28/5 -30/5 Geomagnetic storms - how concerned?
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28/5 -30/5 Geomagnetic storms - how concerned?
Are we likely to see GPS scintillation errors over the next three days with this A index level of geomagnetic disturbance Space Weather: Geomagnetic Disturbance Index
As RAIM is predicated on the assuption that a majority of the GPS constellation is operating properly it may not even be able to detect a loss of integrity (let alone provide corrections).
At what level A index level does this become an issue?
Also what level are coms frequencies likely to be affected?
I understand the Americans and some UK carriers are notified of these events but it doesn't appear in our NOTAMs. Does anyone else in the UK have this stuff promulgated?
As RAIM is predicated on the assuption that a majority of the GPS constellation is operating properly it may not even be able to detect a loss of integrity (let alone provide corrections).
At what level A index level does this become an issue?
Also what level are coms frequencies likely to be affected?
I understand the Americans and some UK carriers are notified of these events but it doesn't appear in our NOTAMs. Does anyone else in the UK have this stuff promulgated?
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Not concerned at all
Not likely to see any effects on GPS. The small line you see in the graph is what happened during the previous 27 day rotation. Nothing happened then as far as I know.
The values that you see there are not really high anyway, beginning of April they where much higher.
If you look here you will see the following:
I know that graphs can look scary sometimes, but this really is storm in a teacup.
ATCast
The values that you see there are not really high anyway, beginning of April they where much higher.
If you look here you will see the following:
Outlook For May 26-June 1 No space weather storms are expected.
ATCast
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How much higher than A index 40 were they in April...I get NASA geomagnetic warnings emailed to me daily (since I was last caught out by this). Don't remember any recent warnings being highlighted like this one was ?
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Hi,
We didn't have GPS in the old days. Even if GPS is unavailable - it's only one of several ways to update your position. You'd still have Runway update on Take Off, and DME/DME update over areas with coverage.
We didn't have GPS in the old days. Even if GPS is unavailable - it's only one of several ways to update your position. You'd still have Runway update on Take Off, and DME/DME update over areas with coverage.
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You can see the recent history of the Kp index here.
The higest index on April 5 was 8-. This corresponds to an Ap of around 179.
This might have gone unpredicted as the cycle preceding that one that was quiet. How did the predictions for the beginning of this month look like? I would expect that those were more intense than the ones for the coming days.
The higest index on April 5 was 8-. This corresponds to an Ap of around 179.
This might have gone unpredicted as the cycle preceding that one that was quiet. How did the predictions for the beginning of this month look like? I would expect that those were more intense than the ones for the coming days.
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RAIM probably would detect it.
That statements deserves an explanation. So here we go:
For determining the position, the GPS receiver needs to receive signals from four GPS satellites. These four signals constitute four equations which are solved to find four unknowns. These are 3D position of the receiver (x,y,z or lat,lon, h) and receiver clock bias.
When there are more than four satellite in view, these are added to the list of equations. The total problem is now overbounded (e.g. seven equations and four unknowns), and solved by a least square estimate. The solution is most likely not an exact solution to all equations, but gives the best fit.
The reason that there is not an exact fit is due to small errors in the measurement. These are due to various causes such as: ionospheric disturbances, ephemeris errors, receiver errors and others.
With the clock bias estimated, it is possible to determine the difference in time between transmission and the reception of a satellite signal. When you multiply the time difference with the speed of light, you obtain the measured distance to the satellite called pseudorange.
When there are four satellites in view, the pseudorange is always equal to the distance between the measured position and the reported position of the satellite.
If there are more than four satellites that is usually not the case.
RAIM compares the pseudorange to the distance between the satellite (known, transmitted from the satellite) and the receiver reported position. The difference is called pseudorange error. Normally, the pseudorange errors are small in the order of a few meters. As long as the range error is within certain bounds, RAIM assumes that it is due to standard measurement noise. Only if the range error grows over a certain threshold it is unlikely that the error is due to normal uncertainty in the measurements. In that case RAIM triggers an alert.
When only one satellite fails (drifts away from its reported orbit, clock failure) while other satellites are doing fine it is possible to determine how big the position error can grow before RAIM kicks in. This is called the HPL or horizontal protection limit. When multiple satellites fail, it is not sure when RAIM sounds the alarm. However, it is very unlikely that the solution of the overbounded problem will deviate far from the true position while at the same time all the pseudoranges errors stay within the limits.
Of course for RAIM it is always necessary to receive signals from at least five satellites. And in general the more satellites the better.
ATCast
That statements deserves an explanation. So here we go:
For determining the position, the GPS receiver needs to receive signals from four GPS satellites. These four signals constitute four equations which are solved to find four unknowns. These are 3D position of the receiver (x,y,z or lat,lon, h) and receiver clock bias.
When there are more than four satellite in view, these are added to the list of equations. The total problem is now overbounded (e.g. seven equations and four unknowns), and solved by a least square estimate. The solution is most likely not an exact solution to all equations, but gives the best fit.
The reason that there is not an exact fit is due to small errors in the measurement. These are due to various causes such as: ionospheric disturbances, ephemeris errors, receiver errors and others.
