From 2011 to 2013, the United States' famous manned sub Alvin went through a series major upgrades. This image shows Alvin leaving its operators in Woods Hole, Mass., for the U.S. West Coast, where it successfully underwent sea trials in November 2013. The Navy certified Alvin in January 2014 to dive up to 12,467 feet (3,800 meters), opening the door for science missions aboard the vessel.
Alvin's New Sphere
The upgraded submersible Alvin features five viewing ports (three visible here) for up to three passengers.
Alvin's Sphere Test
Alvin's new titanium sphere, wired up for a pressure test in June 2012.
The old sphere is on display at the Woods Hole Oceanographic Institution.
This artist's rendition of the newly upgraded Alvin shows larger the new interior sphere of the sub, which now has five viewports instead of three to improve visibility.
The upgraded submersible Alvin is loaded onto the R/V Atlantis on May 13, 2013.
Alvin Put to the Test
Alvin off the stern of its support vessel R/V Atlantis during sea trials in Nov. 2013 in San Diego, Calif.