What makes a ship impossible to scan down? And what ships can be set up to do this? Is it still possible to find a ship that is set up this way?
do won [ Editor ]
Target size is calculated as sig radius / sensor strength. The smaller your ship's target size, the harder it is for people to probe you down. Below 1.08012498 no one in game can scan you out.
For an unscannable Tengu handy for low/null-sec missioning you'd need:
Gravimetric Backup Array II (low-slot)
ECCM - Gravimetric II x2 (mid-slots)
And nothing that increases sig radius i.e. MWD usage.
(I would have put this in a comment, but they can't be formatted)