Good attempt to explain the need for sensitivity in KKV, but u miscalcuated the 'miss distance'.
Forward 'closing' velocity and the lateral velocity are not the same
If IIR seeker is of higher resolution, that would facilitate a more accurate trajectory then a lower 'reaction' time (via the divert thursters) may suffice - because the KKV would put itself in the precise trajectory of the target, that may not require too many last millisecond corrections.
I didn't miscalculate anything. I had never said lateral velocity is equal to closing velocity.
The miss distance figure of 10 metres that I had quoted isn't lateral motion.
Having said that, yes if one uses a higher resolution FPA, then the kinetic kill vehicle will be able to make precise corrections to its path from a good distance away and hence a divert altitude control system with a less than millisecond accuracy won't be needed.
BUT this is possible only for satellites that follow a fixed predictable trajectory.
Let us consider a maneuvering RV. Which alters it's trajectory every now and then while traveling towards the same general direction. Then no matter how high your IIR seeker resolution is, the KKV will have to adjust its course accordingly until the point of impact. Because the RV itself isn't following a ballistic predictable trajectory but it's changing course to complicate ballistic missile defenses. The last stage of any ballistic missile which has the RV also has a post boost control system PBCS most of the time. It is through this, that the last stage can make course corrections even before the RV is deployed.
Hence to intercept a maneuvering RV with a high degree of Pk or an ICBM in its mid course, you need a kv with a Divert attitude control system having less than a millisecond accuracy.
This same setup can also be used to intercept a Post boost glide vehicle (PBG) ie HGV like the Chinese DF-ZF before it comes even close to its destination
If you look at the DRDO clip on Mission Shakti and pay attention to the details, you will find that the Kinetic kill vehicle has altered its course/made some final adjustments atleast 6-7 times in the very last second of its flight. You can see the target lock ON rectangular blue box on the satellite shifting a no of times in the last sec of the KKV flight. That is even in the final moments, the KKV is fine tuning its approach to guarantee a direct hit.
That portion of the video showing the final moments before the hit has been slowed down for the viewers so that we can keep a track of things.
Having said that, we have used a Constant Bearing Decreasing Range (CBDR) approach in this Mission. In this, the KKV moves in a such a manner that the IIR seeker always has the target satellite / RE entry vehicle in its field of view. This is made possible by constant corrections by the Divert and altitude control thrusters. Initially, he KKV is moving in a particular direction but the onboard IR seeker is looking at a slightly offset direction so that it has the target in its sight from very early on. In this way, the seeker can make adjustments and fine tune its approach from a great distance away and ensure a direct hit.
An advantage of the Constant bearing decreasing range approach is that you won't be requiring a seeker with a very large field of view since the KKV is itself positioned to ensure that the target is always in the IIR seeker cross hairs.
This approach has also been used in Operation Burnt Frost.