Another Rhode Island National Guard unit is heading to Afghanistan. A send-off ceremony was held Sunday for the 169th Military Police Company, which is based in Warren. Captain Michael Calcagni said the unit has been in training for 10 months. It will depart later in the week for Camp Shelby in Mississippi and will head overseas in about a month. The 150 soldiers from the 169th are scheduled to spend 10 months in Afghanistan and will be responsible for providing security at military facilities and guarding prisoners. The same unit had been deployed in Iraq in 2007 and 2008.