One wing of the Hubble Space Telescope SA was retrieved from space in December 1993, after more than 3.5 years operating in a low earth orbit. The SA of the Hubble Space Telescope consisted of two wings of a double roll-out concept using two flexible solar cell blankets on each wing. The 48760 Silicon BSFR solar cells should provide the required 4.4 kW after two years in operation.
The post-flight investigation programme carried out between 1994 and 1995
[28] had the following main objectives:
• Assess the effect of different LEO interaction and environments as: thermal fatigue, ATOX, meteoroid and space debris damage, contaminations, UV, etc.
• Explain the anomalies experienced in orbit.
During the investigation programme the SA was submitted to several tests like detailed visual inspections, EP and health checks, wipe testing etc. The SA mechanisms were also mechanically tested to study their deploy/retract performance and finally the SA was totally disassembled for detailed investigation of all its components.
The main conclusions of the post-flight investigation programme related to the SA blankets are the following: [20]
Random failures are the main contributors to SA degradation. SA overall degradation excluding failures was less than predicted, mainly as radiation model used was pessimistic.
• Solar cell interconnectors: No fatigue effects on interconnection loops were detected as expected from pre-flight qualification data.
• Harness: Fatigue effects were evident on flexible data harnesses, but no full detachments were found.
• Adhesives for ATOX protection: Darkening due to UV could increase SA operational temperature.
• Micrometeoroids: More than 4000 impacts were detected on the SA, but none of them produced permanent short circuits. The loss factor applied in the design is in full agreement with the results of the observed degradation (1.8%).
