They Knew That He Was Coming

The Fleet Of Stars.

When download Guthrie arrives in the Alpha Centaurian system thirty years after leaving Beta Hydri:

"They were expecting him. The laser beam bearing the word had left Amaterasu shortly before he did, and would have arrived about three Earth-years ago. He wasn't much off his ETA, either; and till just lately, his speed had raised a shout in the interplanetary medium. The ship wasn't big, and her mass tanks were nearly empty, but probably optics were registering her, and maybe, by now, gravitics." (p. 26)

The laser beam should have been detected three years previously and, even if it was not, he should have become visible and possibly also gravitationally detectable by now. And, indeed, he is immediately greeted.

When Guthrie remarks that:

"'Dialogue's kind of slow and awkward across light-years.'" (3, p. 32)

- Jendaire responds:

"'Truly the waiting for you grew long... Also to me, who am not young.'" (ibid.)

So the Centaurian Lunarians did receive that laser message. But the waiting was for three years, not for thirty. They could not possibly have known that he was en route before they had received the message.

Similarly when, after another thirty-five years, he arrives at Sol:

"By agreement, the Centaurians had beamed an encrypted update to overtake Dagny a little earlier than now." (17, p. 211)

Again, he is greeted on arrival and asked who he is. He replies:

"'Come off it, amigo. You know damn well who I am. I'd guess your honchos have been expecting me since before you were born.'" (p. 212)

Two observations:

(i) The update seems to have been aimed at Guthrie himself. First, it is "encrypted." Secondly, we are told that its news is, of necessity, "...four and a third years old..." (p. 211)

(ii) Even if the arrival of the update had alerted the Proserpinans to Guthrie's approach, it could have given them only very short notice of his arrival so why does he claimed that he must have been expected for decades? 

The Proserpinans know that Guthrie led the exodus and that, if anyone were to come back some time, then it would probably be him. But that's it.