Sellers began working for NASA as a scientist in 1982.
He then joined NASA's astronaut corps in 1996.
In 2002, he did not just become the third Briton to go into space — after Helen Sharman and Michael Foale ...
... he made a total of three Space Shuttle flights to the International Space Station, between 2002 and 2010.
One of his missions was in 2006, where he and his team had to test improved safety measures following a disaster in 2003, in which seven astronauts died.
"In his three journeys to orbit as a NASA astronaut, he demonstrated robotics, performed research and helped build the International Space Station. These journeys and his ongoing dedication to scientific inquiry inspired a new generation to take up his challenge to become better caretakers of Earth and extend humanity’s reach in space," said NASA administrator Charles Bolden.
He won many awards for his outstanding contribution to science, which included six spacewalks and hundreds of hours in space on his three shuttle flights. He was also one of the world's leading climate scientists.
In 2011, Sellers obtained an OBE from the Queen.
"Piers devoted his life to saving the planet. As a climate scientist, his work in computer modeling of the climate system, satellite remote sensing studies and field work using aircraft, satellites and ground teams broke new ground in our understanding of Earth’s systems," said NASA administrator Bolden.
"His legacy will be one not only of urgency that the climate is warming but also of hope that we can yet improve humanity’s stewardship of this planet," added Bolden.
Then in 2015, he was diagnosed with stage four pancreatic cancer. NASA's Bolden said "[Sellers'] cancer diagnosis became a catalyst for him to work even harder on efforts to save the planet from global warming for the benefit of future generations."
That year he went on CNN and said as NASA Earth Science Director with "only 500 days left on this planet," he said he wanted to use his time to focus on climate change.
In April this year, he met with actor and environmental activist Leonardo DiCaprio, where they discussed "the different missions NASA has underway to study changes in the Earth’s atmosphere, water and land masses for a climate change documentary that Mr. DiCaprio has in production," said NASA.
"We lost a tremendous public servant who was dedicated to NASA, the nation and the world. He was a strident defender and eloquent spokesperson for our home planet, Earth. Spacewalker and scientist, free thinker and friend to our planet, and all who seek new knowledge, to say he will be missed would be a gross understatement," said Bolden from NASA.
