Work on the new radar base at Saxa Vord in Unst is progressing well and could soon be operational, according to the Ministry of Defence (MoD).
The £10 million project will track Russian military aircraft which approach the north of the UK and over the North Sea.
Just last week a Quick Reaction Alert (QRT) operation, which will receive information from the new Unst base, located two Russian Blackjack bombers in the area. Although not actually in UK sovereign airspace, they were intercepted by Typhoons from RAF Lossiemouth.
The MoD said there had been 59 QRA launches in the past five years. The Saxa Vord base would improve RAF and Nato understanding of the airspace north of Britain at a time of increased Russian military activity.
Back in the 1960s and 70s, when around 300 RAF personnel were stationed at Unst, the site was used as an early warning station. However, the new base will be operated remotely.
The site was visited on Friday by Air Chief Marshal Sir Stephen Hillier, the head of the RAF, who paid tribute to the construction team who had been working at Saxa Vord throughout the winter.