 64QAM).  For all 4000 MHz  are 32 Gbit. (I hope you know where these values are given?? Minimal amount of research is needed for it) ..
And  I hope you understand why  in real StarLink network  these values are unreachable..
If not - ask me..

[SpaceCadet1980]

Feeder lines? What are you talking about? This is a phased array not a monolithic antenna and the way to describe its architecture is simply different, there is not some single "feeder line" but separate signals transmitted by many different elements in an array. Your question does not make sense, it is like asking how someone holding 2 buckets with 1 gallon each can possibly carry 2 gallons
//
Please try to do the most minimal amount of research before posting, it really doesn't look good when you act like an expert but get basic facts wrong.

Oh my god, do you Google sometimes?? or not at all aware of elementary terms in the satcom industry??
Okay, let's start with the elementary:

A feeder link is

Not a feeder line. You said line now you changed it to link. See https://en.wikipedia.org/wiki/Feed_line. (note that the article explicitly lists "feeder" as an alternate term, so this is a closer match to what you wrote than "feeder link") Either way doesn't change the important part of I wrote, it is still an irrelevant term to what I was talking about.

You can claim a typo if you want, but blaming me for your own mistake is insulting.

Earth Station  in our case is parabolic Antenna +50 W tranceiver+modem  on GateWay ...  Space Station - StarLink satellite with parabolic antenna
And Link between  GW and Sats is feeder link.

And all this proves is that you refuse to pay attention. The subject in my post was the number of beams that may be transmitted or received from the phased arrays on the satellite. Anything involving parabolic antennas remains irrelevant, so whether you meant to write line or link, you are still simply changing the subject.

For feeder link SpaceX can use 2000 MHz in Ka band in both polarisation divided in channels  500 MHz or
250 MHz or 125 MHz or 62,5 MHz.  Theoretically   one 500 MHz channel can transmit  up to 4000 Mbit (for 64QAM).  For all 4000 MHz  are 32 Gbit. (I hope you know where these values are given?? Minimal amount of research is needed for it) ..
And  I hope you understand why  in real StarLink network  these values are unreachable..
If not - ask me..

I will ask you to apologize, for insulting me, but I will not ask for technical explanations of RF from someone who does not know that the technical capabilities of a parabolic dish and a phased array have fundamental differences. How bands are divided and what modulation is used does nothing to change the fact that a phased array can transmit or receive distinct signals at the exact same frequency and polarization from different directions.

[Asteroza]

Remember how we talk about space weather and geomagnetic storms and how they can affect our satellites in orbit… update on the #Starlink satellites launched last week, lost to a geomagnetic storm on Friday.

https://twitter.com/ChrisG_NSF/status/1491209745839300610

So that solar flare did a number on the recent batch. Operationally that sucks for them (or for that matter anybody else doing very low insertions during a solar cycle uptick), but to what extent is that avoidable, other than higher insertions? I would imagine anybody using chemical propulsion wouldn't be having a good day either if they started low as well...

[kevin-rf]

So that solar flare did a number on the recent batch. Operationally that sucks for them (or for that matter anybody else doing very low insertions during a solar cycle uptick), but to what extent is that avoidable, other than higher insertions? I would imagine anybody using chemical propulsion wouldn't be having a good day either if they started low as well...

Starting that low then boosting to a higher orbit is kind of unique to starlink. Many GEO transfer orbits have perigees that low, but spend very little time that low, so it has little effect. ( I do remember one launch,  where they didn't properly take into account lunar effects on the transfer orbit and almost lost the satellites. EDIT: looked it up Atlas IIAS AC-163 Superbird 6 in 2004)

That said,  I do wonder if the penalty from the dogleg going south played into them starting in a lower initial orbit. Seems to prevent a repeat they need to launch to a higher orbit by either offloading more satellites or switching back to launching on the ascending node. Both are tradeoffs,  but on the surface the switch to the descending node for better weather seems to have not paid off in this case.

[DanClemmensen]

So that solar flare did a number on the recent batch. Operationally that sucks for them (or for that matter anybody else doing very low insertions during a solar cycle uptick), but to what extent is that avoidable, other than higher insertions? I would imagine anybody using chemical propulsion wouldn't be having a good day either if they started low as well...

Starting that low then boosting to a higher orbit is kind of unique to starlink. Many GEO transfer orbits have perigees that low, but spend very little time that low, so it has little effect. ( I do remember one launch,  where they didn't properly take into account lunar effects on the transfer orbit and almost lost the satellites. EDIT: looked it up Atlas IIAS AC-163 Superbird 6 in 2004)

That said,  I do wonder if the penalty from the dogleg going south played into them starting in a lower initial orbit. Seems to prevent a repeat they need to launch to a higher orbit by either offloading more satellites or switching back to launching on the ascending node. Both are tradeoffs,  but on the surface the switch to the descending node for better weather seems to have not paid off in this case.

