Have you ever...

In article , Newps
wrote:

Suppose you are navigating solely by GPS. What are you going to do in
the event the military chooses to disable the GPS system while you're
airborne

Can't be done. There is no on/off switch.

don't bet on it.

--
Bob Noel
looking for a sig the lawyers will like

"Bob Noel" wrote in message
...
Can't be done. There is no on/off switch.

don't bet on it.

And besides, even if you could bet on it, the GPS receiver itself is a
possible point of failure (and probably more likely than the satellite
network).

Newps wrote:


Suppose you are navigating solely by GPS. What are you going to do in
the event the military chooses to disable the GPS system while you're
airborne

Can't be done. There is no on/off switch.

I'm involved with supporting spacecraft operations of NASA's constellation
of EOS spacecraft. Somewhere, there's a satellite control center that
operates the constellation of GPS spacecraft. It may be true that the
military can't "throw a switch", but there's no doubt that they can
command each satellite to shut itself down and go into "safe hold",
effectively shutting down the GPS system.

--- Jay


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Jay and Teresa Masino ___(_)___
http://www2.ari.net/jmasino ! ! !
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On 16 Apr 2005 00:26:54 GMT, (Jay Masino)
wrote:

Newps wrote:


Suppose you are navigating solely by GPS. What are you going to do in
the event the military chooses to disable the GPS system while you're
airborne

Can't be done. There is no on/off switch.

I'm involved with supporting spacecraft operations of NASA's constellation
of EOS spacecraft. Somewhere, there's a satellite control center that
operates the constellation of GPS spacecraft. It may be true that the
military can't "throw a switch", but there's no doubt that they can
command each satellite to shut itself down and go into "safe hold",
effectively shutting down the GPS system.

I wrote some articles on GPS for Trimble in the early '80s. I don't
have my notes from then, but there are a few things I sort of remember
that sort of come down evenly on both sides of the debate.

One is that the Navstar system was a joint military/civilian effort,
implying a promise to keep it operational in most circumstances.

The other is that the satellites' orbits have to be tracked and
corrected ephemerides regularly updated with an uplink from the Naval
Observeratory, which I assume is how they can deliberately degrade C/A
coverage over specific geographic areas.

(The NO would have been a single point of failure. By now, there is
probably some redundancy.)

Feel free to bring me up to date.

Don

Larry Dighera wrote:
On Fri, 15 Apr 2005 04:37:47 GMT, "Jay Honeck"
wrote in vyH7e.15254$xL4.5745@attbi_s72::


... to put those kind of questions on the Private written exam is just
another way to weed out potential pilots.

That's true. The potential pilots it weeds out are those who are
incapable of understanding VOR operations. Would you prefer to share
the skies with them?

Actually, it doesn't even do that. There are what? Maybe 2 or 3 questions on the
test that deal with VORs? Anybody who flunks 'cause they missed those is also
missing a lot of other knowledge that they really should have.

George Patterson
There's plenty of room for all of God's creatures. Right next to the
mashed potatoes.

Mortimer Schnerd, RN wrote:

Way back in the 30s, some pilots would spin through an overcast and then recover
underneath in the clear. Unless the ceiling was 200', that is. Can you
imagine? Open cockpit, rain spraying you and there you go into an intentional
spin into the merk. Must have had huge balls and tiny brains....

I agree. According to Gann in his autobiography, the conventional wisdon in
those days was that the best way to handle thunderstorms was to bull right
through the center. I guess that, either way it works out, that technique gets
you through the storm the most rapidly.

George Patterson
There's plenty of room for all of God's creatures. Right next to the
mashed potatoes.

Mortimer Schnerd, RN wrote:
Way back in the 30s, some pilots would spin through an overcast and then
recover
underneath in the clear. Unless the ceiling was 200', that is. Can you
imagine? Open cockpit, rain spraying you and there you go into an
intentional
spin into the merk. Must have had huge balls and tiny brains....

How then would you suggest getting down through an overcast without
IFR-capable instruments?

[Let's ignore the decision making to put them there in the first place.
Let's just assume you're on top of an overcast that has 1000' bases, and you
don't have enough fuel to go far enough to see the ground]

A spin is a perfectly safe and controlled maneuver at a very slow airspeed
that puts very managable forces on the plane - remember, it is stalled.

