Satellite market trends and the enabling role of multi-junction space solar cells

This paper describes an overview of the satellite market trends and the role of high-efficiency multi-junction solar cells in enabling the realization of the high-power spacecrafts for the geosynchronous orbit (GEO), the low-earth orbit (LEO) and interplanetary applications. The global GEO telecom satellite orders in the past few years have seen a relatively stable period since the year 2002 when only 13 satellites were on order worldwide. In the 2003–2007 period, however, 23 to 39 yearly orders were placed, totaling 136 satellite orders in 5 years. New markets such as digital radio and broadband, as well as, emerging markets in regions such as Asia have contributed to this trend. Science & observation and military satellites, typically operating in the LEO and polar orbits, and interplanetary missions to the Moon, Mars, Mercury and the Asteroid Belt have also expanded the smaller size spacecraft orders by government agencies. The gradual replacement of solar arrays powered by silicon cells with arrays powered with much higher efficiency multi-junction cells has significantly augmented the operational capabilities of these satellites. The most recent triple-junction solar cells, for example, exhibit 30% conversion efficiency under air-mass zero (AM0) conditions. These cells produce more than twice the end-of-life (EOL) power than the best space silicon solar cells ever produced. Higher performance (i.e., 33% efficiency) and thinner multi-junction cells, such as the inverted metamorphic (IMM) solar cell technology, presently under development will further enable higher power and lower mass (W/Kg) solar arrays, enabling satellites with greater power and capabilities.