UK Space Agency chief Paul Bate has announced he will leave the organisation.
Bate said his four and a half years leading the agency had been "the greatest privilege" of his career.
His departure comes as the UK Space Agency merges into the Department of Science, Innovation and Technology’s Space Directorate, forming a new single unit within DSIT responsible for civil space policy and delivery. The new unit will retain the UK Space Agency name and brand identity.
Announcing his departure, Bate said: "To be trusted to deliver the government’s civil space ambitions, and to lead an agency of expert professionals who are passionate about their craft, has been the greatest privilege of my career and proof that space is a team sport.
"As the UK Space Agency becomes part of DSIT, now is the right time to pass the baton on. Whoever is successful will have one of the best jobs in the civil service, leading the new UK Space Agency, delivering innovation and world class science across space, working closely with ministers, and combining policy, strategy, delivery and technical expertise to help make the UK a leading space nation."
Recruitment for a director to replace Bate is now underway.
Commenting on his departure, space minister Liz Lloyd said working with Bate had been "a pleasure".
"I particularly valued working with him on the European Space Agency Council of Ministers work agreeing £1.7bn of investment on priority ESA programmes supporting jobs, resilience and science across the UK," she said.
David Willetts, chair of the UK Space Agency, said Bate "has done an enormous amount not just for the UK Space Agency but more widely for the British space sector as a whole".
"He is an excellent leader committed to promoting British science and technology," Lord Willetts added. "All of us at the Space Agency wish him well for the future."
Doug Liddle, chair of the UKspace trade association, added: "I have always appreciated his willingness to engage with companies large and small, to listen to our concerns and to understand the commercial realities of operating in such a fast-moving sector."