Why do satellite solar arrays degrade in orbit? The gradual loss of power output from a communications satellite’s solar cell arrays over mission life is mainly caused by:

Introduction / Context:
Solar array degradation is a key factor in end-of-life (EOL) power budgeting for satellites. Understanding the physics of degradation helps in selecting cell types and shielding strategies.

Given Data / Assumptions:

• GEO environment includes trapped electrons and protons, and solar radiation.
• Solar cells typically GaAs/Ge or multi-junction designs with coverglass.

Concept / Approach:
Radiation damages the semiconductor lattice, creating defects that act as recombination centers. This reduces minority carrier lifetime, open-circuit voltage, and fill factor, thus decreasing power output. Coverglass thickness is chosen to mitigate electron/proton damage while balancing mass.

Step-by-Step Solution:
Identify dominant GEO hazards: electrons and protons from radiation belts; solar UV.Recognize displacement damage in cell materials reduces efficiency.Model degradation as percent loss per year; include in EOL power sizing.

Verification / Alternative check:
Flight data consistently shows radiation-induced degradation; meteoric dust is negligible in GEO; outgassing/oxidation minimal in vacuum at GEO.

Why Other Options Are Wrong:
Meteoric dust: Insignificant deposition at GEO.
Intrinsic resistivity increase/leakage: Not the primary mechanism; radiation damage dominates.
Oxidation at GEO: Negligible atmospheric oxygen.

Common Pitfalls:
Attributing degradation primarily to thermal cycling; it contributes but radiation is the main driver.

Final Answer:
Bombardment by energetic charged particles (e.g., electrons) in the space environment