In Akash Mk1S the newly added active radar seeker works in conjunction with the original command guidance module retained from Akash Mk1.
The RPF ( radio proximity fuze ) receiver antenna which was in the nose of the missile was replaced with the Ku band active radar seeker . A new miniaturised and modified RPF antenna was placed behind the seeker which can be seen in the form of 2 new antennas protruding from the airframe.
I now present a general idea on how the dual guidance of Akash Mk1S works.
Case 1. Either standalone with command guidance only.
Case 2. Either standalone with active radar seeker only ( LOBL )
Case 3. combined guidance , initially with command guidance and than handover to active radar guidance in terminal stage. ( LOAL )
Case 1 :
When the akash is launched initially it will be command guided and if conditions permit , akash will enter end game manuvers with command guidence only. This offers guaranteed kill probability if the target is within LOS ( line of sight ) of the Rajendra guidance radar . It is very difficult to jam a GBR ( ground based radar ) compared to jamming of an onboard radar seeker. Also if for whatever reasons ( like airborne jamming or EW ) the onboard radar seeker is not able to or fails to acquire and lock on its target, command guidance will guide the missile to the target.
Case 2 :
Again depending on real time operational requirements
1. If the target is within the range of the onboard radar seeker, the seeker will lock on the target before launch . This is same as LOBL ( lock on before launch ) , it allows for faster engagement of the target provided the target is within the onboard seeker range.
2. If the Rajendra radar at any point of time detects it is in the danger of losing target lock due to action by airborne jammers/ECMs etc or is in the danger of being fired on by ARMs ( anti radiation missiles ), the GBR will switch off. The last known command guidance inputs preserved in the onboard computer of the missile will take the missile within the precalculated/anticipated zone where the onboard RF seeker will be activated to begin search for the target and initiate target lock for autonomous homing ie the onboard memory module preserves the previous command guidance inputs and the guidance algorithms calculates the intercept trajectory based on them which will guide the missile close to the target where the RF seeker can be switched on to search and lock on its target.
Case 3 :
Again depending on real time operational requirements
The missile will be launched and command guided from the GBR to take the missile to the optimal intercept point where the NEZ ( no escape zone ) of the missile is highest possible. And from within this NEZ the onboard radar seeker will be switch on to acquire and lock on the target in minimum time and with near 100% guaranteed lock . This will ensure the highest KP ( kill probability ) . This mode is similar to LOAL ( lock on after launch ) .
Conclusion :
One must realise onboard seeker must be within a predesignated distance from the target before it can successfully search locate and lock on its target with high kill probability. The closer the seeker is to its target before switching on, the higher is its ability to positively acquire and lock on its target and hence higher is the missile kill probability.
Rough analogue will be mid course guidance which must be provided first to take the missile close to the target so that the onboard seeker can come into play for guaranteed target kill.
Here Akash Mk1S command guidance comes into play both for mid course guidance as well as for end game guidance, with the added benefit that the onboard active radar seeker takes over the end game guidance if the command guidance is terminated after mid course guidance phase (or even earlier ) due to adverse conditions or enemy countermeasures. Additionally even without involving the command guidance ( ie the rajendra fire control radar ) the missile can be launched with the help of the onboard active radar seeker in LOBL mode.
In my knowledge Akash Mk1S is the only missile in the world with such unique guidance capabilities. Hopefully they will increase its range to 45 km by simply replacing the current propellant with the Al based propellant ( fuel rich propellant ) , already developed and tested by iit Madras team.
Note : anybody wanting to use it , feel free to use , just give the due credit .
