Totoro said:
Fitting two seekers has already been done though, the new standard missile in use with USN has passive radar guidance coupled with an IR seeker. Another way to do it would be putting the IR seeker on the tip of the missile, on the gymbal if you wish, and then make a ring of radar reciever modules around it, little further back.
It is obvious that the IR seeker and radar seeker cannot be turned on at the same time, because in war-conditions they are likely to contradict each other.
Anyway, even if they do not contradict each other, they cannot complement each other either, as only one of the 2 systems is sufficient to guide the missile towards the target.
The Arrow 2 missile of Israel has this technology :
The missile has a dual mode seeker with a passive infrared seeker for the tracking of tactical ballistic missiles and an active radar seeker used to home on air breathing targets at low altitudes.
Source:
The advantage of turning the radar seeker at the end in this case is to home-on ramjet targets that are cruising at a low altitude. It may be that the heat signatures at this stage may be insufficient.
The example of the USN missile as mentioned above, is the Raytheon AM-2MR Block 3, whose details are as follows:
SM-2MR Block III introduced an improved MK 45 MOD 9 TDD (Target Detecting Device) for better performance against low-altitude targets. Block III A has a new MK 125 warhead with heavier grain explosive, and
Block III B (for Aegis/VLS only) incorporates an MHIP (Missile Homing Improvement Program) combined radar/IR seeker for terminal homing. The IR sensor is in a side fairing of the missile. The MHIP seeker was also intended for the cancelled AIM/RIM-7R Sparrow missile. The designation RIM-66K applies to Tartar system missiles (RIM-66K-1 Block III, RIM-66K-2 Block III A), RIM-66L is the Aegis missile (RIM-66L-1 Block III, RIM-66L-2 Block III A), and RIM-66M is the Aegis missile for the MK 41 VLS (RIM-66M-1 Block III, RIM-66M-2 Block III A, RIM-66M-5 Block III B). Block III production began in 1988, with the Block III A following in 1991. Blocks III A and B are the current production versions.
Source:
A recent BMD missile project called Aegis BMD Block 2004 also has similar technology :
In FY03, the operational robustness of the Aegis BMD Block 2004 test program was enhanced by increased operational realism in the test strategy.
some important operational scenarios remain untested by the end of the Block 2004 test program. These include multiple simultaneous engagements and separating targets.
Development and integration of critical technologies pertaining to threat discrimination (e.g., AWS discrimination logic, radar and infrared seeker upgrades) and missile propulsion (e.g., kinetic warhead divert system, SM-3 booster propulsion) could improve operational capability as they are introduced in Block 2004 and subsequent upgrades.
Source:
