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#1120
by
clongton
on 14 Feb, 2020 22:41
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Are there any more details on the comms issue(s) during the test? I really have a hard time understanding the claim about cell phone tower signals having a critical impact on comms -- if so, why haven't other missions experienced this, and why wasn't it anticipated? (And how the heck do cell towers impact on communications with a craft 100km away and above them?)
Typically the radius of a mobile phone cell tower is from a few hundred meters (LTE 2.6 GHz in dense urban environment) to some 50 km (450 MHz for cdma and 1G networks, but in near future also for LTE). So I too am puzzled by this claim. It makes no sense to me.
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#1121
by
Barley
on 15 Feb, 2020 03:46
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Are there any more details on the comms issue(s) during the test? I really have a hard time understanding the claim about cell phone tower signals having a critical impact on comms -- if so, why haven't other missions experienced this, and why wasn't it anticipated? (And how the heck do cell towers impact on communications with a craft 100km away and above them?)
Typically the radius of a mobile phone cell tower is from a few hundred meters (LTE 2.6 GHz in dense urban environment) to some 50 km (450 MHz for cdma and 1G networks, but in near future also for LTE). So I too am puzzled by this claim. It makes no sense to me.
The radius of the cell does not matter here. In principle radio waves travel to infinity, dropping in power as the inverse square of distance.
What matters is the transmitted power and the direction. Some, but not all, cell towers use simple dipole antennas which transmit in most directions, including say 45 degrees to the vertical. If such a tower is transmitting enough power to be received by a dinky cell phone through trees or walls at 50 km it should not be surprising it can interfere with a more sensitive spacecraft receiver with a clear line of sight a few hundred km away.
In practice the radius of a cell is limited by interference from nearby cells, objects in the line of sight (including walls, trees and the curvature of the Earth) and at extreme distances lightspeed delays that exceed the tolerances of the protocols. These don't affect how far away the cell tower can cause interference to an object in space.
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#1122
by
Nomadd
on 15 Feb, 2020 04:09
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Are there any more details on the comms issue(s) during the test? I really have a hard time understanding the claim about cell phone tower signals having a critical impact on comms -- if so, why haven't other missions experienced this, and why wasn't it anticipated? (And how the heck do cell towers impact on communications with a craft 100km away and above them?)
They can if you have incompetent designers. A cell tower meant to work a phone with a low gain antenna 10 miles away would have a pretty good impact on a 30db antenna 200 miles away. (Sats aren't always straight up, you know)
If you design a spacecraft antenna, and it's similar to cell frequencies and pointed toward the earth, you take cell signals into account when you figure background noise. It's such a basic factor, like Doppler shift for a Titan bound probe to mothership link, it's kind of hard to see how it would be missed.
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#1123
by
Rocket Science
on 15 Feb, 2020 05:52
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IMHO a spacecraft should be able to make orbit successfully while out of com with onboard GNC/IMU...
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#1124
by
DigitalMan
on 15 Feb, 2020 06:03
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IMHO a spacecraft should be able to make orbit successfully while out of com with onboard GNC/IMU...
If there is no abort at T-0 they will launch and then stream telemetry regardless if it can be picked up, no? The only communication up would be range safety, correct?
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#1125
by
EeeVee3
on 15 Feb, 2020 06:06
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I was led to believe that the comms problem occurred in the first 10 to 20 minutes. After separation the anomaly was noticed but they couldn't communicate with the craft to immediately rectify the situation. I thought well if the craft thought it was 11 hrs into the mission, it would think its 'here' so TDRS would be 'over there' and the craft be pointing at 'nothing there'. This I can understand.
But this mobile phone tower interference story thats out now?
I do not. As the first 30 minutes of flight crosses the Atlantic ocean, what cell towers?, I'm sure there are no Cell towers out there, I could be wrong, maybe some cruise ships have one for their passengers?? Or are they saying that comms with the craft were bad the whole flight?
Confused.
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#1126
by
Rocket Science
on 15 Feb, 2020 06:56
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IMHO a spacecraft should be able to make orbit successfully while out of com with onboard GNC/IMU...
If there is no abort at T-0 they will launch and then stream telemetry regardless if it can be picked up, no? The only communication up would be range safety, correct?
Yes, in conjunction with EDS...
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#1127
by
HVM
on 15 Feb, 2020 07:46
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...Some, but not all, cell towers use simple dipole antennas which transmit in most directions, including say 45 degrees to the vertical...
