Boeing 702 Solar Arrays

Satellite Launch date Operator Model
Galaxy XI   [Orbit] 22 Dec 1999 PanAmSat Boeing 702
Thuraya*  
[in graveyard orbit since May 2007]
21 Oct 2000 Thuraya Boeing GEM*
PAS 1R   [Orbit] 16 Nov 2000 PanAmSat Boeing 702
Anik F1   [Orbit] 21 Nov 2000 Telesat Canada Boeing 702
XM-2 ("Rock")   [Orbit] 18 Mar 2001 XM Satellite Radio Boeing 702
XM-1 ("Roll")   [Orbit] 8 May 2001 XM Satellite Radio Boeing 702

* Boeing Geosynchronous Mobile (GEM) satellite, based on the 702 design.

Satellite operators in September 2001 were advised by Boeing Satellite Systems of a potential long-term issue in the solar array output power on 702 model satellites. The concentrator panels, which so far have only been used on these spacecraft, show a more rapid decrease in power output than expected.

Angled reflector panels along both sides of the 702's solar wings form a shallow trough and concentrate the sun's rays on the solar cells - in theory. Boeing had to admit that the newly developed arrays were "not concentrating as much solar energy as predicted" because they were "losing their optical quality and becoming foggy." It is yet unknown what exactly causes the effect.

As a consequence, future 702 satellites will be equipped with conventional solar arrays.

A typical Boeing 702 starts with about 16 kW of power at the beginning of its life, which drops to about 15 kW after 15 years. The 702s in orbit, however, are currently expected to have only 12 kW after 15 years.

XM announced that the problem "could result in an earlier than expected replacement of its satellites in order to maintain acceptable power output levels and service quality." The company projected that their satellites' solar arrays wouldn't fall below specifications "before the latter half of the decade."

The XM satellites are among the most powerful commercial ones ever built, with a total power of 18 kW at the beginning of life.