The launch is the first step in a five-year partnership that will add millions of images and thousands of hours of video and audio content, with enhanced search and viewing capabilities and new user features.
Over time, the integration of Nasaimages.org will become more seamless and comprehensive with the main Nasa site.
"This partnership enables Nasa to provide a vast collection of imagery from one searchable source, unlocking a new treasure trove for students, historians, enthusiasts and researchers," said Nasa deputy administrator Shana Dale.
"This new resource also will enable the agency to digitise and preserve historical content now not available on the internet for future generations."
The content of the site covers all the diverse activities of America's space programme, including imagery from the Apollo missions, Hubble Space Telescope views of the universe and experimental aircraft past and present.