James Webb Space Telescope

The primary mirror was 6.5 metres across, eighteen gold-coated beryllium segments folded to fit inside an Ariane 5 fairing. The sunshield, larger than a tennis court when deployed, was packed alongside in five layers. Neither could ever be repaired — JWST was bound for L2, far beyond reach.

Engineers had catalogued 344 single points of failure in the deployment sequence — mechanisms that each had to succeed without a fallback.

On Christmas Day 2021, an Ariane 5 ECA lifted from ELA-3 at the Guiana Space Centre carrying the James Webb Space Telescope, a joint NASA, ESA, and Canadian Space Agency observatory roughly three decades in the making at a programme cost of approximately $10 billion.

The sunshield tensioned by day eight, the final mirror segment latched on 8 January 2022, and on 24 January 2022 the observatory entered its halo orbit at the Sun-Earth L2 point, 1.5 million kilometres from Earth. All 344 succeeded.