Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5(agupubs.onlinelibrary.wiley.com)
agupubs.onlinelibrary.wiley.com
Circular Shock Acoustic Waves in Ionosphere Triggered by Launch of Formosat‐5
https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2017SW001738
67 comments
This is ELI5 territory, which is cool because we probably need one of these as well.
The rocket made the air go funny which meant your phone got confused about where it was.
Spot on!
The really fast up goer made the air go funny which meant your phone got confused about where it was.
https://xkcd.com/1133/
https://xkcd.com/1133/
I call it EOD explanation.
EOD?
I'm assuming "End Of Day."
As in, after a full day, my brain is fatigued from overly-complex discussions and just needs the most direct, un-fussy information possible.
That sound right, mk3w9?
As in, after a full day, my brain is fatigued from overly-complex discussions and just needs the most direct, un-fussy information possible.
That sound right, mk3w9?
Yes, the - at the “End of the Day” EOD
Esoteric Order of Dagon
Explosive Ordnance Disposal
The ionosphere is not the same thing as the atmosphere. The ionosphere is a shell of super hot gas outside of the atmosphere.
The ionosphere is not outside the atmosphere, it's part of the atmosphere.
The atmosphere consists of many layers. From the ground up, these are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
You may be thinking of the thermosphere, which is indeed very hot (thus the name), albeit with such low density that it wouldn't transfer much heat to your spacesuit or spacecraft. But the thermosphere is part of the atmosphere too.
https://spaceplace.nasa.gov/thermosphere/en/
The ISS and other low earth orbit satellites are orbiting inside the thermosphere. Yes, the ISS is in the atmosphere and suffers from a small amount of atmospheric drag, so it requires occasional reboosts to maintain altitude.
The ionosphere isn't exactly a separate "layer" from these. It's a very tall region of ionized gas that starts near the top of the stratosphere and overlaps parts of the layers above. Its exact limits vary with solar conditions.
The ionosphere is actually made up of several layers of its own, defined by the solar energy wavelength that causes ionization in each layer. These are the D, E, and F layers, and occasional sub-layers within those. Hams and other shortwave radio operators are familiar with these ionospheric layers because of their different effects on radio propagation.
https://en.wikipedia.org/wiki/Ionosphere
https://spaceplace.nasa.gov/ionosphere/en/
https://www.nasa.gov/mission_pages/sunearth/science/atmosphe...
And I finally get to say about one of my own comments: "Username checks out."
https://en.wikipedia.org/wiki/Stratoscope
(I'm actually named after the Truetone Stratoscope radio antennas, not the balloon, but sometimes people do say I'm full of hot air.)
The atmosphere consists of many layers. From the ground up, these are the troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
You may be thinking of the thermosphere, which is indeed very hot (thus the name), albeit with such low density that it wouldn't transfer much heat to your spacesuit or spacecraft. But the thermosphere is part of the atmosphere too.
https://spaceplace.nasa.gov/thermosphere/en/
The ISS and other low earth orbit satellites are orbiting inside the thermosphere. Yes, the ISS is in the atmosphere and suffers from a small amount of atmospheric drag, so it requires occasional reboosts to maintain altitude.
The ionosphere isn't exactly a separate "layer" from these. It's a very tall region of ionized gas that starts near the top of the stratosphere and overlaps parts of the layers above. Its exact limits vary with solar conditions.
The ionosphere is actually made up of several layers of its own, defined by the solar energy wavelength that causes ionization in each layer. These are the D, E, and F layers, and occasional sub-layers within those. Hams and other shortwave radio operators are familiar with these ionospheric layers because of their different effects on radio propagation.
https://en.wikipedia.org/wiki/Ionosphere
https://spaceplace.nasa.gov/ionosphere/en/
https://www.nasa.gov/mission_pages/sunearth/science/atmosphe...
And I finally get to say about one of my own comments: "Username checks out."
https://en.wikipedia.org/wiki/Stratoscope
(I'm actually named after the Truetone Stratoscope radio antennas, not the balloon, but sometimes people do say I'm full of hot air.)
that nasa site was actually interesting. but i think like i'm 5.
But, it is outside the environment?
>Rocket exhaust can have impact with atmosphere, we need to study it more on short and long term effects.
Wasn't this already known? We have been sending rockets to space for a while now, right?
EDIT: Found something from 2014, https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014...
Wasn't this already known? We have been sending rockets to space for a while now, right?
EDIT: Found something from 2014, https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1002/2014...
Spare me your rocketry mumbo jumbo!
That's what I a call a content free sentence.
Saying "can" also implies "might not".
"Need" needs to come with "in order to do X". I don't need to breathe, but if I want to stay alive I do. So do I need to breather or not? It's either.
Saying "can" also implies "might not".
"Need" needs to come with "in order to do X". I don't need to breathe, but if I want to stay alive I do. So do I need to breather or not? It's either.
Can this cause any other issues other than GPS errors? Lines like
It is followed by ionospheric hole (plasma depletions) due to rapid chemical reactions of rocket exhaust plumes and ionospheric plasma.
sound concerning but that's most likely because I only understand half the words, and have even less of an understanding when they're strung together in that manner!
It is followed by ionospheric hole (plasma depletions) due to rapid chemical reactions of rocket exhaust plumes and ionospheric plasma.
sound concerning but that's most likely because I only understand half the words, and have even less of an understanding when they're strung together in that manner!
It is followed by ionospheric hole (should be It was... holes)
A ~900km wide patch of the ion blanket around the earth became thinner. Probably in the density sense, not the size sense: there was less plasma there than normal. (The abstract measures this in terms of how many electrons they counted in that area.)
due to rapid chemical reactions of rocket exhaust plumes and ionospheric plasma.
They think the thin patch was caused because the Falcon's exhaust reacted with the ion blanket. I'm not sure how.
A ~900km wide patch of the ion blanket around the earth became thinner. Probably in the density sense, not the size sense: there was less plasma there than normal. (The abstract measures this in terms of how many electrons they counted in that area.)
due to rapid chemical reactions of rocket exhaust plumes and ionospheric plasma.
They think the thin patch was caused because the Falcon's exhaust reacted with the ion blanket. I'm not sure how.
I'm curious about this too. The Falcon burns RP-1, essentially a very refined kerosene, with liquid oxygen. Exhaust should be water, carbon dioxide, and a bit of carbon monoxide.
Not typically the most reactive things, but perhaps there are different interactions with plasma?
Not typically the most reactive things, but perhaps there are different interactions with plasma?
Anything is reactive when interacting with plasma.
There should be little of those gases naturally up there (mostly so for water), and even throwing a large mass of gases up there may be enough to disturb everything.
There should be little of those gases naturally up there (mostly so for water), and even throwing a large mass of gases up there may be enough to disturb everything.
This other paper [0] seems to indicate that TEC (total electron count) fluctuations are caused by shock waves, not rapid chemical reactions, and can arise from ground explosions as well. IANA ionosphere scientist, so I don't know if the parent paper made a mistake.
[0] https://arxiv.org/pdf/physics/0007043.pdf
[0] https://arxiv.org/pdf/physics/0007043.pdf
I wonder if in the future this means large rockets may have to throttle back while transitioning through the ionosphere to reduce side effects?
Is the altitude stable enough to predict it accurately for a given launch?
Is the altitude stable enough to predict it accurately for a given launch?
It might affect short wave propagation and things like atmospheric electricity.
The worst such event on record caused errors of ~1 meter. I didn't think civilian GPS was that precise anyway, and that's why various schemes are used in conjunction with GPS for greater accuracy? Presumably, military GPS has similar schemes to deal with this sort of event?
Many commercial GPS systems can get to within 2cm (< 1 inch). They all rely on complex antenna schemes and timing analysis combined with correction signals from another GPS at a known fixed point not far away. Search for differential GPS if you want more information.
I don't know if the correction GPS will see the same error and thus give the correct correction factor or not.
I don't know if the correction GPS will see the same error and thus give the correct correction factor or not.
By "another GPS" do you mean a different satellite in the same network, or a different GNSS?
It's another receiver at a known location.
Atmospheric conditions cause errors that are in some cases hard to predict.
If you have a GPS receiver at a known nearby location, you can subtract the difference from what you receive and what you would expect to receive at your actual location, and then add that in to your GPS receiver at the unknown location.
It needs to be nearby because you want the atmospheric conditions between your fixed receiver and your moving receiver to be as similar as possible.
See https://en.wikipedia.org/wiki/Differential_GPS for more information
Also https://en.wikipedia.org/wiki/Real_Time_Kinematic is what's used to get ~1cm accuracy, but RTK would not be useful because while RTK increases precision of the measurements it does not (by itself) eliminate errors introduced by the atmosphere, which are already larger than what can be obtained without taking carrier phase into account.
Atmospheric conditions cause errors that are in some cases hard to predict.