Hilton

On Fri, 15 Apr 2005 11:36:30 -0600, Newps wrote
in ::



Larry Dighera wrote:

On Fri, 15 Apr 2005 09:28:30 -0600, Newps wrote
in ::



Suppose you are navigating solely by GPS. What are you going to do in
the event the military chooses to disable the GPS system while you're
airborne

Can't be done. There is no on/off switch.


True. But the military does have the ability to jam GPS to thwart
incoming missiles. The effect for the pilot would be similar...

Not on an instantaneous basis. Some general somewhere doesn't detect an
incoming missile and then flip a switch to make GPS unreliable. It
takes days.

Truly? What is the source of that bit of information?

Don Tuite wrote in
:

On 16 Apr 2005 00:26:54 GMT, (Jay Masino)
wrote:

Newps wrote:


Suppose you are navigating solely by GPS. What are you going to do
in the event the military chooses to disable the GPS system while
you're airborne

Can't be done. There is no on/off switch.

I'm involved with supporting spacecraft operations of NASA's
constellation of EOS spacecraft. Somewhere, there's a satellite control
center that operates the constellation of GPS spacecraft. It may be
true that the military can't "throw a switch", but there's no doubt that
they can command each satellite to shut itself down and go into "safe
hold", effectively shutting down the GPS system.

I wrote some articles on GPS for Trimble in the early '80s. I don't
have my notes from then, but there are a few things I sort of remember
that sort of come down evenly on both sides of the debate.

One is that the Navstar system was a joint military/civilian effort,
implying a promise to keep it operational in most circumstances.

The other is that the satellites' orbits have to be tracked and
corrected ephemerides regularly updated with an uplink from the Naval
Observeratory, which I assume is how they can deliberately degrade C/A
coverage over specific geographic areas.

(The NO would have been a single point of failure. By now, there is
probably some redundancy.)

Feel free to bring me up to date.

Don

A small hobby of mine is satellite observing, so I asked about
this amongst some of those folks and got the following tidbits.

Individual NAVSTAR sats can surely be shut down, aka sleep mode.
This would be necessary in the event of a satellite sending
erroneous data. You need to be able to shut it off to keep the
system working. If they really wanted to, they could put them
all into sleep mode, but that is near nil probability as it
would also deny the military of their use.

However, it may take a few hours to accomplish for any given
sat as it must be within communications range which isn't
100% of the time.

Although President Clinton ordered the 'selective accuracy' mode
to be turned off, it surely can be turned back on again. This
would degrade the accuracy, but the system woudl still be useable.

Also, it was the military can use 'selective deniability' to
degrade or disabel to civilian signal in a local region.

There are GPS jammers, but their effectiveness is disputed.

Due to the tight control of GPS by the US gov, the Europeans
are develping their own system called GALILEO which will use
the same base frequency (L1) as the NAVSTAR which means most
consumer level GPS units will be compatible. Once this is
available, the idea of the US Gov 'turning off' GPS is moot.

The Russians have GLONASS but it's of limited use.

As for getting rid of VOR training/testing, I think it's silly,
and I don't even have a PPL!!! I know flight sims aren't 100%
accurate but I have no trouble using VOR's in MSFS. Besides,
I think arguing to get rid of VOR training/testing is like
arguing to get rid of parallel parking training/testing in
drivers ed. They've tried making drivers licenses easier to
get and look where it got us. A lot of bad drivers. Now they're
starting to make it tougher again. (too little too late if you
ask me)

Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism

Home of the Seismic FAQ
http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html

Sed quis custodiet ipsos Custodes?

In article ,
Skywise wrote:

There are GPS jammers, but their effectiveness is disputed.

by who?


Due to the tight control of GPS by the US gov, the Europeans
are develping their own system called GALILEO which will use
the same base frequency (L1) as the NAVSTAR which means most
consumer level GPS units will be compatible. Once this is
available, the idea of the US Gov 'turning off' GPS is moot.

Moot? Hardly. You think Galileo couldn't be jammed?

--
Bob Noel
looking for a sig the lawyers will like