100 to 200 feet at night? barely less than a wingspan?
dicey enough during the day.
well, it’s a theory!
With the transponder off they can flash their weather radar within 25 miles or so to get a skin-paint range estimate.
And a portable ADS-B receiver might prove useful for that purpose, and for ID of who they're joining up with. The call sign will be their clue to the destination.