by Haygen Warren, NASASpaceFlight.com
The joint NASA/ESA/CSA James Webb Space Telescope (JWST) has passed its critical final mission analysis review — clearing the way for a late 2021 launch from the Guiana Space Centre in Kourou, French Guiana on an Arianespace Ariane 5 rocket.
With this review completed, Arianespace and JWST teams can now begin final launch preparations. With a launch readiness date of October 31, 2021, Webb will soon be transported to French Guiana where it will be mated with its designated Ariane 5 rocket.
The mission analysis review, carried out by Arianespace and ESA, confirms that all launch systems — such as the telescope, rocket, ground systems, and launch teams — are set for launch. The review also confirms that Webb itself and its flight plan are ready for the mission to begin.
“We are thrilled to have passed this important step towards the launch of Webb and to have received the green light from Arianespace and NASA,” says Peter Rumler. Rumler is the project manager for the JWST at ESA.
When the telescope launches, it will experience a wide range of forces, such as vibrations and temperature changes and radiation. Therefore, Arianespace performed technical evaluations on important milestones of the mission’s ascent for the review, such as the launch trajectory and separation of the telescope from the rocket’s upper stage.
Additionally, as part of the mission analysis review, ESA and other launch teams worked to compute the launch window needed to place JWST at the L2 Lagrange point.
Calculating the launch window is highly complex due to the need to ensure that the Ariane 5’s second stage continues to escape from the Earth, while the telescope enters the L2 point safely.
Following liftoff from pad ELA-3 at the Guiana Space Centre, the Ariane 5 Étage Supérieur Cryotechnique (Cryogenic Upper Stage) will release JWST on a transfer orbit trajectory to the L2 Lagrange point, where the telescope will perform the entirety of its mission. The L2 point is 1.5 million km away from Earth — four times the distance to the Moon from the Earth — in the direction facing away from the Sun.
The telescope will continue on the transfer orbit trajectory for four weeks before entering orbit at L2. Once at L2, the telescope will undergo a six-month commissioning phase before entering full science operations.
After the telescope has been commissioned and Webb is in full science operations, it will observe the universe in the near-infrared and mid-infrared wavelengths. Near-infrared and mid-infrared are wavelengths longer than visible light, allowing JWST to see more of the universe than visible light telescopes like the Hubble Space Telescope.
Observing in the infrared is not easy, though. For Webb to observe in infrared, it will carry state-of-the-art instruments, such as specially designed cameras, spectrographs, and coronagraphs.
Webb will house four total instruments and a guidance camera in its Integrated Science Instrument Module (ISIM). These instruments are NIRCam (Near InfraRed Camera), NIRSpec (Near InfraRed Spectrograph), MIRI (Mid-InfraRed Instrument), and FGS/NIRISS (Fine Guidance Sensor and Near-Infrared Imager and Slitless Spectrograph).
The JWST will need to stay extremely cold to achieve these infrared observations without interference — at temperatures below 50 K (−223.2 °C, or −369.7 °F). To keep its temperature cool enough to perform observations, Webb will carry a large sunshield made of silicon and aluminum-coated Kapton.
But, why infrared?
Observing in the infrared will allow scientists to see farther back into the very early days of our universe, much farther than the telescope’s predecessors, like Hubble. The first light of the universe was ultraviolet and visible light; however, the light now appears to us as infrared due to the universe’s expansion stretching this light over billions of years.
A main focus of Webb’s science mission is to look for this first light — and where it came from.
Furthermore, observing in the infrared will also allow scientists to observe still forming stars behind large areas of dust. Understanding how stars, galaxies, and planets form will help further our understanding of how our universe formed from a mass of hydrogen and helium into what it is today.
Development on the James Webb Space Telescope began in 1996, with an initial launch date set for 2007. However, due to numerous cost overruns, redesigns, the COVID-19 pandemic, and development/construction delays, the telescope’s launch date has been moved several times during the telescope’s development.
The assembly of the telescope’s mirror began in 2015 and was completed in early 2016. Later in 2016, full construction on the telescope was completed, and extensive testing began shortly after.
In early 2018, JWST teams were testing the deployment of the telescope’s sunshield when the sunshield’s fabric ripped and the cables did not tighten sufficiently. Initially, NASA delayed the telescope’s launch to May 2020, but later had to delay the date again to March 2021 due to the severity of the issue, along with several other issues found during a review.
As Webb’s sunshield was replaced and testing continued, the telescope’s launch date was delayed once again to October 2021 due to a payload fairing issue on the Ariane 5 rocket.
However, since then, the Ariane 5 fairing issue has been resolved, and the telescope and launch teams remain on track for a late 2021 launch, with the telescope finishing up final testing. On May 11, 2021, Webb fully extended its massive 6.5-meter mirror for the final time before launch.
James Webb is the successor to the iconic Hubble Space Telescope and is an international collaboration between NASA, the European Space Agency (ESA), and the Canadian Space Agency (CSA).