Regarding radars used in anti-missile defense

[bobus67]

Hi guys,

As the ground radar and tracking mechanism guide a missile to its target (say a ballistic missile or an aircraft), is it safe to say that the radar is "aware" of the position and velocity vector of both the target and the missile?

Approaching the problem from a noob standpoint, I think that, if that is the case, the ground station can calculate the current distance between missile and target, estimate where the target will be, say, 1sec later, and direct the missile to that location in space (using some complicated but rather straight-forward 3D trigonometry). Then repeat 1sec later, and keep going every 1sec till the missile is close enough to the target (say 1km away) that it can deploy its own infrared seeker and guide itself to the target and its hot exhaust.

The above thought process has to be wrong, otherwise even I could design such a system.

Cheers!

 

[Todjaeger]

Hi guys,

As the ground radar and tracking mechanism guide a missile to its target (say a ballistic missile or an aircraft), is it safe to say that the radar is "aware" of the position and velocity vector of both the target and the missile?

Approaching the problem from a noob standpoint, I think that, if that is the case, the ground station can calculate the current distance between missile and target, estimate where the target will be, say, 1sec later, and direct the missile to that location in space (using some complicated but rather straight-forward 3D trigonometry). Then repeat 1sec later, and keep going every 1sec till the missile is close enough to the target (say 1km away) that it can deploy its own infrared seeker and guide itself to the target and its hot exhaust.

The above thought process has to be wrong, otherwise even I could design such a system.

Cheers!

It seems you are blending two (or more, it depends) systems together.

First, with respect to radar, there are a number of different types of radars which operate on different bands and these radar systems have some different capabilities depending on what type and band it is being used.

Second, you seem to be mixing in some type of targeting and/or fire control system in with the radar. Now there are radars dedicated for use in fire control systems, but that does not seem to be what you were referring to initially. Relating to the targeting/fire control portion, there are actually a number of different ways for GBAD (ground-based air defence) systems to guide SAM's to the target, with there being a number of different potential pros and cons for various methods of guidance.

Lastly, with respect to timing... updates every second when operating in an anti-missile and/or BMD role would likely provide inadequate. For a comparatively old and slow LACM like a TacTom, the inbound missile's position would change by ~250 m every second. For an inbound ballistic missile, that range difference could be 5 km or more every second. This is why missiles with active seekers usually try to be able to detect targets on their own from further out. As a side note, the effectiveness of the seeker can also depend on the type or warhead and fuse in the SAM.

 

[bobus67]

Thanks for answering, to begin with.

Let's take it from the start, i.e. my initial question. Does the GBAD know the position and velocity vector of the target and SAM?

I wrote 1sec as an example. It could be less if necessary. The concept is what I'm asking about, the specifics are secondary. Having said that, the ballistic missile will not swerve, right? So its orbit is rather predictable. Every 1sec the SAM would adjust its course towards the point where the target would be after X seconds, were X= distance (in seconds) between current positions of SAM and target. This would guide the SAM to the "general neighbourhood" of the target, close enough (a few km perhaps?) for the infrared seeker to take over for the final hit phase (I see I didn't explain it clearly in my previous post). I think this methodology would work, IF the position and velocity of the target and SAM are always known to the GBAD.

You talk about SAMs with active seekers. Of what type? Can these operate from, say, 100km out? I know they can work for short distances as in the Stinger, but do they work for long range defense?

Generally if you know of a site that explains these things, it would be terrific. Theoretical stuff or more product-specific, e.g. the Patriot system.

 

[Todjaeger]

The subject itself is actually quite a bit more complicated, simply because there are more systems or subsystems involved.

In order for GBAD systems to engage an aerial target, something needs to first detect the target. The now detected target then needs to be identified as a valid target (as opposed to a Blue Force object or clutter, etc.) and the GBAD system would then need to be cued to the target, preferably with target quality data (position including altitude, velocity, heading/vector, etc.) depending on the detecting system AND the comms/data links in use, that might very well not be possible. If the data is target quality and constantly up to date, then the GBAD system might be able to calculate a plot and launch a missile without even using it's own organic radar systems. OTOH the cuing might be necessary to give the GBAD system an idea of where to look and/or direct their radar systems at, since a number of the GBAD radar systems are directional, and then the organic GBAD radar might be able to provide the needed target quality data so that the on board fire control system can calculate an interception track and then launch.

One of the things to keep in mind is that in order for an interception to be successful, the GBAD system needs to calculate where an aerial target is going, as opposed to 'just' knowing where the target is at a given moment

With missiles, particularly SAM's, there are all types of guidance systems available. Some missiles have active seekers, with IR and ARH (active radar homing) being examples. Other missiles use semi-active homing systems, where the seeker heads towards an "illuminated" target which would be getting 'painted' by another radar and/or laser system, then there are beam riders, and a whole host of other guidance options.

I do not know of a single or specific book or site one could visit to gain a better understanding of the topic, but it might help if one were to chose a specific GBAD missile or platform, and then examine what is involved in the operation of the chosen kit, as well as what the whole unit consists of. By way of example, a S-300PMU 2 SAM unit consists of more than just the missiles and launch vehicle.