With the clock bias estimated, it is possible to determine the difference in time between transmission and the reception of a satellite signal. When you multiply the time difference with the speed of light, you obtain the measured distance to the satellite called pseudorange.
When there are four satellites in view, the pseudorange is always equal to the distance between the measured position and the reported position of the satellite.
If there are more than four satellites that is usually not the case.
RAIM compares the pseudorange to the distance between the satellite (known, transmitted from the satellite) and the receiver reported position. The difference is called pseudorange error. Normally, the pseudorange errors are small in the order of a few meters. As long as the range error is within certain bounds, RAIM assumes that it is due to standard measurement noise. Only if the range error grows over a certain threshold it is unlikely that the error is due to normal uncertainty in the measurements. In that case RAIM triggers an alert.
When only one satellite fails (drifts away from its reported orbit, clock failure) while other satellites are doing fine it is possible to determine how big the position error can grow before RAIM kicks in. This is called the HPL or horizontal protection limit. When multiple satellites fail, it is not sure when RAIM sounds the alarm. However, it is very unlikely that the solution of the overbounded problem will deviate far from the true position while at the same time all the pseudoranges errors stay within the limits.
Of course for RAIM it is always necessary to receive signals from at least five satellites. And in general the more satellites the better.
ATCast
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Bizjetlock - As ATCast says RAIM needs to recieve signals from at least five satellites.
In my original post I said
"As RAIM is predicated on the assuption that a majority of the GPS constellation is operating properly it may not even be able to detect a loss of integrity"
Most people remember the severe geomagnetic storm of March 1989
NASA's TDRS-1 communication satellite recorded over 250 anomalies caused by the increased particles flowing into its own sensitive electronics. Hundreds of satellites lost cotrol.
On Earth the Hydro Quebec power grid blackout left millions of people without power for 9 hours.
My question is at what level of Geomagnetic activity will scintillation errors affect integrity ...what about the less publicised storm of Feb 2008...did this affect GPS?
Also the Report of Solar Geophysical Activity forecasts are more accurate than our met forecasts...if they predict a disturbance in two days time there will probably be one.
Rudderrat....understand what you are saying about the Take off position / DME/DME...my concern is an incident from lining up of holes in the swiss cheese. A few years ago at the end of a long flight to AMS I had a total GPS failure...the take off position had drifted...there was a temporary dme replacing one of the normal stations and it happened on approach where line of sight meant fewer dmes to sample.
Tomorrow I fly to Bergamo
1 - No radar (procedural approach)
2 - Very high ground ..very close.
3 - Promulgated GPS inaccuracy due to ALPs
4- At the height of this particular solar event
Not an issue as (like women) I love GPS to bits...but don't trust it with my life (unless I know exactly what its up to...hence the question ). The approach will be done raw data...but we are in danger of breeding a generation of pilots who fly managed approaches below MSA without even selecting raw data backup. The problem with GPS errors is that when they happen they tend to be significant....blindly following the magenta line can really ruin your day.
In my original post I said
"As RAIM is predicated on the assuption that a majority of the GPS constellation is operating properly it may not even be able to detect a loss of integrity"
Most people remember the severe geomagnetic storm of March 1989
NASA's TDRS-1 communication satellite recorded over 250 anomalies caused by the increased particles flowing into its own sensitive electronics. Hundreds of satellites lost cotrol.
On Earth the Hydro Quebec power grid blackout left millions of people without power for 9 hours.
My question is at what level of Geomagnetic activity will scintillation errors affect integrity ...what about the less publicised storm of Feb 2008...did this affect GPS?
Also the Report of Solar Geophysical Activity forecasts are more accurate than our met forecasts...if they predict a disturbance in two days time there will probably be one.
Rudderrat....understand what you are saying about the Take off position / DME/DME...my concern is an incident from lining up of holes in the swiss cheese. A few years ago at the end of a long flight to AMS I had a total GPS failure...the take off position had drifted...there was a temporary dme replacing one of the normal stations and it happened on approach where line of sight meant fewer dmes to sample.
Tomorrow I fly to Bergamo
1 - No radar (procedural approach)
2 - Very high ground ..very close.
3 - Promulgated GPS inaccuracy due to ALPs
4- At the height of this particular solar event
Not an issue as (like women) I love GPS to bits...but don't trust it with my life (unless I know exactly what its up to...hence the question ). The approach will be done raw data...but we are in danger of breeding a generation of pilots who fly managed approaches below MSA without even selecting raw data backup. The problem with GPS errors is that when they happen they tend to be significant....blindly following the magenta line can really ruin your day.
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WWV
You can get updates on solar weather at 18 minutes past each hour by
listening to WWV on 2.5 MHz, 5.0 MHz, 10.0 MHz, 15 MHz, and 20 MHz.
Or, you can call WWV at 303-499-7111 (U.S. number) at 18 minutes past
each hour. (Call on the 17th minute, so you don't miss the beginning of the message on the 18th minute.)
Fly safe,
PantLoad
listening to WWV on 2.5 MHz, 5.0 MHz, 10.0 MHz, 15 MHz, and 20 MHz.
Or, you can call WWV at 303-499-7111 (U.S. number) at 18 minutes past
each hour. (Call on the 17th minute, so you don't miss the beginning of the message on the 18th minute.)
Fly safe,
PantLoad
