Helina on the other hand needs a heat emanating target....more or less confines its operations to a tank/vehicle that has a running engine!!! So, it's quite limited.
I am sorry but I will strongly disagree ,
Helina IIR seeker's cryogenic cooling unit is used to cool the highly sensitive detectors for sensing even minute heat or infra red signals. This allowed the seeker to discriminate the thermal signatures of its targets in three different thermal scenarios.
1. Thermal differential within the target
2. Thermal differential between the target and the background
3. Surrounding temperature variations.
The inputs from the above 3 are combined and run through complex algorithms to generate a positive thermal image even with a very low thermal contrast of target vis a vis the background , vis a vis the different portions of the target itself, etc to the tune of a mere 0.2 degree Celsius.
So the helina seeker is capable enough to achieve lock on a target tank due to the thermal variations within the different portions of the tank itself eg between tank turret, tank barrel, tank track, tank engine compartment ( even when off ) etc and then combining/comparing with the background thermal differential and then again comparing/combining with the surrounding thermal anomalies/hotspots due to presence of the tank itself.