If you have a GPS receiver at a known nearby location, you can subtract the difference from what you receive and what you would expect to receive at your actual location, and then add that in to your GPS receiver at the unknown location.
It needs to be nearby because you want the atmospheric conditions between your fixed receiver and your moving receiver to be as similar as possible.
See https://en.wikipedia.org/wiki/Differential_GPS for more information
Also https://en.wikipedia.org/wiki/Real_Time_Kinematic is what's used to get ~1cm accuracy, but RTK would not be useful because while RTK increases precision of the measurements it does not (by itself) eliminate errors introduced by the atmosphere, which are already larger than what can be obtained without taking carrier phase into account.
Military GPSs use multiple frequencies which helps them mitigate errors from the ionosphere. NOAA publishes enough space weather data to let commercial receivers make their own corrections, but I don't know if any actually do.
In the relatively near future, GPS satellites will broadcast multiple frequencies for civilian use, once commercial receivers catch up everyone should be able to reduce the error due to atmospheric conditions
In the relatively near future, GPS satellites will broadcast multiple frequencies for civilian use, once commercial receivers catch up everyone should be able to reduce the error due to atmospheric conditions
Civilian devices can use two frequencies as well, they just don't for cost and complexity reasons. The new L5 frequency has been available for some time and new devices supporting it are coming out this year. There are also multiple augmentations users can use to increase their accuracy to even greater levels than military users: https://www.gps.gov/systems/augmentations/
US currently claims 4m RMS (7.8m 95% Confidence Interval) horizontal accuracy for civilian (SPS) GPS. Some devices/locations reliably (95% of the time or better) can get 3m accuracy.
Yes, my expectation is that standard consumer-grade devices with GPS capability (even using tiny chip antennas) can achieve ~2.5M horizontal on L1 when using WAAS/SBAS augmentation.
I don't have firsthand knowledge, but I'd be surprised if mission critical military gear uses GPS for more than a secondary / corrective role.
I can't imagine the signals play that well in a heavily-jammed environment.
High probability rough GPS fix + radar / optical terrain comparison & dead reckoning for terminal guidance seems more likely.
I can't imagine the signals play that well in a heavily-jammed environment.
High probability rough GPS fix + radar / optical terrain comparison & dead reckoning for terminal guidance seems more likely.
I'm not sure if you consider this "mission critical" but US military drones use GPS for navigation. There have been several cases of them being captured via GPS jamming.
From what I heard, that extended to GPS spoofing.
Military GPS devices have access to more frequencies and channels that consumer devices don't have. These frequencies use anti-jamming techniques (frequency hopping using pseudo-random patterns, etc). They also have much better accuracy available to them than the consumer devices. Typical dumb jamming systems aren't really going to do much against military anti-jamming techniques and if it really is hurting comms they can send in an anti-radiation missile and blow up the jammer, no GPS needed.
Do you have a source for the better accuracy claim?
I know they turned off Selective Availability ( https://en.m.wikipedia.org/wiki/Error_analysis_for_the_Globa... ) in 2000, so not sure if it's been true since then.
From what I was reading, it seems like semi-codeless approaches to the P(y) (aka military) signal offer approximately similar accuracy to actually being in possession of the key.
Furthermore, the P(y) signal uses the same L1 and L2 frequencies as civilian devices. Which makes sense when you're designing a system with 1970s broadcast technology.
From Wikipedia, it seems like the soon-to-be-launched Block IIIA satellites are the first that will incorporate the ability to spot-beam at higher power ( https://en.m.wikipedia.org/wiki/GPS_Block_IIIA#New_navigatio... ).
I know they turned off Selective Availability ( https://en.m.wikipedia.org/wiki/Error_analysis_for_the_Globa... ) in 2000, so not sure if it's been true since then.
From what I was reading, it seems like semi-codeless approaches to the P(y) (aka military) signal offer approximately similar accuracy to actually being in possession of the key.
Furthermore, the P(y) signal uses the same L1 and L2 frequencies as civilian devices. Which makes sense when you're designing a system with 1970s broadcast technology.
From Wikipedia, it seems like the soon-to-be-launched Block IIIA satellites are the first that will incorporate the ability to spot-beam at higher power ( https://en.m.wikipedia.org/wiki/GPS_Block_IIIA#New_navigatio... ).
A non-insignificant portion of what GP said is mumbo jumbo. The reason military usage of GPS is more accurate is most significantly due to usage of multiple frequencies (which is now available to civilian too). What you’ve stated indicates you have good sources, so I recommend trusting those and asking questions if there’s gaps rather than trusting random folks commenters (yes, guess this includes me).
