Delay Lines. This third set of evacuated pipes contains mechanisms that move mirrors back and forth with a very high degree of accuracy. These compensate for the movement of the mirrors as they track an object across the sky, and for other effects. Finally, the light leaves the pipes inside the BCF and goes to the Beam Combining Table, where the light is combined in a way that allows images to be formed. Both types of station have three elements: a siderostat, a Wide Angle Star Acquisition (WASA) camera, and a Narrow Angle Tracking (NAT) mirror. The first is a precisely-ground flat mirror in diameter. The WASA cameras control the aiming of the mirror at the celestial target. The reflected light from the siderostat is directed through a telescope which narrows the beam down to the diameter of the pipes, which is . The light then hits the mirror of the NAT, which compensates for atmospheric effects and directs the light into the feed system. In 2009 NOFS began final plans for NPOI to incorporate four aperture optical-infrared telescopes into the array, which were accepted by the Navy in 2010, and assigned to the Naval Observatory Flagstaff Station. They were originally intended to be "outrigger" telescopes for the W. M. Keck Observatory in Hawaii, but were never installed and incorporated into Keck's interferometer. Three telescopes are being prepared for near-immediate installation, while the fourth is currently at Mount Stromlo Observatory in Australia and will be incorporated at some point in the future. The new telescopes will help with faint object imaging and improved absolute astrometry, due to their greater light-gathering abilities than the existing siderostats. NOFS operates and leads the science for the Navy Precision Optical Interferometer, as noted, in collaboration with Lowell Observatory and the Naval Research Laboratory at Anderson Mesa. NOFS funds all principal operations, and from this contracts Lowell Observatory to maintain the Anderson Mesa facility and make the observations for NOFS to conduct the primary astrometry. The Naval Research Laboratory (NRL) also provides funds to contract Lowell Observatory's and NRL's implementation of additional, long-baseline siderostat stations, facilitating NRL's primary scientific work, synthetic imaging (both celestial and of orbital satellites). When complete by 2013, NPOI will run the longest baseline interferometer in the world. The three institutions – USNO, NRL, and Lowell – each provide an executive to sit on an Operational Advisory Panel (OAP), which collectively