As I understand it (probably incorrectly) the other reason to start in a lower orbit is increased precession rate. When one launch has satellites for multiple planes, you can wait for precession to shift a satellite's plane before you raise the orbit.

[vsatman]

Feeder lines? What are you talking about? This is a phased array not a monolithic antenna and the way to describe its architecture is simply different, there is not some single "feeder line" but separate signals transmitted by many different elements in an array. Your question does not make sense, it is like asking how someone holding 2 buckets with 1 gallon each can possibly carry 2 gallons
//
Please try to do the most minimal amount of research before posting, it really doesn't look good when you act like an expert but get basic facts wrong.

Oh my god, do you Google sometimes?? or not at all aware of elementary terms in the satcom industry??
Okay, let's start with the elementary:

A feeder link is

Not a feeder line. You said line now you changed it to link. See https://en.wikipedia.org/wiki/Feed_line. (note that the article explicitly lists "feeder" as an alternate term, so this is a closer match to what you wrote than "feeder link") Either way doesn't change the important part of I wrote, it is still an irrelevant term to what I was talking about.

You can claim a typo if you want, but blaming me for your own mistake is insulting.

Earth Station  in our case is parabolic Antenna +50 W tranceiver+modem  on GateWay ...  Space Station - StarLink satellite with parabolic antenna
And Link between  GW and Sats is feeder link.

And all this proves is that you refuse to pay attention. The subject in my post was the number of beams that may be transmitted or received from the phased arrays on the satellite. Anything involving parabolic antennas remains irrelevant, so whether you meant to write line or link, you are still simply changing the subject.

For feeder link SpaceX can use 2000 MHz in Ka band in both polarisation divided in channels  500 MHz or
250 MHz or 125 MHz or 62,5 MHz.  Theoretically   one 500 MHz channel can transmit  up to 4000 Mbit (for 64QAM).  For all 4000 MHz  are 32 Gbit. (I hope you know where these values are given?? Minimal amount of research is needed for it) ..
And  I hope you understand why  in real StarLink network  these values are unreachable..
If not - ask me..

I will ask you to apologize, for insulting me, but I will not ask for technical explanations of RF from someone who does not know that the technical capabilities of a parabolic dish and a phased array have fundamental differences. How bands are divided and what modulation is used does nothing to change the fact that a phased array can transmit or receive distinct signals at the exact same frequency and polarization from different directions.

1) "link and line". Yes, this is my mistake. In my native language both words have the same meaning. And I mistakenly used a "line" here. I apologize.
2) The ability of the FAR Antenna is known to me -  I know about 16 beams from 3 DownLink Antennas on Sat. I never questioned that "a phased array can transmit or receive distinct signals at the exact same frequency and polarization from different directions." The only add-on :  StarLink FAR uses only one polarization..
3) The comment thread is dedicated specifically to the feeder link, since I have seen in  Internet the statements of individual commentators that StarLink uses 2 feeder lines at the same time, each of the 2 antennas with its own gateway, which I consider impossible.

[Jim]

I would imagine anybody using chemical propulsion wouldn't be having a good day either if they started low as well...

No, it wouldn't bother them

[Jim]

So that solar flare did a number on the recent batch. Operationally that sucks for them (or for that matter anybody else doing very low insertions during a solar cycle uptick), but to what extent is that avoidable, other than higher insertions? I would imagine anybody using chemical propulsion wouldn't be having a good day either if they started low as well...

Starting that low then boosting to a higher orbit is kind of unique to starlink. Many GEO transfer orbits have perigees that low, but spend very little time that low, so it has little effect. ( I do remember one launch,  where they didn't properly take into account lunar effects on the transfer orbit and almost lost the satellites. EDIT: looked it up Atlas IIAS AC-163 Superbird 6 in 2004)

That said,  I do wonder if the penalty from the dogleg going south played into them starting in a lower initial orbit. Seems to prevent a repeat they need to launch to a higher orbit by either offloading more satellites or switching back to launching on the ascending node. Both are tradeoffs,  but on the surface the switch to the descending node for better weather seems to have not paid off in this case.

As I understand it (probably incorrectly) the other reason to start in a lower orbit is increased precession rate. When one launch has satellites for multiple planes, you can wait for precession to shift a satellite's plane before you raise the orbit.

As stated by them, it is to weed out the no ops.  If the spacecraft responses to commands and works, it is boosted.  Otherwise it quickly deorbits.

