So, this stuff is obviously not perfectly documented, but this is how I believe functions currently. Raid assessment (the details are available online) is using some radar magic to change the actual radar processing and try to break out if there are multiple returns near one of the targets. (Helps break out a formation for example). In contrast, EXP mode doesn't do anything to the radar or the mission computer track files and it simply zooms in on the display. The APG-73 has a few different type of raid modes.
1.) SCAN RAID: This is available in TWS if you have an L&S designated, and it concentrates on the L&S with a 10nm zoomed in area at 22 degrees of azimuth. If you designate a different L&S, you move the raid area. You can enable it with the SCAN RAID/FOV/HARM button on the throttle.
2.) 1LOOK RAID: This is an automatic function when you're in STT, it's available when boxed, and it looks for targets near the STT track and produces trackfiles for them.
3.) SAM mode: I unfortunately don't know for sure what this does, the documentation I have doesn't describe its functionality, other than noting that it's an option for RAID assessment in STT.
Now, so far this is stuff that I'm reasonably certain to be correct. My speculation is that when you press the raid button in STT, you go to the 'STT raid mode', now calling this SAM mode would make sense, since this has a TWS scanning function interleaved with an STT tracking function. I believe that when using this function, you can have an 'STT' track on two different targets at least and you can have multiple L&S designated at the same time(based on the document), but I'm not entirely sure. The functionality of this mode in DCS seems to be fairly finnicky at the moment, when I was testing it sometimes it messed up my radar and I had to reset, so further testing is definitely required.
