Nancy Roman, who has died aged 93, was the first woman to hold an executive position at Nasa. As the space agency's chief of astronomy for almost two decades, she was responsible for developing and promoting the technology that made deep space observation possible.
Perhaps the most famous legacy of her time with Nasa was the Hubble space telescope, which launched in April 1990 and remains in operation to this day. The idea of an observatory that would orbit the Earth, beaming back images unobstructed by the absorbing layers of the planet's atmosphere, had been proposed as far back as 1946.
But it took years of lobbying and painstaking research by Roman and her colleagues to convince politicians and fellow astronomers that the project could ever get off the ground. As overall costs ballooned to $1.5bn (€1.3bn), senators demanded to know why the American taxpayer should be happy to see funding continue.
In reply, Roman pointed out that the cost per person for several decades of groundbreaking discoveries was equivalent to "a single night at the movies".
Even after her formal retirement from Nasa in 1979, she continued to work as a consultant for contractors that supported the Goddard Space Flight Centre - one of Nasa's major research laboratories and the Hubble telescope's operational "nerve centre".
In 1994, Nasa's chief scientist Edward Weiler paid tribute to Roman as the "mother" of Hubble, and the person upon whose work a generation of astronomers has depended.
Nancy Grace Roman was born in Nashville, Tennessee, on May 16, 1925. Her father Irwin was a geophysicist; her mother Georgia was a pianist and music teacher. Although not scientifically minded herself, Georgia encouraged her daughter's early interest in the stars, taking her to watch the Northern Lights from their home, by then, in Michigan.
Later, the family moved to Baltimore and Nancy founded an astronomy club for her fellow secondary school students - though support from teachers or mentors was decidedly lukewarm. One guidance counsellor poured cold water on her plans to study algebra for two years running, asking: "What lady would take mathematics instead of Latin?"
Later, at Swarthmore College in Pennsylvania, a professor told her that he usually tried to dissuade girls from majoring in physics, "but I think maybe you might make it". After graduating with a BA in astronomy, she studied for her PhD at the University of Chicago, staying on as an instructor and assistant professor.
While there, she studied differences in stars bright enough to be seen with the naked eye, observing how their compositions varied and that these variations correlated with differences in the stars' velocities and directions.
Her work helped to lay the foundations for understanding the structure of the Milky Way - but a lack of funding made it hard for her to progress further. Having resigned herself to the idea that she would never be offered a tenured position, she moved instead to the US Naval Research Laboratory.
There, she worked in radio astronomy, using radar to calculate the Earth's precise distance from the Moon, before being recruited by a fledgling Nasa.
From 1961 to 1963, she was chief of astronomy and solar physics, followed by 14 years as chief of astronomy and relativity programmes.
Her remit included launching and overseeing three orbiting solar observatories, three astronomical satellites and four geodetic satellites, which measure the form and dimensions of the Earth.
She also took part in the development of the Cosmic Background Explorer, a satellite which launched in 1989, and spent four years mapping the cosmic microwave background radiation of the universe, providing evidence to support the validity of the "Big Bang" theory.
Nancy's work was recognised by Nasa in 1969, when it presented her with its Exceptional Scientific Achievement Award. In 2017, she was rendered in plastic by the toy manufacturer Lego, as part of its "Women of Nasa" set. Nancy Roman died on December 26, 2018.