Radar versus Stealth: Passive Radar and the Future of U.S. Military Power

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RedParadize 10/18/2009 2:24:41 AM

ho! yea there is something i really want you explain, cause when i first read it it was a complete mystery for me. Wait i will post them:

Because you can't get a doppler a change of frequency rate if you don't have a signal bearing or signal return that measures speed of the target in a moving three body problem using occultation or background contrast imaging techniques. The standard radar technique is to get a signal return off the object target come back directly on the bearing of the transmitter and use the change in frequency as TIMED by a clock at the transmitter receiver to establish speed.

Also that:

"Signal smear across the wavelength was my point"

well... are you talking about doppler effect here? cause thats not very clear.

Yes it isvery clear.. Doppler is measured as a change in the nature of frequency of the return as interval measured by the comparison against the time of the transmitted signal.

My question is: How can whe predict how planet, star and galaxy move then?

I am prety sure whe never got any return from any transmited signal

I would be happy if you could incorporate the blob detector and the signal smearing in your answer, just to had some colour.

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WarNerd 10/18/2009 3:16:00 AM

Passive radar is still in development, but it seems to have a number of limitations/problems.

The system is NOT mobile. It requires a large fixed array of antennas, a number of independent stationary signal sources that meet specific requirements, and a fair amount of time to calibrate before it becomes fully operational.

It is a search system only, the inherent limits of accuracy and slow updating allow it to guide a missile to the vicinity of the target, but another system must be used for the actual intercept. It may also be limited in it's capability to track very fast targets.

Some systems can get a doppler shift off the target IF they a clean enough signal source.

Some systems have large enough arrays of antennas to use interferometric phase shift techniques to determine range. Others really on triangulation using bearings from multiple systems.

Passive radar is not a panacea and does not look to be practical except as a prepositioned defense system, but in that role at the outbreak of a conflict it may excel. The better it works, the more likely that potential signal sources will be targeted to shut it down. Disposable emitters can help, but will be obvious and easily targeted because of a need for them to be powerful, continuously emitting, and stationary.

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WarNerd 10/18/2009 3:35:49 AM

"Signal smear" effect appears to be a limitation of passive radar systems created by the time sampling of the signals required as part of the reconstruction process. The time sampling is required because the signal sources are non-coherent, and the "signal smear" is due to target motion during the sampling period and is manifested as a larger uncertainty in the targets location and speed.

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WarNerd 10/18/2009 3:55:56 AM

The Serbian shot down a f-117 using a primitive but similar method. Missile used was locally modified SA-3. and thats a old design (1963). They where lucky, no doubt about that. But the technique could be refined and achieve a decent hit probability.

Nope. Serbia shot down that F-117 because they were smart and NATO was dumb.

The F-117's used the same route up a valley to get into Serbia every time. So the Serbians put ground observers at the end of the valley to provide raid warning and then fired the missiles using the backup optical tracker system that is part of the SA-3 system. The real trick was guessing when to launch the missiles so that they would arrive at the correct altitude so the F-117 would trigger the proximity fuse without range data, so they fired a lot of missiles.

So no fancy technology, just bad raid planning, a smart battery commander, and a backup system to simple to jam.

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RedParadize 10/18/2009 11:09:06 AM

Hello WarNerd

Thank you for your post

About the F-117 even over Serbia, I agree, it was a bad plan to send F-117 on predictable path. It does show that low CRS don't negate other Strategic/tactical advantage. Serbia had a number of low tech SA-3. About exactly how they shot down the F-117, there is allot of speculation. I would be very surprise if they got it with time fuse only. It is not impossible that the missile did achieve a lock on at some point.

About passive radar, their accuracy and update date limit depend on the frequency used, and also depend how powerful the signal from transmitters of opportunity is.

I must also say that even if the EASA radar used on the raptor, while being particularly hard to pick, can be detected. EASA broadcasts on a large sets of frequency to avoid the detection. But if you have the ability to scan a large part of the radio spectrum, the EASA radar will become visible. After all the EASA need to emit strong enough to have a echo that can be discriminated from the background noise. In short, it is possible pick a EASA broadcasts if... you have a EASA radar.

