The American astronaut David Walker, who died on April 23rd aged 56, made history in 1984 as the pilot of the US space shuttle Discovery on the first mission to succeed in retrieving satellites from orbit.
The venture was a milestone in proving the ability of astronauts to leave the safety of their spaceships and carry out particularly intricate jobs in orbit. The technology they employed in the weightless conditions of space was developed for routine use in the creation of the huge international space station that is now visible from Earth.
The flight was the first of four shuttle missions flown by David Walker, including the 1989 voyage that launched the Magellan probe, which went on to successfully map the surface of Venus.
Before he retired in 1996, he had logged more than 724 hours in space.
Although one of the new generation of astronauts recruited by the National Aeronautics and Space Administration in 1978 for the space shuttle, David Walker had a touch of the swashbuckling, derring-do image of the first generation of spacemen who flew the Mercury, Gemini and Apollo programmes. He had been a test pilot, and a highly-decorated US navy fighter pilot, flying F4 Phantoms during the Vietnam War.
He was born on May 20th, 1944, in Columbus, Georgia. He entered the US naval academy at Annapolis, Maryland, from high school in 1962, got a BSc in 1966, and was posted for flight training by naval aviation training command at bases in Florida, Mississippi and Texas.
In 1967, he was assigned to the naval air station at Miramar, California, to fly F4 Phantoms aboard the aircraft carriers Enterprise and America before being sent, in 1970, for test-pilot training to the USAF aerospace research pilot school at Edwards airforce base, California.
He was a member of the experimental engineering and testpilot team that perfected the F14 Tomcat's missile system.
David Walker's first shuttle mission generated excitement in the space industry because it carried, and released, two communications satellites, Canada's Anik D-2 and Hughes's Leasat1, before rescuing two earlier satellites that were stranded in the wrong orbits; they were the Palapa and Westar communications spacecraft.
The underwriters had paid out $180 million on the loss of the misplaced satellites, and offered another $10 million to NASA for the rescue attempt in the hope of recouping some of their loss by reselling the space equipment.
The value of the pilots' work to the insurance world was recognised when the five crew members were awarded the Lloyd's silver medal.
His second flight was as commander of the Atlantis shuttle in 1989, which sent the unmanned Magellan spacecraft on its way to Venus. It was the first US planetary science mission launched for more than a decade, and the first planetary probe to be deployed from the shuttle.
Magellan arrived at Venus in August 1990, and successfully mapped more than 95 per cent of the planet's surface.
The mission was later to prove eventful for David Walker for a less auspicious reason. He was briefly grounded in 1990 after the T38 jet trainer he was flying came within 100 feet of an aircraft outside Washington - he had flown to the US capital for White House ceremonies to honour the crew for the Magellan mission.
While preparing to return to space flight in 1992, he revealed one of those glimpses of the tensions at work in any large organisation.
He observed: "If I had decided to leave the space programme some time back, I probably could have done so with at least some people happy to see me go. But I didn't, and the opportunity to fly again is satisfying for me."
He was back in command of Discovery in 1992 to launch a classified defence department payload, DOD-1, and try out several military man-in-space and NASA experiments.
His fourth mission, on the shuttle orbiter Endeavour in 1995, deployed and retrieved a Spartan satellite along with a number of other experiments.
He eventually logged more than 7,500 hours flying time, including 6,500 hours in jet aircraft. He described flying in space as "the most spectacular human experience".
After leaving NASA in 1996, he became vice-president of a telephone company in southern California, and was later a consultant for the aerospace industry.
He was a technical consultant on the film Deep Impact (1998), about a comet striking the Earth.
David Walker: born 1944; died, April 2001