KEO, the satellite that never left
It invited every living person, not a committee, to write to a future fifty thousand years away, and its end in 2025 showed that such messages depend on the living who must carry them.
- Dated
- Place
- France · Jean-Marc Philippe and the Association Programme KEO, with messages written by people around the world
- Remains
- Digital
NASAPDMOriginal record
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From the archivist
Not every message this civilization prepared ever left. This is one that did not.
In 1994 a French artist and scientist, Jean-Marc Philippe, imagined a hollow sphere of titanium with wings, to be carried into orbit and left there for fifty thousand years, until the thin air slowed it and it fell back to Earth, its outer layers burning into a glow across the sky. Inside would travel messages from anyone who wished to write, four pages each, to whoever lived then. A great many people wrote.
The launch was announced, then postponed, then announced again. The years passed, and Philippe died in 2008. His team kept gathering letters to the future for seventeen more years.
In the summer of 2025 they published a last notice: the satellite would not go into space. The letters, stripped of names, were kept on a storage medium, waiting for no launch at all.
We keep it here because it too is what we leave behind: the intention, and the unfinished.
Established
- KEO was conceived in 1994 by the French artist and scientist Jean-Marc Philippe; its name was taken from sounds described as among the most frequent in the world's languages (Gunter's Space Page).
- It was designed as a passive satellite, a hollow titanium sphere about 80 cm across with protective layers and two wings, to be placed by an Ariane 5 rocket in an orbit about 1,800 km high and to fall back to Earth after some 50,000 years, its re-entry producing an artificial aurora (Gunter's Space Page).
- Anyone could send a message of up to four pages; the messages were to travel on radiation resistant discs with symbolic instructions for building a reader, together with a drop of human blood and samples of air, seawater and earth (Gunter's Space Page).
- The project received the patronage of UNESCO and was shown in exhibitions in many countries; its launch, first announced for the early 2000s, was postponed many times (Association Programme KEO; Gunter's Space Page).
- Jean-Marc Philippe died in November 2008; in the summer of 2025 the association announced that the satellite would not go into space, stopped collecting messages, and kept those already received, anonymised, on an external storage medium (Association Programme KEO).
Interpretation
Descriptions of KEO's design, contents and launch dates come mostly from the project's own announcements, which changed over three decades; what was designed was never flown, and the association gives the loss of its founder and the lack of funding as the reasons. Whether its end is a failure or a lesson depends on the reader: it shows how much a message to the far future depends on those who must carry it.
In 10,000 years
In 50,000 years no bright trail will cross the sky; who will read the letters we wrote to those who would have seen it?
Sources (2)
- Association Programme KEO (Patrick Tejedor, president). End of the KEO project, July 2025. · www.keo.org
- Krebs, G. D. KEO. Gunter's Space Page. · space.skyrocket.de
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