NASA astronaut Capt. Mark E. Kelly with his wife, Democratic congresswoman Gabrielle Giffords, who was critically wounded on Saturday during a mass shooting in Arizona. ((Reuters))

NASA has named a backup commander to replace Capt. Mark Kelly, the astronaut husband of wounded U.S. congresswoman Gabrielle Giffords, on the April mission of the space shuttle Endeavour if necessary.

NASA announced Thursday that astronaut Rick Sturckow will serve as a backup commander on the STS-134 space shuttle mission so the crew and support teams can continue training while Kelly is away caring for his wife, who was shot in the head outside a Tucson, Ariz., grocery store last Saturday.

The appointment will allow Kelly to keep his attention on his family, chief astronaut Peggy Whitson said. Kelly and Giffords have been married for more than three years.

Giffords remains in hospital and is beginning to show progress in her recovery, having opened her eyes for the first time since the shooting Wednesday .Six people died and 13 were wounded in the shooting.

The space agency emphasized that Kelly remains the commander for the final scheduled flight of the space shuttle program. The shuttle Endeavour is scheduled to launch April 19 on a trip to the International Space Station.

Kelly said in a written statement released by NASA that he recommended to the space agency that it should "take steps now to prepare to complete the mission in my absence if necessary."