These aircraft have now become very important to any force nowadays.
added to all these ESM Functions, A New role SAR Mapping has become very important.
There are only two Aircraft dedicated to SAR mapping are US E-8 JSTARS & UK Astor Aircraft.
Their job is to search, detect, track Ground targets, including small vehicles, tanks etc and send the information to Fighter immediately for targeting.
And These Aircraft with powerful radars detect even small ground targets hundreds of kilometers away with high precision of less than 1 meter.
Fighters & UAVs Radars have SAR Modes, But they don't have enough range to detect small targets from long distance.
In other words, E-8 JSTARS & ASTOR Aircraft are like AWACS but they detect ground targets instead of airborne targets.
Coming back to ELINT, COMINT Role, Even AWACS Can do job.
But dedicated Platforms with good processing power, threat library is more important.
ELINT Aircraft are very critical nowadays because they can detect any kind radar signals, They process those signals, find out their frequency, the position of platform emitting them, distance etc other factors.
So we can map which radar of enemy operates at which frequency at what position regular, at what time etc
These will be quite helpful in using Anti-Radiation Missiles against Radars coz we have to know the frequency range in which radar operates.
Besides that we can find the gaps between enemy radar coverage, So that our aircraft can penetrate those gaps and attack in surprise.
Almost every Fighter will have some ESM equipment, But the difference between dedicated platforms & fighters is processing power & hardware, endurance etc
Even DRDO is developing a comprehensive ground based ESM System.
Back AF ESM Fleet, there are so many Aircraft in IAF doing this job.
3 GulfStream SR-IIIA
2 or 3 Boeing 737
Seven IAI Astra SPX
3 An-32
2 IL-76
2 Learjet-29
5 HS-748
2 Boeing 707
Navy operates Do-228 equipped with ESM, maritime radar.
little is known abt these Aircraft, IAF prefers to keept them classified