Stepping down well is an important leadership skill — and one that is rarely named or valued.

I will never forget standing in steamy French Guiana on 25 December last year as the James Webb Space Telescope (JWST) lifted into the sky on the Ariane 5 rocket. A fortnight later, I watched as the final wing of the telescope’s 18-segment primary mirror, the largest mirror ever built for space, seamlessly expanded into its fully deployed form. And months on, I looked — through teary eyes — at JWST’s first images. I was one of the first people on Earth to see the infrared Universe in high resolution.

For more than six years I have had a front-row seat for NASA’s science programme. Now it is time to give my seat to someone else…