D-1: the astronomical and space event of the decade will take place on December 25!

Finally ! After more than 10 years of delay on its initial schedule, which provided for a launch in 2009, the James-Webb observatory of the American, European and Canadian space agencies, is about to take off. Its launch, aboard a launcher Ariane 5, is scheduled for Christmas Day, as soon as possible inside a window shooting range which opens at 1:20 p.m. and closes at 1:52 p.m. KST. The total performance required of the launcher for this flight is a maximum of 6,173 kilos. About the separation with the launcher, it is scheduled 27 minutes after takeoff.

Position yourself “behind” the Earth seen from the Sun

James-Webb (JWST) will be launched towards Lagrange point number 2, some 1.5 million kilometers from Earth, his journey is scheduled to last 29 days. On the third day after launch, the heat shield will begin to deploy. On the eleventh day, the secondary mirror will begin its positioning. Between the thirteenth and the fourteenth day, the primary mirror 6.5 meters in diameter and composed of 18 hexagons will be assembled. If this is not the first time thatAriane 5 launches a payload bound for Lagrange point 2 – it had launched the Herschel and Planck satellites in May 2009 – is the ” first time that the launcher has to take into account very restrictive parameters », Explained Daniel de Chambure to us in July, responsible for the development of Ariane 5 and adaptations for specific missions at ESA.

Although Ariane 5 will inject the observatory on a direct trajectory bound for its final position, James-Webb will have to carry out several attitude checks and three course corrections. The first and most important maneuver is the only time-critical operation, aside from deploying the solar panels during Webb’s commissioning period. It should occur between 12.5 hours and approximately 20 hours after launch. It’s about a combustion continuous lasting up to a few hours. The second maneuver is a shorter burn performed approximately 2.5 days after launch, just before the start of the deployment of the solar panel. The last maneuver will be carried out 29 days after launch and should allow the satellite to insert itself into a orbit optimal around L2.

The start-up of the instruments will be spread over two to three months and will be followed by a period of two months which will be used to check their correct functioning. The start of scientific operations is scheduled for six months after takeoff, in June 2022.

The causes of the James-Webb delay

The successive postponements throughout the development of the program can be explained by a cascade of technical problems on almost all the elements of the observatory: the easements like the scientific part (mirrors, heat shield, instruments). With each technical problem solved, new test sessions open which also contribute to postponing the delivery date of the JWST a little further.

The delay in the development of the space observatory has five main causes:

• ofundeniable technical difficulties, which explains the complexity of the systems;
• new technologies, such as the sun visor, insufficiently mastered;
• intrinsic problems;
• human errors;
• excessive optimism in the timing of the program.

Recall that at the origin of the project, the JWST, then known under the name of telescope Next Generation Space Station (NGST), was slated for launch in the late 2000s.

From a first workshop in 1989 to its launch in 2021, a look back at the main dates that marked the history of JWST

1989: the Space Telescope Science Institute (STScI) of Baltimore, Maryland, and the Nasa organize the workshop Next Generation Space Telescope, where engineers and astronomers discuss the scientific and technical capabilities of a space observatory that would succeed the hubble space telescope.

1996: first formal recommendation that this future NGST should operate in the wavelengths infrared and have a primary mirror longer than four meters.

2002: NASA selects the consortia in charge of construction instruments and satellite.

2004: construction of the James-Webb observatory begins.

2005: James-Webb will be launched by Ariane 5. The European launcher was provided by the European Space Agency as part of its participation in the James-Webb program. In addition to launch services, ESA contributes two of the four scientific instruments and provides personnel for mission operations.

2011: the 18 segments of the primary mirror are built and their compliance with the required specifications proven by tests. This year is also the year when the program is threatened with abandonment by the US Congress because of the explosion of its cost from a small billion to more than six billion in 2011. Its cost is around 10 billion dollars. today.

2013: start of construction of the heat shield. An absolute necessity to guarantee the correct functioning of the instruments, whether they are sensors or the optics which will have to remain extremely cold. The size of this shield leaves one wondering. 22 meters long and 10 meters wide, it is almost as big as a tennis court! Due to its size, the shield will launch folded and unfold into space. The challenge was therefore to design a mirror folded at launch, then deployed in orbit.

2017: start of satellite assembly and integration operations with its payloads and easements. The James-Webb Observatory is taking shape.

2019: the observatory is fully assembled and the environmental, electrical, functional and communication tests begin, which will run until Webb be folded one last time in preparation for its launch, on Christmas Day 2021.