Iridium Qualifies multijunction solar panel system
50 percent more solar cell surface area for next generation satellite constellation
Iridium Communications has completed the testing program for qualification of its new solar panel design for powering the Iridium NEXT constellation, expected to begin launching in 2015. The solar array contains four panels and will span 9.4m when fully extended, developing more than 2kW of power over a demanding charging cycle in Iridium's low earth orbit.
The panel was developed by Spectrolab, which makes multijunction space solar cells and panels, and Mitsubishi Electric Corporation (MELCO), a supplier of lightweight solar panel substrates. These companies are part of the Iridium NEXT Mission Team, led by Iridium's prime contractor and European satellite manufacturer, Thales Alenia Space.
The solar arrays use Spectrolab's new, larger triple-junction (XTJ) GaInP2/GaAs/Ge cells manufactured from six-inch wafers. These yield 50 percent more solar cell surface area than cells used in Iridium's current constellation and deliver higher performance, while reducing costs.
"The successful completion of qualification testing for the solar panel design marks yet another important milestone on our journey to launching Iridium NEXT," stated Scott Smith, chief operating officer, Iridium Communications Inc. "The innovation at the heart of the solar panels demonstrates how we're fundamentally rethinking the design of every aspect of our constellation with improved efficiency, performance and longevity in mind."
Working closely with Spectrolab, the new design was put through a grueling life test and qualification program to ensure it works to specification using representative sections of the actual panels. The design verification test represented every mechanical and electrical configuration and was tested with a simulation of the rigorous low earth orbit charging environment into which the arrays will be deployed.
The solar array was tested to 1.5 times its planned lifespan in space to ensure it can meet and exceed the expected lifetime of the satellite. The solar cells were put through 75,000 thermal cycles, each one representing the Iridium NEXT satellite's movements in and out of the sun's radiating heat as it orbits the Earth.
The Iridium NEXT satellite network will consist of 66 in-orbit satellites and a number of in-orbit spares. The constellation is expected to begin launching in 2015 and will be fully operational in 2017.
