NASA is now targeting May 2020 for the launch of its James Webb Space Telescope, the $8 billion dollar Hubble successor. The announcement on Tuesday made after an independent assessment of remaining tasks for the highly complex space observatory further pushes the launch target of the next-generation space telescope by about a year. "Webb is the highest priority project for the agency's Science Mission Directorate, and the largest international space science project in US history," said acting NASA Administrator Robert Lightfoot. "All the observatory's flight hardware is now complete, however, the issues brought to light with the spacecraft element are prompting us to take the necessary steps to refocus our efforts on the completion of this ambitious and complex observatory," Lightfoot said. Testing the hardware on the observatory's telescope element and spacecraft element demonstrate that these systems individually meet their requirements. However, recent findings from the project's Standing Review Board (SRB) indicate more time is needed to test and integrate these components together and then perform environmental testing at Northrop Grumman Aerospace Systems in Redondo Beach, California, the project's observatory contractor. NASA said it is also establishing an external Independent Review Board (IRB), chaired by Thomas Young, a highly respected NASA and industry veteran who is often called on to chair advisory committees and analyse organisational and technical issues. NASA will consider the findings and recommendations of both the boards' findings for defining a more specific launch time frame. The US space agency will then provide its assessment in a report to Congress this summer. Webb is an international project led by NASA with its partners, ESA (European Space Agency) and the Canadian Space Agency. NASA will work with its partner, ESA, on a new launch readiness date for the Ariane 5 vehicle that will launch Webb into space. ESA is providing the Ariane 5 as part of its scientific collaboration. Once a new launch readiness date is determined, NASA said it will provide a cost estimate that may exceed the projected $8 billion development cost to complete the final phase of testing and prepare for launch. Additional steps to address project challenges include increasing NASA engineering oversight, personnel changes, and new management reporting structures. "Considering the investment NASA and our international partners have made, we want to proceed systematically through these last tests, with the additional time necessary, to be ready for a May 2020 launch," said Thomas Zurbuchen, Associate Administrator for NASA's Science Mission Directorate.