Seeker Heads: IR vs. Radar

There is an antenna on the nose. That’s just a pure emitter. There is a first receiver just behind the antenna. And then there is a second receiver right at the tail. The homing systems takes the radar echoes received from both points and makes a comparison. If the signal is stronger in one end or the other, then that is where the target should be.

The rear-facing antenna is used to sample the radar beam that the fighter is using to illuminate the target, so that a semi-active radar seeker can measure the Doppler shift in the return form the target by comparing the frequency of the transmitted and reflected energy.

What would be nice is a datalink that goes between missiles.

For instance you fire the Mica IR and Mica EM, and the Mica EM feeds the radar data to the IR as long as the IR hasn’t found the target on its seeker, and once it has it it can feed the data to the EM in case the plane manages to jam the Mica EM seeker.

Sensor fusion between missile in other words. And probably much easier than to fit several sensors on a single missile. You have to fire two missiles at the same target, but I suspect they already do that more often than not to be sure of a kill don’t they ?

Other advantage is the missles won’t have the same trajectory, so it will be harder to defend against both at the same time. And if launch is simulateous, the Mica IR might go undetected for a while, making it even more dangerous!

Nic

That won’t work. The radar system used in seekers isn’t compatible in producing the kind of information used on mid phase update via datalink. An active missile using CWI and measures-compares signal strength along receiver points, then simply goes to where the signal is the strongest. Its really a very simple system. If you have to have one missile leading another, or a whole bunch of them working autonomously in a network, you need PRF seekers which all going to use up space and two way datalinks. This is more doable on antiship missiles.

If MICA EM uses a datalink in theory, then this datalink has to be fed from a PRF radar from the launching aircraft, and in this case you might as well feed the MICA IR (in theory if you want to fit a data link on it) simultaneously. Fire control systems can guide multiple missiles simultaneously via midphase uplinks. So there is no need for one missile to feed into another. If the MICA EM gets successfully jammed in the first place, it should go into HOJ, meaning it will home in on the source of the emissions that have managed to somehow replicate the complicated waveform it uses, causing the seeker to be spoofed. HOJ by the way, does not go around chasing any other radar emission, jammer or any other ECW source—only the very one that managed to replicate the seeker’s waveform.

What would be nice is a datalink that goes between missiles.

For instance you fire the Mica IR and Mica EM, and the Mica EM feeds the radar data to the IR as long as the IR hasn’t found the target on its seeker, and once it has it it can feed the data to the EM in case the plane manages to jam the Mica EM seeker.

Sensor fusion between missile in other words. And probably much easier than to fit several sensors on a single missile. You have to fire two missiles at the same target, but I suspect they already do that more often than not to be sure of a kill don’t they ?

Other advantage is the missles won’t have the same trajectory, so it will be harder to defend against both at the same time. And if launch is simulateous, the Mica IR might go undetected for a while, making it even more dangerous!

Nic

Lookup JDRADM.

It is the planned replacement for the AMRAAM and HARM family of missiles.

It will have 3 seeker technologies. Active Radar (same as AMRAAM), Passive Radar (same type as harm), and IIR (think AIM-9x).

The hardest part of the missile will be the seeker/fuse. Yes, they will be one in the same to sonserve space. Boeing received a few contacts last year to do dev work on the seeker (SITES)

No. Datalinks tend to be placed in the middle of the missile. You’re talking about a little stub on the airframe, whereas these receivers should be cylindrical around the body. For a homing system to work, you need two positions, and these positions have to have a significant difference in distance because the guidance system works by comparing the signal received from the two positions. If it’s stronger on the A than on B, then the target is closer to A or on the front. If the signal is equal on both, then the target is perpendicular. If its stronger on B, then the target is behind.

The ass antenna is for the datalink, not for the seeker. You wouldn’t want to pipe a GHz signal thru the whole missile body forward to the superhet.

Radar seeker head is quite a misnamed proposition. This is how a radar seeker actually looks.

There is an antenna on the nose. That’s just a pure emitter. There is a first receiver just behind the antenna. And then there is a second receiver right at the tail. The homing systems takes the radar echoes received from both points and makes a comparison. If the signal is stronger in one end or the other, then that is where the target should be.

In contrast an IR seeker is entirely on the nose. There is something like a camera eye that is set on a socket that provides a gimbal movement like your arm joint in your arm socket. The camera follows the target and its movement therefore signals where the missile should follow.

There is some very contrasting working principles here, that does not make it easy to modify one missile to another.

IR seekers work based on the contrast between the target and the background. Long range BVR missiles follow a lofted trajectory and plunge down onto their targets from above. IR seekers have great difficulty picking out a hot target (airplane) from a hot background (earth) at distances that an RF seeker can.

So you want AIM-120 to become another R-27T ?!

Where i said that? Please quote me.

Passive seekers, such as IR or HOJ, do not give range data and therefore requires a more agile missile than AMRAAM. Meteor might be more suitable, but I’m not sure and I have not heard of any plans for any IR seeker for it.

And R-27T goes over 4M so this is not true.

So you want AIM-120 to become another R-27T ?!

IR Seeker generally works well only at low mach speed, but AIM-120 need to speed up to M4. The heat generated will interfere with the heat sensitive IR Seeker.

And R-27T goes over 4M so this is not true.

IR Seeker generally works well only at low mach speed, but AIM-120 need to speed up to M4. The heat generated will interfere with the heat sensitive IR Seeker.

NCADE?