The IRST issue is an interesting one. I don't think anyone has quoted an official, unclassified range for any IRST, which in any event would need to be qualified for target size and thermal signature - which is affected by speed, altitude and propulsion mode - not to mention altitude and weather. There are also IR suppressive coatings and (at least in theory) the ability to cool things. However, IRST has presumably improved with time (physics not, processing yes) and has its advantages.
There have been some quotes that suggested a range of ~80nm for a fighter sized object (this was quite a while back now, So I assume that PIRATE has changed a little bit).
It all depends on the conditions, and its also been said the Pirate system has picked up Venus
, so range is rather dependent on the objects tempreture and its background context.
Are there any public domain pictures taken from a pirate sensor?