Is this court-martial necessary?

This post concerns a case from a few months ago. An Air Force officer has been convicted of accessing child pornography by a federal district court. His sentence could be 20 years and a quarter-million-dollar fine. He is also being prosecuted in a court-martial:

Lt. Col. Scott Meakin, 39, a combat systems officer with the 563rd Rescue Group of the 23rd Wing at Moody Air Force Base, Georgia, faces charges that he communicated indecent language and an image on the Internet. 

"During 2013 and 2014, Meakin entered multiple internet chat rooms and discussed graphic sexual abuse of children with other individuals," said a statement from Davis-Monthan Air Force Base in Arizona, where Meakin had been assigned. 

Meakin also sent a picture of male genitals to other chat room users, according a Davis-Monthan spokesperson who referenced official charge records.

Plainly the charges are different in the two forums, so no concern arises about double jeopardy even though it's the same sovereign. And the Air Force has an interest in wanting to separate the officer. But is a second trial necessary? Could he be boarded out for misconduct or dropped from the rolls if he is confined as a result of his federal conviction? Perhaps he is retirement eligible, and could therefore thwart a mere separation by retiring voluntarily (presumably at a lower pay grade). And perhaps he will not be jailed for his civilian federal offense, thus preventing the government from dropping him from the rolls due to confinement. Hence there may be a need to obtain a dismissal.

Additional information or insights, anyone? (Real names only, please.)