Who was Margaret Hamilton?

Tributes are being paid to computer scientist Margaret Hamilton, who has died aged 90.

Hamilton helped astronauts land safely on the Moon during Nasa's first crewed missions there in the 1960s and 1970s.

She led a team that created the software used during Nasa's famous Apollo 11 mission.

Her work became a very important part of the historic landing, and she went on to become one of the most famous people in the early history of computer software.

But what was Apollo 11 and why was her work so important? Keep reading to find out.

Margaret Hamilton was born in Indiana in 1936 and studied maths at university before moving to Boston, where she began working at the Massachusetts Institute of Technology (MIT) in 1959.

While working there, she became a leader in a team developing software for Nasa's Apollo missions.

At the time, writing software was a new type of work, and Hamilton helped give it a name that we still use today - software engineering.

In a statement, MIT paid tribute to her saying: "To say Hamilton was a pioneer - to say she was ahead of her time - would be a dramatic understatement."

They added that she was doing the job of a software engineer before it was widely recognised as a career.

On 20 July 1969, US astronauts Buzz Aldrin and Neil Armstrong became the first people to walk on the Moon.

A camera was able to transmit the historic moment to around 650 million people around the world, who were watching the Apollo mission on television.

As Neil Armstrong stepped onto the surface of the Moon, he spoke the famous words: "That's one small step for man, one giant leap for mankind."

Armstrong was closely followed by fellow astronaut Buzz Aldrin, who described the Moon as "magnificent desolation".

They spent 21 hours on its surface, including a seven-hour sleep, before returning to Earth.

Read more about Nasa's Apollo 11 Moon mission here.

The Moon is about 240,000 miles from Earth - so the Apollo 11 mission was not an easy task. It was also a dangerous mission.

In the 1960s, technology was much less advanced than it is today, and nobody had ever stepped on the Moon before.

Hamilton led a team of engineers who wrote and tested the software on board the spacecraft before it set off on its lunar journey.

And her work ended up being critical to the success of the landing.

As Armstrong and Aldrin were getting ready to land on the Moon, the computer on their spacecraft sounded an alarm.

The computer was becoming overloaded with information, and there was a risk that the landing might not happen.

Luckily, Hamilton and her team had planned for something like this.

Their software was designed to give the jobs that mattered most - such as helping with the Moon landing - priority.

This meant the computer could stop doing less important jobs, and could concentrate on helping the spacecraft to land.

As a result, the landing was successful and Armstrong and Aldrin became the first people to walk on the Moon.

After Apollo 11, Hamilton continued working in computing and went on to start her own software companies.

In 2016, she was awarded the US Presidential Medal of Freedom for her contribution to science and space exploration.

The simple reason is that it had never been done before - and it was a big ambition for countries, and their space programmes, to be the first to land humans on the Moon's surface.

In the run-up to the Moon landing, the US was competing with the Soviet Union in something called the Space Race. This was a competition to be the first to complete missions exploring the world outside the Earth's atmosphere.

This race started when the Soviets - the US's enemy during the Cold War - launched the first Soviet Sputnik satellite in 1957.

Then, Soviet cosmonaut Yuri Gagarin became the first human in space on 12 April 1961.

The Americans wanted technological superiority - and it looked like the Soviets were winning in the Space Race.

So, in 1962, US President John F Kennedy announced a big ambition, in a speech which is now very famous.

"We choose to go to the Moon!" he said.

US space agency Nasa invested lots of money (around $25 billion, which is around £20 billion) and effort into making this happen.

The mission would come to be known as the Apollo programme and its goal was to land humans on the Moon and bring them safely back to Earth.

And in July 1969, the US achieved what it had set out to do: its astronauts became the first humans to walk on the Moon.