Jesus' ascension is customarily considered from the vantage point of earth, as we have recorded in the accounts in Acts 1, St. Luke 24, and St. Mark 16.
But there is also a heavenly vantage point from which this event may be considered, namely the perspective of the holy angels. This is what is seen in the 24th Psalm, in which the angels are heard calling to one another. The herald call, "Lift up your heads, O ye gates; and be ye lift up, ye everlasting doors; and the King of glory shall come in" is greeted with incredulity by the reply, "Who is this King of glory?" For what the second group of angels see is the approach of a man. Hence the first replies, "The Lord strong and mighty, the Lord mighty in battle," and repeats the command, "Lift up your heads, O ye gates; even lift them up, ye everlasting doors; and the King of glory shall come in." But reply is repeated, as it is scarcely to be believed, even by angels: "Who is this King of glory?" And the herald insists, "The Lord of hosts, he is the King of glory."
Another perspective is that of the prophet Isaiah, who in his well-known vision is seeing this same event, namely Jesus' ascension: "I saw also the Lord sitting upon a throne, high and lifted up, and his train filled the temple" (the angels present are clearly the very angels whose conversation is the substance of Psalm 24, above, recorded here as "Holy, holy, holy, etc.").
And in today's Gospel, Jesus declares that he will send the Spirit and these apostles, which is one and the same sending. That is to say, through the same heavenly portal through which he ascends, the Spirit descends, and flows out through the mouths and preaching of the apostolic band. The preaching of the Gospel is the result of the sending of the Spirit, something that is writ large on Pentecost Day.
But the channel between earth and heaven (which can also be called Jacob's ladder) remains open, and the people of God who receive the Gospel and mercy of God may confidently expect that they, too, shall ascend to the right hand of God. For their flesh and blood is already there in the person of Jesus, as the hymn writer puts it: "Thou hast raised our human nature on the clouds to God's right hand. There we sit in heav'nly places, there with Thee in glory stand. Jesus reigns, adored by angels, man with God is on the throne. Mighty Lord, in Thine ascension we by faith behold our own."
So let us with heart and mind thither ascend. And we do this whenever we sing the Sanctus, which comes out of Isaiah's vision of the Ascension. And when we then immediately receive the Body and Blood of Christ, these come down to us also, through the Spirit, from the right hand of God. We become partakers of the divine nature.