

The 50-year milestone is also being celebrated with the Apollo 13 in Real Time project, which is relaying the official audio of the mission in real time exactly 50 years later. 'You do wonder where they thought the footage would end up and how it would be viewed, not knowing if they'd make it home alive.' 'They also tended to use the camera in between the critical events – although it was all critical.

'It's difficult to be accurate as the cameras were just picked up and put down but, based on the existence of the filter in the images they were all almost certainly day five and six of the six-day mission. They were the best of the best back in the day too, remember. 'They were no doubt trying to put on a brave face and trying to keep each other going. They looked surprisingly relaxed despite the dire circumstances, Saunders told MailOnline, who said that all of the pictures were from film taken after the famous explosion. 'This perhaps belies their true feelings as we know that, in reality, the crew doubted if they would make it home alive.'

'One striking thing about the 16mm footage is how calm the crew appear, given the grave nature of the situation, the conditions, and the critical mission tasks that lay ahead,' Saunders told BBC News. Lovell (left), Swigert (centre) and Haise (right) sit together as they prepare for re-entry through Earth's atmosphere on April 17, 1970, after an oxygen tank rupture turned Apollo 13 into a survival mission
