parmentier@iowasp.physics.uiowa.edu (01/22/91)
From: parmentier@iowasp.physics.uiowa.edu In article <1991Jan21.041430.5413@cbnews.att.com>, ar73+@andrew.cmu.edu (Aymerik Renard) writes: > > The B-2 is the stealth bomber. The F-117A is the stealth fighter. > It's also interesting to note that the F-117A can be detected by radars > on some of the Mirage planes. > Stealth technology only allows an aircraft to be invisible to a small range of frequencies. I would think that weather radars would pick up F-117As with little trouble, other than the fact that weather radars would make it very difficult to distinguish the plane from all of the noise. Dean Ing wrote a novel _The Ransom of Black Stealth One_, which while mediocre as a novel had some interesting action and discussion on this topic. Does anyone know the frequencies of the radras of the Mirages in question and the normal frequencies for air radar? -- ___ Gregg Parmentier ____ parmentier@iowasp.physics.uiowa.edu ___ If at first you don't succeed, get a bigger hammer.
fiddler@Eng.Sun.COM (Steve Hix) (01/23/91)
From: fiddler@Eng.Sun.COM (Steve Hix) > From: parmentier@iowasp.physics.uiowa.edu > In article <1991Jan21.041430.5413@cbnews.att.com>, ar73+@andrew.cmu.edu (Aymerik Renard) writes: > > The B-2 is the stealth bomber. The F-117A is the stealth fighter. > > It's also interesting to note that the F-117A can be detected by radars > > on some of the Mirage planes. Heard a report that the Saudi's were tickled pink that one of their new French radars was clearly picking up F-117's. At least until they were told that they were getting it because the 117's were either using transponders or radar reflectors to avoid mid-airs during the training operations before the fighting started. According to the report, when hostilities commenced, the 117's disappeared again. > Stealth technology only allows an aircraft to be invisible to a > small range of frequencies. One of Lockheed's methods used on the F-117 was to shape it so that radar hitting it would be reflected back in sharply-defined directions. Radar units get returns from them, but rarely returns to the radar unit sending the signal. The returns they do get tend to be brief "sparkles", and some equipment filters out such returns as noise. -- ------------ The only drawback with morning is that it comes at such an inconvenient time of day. ------------
lang@hpfcso.fc.hp.com (John J. Lang) (01/27/91)
From: lang@hpfcso.fc.hp.com (John J. Lang) I don't know about what kinds of radars may be able to see a Stealth, but I did see a reference in a recent USNI Proceedings that a Navy experimental(?) satellite was able to locate a Stealth fighter based on IR detection. I can find the reference if anyone is interested. It did not provide much detail though. John Lang lang@hpfcla.fc.hp.com HP-GTD Fort Collins
rakoczynskij@ncar.UCAR.EDU (Jurek Rakoczynski) (02/04/91)
From: asuvax!gtephx!rakoczynskij@ncar.UCAR.EDU (Jurek Rakoczynski)
Since someone else has also raised the question of stealth detection, I
would like to repost a question I had asked a few months ago with no
response:
Does anyone know anything more about an advancement in radar image
processing that could track the B2 bomber and other stealth plane.
I remember a report on the TV news that a few weeks after the rollout of the
B2 for it's 1st flight, the Australian (some organization?) released
information that they had developed a new algorithm that would look for
counter-rotating vortices (from the wing tips) in the echo returns to
identify a plane in flight. This would negate any current stealth technology
used on B2 and other planes.
Here's some guesses/assumptions on my part:
1. In IEEE Spectrum dated July 1990, article 'Looking over the horizon',
discusses over-the-horizon radar. In there is a brief portion discussing the
Australian Defense Science Technology Organization experimenting with it's
Jindalee radar. It is in quasi-operational status and is part of a future
network of High Frequency Over the Horizon (HF OTH) radar. The US provided
considerable assistance in the early stages of Jindalee.
"For several years now, the Jindalee has also provided the Australian
weather services with data on sea surface winds based on examination of the
spectrum of the sea echo. Wind direction data derived from the U.S. Navy's
Rothr (Relocatable OTH Radar) has been shown to compare favorably with Fleet
Numerical predictions."
2. Assuming conventional radar is used measure the doppler shift of water
droplets in a storm to track wind velocity, HF OTH may also be able to
detect this. (I think Clear Air Turbulence-CAT is typically tracked with
infrared.)
3. The exhaust of a jet plane adds alot of moisture in the air which would
probably mix well with the vortex to reflect radar pulses.
4. As long as the vortex is not perpendicular to the radar beam, some
doppler shift should be measurable.
5. I didn't think the resolution of HF OTH radar could identify 2 counter-
rotating vortices say 100 feet apart.
Does anyone have any other info on this or other means of tracking stealth
planes.
--
UUCP: {ncar!noao!asuvax | uunet!zardoz!hrc | att}!gtephx!rakoczynskij
Inet: gtephx!rakoczynskij@asuvax.eas.asu.edu
Voice: +1 602 581 4867 Fax: +1 602 582 7111