With this many spacecraft, there is only checkout at the factory and likely none at the launch site. Much like consumer electronics, check out and ship to launch site.

[SpaceCadet1980]

1) "link and line". Yes, this is my mistake. In my native language both words have the same meaning. And I mistakenly used a "line" here. I apologize.

Thank you.

2) The ability of the FAR Antenna is known to me -  I know about 16 beams from 3 DownLink Antennas on Sat. I never questioned that "a phased array can transmit or receive distinct signals at the exact same frequency and polarization from different directions." The only add-on :  StarLink FAR uses only one polarization..

You are contradicting yourself here. If you understood phased arrays, you would not be making the claim about the number of beams. There is no public information we can use to reliably determine this number. You previously pointed to an article that did 8 frequency bands times 2 polarizations to reach this 16 number and which showed no understanding of the capability to receive/transmit from an arbitrary number of different directions at the same time. You also linked to an irrelevant document about OneWeb to make the 16 beam claim. This claim inherently is based on denial of ability to transmit or receive an arbitrary number simultaneous beams from a phased array.

https://forum.nasaspaceflight.com/index.php?topic=48297.msg2335914#msg2335914

3) The comment thread is dedicated specifically to the feeder link, since I have seen in  Internet the statements of individual commentators that StarLink uses 2 feeder lines at the same time, each of the 2 antennas with its own gateway, which I consider impossible.

First of all, no, this thread goes back to me pointing out one of you many incorrect claims you have made. I have only been talking about the phased arrays and you changed the subject.

Second, this claim of "impossible" ranks as one of the most absurd things I have ever seen you write (which is saying something.) Claiming that 2 separate parabolic antennas cannot be pointed in different directions and used at the same time is far more obviously wrong than the same fact about a single phased array. I hadn't bothered to point this one out, because I was under the assumption that you had actually read the other recent posts that pointed out how absurd that claim is. (Others have already ripped this claim to shreds, so reply to their points on that.)

[envy887]

3) The comment thread is dedicated specifically to the feeder link, since I have seen in  Internet the statements of individual commentators that StarLink uses 2 feeder lines at the same time, each of the 2 antennas with its own gateway, which I consider impossible.

The only reason you gave to support this being impossible was the need to do handoffs. Which isn't actually a reason, as the user link also needs to do handoffs, and these can coincide. With multiple satellites always visible to every user, they don't need continuous uptime on every satellite. Giving up 1 second or so of transmit time every minute in order to double the uplink throughput is a huge overall increase.

[vsatman]

Second, this claim of "impossible" ranks as one of the most absurd things I have ever seen you write (which is saying something.) Claiming that 2 separate parabolic antennas cannot be pointed in different directions and used at the same time is far more obviously wrong than the same fact about a single phased array. I hadn't bothered to point this one out, because I was under the assumption that you had actually read the other recent posts that pointed out how absurd that claim is. (Others have already ripped this claim to shreds, so reply to their points on that.)

well, let's analyze it separately
 Each StarLink satellite changes its gateway at least once every  2...4 minutes 10 seconds (max time). In order to change the gateway, the Ka-band antenna on sat must turn back  up to  130 degrees.

Have you ever seen how a SeaTel or Intellian marine antenna is tuned? How many time they need to turn? (in seconds?) Please "quickly" is not answer , Answer is X seconds..

After prime pointing "in direction" , if it receives the signal from the beacon on GW begin  precise pointing both (!!!) Antennas - on Sat and on GW. After that, as fine pointing is completed, the Antenna  and link Sat-GW 2 is ready for operation with nesessary SNR, server on the gateway can send a message to the NMС that GW2 is ready to serve satellite X and the corresponding cells NN  was served from  Gateway 1, now it must be served by Gateway 2.
At the same time, the NMS should redirect traffic for users from POP 1 to which GW1 is connected to POP2 to which GW2 is connected ..

And only after all these processes are implemented, the operating configuration of the full StarLink Network "Gateway - satellite- cell" for the next 15 seconds is created, service through the gateway 2 can begin. A temporary break for these processes is at least 15 seconds, and maybe more.
(I would personally take an additional 15 seconds as a margin of time so that if it is not possible to сonnect to GW2. will be time to switch to GW3)

 That is why OneWEB Engineers (who created early O3B NGSO Network) have chosen the method described above to ensure the 100% continuity of the service.

If the Space X Engineer believed that it was permissible to interrupt the service for the user every  4 minutes for 15-30 seconds per, they would have been fired on the same day.

And I am happy to read any SpaceX document that can confirm your words each Sat will be served from 2 GW in one moment.

P.S. I have a question Have you ever worked in Telecom in the field of service quality? or Satellite Networks?
What service availability should StarLink provide in your opinion?