Date: March 28, 2018 (updated April 28)
Some of the background to the JWST launch delay into early 2020 is given here. The presentation charts are from NASA SMD AA Thomas Zurbuchen’s presentation (PDF below) at the National Academy on Sciences on the afternoon of Tuesday March 27.
The image on chart 2 (also shown here) shows all the JWST hardware in the large clean room at Northrop. What you can see in that image represents $7.3B of effort and hardware (this is all of JWST in two components!). The optical telescope and instrument assembly (OTIS — hanging upside down here in this image — though OTIS is now standing on the floor in the corner) will be mated this coming fall with the spacecraft+sunshield in the background left, once the spacecraft+sunshield (called the Spacecraft Element — SCE) completes its “environmental” testing (vibration; acoustics; thermal vac). The sunshield on each vertical arm is wrapped up ready for the environmentals, with the OTIS simulator in the middle. The OTIS simulator matches the OTIS in mass and dynamical characteristics to ensure that the SCE environmental testing is realistic. The environmental testing has started with acoustics and progresses soon to vibration. OTIS will replace the simulator once the SCE has finished its environmental tests later this summer. At that point the full JWST Observatory environmental testing will start.
The charts that provide a good summary and background to the reasons why the delay occurred for JWST are charts 3 and 4.
More detailed updates will be forthcoming soon.
This is not in the charts, but I will note that the near-term budget impact through 2021 is expected to be small. There is not expected to be any significant impact on WFIRST (nor on any other elements of the Astrophysics portfolio in SMD at NASA), as per Paul Hertz, Astrophysics Division Director.