Guernsey's Lieutenant Governor, the Queen's representative in the Bailiwick, is due to leave the island on board HMS Daring on Wednesday.
Vice Admiral Sir Fabian Malbon and Lady Malbon will officially leave Government House using the ship's Lynx helicopter.
Weather permitting it will fly over the coasts of Guernsey, Sark and Alderney before landing aboard the ship.
Once aboard the Type 45 destroyer, which is affiliated to Guernsey, they will cross the Channel to Portsmouth.
HMS Daring is passing through island waters after a period of sea training and her Captain Guy Robinson said he felt it was appropriate Sir Fabian and his wife should travel back to the UK on board.
Members of the public have been invited to join official guests, the couple's friends and representatives of their various patronages in saying farewell.
However, islanders have been warned that parking is not available for the event, which is due to underway at 1230 GMT.
Sir Fabian's replacement, Air Marshal Peter Walker, is due to take up the post in April.