At a glanceNASA's 2021 recovery used backup spacecraft hardware after an interruption to the payload computer. 'Repaired' did not mean astronauts had just visited Hubble to replace a part.
What stopped working
NASA reported that Hubble's payload computer halted on June 13, 2021, interrupting science operations. The instrument system entered a safe configuration while the team investigated. A halt in science observations was therefore not the same as the spacecraft being lost.
The payload computer coordinates and monitors the science instruments. Keeping that function distinct from the telescope's optics helps explain how an observatory can remain intact while unable to collect its normal observations.
Source [1]How the team recovered operations
NASA's dated updates describe tests of memory and computer hardware, an investigation of the power-control unit, and the July switch to the backup side of the Science Instrument Command and Data Handling unit. The agency then reported the return to science operations.
Redundancy is a practical form of preparation: an alternative component or path is already present when the primary one fails. Switching to it still requires diagnosis and careful procedures. It is not equivalent to proving that every original component has been physically repaired.
Source [1]Reading a spacecraft-recovery report
Notice the sequence of verbs in a mission update. Diagnosing a possible cause, beginning a hardware switch and returning instruments to use describe different milestones. The later result should not be backdated to the first day an investigation identified a suspect component.
The same distinction between a plan and a completed event is useful in human-spaceflight reporting. Our account of Blue Origin's July 2021 flight follows the launch announcement through the reported outcome.
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