Re: NSA abandons some cool stuff
At 6:09 PM -0800 1/8/2001, David Honig wrote: At 07:51 PM 1/8/01 -0500, Arnold G. Reinhold wrote: ... By shielding the fixtures, they effectively place the lights outside of the enclosure. Yes. But 1. you'd still want a filter the power mains inside your physically secured zone 2. The site had a generator... and presumably a guarded perimeter (think 1/R^2) so emissions were probably less important than listening sensitivity... I suspect they would not rely on the guarded perimeter for TEMPEST, at least not back then. The 1/R^2 attenuation applies to reception as well. One would put distance between the antennae and the buildings housing the computers and other sources of noise. I'll bet the wiring to those fixtures is within carefully grounded conduit. Building codes often require this, anyway, though probably not grounded to the extent of someone concerned with emissions. I doubt they require conduit in rural NC. And my guess is you'll see welded straps bridging each joint. Again, it makes much more sense (cost, number of items to check periodically) to put isolation centrally. The kind of filtering you need for TEMPEST is pretty fancy (and expensive no doubt). I have heard numbers like 100+ db. The filters have to be located at boundary of the shielded enclosure. I don't believe you can do it centrally. The more I think about it, the less convinced I am that this was a intercept receiving site. If it were, why was it abandoned? Surely NSA does not have less need for that sort of thing in the post-cold war era? And why put one in North Carolina? It may have been a site for operational control of NSA satellites. The large antennae and secluded location would make jamming more difficult. The dual systems and self-contained power would insure high availability and the shielding and fibre optics might also be directed to EMP protection. The 1995 abandonment might have been due to a realization that NSA could safely share satellite control facilities with other DOD satellite owners, once the money-is-no-object era ended. It would be fun to take a tour! It looks like those RF astronomers would be willing, if you shut your cell phone off while visiting :-), though likely miffed that you're more interested in the facility than in the astronomy... - Another possibility is that they were so freaked by the static sensitivity of early MOS devices that they grounded the carpets...
Re: NSA abandons some cool stuff
At 01:27 PM 1/7/01 -0500, Arnold G. Reinhold wrote: "Every inch of floor in more than four buildings was covered with two-by-two-foot squares of bleak brown carpet. When the astronomers tried to replace it, they discovered it was welded with tiny metal fibers to the floor. The result, they eventually realized, is that the rugs prevent the buildings from conducting static electricity. Even the regular lighting looks different, covered by sleek metal grids that prevent the light bulbs from giving off static interference. " Sounds more like TEMPEST shielding. It resembles TEMPEST, but shielding works both ways. The spooks chose the site because it was RF quiet, but had to run their computers in the same area as sensitive dishes. It makes sense that the shielding was to quiet their own emissions to help their receiving. After all, fluorescent bulbs don't leak much intelligence :-) but they sure cause electrical noise. You may be right about their concern being to prevent interference with their listening equipment, but I don't agree with your last point. As I understand it, all electrical wiring coming out of a TEMPEST enclosure has to be carefully (and expensively) filtered. The power wiring to lighting fixtures can pick up and re-radiate compromising signals. By shielding the fixtures, they effectively place the lights outside of the enclosure. I'll bet the wiring to those fixtures is within carefully grounded conduit. It would be fun to take a tour! Arnold Reinhold
Re: NSA abandons some cool stuff
At 07:51 PM 1/8/01 -0500, Arnold G. Reinhold wrote: After all, fluorescent bulbs don't leak much intelligence :-) but they sure cause electrical noise. You may be right about their concern being to prevent interference with their listening equipment, but I don't agree with your last point. As I understand it, all electrical wiring coming out of a TEMPEST enclosure has to be carefully (and expensively) filtered. The power wiring to lighting fixtures can pick up and re-radiate compromising signals. Yes. By shielding the fixtures, they effectively place the lights outside of the enclosure. Yes. But 1. you'd still want a filter the power mains inside your physically secured zone 2. The site had a generator... and presumably a guarded perimeter (think 1/R^2) so emissions were probably less important than listening sensitivity... I'll bet the wiring to those fixtures is within carefully grounded conduit. Building codes often require this, anyway, though probably not grounded to the extent of someone concerned with emissions. Again, it makes much more sense (cost, number of items to check periodically) to put isolation centrally. It would be fun to take a tour! It looks like those RF astronomers would be willing, if you shut your cell phone off while visiting :-), though likely miffed that you're more interested in the facility than in the astronomy... - Another possibility is that they were so freaked by the static sensitivity of early MOS devices that they grounded the carpets...
Re: NSA abandons some cool stuff
At 01:27 PM 1/7/01 -0500, Arnold G. Reinhold wrote: "Every inch of floor in more than four buildings was covered with two-by-two-foot squares of bleak brown carpet. When the astronomers tried to replace it, they discovered it was welded with tiny metal fibers to the floor. The result, they eventually realized, is that the rugs prevent the buildings from conducting static electricity. Even the regular lighting looks different, covered by sleek metal grids that prevent the light bulbs from giving off static interference. " Sounds more like TEMPEST shielding. It resembles TEMPEST, but shielding works both ways. The spooks chose the site because it was RF quiet, but had to run their computers in the same area as sensitive dishes. It makes sense that the shielding was to quiet their own emissions to help their receiving. After all, fluorescent bulbs don't leak much intelligence :-) but they sure cause electrical noise. I'd bet the large amount of fiber that was reported was also used for that reason.
