Astronauts Vande Hei and Acaba at the Arlington National Cemeter

Tim Frank describes the history of the Tomb Guard to NASA astronauts Mark Vande Hei, left, and Joe Acaba, center, Friday, June 15, 2018 at Arlington National Cemetery in Arlington, Va. Photo Credit: (NASA/Aubrey Gemignani)

Tim Frank describes the history of the Tomb Guard to NASA astronauts Mark Vande Hei, left, and Joe Acaba, center, Friday, June 15, 2018 at Arlington National Cemetery in Arlington, Va. Photo Credit: (NASA/Aubrey Gemignani)

ArlingtonArlington National CemeteryExpedition 54Expedition 54 PostflightJoe AcabaMark Vande HeiTim FrankTomb of the UnknownsUSAVirginia