The U.S. Navy is upgrading the AN/BLQ-10 EW (electronic warfare) system used on most American nuclear submarines. This latest upgrade will make it easier to do the software and hardware upgrades that are now done every two years. This is necessary to keep the EW system current with whatever militarily significant signals the EW sensors detect when the submarine gets to periscope depth (about 15 meters/45 feet beneath the surface) and seeks to find out what is out there. The periscope is now electronic and the crew gets a visual as well as an electronic view of what is on the surface. EW is a rapidly changing field and thus the need for frequent upgrades. Thus the current upgrades concentrate on making it even easier to do software and threat library (a database of different electronic signals and who they are probably from) upgrades.
Periscopes have changed a lot in the last few decades. Since the 1990s the navy has been converting its submarine periscopes from the traditional one using lenses and prisms. That system allowed one user, at a time, in the control room to see what was 10-15 meters above, just above the surface. The new periscopes are all-digital sensors (vidcams, thermal imager and laser rangefinder, EW sensors) located at the top of a telescoping mast that doesn’t penetrate the pressure hull like old lens based ones were. The new "photonics masts" use standard telescoping masts, and each American Virginia class SSN carries eight of them. Two of these masts carry sensors for the usual periscope functions (in case one breaks down). But the other six carry communications or electronic listening devices, or one is a spare for the top-of-the mast modules (some of which can be quickly swapped in or out). Thus an SSN comes to periscope depth and deploys several masts to see what's out there via the vidcams and electronic eavesdropping. One of the masts can also connect with communications satellites, to send and receive email. This is a big morale booster for the crew.
The new masts make it easier to handle information. Everything picked up by the new system is instantly sent down to the control room using fiber optics. The images and other information can be viewed on flat-screen displays in the control room, or anywhere else on the sub. This digital data can also be studied in more detail, and enhanced if needed. The Navy upgraded existing periscopes on older submarines by putting electronics at the top of a traditional hull-piercing periscope and replacing the optical components with fiber optic cable. Removing all these mechanically operated optics increases reliability.
The navy is also experimenting with small buoys that can be sent to the surface via a cable (containing a power and fiber optic link with the sub). These buoys can be expendable (used once) or retrievable. Another system in development uses a light sensor on the top of the sub that can, during daylight, capture images of what's on the surface while the sub is at a depth of 60 meters (183 feet). Meanwhile, the types of sensors carried on the photonics mast continue to improve, both because of improvements in digital cameras and thermal (heat) images, and because new types of sensors are being developed.
One other modification is to change the shape of the photonics mast to make it look less distinctive (and identify the ship as an American nuclear sub). The new LPPM (Low-Profile Photonics Mast) will resemble a traditional submarine periscope, at least from a distance. This will give the sub’s EW system a chance to detect who is up there and get the mast down and the sub out of danger.