Tracking what? When on a stealth mission, stealth planes do as much to minimize their own electronic emissions as they do to reflect, absorb, and avoid radar.
This link is I think an original press release from when the cellular interference detection methods were announced.
http://www.globalsecurity.org/org/news/2001/e20010619stealths.htm
and this link describes how it works, complete with a nifty little diagram:
http://www.roke.co.uk/sensors/stealth/cell_phone_radar_concept.asp
This is hearsay, but:
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A few years ago, I remember hearing that the US built a climate-controlled hangar to store all of the stealths in Utah, because it’s so dry. They had previously been deployed around the world, but were requiring too much maintenance.
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Apparently, when the stealths were still being tested, designers were frustrated because the low radar profile was being disrupted, and they couldn’t figure out why. Eventually, they determined that it was the pilot’s head that was bouncing the radar signal back, so a special helmet was developed.
Oooh, you rotter, I was just about to come in here and point out that Roke came up with that, and that I was working for them when they did. 
Then in much smaller text I planned to casually mention that I had nothing to do with it whatsoever…
The F-117 and B-2 have an indium-tin-oxide film on the cockpit canopy and windscreen to make the glass reflect radar waves, so that they don’t enter the cockpit and reflect back randomly from the pilot’s helmet and other interior bits. This allows the reflection to be controlled and bounced in the desired direction.
One thing I never quite understood was the way folks would describe a stealth plane’s radar cross-section (or reflectance, or whatever the appropriate term is) as “no bigger than a bird’s” under certain conditions.
So, the thing I always wondered is, if I’m a radar operator and I see a freaking bird flying at 500 MPH across my screen, isn’t that going to be a red flag?
Clearly, that’s not an issue in real life, so what part of the puzzle am I missing?
All operational B-2’s are based at Whiteman AFB in Missouri and fly combat missions from there. All operational F-117’s are based at Holloman AFB in New Mexico, but are redeployed closer to the war when needed.
Malice, the idea is that you wouldn’t notice a bird’s eye even if your equipment were sensitive enough.
The Bosnian Serbs were helped immensely by the fact that an F-117 was sent over the location every day at the same time, the same altitude, and the same direction. Also, even if the plane doesn’t reflect much radar energy, you can see it, you can hear it (hoo boy, can you hear it), and it can’t maneuver its way out of a paper bag.
An old girlfriend’s brother was an F-16 fighter jock stationed out of Ogden, Utah. One of his duties was, quite literally, to take fighters out and beat the hell out of them on a periodic basis. This was mostly done for reliability testing, and because he was a superior pilot, he had superior fighter-abusing skills.
This sorta-test-pilot status gave him the opportunity to get to know some F-117 pilots, and even poke around the planes himself (though he did not fly them). This was maybe a year before the loss of the plane in Bosnia, and he predicted back then with rather uncanny accuracy one would be shot down during the day. Slow and unstable; that summed up his assessment of the stealth “fighter”. He had a very low oppinion of the F-117 as anything but a light nighttime bomber, and even then he couldn’t see why his plane couldn’t do the job of the F-117 with reasonable effectiveness in nighttime sorties. In other words, he thought the thing was a waste of money, given how rare losses of conventional supersonic fighters and fighter-bombers were in the theaters of operation the US was now flying in.
Here’s a way it was presented to me that helped clear up the picture in my mind. First of all, you’re not seeing a continuous image on a radar screen-it’s updated periodically as the radar pulses are sent out and returned. So you don’t see a moving object-just a dot, that’s replaced by another dot, then by another, with that sequence moving across your screen at a scale 500 MPH. (Of course, that’s always true with a CRT image, but a radar image isn’t updated 24 times per second like the one on your TV screen.)
Now, tune your receiver so that it shows objects with bird-sized radar cross-sections. What do you see? Eight million and one dots, representing the eight million birds in your radar’s sweep area plus the one stealth bomber. Which are replaced by another eight million and one dots, then again … Can you pick out the one dot that’s moving 500 miles per hour against that backdrop? Or even tell if there is one?
This is where the computer power issues that Triskadecamus mentioned come into play. A powerful enough computer can pick that out, and you can have it control the radar display to only show, say, birds with airspeeds of over 100 knots. That’s too fast for a bird to fly, but below the stall speed for a stealth bomber …
Good explanation, SCSimmons. To expand on that, the radar actually measures speed in two different ways. There’s the range rate which is what was described above. You look at how far the blip has moved between updates, and calculate the speed based on that.
There’s also the Doppler rate which looks at how the frequency of the echo has shifted due to the aircraft’s speed.
Both speed measurements are important. Radars compare the two to help distinguish targets from clutter.
Perhaps a bit more about the nature of radar interception, and computer enhancement of radar capabilities would be of value.
The old time movie standard of a CRT with a green line sweeping around leaving behind bright green dots is a fairly old concept. The current wave of radars present a far different and more tactically useful display, which does come from the same sort of sources as the old one, but with added information from newer radar technologies. All this information is controlled by computers, which almost completely insulate the operator from the sweep of that beam.
For the most part, this is a very important characteristic. It isn’t only birds that throw back detectable radar signals. New radars are able to detect reflected signals from differences in the temperature, and wind speed and direction of clear air. Clouds, rain, dust, all of it can be “seen” by modern radar. The fact is that most air defense interceptor operators see text tags on their screens, giving important information about velocity and heading of targets, and automatic warnings in color, or sound for “suspicious” or unidentified sources of reflection. And now days, we can sweep that sucker back and forth over the same target a lot faster.
That also happens to be the main reason that Air Force descriptions of UFOs “sighted” during radar operations are not actual sightings of anything at all. A ripple of air pressure can move at the speed of sound, and under some conditions, a radar will report that as an unidentified target, possibly an aircraft. When the pressure wave bounces off a cold air mass, and then travels backward at the speed of sound, it looks like a space ship. Only air defense folks know that sort of stuff happens all the time.
They still scramble fighters, though.
So, the stealth plane requires you to set your “acceptable level” of return for a target very low. Since you set it low, you get lots more targets. Most of them are not stealth aircraft. Most of them are natural phenomena, or unusual reflections of radar from other aircraft. (Very sensitive reception can see a reflection from an already reflected high power radar as a second target.) In war time, a large number of them are probably targets provided by the enemy for no reason other than to saturate your radar abilities.
So, when you are trying to decide how sensitive your want your radar to be, you have to keep in mind the dollar cost of every false image you report. In combat, that also means you are using war resources for trivial targets, and may not have assets in the air when you need them.
The biggest effect in strategic military terms of ongoing stealth development is to increase the cost of air defense for the enemy. The cost includes money, manpower, ordinance, and morale.
And that all happens before you actually fly the damned plane!
But, arms races are never really over. Someone will figure out stealth, and then stealth planes will be like a guy with a black stocking mask in a department store. Maybe you don’t know who it is, but you know he ain’t a “friendly.”
Tris