A Dambuster Distinguished Flying Cross medal will sell on December 15 to raise funds for a dam project in Uganda.
The lot carries an estimate of £30,000-40,000 ($45,389-60,519) ahead of the auction at Morton & Eden in London.
Hopgood was killed during the mission in May 1943
It was awarded to flight lieutenant John Vere Hopgood, who piloted one of the Lancaster bombers. He was killed during the operation.
The Distinguished Flying Cross includes a 1943 bar and was awarded posthumously. It has remained in Hopgood's family ever since.
David Kirk of the auction house told the BBC: "Flight Lieutenant Hopgood's family has agonized over the decision to part with the medal but feel that John Hopgood himself would approve.
"He was evidently a very thoughtful and idealistic young man who, we believe, would be glad to know that the proceeds from the sale of his medal will go towards the building of a much-needed sand dam to benefit thousands of people in Uganda."
Dambuster medals have sold for significant sums at auction in recent years. One pair presented to flight lieutenant Richard Dacre Trevor-Roper made £148,000 in March this year.
Les Munro, the last surviving Dambuster, recently sold his medals for £75,000 ($111,613). He donated the money to the RAF Benevolent Fund.
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