[c_of_red]

AFAIK, helios don't see things ( observe, search) as well as leg units. Sort of between a ground vehicle and a leg unit. Or at least that is the way the original SP2 worked. Not sure if that was changed or not during the port to windoze. What little testing I have done says 'no', but an 'expert' told me I was wrong. I think it is confusion created by the term 'spotting'. which in the real world means seeing something but in the SP world it means calling artillery and nothing else. I suppose that helps keep the confusion level down, at least if everyone is aware of the jargon.
A thread at the blitz went past the post limit on this topic. It seems every SP player ( about 15,000 on the 'net, and growing) has an opinion on this topic.
No absolutes in SP. I like to 'hide' my FO's, 2-man scouts, sniper teams and snipers. By hide I mean find a hex with concealment (cover is better, but sometime Mars isn't that helpful), redline your weapons and stay quite as a mouse at an Ally Cat convention. I have had enemy tanks park in the same hex. I have had AH's hovering over an FO while it called in arty.
So you never really know how much of the enemy you are seeing at that moment. Nor do you know how much of your force he can see.
FoW.