I thought orbiting was all about horizontal velocity, otherwise what comes up must come down!
Did the rocket just turn sideways to accumulate the necessary horizontal velocity to actually maintain an orbit at a much later phase in its flight?
Did the rocket just turn sideways to accumulate the necessary horizontal velocity to actually maintain an orbit at a much later phase in its flight?
Yes, absolutely. The total sideways velocity required is fixed, going on a steeper trajectory requires more fuel for the same target orbit.
The reason Falcon 9 still does that sometimes is that a more vertical trajectory makes the return flight back to the launchpad easier. So if the payload is light enough that there is enough free delta-v, they want to do that. If there isn't, they land on the barge or fly expendable.
The reason Falcon 9 still does that sometimes is that a more vertical trajectory makes the return flight back to the launchpad easier. So if the payload is light enough that there is enough free delta-v, they want to do that. If there isn't, they land on the barge or fly expendable.
It is almost, but not quite, entirely about horizontal velocity. You also need sufficient altitude to be outside the atmosphere, as orbits with altitudes of under 100km are very short lived.
Additionally, it's generally not great to try to spend a lot of time accelerating through the atmosphere. For this reason rockets tend to fly upwards and then once they are out of the bulk of the atmosphere they fly mostly sideways.
Additionally, it's generally not great to try to spend a lot of time accelerating through the atmosphere. For this reason rockets tend to fly upwards and then once they are out of the bulk of the atmosphere they fly mostly sideways.
I'd be curious to know roughly how long the disturbance lasted. Did it dissipate/recover in minutes, or did it stick around for the better part of a day (or two, or three)?
According to arstechnica's reporting on the paper (I don't have access to full text):
"In the case of this Falcon 9 launch, it induced a plasma hole that lasted for two to three hours, which a magnitude comparable to a magnetic storm"
https://arstechnica.com/science/2018/03/spacex-launch-last-y...
"In the case of this Falcon 9 launch, it induced a plasma hole that lasted for two to three hours, which a magnitude comparable to a magnetic storm"
https://arstechnica.com/science/2018/03/spacex-launch-last-y...
Can someone ELI5 how this would cause GPS errors?
GPS works by computing your distance from satellites by measuring how long it takes radio signals from those satellite to reach you. As an electromagnetic wave, radio moves at a different speed through plasma (which is full of charged particles) than through holes in that plasma, so this will change how long those radio signals take to reach you, which will change how far away from the satellite you think you are.
Ionosphere's charge density introduces change in speed of the radio waves passing through it. This messes up with the GPS' calculations which assumes that ionosphere's density doesn't changes rapidly.
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SAW also means Surface Acoustic Wave which is a different type of wave like what travels along the ground in an earthquake. That's a terrible double use of an acronym! I think the author of this story might have just made it up and not seen the existing meaning.
Did anyone try downloading the actual paper? My browser opened and then closed a tab. Kind of odd.
Every time somebody else burns a hole in the ozone layer I wonder if they did it over their home or over mine. Somehow I don't expect to be pleased by the answer.
As an Australian this is what we've had to deal with for decades. We don't produce much pollution but the hole is largely over us and giving us skin cancer.
Could major GPS issues become a nonstarter for the BFR intercontinental transport vision?
Maybe that's why the BFR interplanetary version is the focus. Screwing up GPS is less of a deal when you're leaving the planet for good... ;)
Are there any noted events in history that have exploited such ionosphere disturbances?
Related at all to the flight delays earlier today?
Plainer news headline style "SpaceX Falcon 9 launch might have interfered GPS signal coverage in area three times larger than California"
I wonder why a SpaceX Falcon-9 was singled out. Wouldn't any sufficiently large rocket have the same effect? And if so, wouldn't the Falcon heavy cause an even more dramatic effect?
Read the article before asking questions.
"This unique nearly vertical trajectory is different from the usual satellite launches that the rockets fly over horizontal trajectory "
"This unique nearly vertical trajectory is different from the usual satellite launches that the rockets fly over horizontal trajectory "
To add to that, also from the article: "This is the largest rocket‐induced circular SAWs on record."
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I would but the site's not responding for me.
A sufficiently large rocket with a similar payload being launched to reach a similar orbit.
Apparently that combination is not very common.
Rocket exhaust can have impact with atmosphere, we need to study it more on short and long term effects.