The SA-16 Albatross came from Mombassa and was flown and operated by Pan-Am!! The ground engineer was from the UK?? I use to chat with them when passing through Mombassa with a Comet on the way to Nairobi.
As you said the runway was being built, and long before that the Albatross was the only way to get there by air. As you said it was to supply the tracking station on the island.
Brian.