What ongoing environmental challenge did the telescope's temperature control systems need to manage?

Answer

Extreme thermal swings as it cycled between sunlight and Earth's shadow every 96 minutes.

The temperature control systems had to manage cycling between intense sunlight and shadow every 96 minutes, as failure to do so could cause the mirror structure to expand or contract, throwing the alignment out of tolerance.

What ongoing environmental challenge did the telescope's temperature control systems need to manage?
HubbleSpaceastronomytelescopeIssues