Lockheed Martin's new GPS satellite, the newest iteration of the company's GPS III design, has reached preliminary design review (PDR).
The design changes will enable dual-launch capability, allowing two satellites to launch on a single launch vehicle (LV). Thus far all GPS satellites have been launched one per LV, inserted directly into its target orbit. In order to launch two at a time the satellites will instead be released into a transfer orbit, with individual thrusters to direct the two satellites into different orbits.
The first GPS III satellites capable of dual-launch will be the ninth and 10th of the series, in what is scheduled to be a 2018 launch. Those satellites will also be the first with the ability to be substantially reprogrammed in orbit, allowing the satellites to change their broadcast signals as needed.
The GPS III are set to gradually replace ageing GPS II series satellites in the 32-strong constellation, deemed essential for military and civilian navigation worldwide. Eight of the satellites have been ordered from Lockheed, with a planned production run of 32.
Lockheed has largely completed a non-flyable version, a pathfinder to test the satellite's manufacturing and design processes. The non-flight example will soon enter radio interference testing, says the company.
The first GPS III is scheduled for launch in 2015.
GPS satellites are usually launched on a regular schedule as the old in-orbit satellites reach the end of their design lives. Two Boeing-built GPS IIF satellites are scheduled for launch in 2013, and several years' worth remain in storage awaiting scheduled launches.