Practically all base stations from GSM up, use phased arrays, and are divided to multiple cells, and are very directed. But no antenna of course is totally ideal. All base stations combined raise the noise level, but that interference is already simulated in design phase of the broadband system. And now specs and both simulated +actual measured data are available. So it odd that Boeing didn't catch that at the EM interference testing. Boeing seems to struggle very basic level of the spacecraft design and testing.
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#1128
by
ZachS09
on 15 Feb, 2020 10:41
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Could there have been a possibility that ULA would have noticed the wrongly-set timer during the L-7 minute GO/NO GO poll and scrub the attempt to investigate it?
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#1129
by
ugordan
on 15 Feb, 2020 11:08
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Could there have been a possibility that ULA would have noticed the wrongly-set timer during the L-7 minute GO/NO GO poll and scrub the attempt to investigate it?
Why would ULA have insight into their payload state machine or be bothered about it at all? That is on the spacecraft owner to do. All ULA needs is a GO decision from the spacecraft side to proceed with the launch.
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#1130
by
ZachS09
on 15 Feb, 2020 11:17
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Could there have been a possibility that ULA would have noticed the wrongly-set timer during the L-7 minute GO/NO GO poll and scrub the attempt to investigate it?
Why would ULA have insight into their payload state machine or be bothered about it at all? That is on the spacecraft owner to do. All ULA needs is a GO decision from the spacecraft side to proceed with the launch.
That’s kind of the point I was making. I meant to say I was wondering what if the spacecraft side noticed the timer issue and relayed it to ULA during the poll.
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#1131
by
ugordan
on 15 Feb, 2020 11:26
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Could there have been a possibility that ULA would have noticed the wrongly-set timer during the L-7 minute GO/NO GO poll and scrub the attempt to investigate it?
Why would ULA have insight into their payload state machine or be bothered about it at all? That is on the spacecraft owner to do. All ULA needs is a GO decision from the spacecraft side to proceed with the launch.
That’s kind of the point I was making. I meant to say I was wondering what if the spacecraft side noticed the timer issue and relayed it to ULA during the poll.
Spacecraft side is not ULA, though. Well, had the spacecraft side (Boeing) noticed it, they would have halted the countdown. Unless there was someone who
did notice it up but didn't voice their "Huh, that's odd. Maybe we should stop and regroup until we understand this." thoughts.
In either case, as they say,
the rest is history.
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#1132
by
clongton
on 15 Feb, 2020 13:00
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So it's odd that Boeing didn't catch that at the EM interference testing. Boeing seems to struggle very basic level of the spacecraft design and testing.
Agreed. Boeing didn't catch fundamentally basic software issues. Boeing tried to cover up another potentially LOV software issue by saying "it didn't happen so we didn't report it". Boeing didn't catch the cell tower EM interference issue. What else didn't they catch and what else didn't they bother reporting "because it didn't happen"? Boeing does not seem to be very competent in catching problems with pretty basic things in their crew spacecraft design. This is beyond disturbing.
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#1133
by
ZachS09
on 15 Feb, 2020 14:11
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So it's odd that Boeing didn't catch that at the EM interference testing. Boeing seems to struggle very basic level of the spacecraft design and testing.
Agreed. Boeing didn't catch fundamentally basic software issues. Boeing tried to cover up another potentially LOV software issue by saying "it didn't happen so we didn't report it". Boeing didn't catch the cell tower EM interference issue. What else didn't they catch and what else didn't they bother reporting "because it didn't happen"? Boeing does not seem to be very competent in catching problems with pretty basic things in their crew spacecraft design. This is beyond disturbing.
Speaking of "competent", in the words of Gene Kranz when he gave his dictum after Apollo 1, he suggested that the Houston flight controllers remember the phrase "Tough and Competent" so that they should know to speak up if something bad happens and not cover it up.
Not to offend Boeing, but I don't know if they remembered the dictum's moral beforehand.
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#1134
by
Rebel44
on 15 Feb, 2020 14:26
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Are there any more details on the comms issue(s) during the test? I really have a hard time understanding the claim about cell phone tower signals having a critical impact on comms -- if so, why haven't other missions experienced this, and why wasn't it anticipated? (And how the heck do cell towers impact on communications with a craft 100km away and above them?)
Typically the radius of a mobile phone cell tower is from a few hundred meters (LTE 2.6 GHz in dense urban environment) to some 50 km (450 MHz for cdma and 1G networks, but in near future also for LTE). So I too am puzzled by this claim. It makes no sense to me.
The radius of the cell does not matter here. In principle radio waves travel to infinity, dropping in power as the inverse square of distance.
What matters is the transmitted power and the direction. Some, but not all, cell towers use simple dipole antennas which transmit in most directions, including say 45 degrees to the vertical. If such a tower is transmitting enough power to be received by a dinky cell phone through trees or walls at 50 km it should not be surprising it can interfere with a more sensitive spacecraft receiver with a clear line of sight a few hundred km away.
