Satan had access to God in heaven in the time of Job. Ay some point he was
cast down and no longer has access to heaven. According to Zec, 3, Satan was there in heaven to accuse the resurrected Jesus before Jesus was justified by God and restored to His former glory and position.
Jesus was speaking prophetically,
Luk 10:18 And he said (εἶπεν δὲ) to them (αὐτοῖς ), I was perceiving (Ἐθεώρουν, imperfect active indicative) the Satan (τὸν Σατανᾶν) as lightning (ὡς ἀστραπὴν) out of the heaven (ἐκ τοῦ οὐρανοῦ) fallen (πεσόντα, aorist active participle).
The aorist form of the verb is timeless. It does not alone establish the time of the event,, There must be other contextual time markers to establish the action at a particular time.
TheOreO means to observe as a spectator. It is in the imperfect tense. It is aorogressive action if the past - I was observing.
pesonta is the aorist active participle of piptO to fall. It does not necessarily mean to be cast out or down. One can fall without being thrown down.
I think Jesus was in a vision in the Spirit observing Satan losing his confidence, losing his footing in heaven, as His disciples were casting out demons and healing those oppressed of the devil. I don'r think Satan was yet (in Luke10:18) cast out of heaven and down to the earth to be limited to the bounds of the earth's atmosphere.