I wont be surprise that the EASA radar mounted on the raptor have a passive mode to counter that.

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Slim Pickinz 10/18/2009 10:08:55 PM

Hello WarNerd

Thank you for your post

About passive radar, their accuracy and update date limit depend on the frequency used, and also depend how powerful the signal from transmitters of opportunity is.

I wont be surprise that the EASA radar mounted on the raptor have a passive mode to counter that.

Exactly. If the F-117 flys directly over an SA-3's missile guidance radar, stealth isn't going to mean shit when all the radar sees is a big flat diamond overhead, the missiles won't have a hard time hitting the target at all.

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warpig 10/19/2009 12:25:31 AM

Of course, it didn't literally fly directly over, but being 13km from a LOW BLOW is almost the same thing. Missile guidance radars tend to be high power and quite focused, hence at very short range can get a return from even an LO aircraft, especially at some angles that are better than others. It's not mysterious nor out-of-the-ordinary at all.

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RedParadize 10/19/2009 1:05:30 AM

Hello again Warpig

What you said is pretty much what I have in mind.

As you mentioned before, SPOON REST L-band probably helped to.

Current Stealth technique is only possible because of the lack of diversity of the detector used.

I might be a bit out of the subject, but did you ever ear about the impossibility of stealth in space?

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WarNerd 10/19/2009 5:33:29 AM

The SA-3 missile uses command guidance. The fire control system uses the target tracking radar to tracks both the target and the missile and then sends commands to the missile to steer it on a course to intercept the target. The missile does not have an on board capability to 'lock on' to and track the target the target.

The SA-3 system includes an optical tracker, originally for use if ECM prevented the ground radar from tracking the target, that can feed target direction and angle of elevation into the fire control system, but not range. If the operator then inserts an estimated target elevation the current location can be calculated, add estimates course and speed and the fire control system will project an intercept point and guide the missile to it. The missile is then guided to the projected intercept point using radar tracking of the missile only. It is not very accurate, particularly against a crossing target, but better than nothing.

The warhead can be detonated either by a proximity fuse or on command from the ground.

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warpig 10/19/2009 12:34:49 PM

What you said is pretty much what I have in mind.

As you mentioned before, SPOON REST L-band probably helped to.

Current Stealth technique is only possible because of the lack of diversity of the detector used.

I might be a bit out of the subject, but did you ever ear about the impossibility of stealth in space?

The "current stealth technique" is possible because of the lack of the enemy's ability to create and sustain a significant capability to engage LO aircraft and weapons systems with their own defensive weaponry. In order to "beat" stealth, the enemy has to be able to guide missiles to hit the LO aircraft. In order to do that, their fighters and SAM battalions have to be able to find and track the LO aircraft, and then pass target-quality tracking or otherwise provide for guidance to/of the missiles. In order to do that, their C2 elements--like SAM brigades, fighter direction posts and AEW&C aircraft, and air operations centers--have to be receiving tracking of the LO aircraft so proper command and control can be exercised to defend the enemy airspace. In order to do that, the C2 centers have to receive tracking of the LO aircraft from their air surveillance network. In order to do that, their early warning centers have to be able to track LO aircraft. Until all the above is routinely accomplished, the "current stealth technique" is possible. While there may be ways to occasionally manage to score a lucky kill here and there against LO aircraft (like the F-117 in Serbia) even though all the above conditions may not be met, such random successes are likely to be of little use for anything more than propaganda purposes, and in the meanwhile the bombs will continue to rain down and thus stealth can in no way be said to be "beaten" even then. Furthermore, even after some capability is put in place that may be able to achieve some significant degree of success, it has to be survivable and remain viable in the face of our continued advances in LO itself, and in our development of countermeasures using all the other tools available to us (especially airborne electronic attack and physical SEAD/DEAD).

There are several threads on StrategyPage that talk about multi-static radars. I'm sure if you used the site's search engine and looked for things like "HA-100" "Silent Sentry" "Associative Aperture Synthesis Radar" "bistatic" "bi-static" "multistatic" or "multi-static" you'd find some of them.

For example:

link

There are others.

P.S. SPOON REST is VHF, not L-band.

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