Fresh searches for one of the IRA's so-called Disappeared are to start in Co Meath within days.
Specialist forensic investigators are preparing to search a bog at Oristown for the remains of Brendan Megraw who vanished in April 1978.
The 23-year-old newlywed from west Belfast was among 17 people abducted, murdered and secretly buried by republicans between 1972 and 2003.
Geoff Knupfer from the Independent Commission for the Location of Victims' Remains, the body set up jointly by the British and Irish governments, said they face a mammoth job.
He said: "No one, least of all Brendan's family, is under any illusion that this is anything other than a huge task.
"But, with the right information, we are confident that we can find Brendan."
Three unsuccessful searches covering 10 acres of Oristown bogland have already been carried out for Mr Megraw, the most recent of which was in 2010.
Forensic archeologists will use ground penetrating radar to try and identify anomalies beneath the surface that may warrant further investigation.
The new search will cover 2.5 hectares (about 5.5 acres) of land not previously analysed.
Mr Knupfer added: "The ICLVR does not carry out speculative operations. We are entirely information led."
Mr Megraw, from Twinbrook, was looking forward to the birth of his first child and was due to start a new job on a ship when he went missing in April 36 years ago.
The IRA claimed he had confessed to being a British provocateur and Military Reaction Force undercover agent in 1978.
The ICVLR was established in 1999 after the Good Friday Agreement and is acknowledged as a world leader in the search and recovery of human remains from bogland.
The remains of ten people, including mother-of-10 Jean McConville, have been recovered but the bodies of seven others have yet to be found.
Others missing include Joe Lynskey, a former Cistercian monk from West Belfast, Captain Robert Nairac of the SAS, and 19-year-old Columba McVeigh from Dungannon, Co Tyrone.
Sinn Féin president Gerry Adams led appeals for information in finding the bodies.
As well as Mr Megraw, at least two other bodies are thought to be buried in Co Meath. Kevin McKee and Seamus Wright were taken from West Belfast in 1972 and searches have been carried out at Wilkinstown, a short distance from Oristown.
The Bishop of Meath Dr Michael Smith has previously led prayers for the Disappeared at the site at Oristown and appealed for fresh information.