This is the third installment in a four-part series of conversations with Paul Geithner Deputy Project Manager - Technical for Webb telescope at NASA's Goddard Space Flight Center in Greenbelt, Maryland about different aspects of the Webb.

The James Webb Space Telescope will gaze into the universe in infrared light and look farther back in time than previous telescopes, allowing scientists to look through cosmic dust to see stars forming. Paul discusses how the Webb telescope is coming together.

Q: The James Webb Space Telescope continues to come together, but what needs to happen between now and launch?

Paul: We plan to launch in 2018. There are still a lot of tests to be conducted, and many components will be traveling to different places between now and then as part of this testing and assembly process.

Q: What progress is planned for 2015?

Paul: The Webb telescope is being built-up and tested now, after many years of technology development and design. Now through the end of 2015, the actual telescope structure gets populated with mirror segments, and the instrument module, or the "heart" of the telescope, gets some work done on it, gets shaken on a big vibration table that simulates the rigors of launch, and goes into the vacuum chamber again for another roughly 4-month duration cold vacuum test.

In the meantime, the sunshield and spacecraft bus are being fabricated and assembled and tested, as are many large pieces of test equipment.

More specifically, the Webb telescope program's next big steps in 2015 include 1) change out of some key components of the Integrated Science Instrument Module (ISIM) prior to further testing, 2) start of assembly of the actual flight telescope, and 3) continued construction of the spacecraft bus and sunshield. The most prominent key components being changed-out on the instrument module are the near-infrared detectors in the three near-infrared instruments. Right now, the near-infrared instruments have been removed from the module and are having their detectors changed-out at Goddard.

The flight telescope structure will arrive at Goddard this summer and the flight mirrors will be installed on it the rest of 2015. Meanwhile, the spacecraft bus and sunshield continue to be put together at Northrop-Grumman in California. 4) Another significant set of activities in 2015 is testing of test equipment at Johnson Space Center in preparation for testing of the integrated telescope and instrument module in 2017.

Also a highlight at Goddard recently has been rehearsing telescope assembly using the prototype "Pathfinder" telescope, in prep for actual flight telescope assembly in 2015. The Pathfinder shipped to Johnson at the beginning of February and will be used in precursor tests leading up to OTIS (Optical Telescope Element plus ISIM) testing.

Excerpt from:

Webb Conversations: James Webb Space Telescope Coming Together