TheTechno Optimist.

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Ariel

by European Space AgencyFR

Find out what planets around other stars are made of and how that depends on their star, by measuring the atmospheres of about 1,000 known planets instead of a few dozen.

ProtoStage 2 of 5

Payload under test with Airbus building the spacecraft; launch on Ariane 6 now listed for 2031.

Updated 16 Mar 2026Checked 11 Oct0 updates this week

Milestones

Next · Whole payload assembled and tested together
  1. Selected as ESA's fourth medium-class science missionMar 2018Complete.
  2. Adopted: moves from study to implementationNov 2020Complete.
  3. Airbus signs contract to build the spacecraft6 Dec 2021Complete.
  4. Payload passes preliminary design reviewMay 2023Complete.
  5. Spacecraft design passes review; construction starts5 Dec 2023Complete.
  6. Structural model assembled and shake-testedOct 2024Complete.
  7. Whole payload assembled and tested togetherTarget 2026Current milestone.
  8. Launch on Ariane 6 to Sun-Earth L2Target 2031+24 mooriginally 2029Not yet reached.

Most important updates

Upcoming

  1. 2026Whole payload assembled and tested together (next)
  2. 2031Launch on Ariane 6 to Sun-Earth L2+24 mooriginally 2029
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