[STS-41B]

THE FIRST UNTETHERED SPACEWALK 

The pictured spacewalk marked the first use of the Manned Maneuvering Unit (MMU), a propulsion unit designed to allow astronauts to perform spacewalks without a safety tether securing them near the spacecraft. Though successful, the unit was retired after its third mission; a safety review following the Space Shuttle Challenger disaster found the unit too risky. 

This photograph is inscribed with a translation of an early scene in Dante’s Paradiso, the third and final part of the Divine Comedy. After travelling through Hell and Purgatory in the earlier installments, the poet ascends to the celestial heavens in Paradiso.  “I have been in the heaven which takes most of his light. / And I have seen things which cannot be told, / Possibly, by anyone who comes down from up there” (Paradiso 1.4-5).