cl@ (Cameron Laird) (02/08/91)
From: cl@ (Cameron Laird)
I've come across a claim that:
1. Iraq bought some number of US Global Positioning
System units within the last decade;
2. everyone, including, in particular, hostiles, has
access to communications from Navstar satellites;
3. automated positioning information of the sort GPS
provides helps missile launching crews speed their
set-up.
The summary conclusion would be then that the USA sold
equipment which has made interdiction of Scud launches
more difficult. My question isn't a loaded one; I
have no policy recommendation to recommend. I'm just
curious about whether the mild irony 1.-3. is factual.
Is it true?
--
Cameron Laird USA 713-579-4613
cl@lgc.com USA 713-996-8546 smb@ulysses.att.com (Steven Bellovin) (02/09/91)
From: smb@ulysses.att.com (Steven Bellovin) In article <1991Feb8.014206.18215@cbnews.att.com>, cl@lgc.com (Cameron Laird) writes: > I've come across a claim that: > 1. Iraq bought some number of US Global Positioning > System units within the last decade; Dunno. > 2. everyone, including, in particular, hostiles, has > access to communications from Navstar satellites; See below. > 3. automated positioning information of the sort GPS > provides helps missile launching crews speed their > set-up. Dunno, but it does seem likely. The GPS satellites transmit two different signals. One is intended for general civilian use, and receivers are commonly available. I have no idea whether or not there are export restrictions on these receivers, but I'd doubt it. There's a second signal, for military use; this signal is transmitted encrypted. It allows calculation of a much more precise location. Additionally, the civilian signal's accuracy can be degraded even further by the Pentagon, thus -- in theory -- denying an enemy precise navigational information. Unfortunately, it turns out not to work that way. For one thing, the military had too few secure GPS receivers; they've been forced to buy large numbers of civilian receivers to support Desert {Shield,Storm}. Thus, they can't degrade the civilian signal any more or they themselves would be hosed. Besides, it turns out that if you have another receiver located in a known location, or an additional source of info such as LORAN, you can do some arithmetic and calculate your position to a very high degree of accuracy. Thus, neither the encrypted signal nor selective degradation have proved to be particularly useful (Source: a recent NY Times article, which has unfortunately been fed to the Recycler.) --Steve Bellovin
roeber@cithe1.cithep.caltech.edu (Frederick Roeber) (02/09/91)
From: roeber@cithe1.cithep.caltech.edu (Frederick Roeber) In article <1991Feb8.014206.18215@cbnews.att.com>, cl@ (Cameron Laird) writes: > ... > 1. Iraq bought some number of US Global Positioning > System units within the last decade; > ... It was reported on comp.protocols.time.ntp that the GPS Global Positioning Service (the unencrypted, public access positioning service) was quitely turned off ca. August 15 last year. So only the military receivers work. -- | Frederick G. M. Roeber | CERN -- European Center for Nuclear Research | | e-mail: roeber@caltech.edu or roeber@cern.ch | work: +41 22 767 31 80 | | r-mail: CERN/PPE, 1211 Geneva 23, Switzerland | home: +33 50 42 19 44 | --