Groton — The most modern and sophisticated attack submarine in the world will be commissioned in a ceremony at the Naval Submarine Base on Saturday.

The ceremony, which is not open to the public, is expected to be attended by a couple thousand people, including family of the crew and those hailing from the ship's namesake state who are members of the USS Illinois Commissioning Committee. Chief of Naval Operations Adm. John Richardson will be the keynote speaker.

The future USS Illinois (SSN 786), sponsored by first lady Michelle Obama, will be the 13th Virginia-class attack submarine to join the Navy's fleet of 52 attack submarines.

Around 120 crewmembers are assigned to the Illinois. As the commissioning crew, they are known as "plankowners," an unofficial term meaning they are the original sailors of the boat.

The Illinois, built by Electric Boat and Newport News Shipbuilding in Virginia, was delivered to the Navy four days early and more than $100 million below target cost. It cost $2.7 billion.

Construction on the Illinois began in June 2014, and the submarine was christened Oct. 10, 2015.

The Illinois features a redesigned bow — first implemented on the USS North Dakota — that includes a new sonar array and two larger payload tubes instead of 12 individual, vertical-launch missile tubes. It can operate in both littoral and deep ocean environments.

Virginia-class submarines displace 7,835 tons, with a hull length of 377 feet and a diameter of 34 feet. They are capable of speeds in excess of 25 knots and can dive to a depth greater than 800 feet, while carrying Mark 48 advanced capability torpedoes and Tomahawk land-attack missiles.

Members of the public wishing to watch the commissioning live can do so online at www.navy.mil.