In practice the radius of a cell is limited by interference from nearby cells, objects in the line of sight (including walls, trees and the curvature of the Earth) and at extreme distances lightspeed delays that exceed the tolerances of the protocols. These don't affect how far away the cell tower can cause interference to an object in space.
Disclaimer: I have been working in telecommunications for over a decade, but my experience is limited to 2 EU countries.
Even years ago, it has been extremely rare for any of my telco employers to transmit cell tower signal this way - all towers for current cell phone networks are using phased arrays and our power output is highly regulated. Plus so we make a conscious effort to direct our signal towards our customers, instead of wasting our transmitter output towards empty space.
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#1135
by
Rebel44
on 15 Feb, 2020 14:30
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I was led to believe that the comms problem occurred in the first 10 to 20 minutes. After separation the anomaly was noticed but they couldn't communicate with the craft to immediately rectify the situation. I thought well if the craft thought it was 11 hrs into the mission, it would think its 'here' so TDRS would be 'over there' and the craft be pointing at 'nothing there'. This I can understand.
But this mobile phone tower interference story thats out now? I do not. As the first 30 minutes of flight crosses the Atlantic ocean, what cell towers?, I'm sure there are no Cell towers out there, I could be wrong, maybe some cruise ships have one for their passengers?? Or are they saying that comms with the craft were bad the whole flight?
Confused.
I agree - this story about cell tower interference makes no sense if the comms issue happened shortly after the launch when Starliner was over the Atlantic.
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#1136
by
Rocket Science
on 15 Feb, 2020 16:52
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Could there have been a possibility that ULA would have noticed the wrongly-set timer during the L-7 minute GO/NO GO poll and scrub the attempt to investigate it?
Why would ULA have insight into their payload state machine or be bothered about it at all? That is on the spacecraft owner to do. All ULA needs is a GO decision from the spacecraft side to proceed with the launch.
That’s kind of the point I was making. I meant to say I was wondering what if the spacecraft side noticed the timer issue and relayed it to ULA during the poll.
I agree Zach, if you go back right after the occurrence I posted the the same question a couple of months back (I know this is a long thread) what were they looking at on the consoles during the final GO/NO GO polls... Something was either: overlooked, over-ruled, incompetent and covered-up on both sides (Boeing and NASA)...
https://www.nasa.gov/feature/how-the-mission-is-controlled-inside-nasa-and-boeing-joint-operations
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#1137
by
mgeagon
on 15 Feb, 2020 20:45
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I agree - this story about cell tower interference makes no sense if the comms issue happened shortly after the launch when Starliner was over the Atlantic.
Not that it should matter, but I believe the interference is claimed to have occurred while over Europe, not the Atlantic.
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#1138
by
Comga
on 16 Feb, 2020 04:46
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I agree - this story about cell tower interference makes no sense if the comms issue happened shortly after the launch when Starliner was over the Atlantic.
Not that it should matter, but I believe the interference is claimed to have occurred while over Europe, not the Atlantic.
Starliner separation from the Centaur was south of Greenland, over the open north Atlantic, according to
this map.The Centaur MECO was well off-shore of Nova Scotia.
The last several posts agree on the logical point that this cell tower interference "explanation" lacks at least some critical detail, and doesn't yet make any sense.
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#1139
by
thirtyone
on 16 Feb, 2020 20:31
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https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20180003337.pdfHas a reference to 4G operating in specific bands interfering with at least part of TDRS operation/testing. Looks like it might outright overlap with part of the S-band spectrum...
TDRS satellites are also in a *higher* orbit than Starliner, which makes it a little odd that ground interference could have a significant effect. It may be that the spacecraft antenna design was not directional enough that some ground interference could be captured. In this case, keep in mind that interference that could be picked up is more likely to be closer to the "horizon" than underneath the spacecraft - if it is passing over the Atlantic, it is more likely sensitive to things broadcasting from the shores, for example.
This is also consistent with the fact that most sane cell towers are designed to send signals sideways instead of upwards to conserve power. If you go sideways enough, well, the earth is round, and eventually those signals make it to space. Tens of thousands of towers later, you can expect a pretty serious problem.
Interesting side note - I've heard that this is a technique some nations have likely been using on some of their satellites to try to spy on others.
I do not. As the first 30 minutes of flight crosses the Atlantic ocean, what cell towers?, I'm sure there are no Cell towers out there, I could be wrong, maybe some cruise ships have one for their passengers?? Or are they saying that comms with the craft were bad the whole flight?