Look at the timeline excerpt from Chapter Four of Windows to the Universe: Revolutions in Astronomy.2004: Construction of the JWST begins.2005: The ESA launch site in French Guiana and the Ariane 5 rocket are selected for the mission.2011: Construction of the 18 mirrors is completed.2013: Sunshield construction is completed.2013-2016: Extensive testing is conducted on all components.2017: Instruments are installed and tested.2018-2019: Final assembly is completed.What was done between 2004 and 2019?