Réunion Astro 06 janvier 2022
Astronomie
Astronomie
JWST :
Le télescope spatial James Webb est le télescope spatial le plus grand, le plus puissant et le plus complexe au monde jamais construit. Webb résoudra les mystères de notre système solaire, regardera au-delà des mondes lointains autour d'autres étoiles et sondera les structures et les origines mystérieuses de notre univers et notre place dans celui-ci.
Astronomie
Le déploiement en résumé :
Lien vidéo : https://drive.google.com/file/d/1glEq46ZbIpIXwvZ8scWsICUJ7aoEQ6S1/view?usp=sharing
Astronomie
JWST : C’est parti !
Décollage d’Ariane 5 samedi 25 décembre depuis Kourou à 13h20.
Le déroulé du déploiement du JWST :
https://webb.nasa.gov/content/webbLaunch/deploymentExplorer.html
https://webb.nasa.gov/content/webbLaunch/whereIsWebb.html?units=metric
Astronomie
JWST :
La préparation
Waiting for Launch :
Preparations for launch phase.
Webb is in Kourou French Guiana at the ESA Launch Facility. Webb has been placed on the Ariane 5 rocket in the tightly packed configuration shown and encapsulated in the nose fairing. For launch, Webb is rolled out to the launch pad and the countdown begins.
Astronomie
JWST :
Le décollage
Liftoff!
Webb is on its way...GO WEBB!
The Ariane 5 launch vehicle provides thrust for roughly 26 minutes after liftoff from French Guiana. The first stages fire, consumes their fuel, cut off and separate. Finally the 'upper' stage fires, giving Webb it's final push up and away from Earth's gravity and onto a trajectory toward its L2 orbit. The upper stage engine completes its burn, cuts-off, and separates. Webb is released from the Ariane 5 and is flying on its own in a fully stowed state.
https://www.youtube.com/watch?v=9tXlqWldVVk
Astronomie
JWST :
La séparation :
Upper Stage Separation
Nominal Event Time: Launch + 27 minutes
The Ariane 5 launch vehicle provides thrust for roughly 26 minutes after liftoff from French Guiana. Moments after upper (second) stage engine cut-off, Webb is released from the Ariane 5 and is flying on its own in a fully stowed state.
Astronomie
JWST :
Les panneaux solaires:
Solar Array
Webb's solar array is released and deployed.
Nominal Event Time: Launch + 33 minutes
After shedding its fairing and booster rocket, the first two deployments are 'automatic,' meaning they happen without the ground giving commands. Once the solar panel is deployed, the telescope will go off of battery power and start generating its own power.
Astronomie
JWST :
Correction de trajectoire
Mid Course Correction Burn 1a
Nominal Event Time: Launch + 12.5 hours
This burn fine-tunes Webb's trajectory after launch. The duration of the burn will depend on Ariane 5 launcher performance.
The James Webb Space Telescope is launched on a direct path to an orbit around the second Sun-Earth Lagrange Point (L2), but it needs to make its own mid-course thrust correction maneuvers to get there. This is by design, because if Webb gets too much thrust from the Ariane rocket, it can’t turn around to thrust back toward Earth because that would directly expose its telescope optics and structure to the Sun, overheating them and aborting the science mission before it can even begin. Therefore, Webb gets an intentional slight under-burn from the Ariane and uses its own small thrusters and on-board propellant to make up the difference.
There will be three mid-course correction (MCC) maneuvers: MCC-1a, MCC-1b, and MCC-2. The first burn, MCC-1a, is the most important and the only other time-critical operation aside from solar array deployment during Webb’s commissioning period.
Astronomie
JWST :
Déploiement des antennes
Gimbaled Antenna Assembly
Nominal Event Time: Launch + 1 day
The Gimbaled Antenna Assembly (GAA) holds Webb's high rate antenna. It is rotated to its parked position pointed back to the Earth. This is an 'automatic' deployment as well as the solar panel which preceded it. All other deployments will be controlled by commands from the ground.
Astronomie
JWST :
Seconde correction de trajectoire
Mid Course Correction Burn 1b
Nominal Event Time: Launch + 2 days
This burn fine-tunes Webb's trajectory after launch. The duration of the burn will depend on Ariane 5 launcher performance.
There are three mid-course correction (MCC) maneuvers: MCC-1a, MCC-1b, and MCC-2. This is the second. The first burn, MCC-1a, is the most important and the only other time-critical operation aside from solar array deployment during Webb’s commissioning period.
The second, MCC-1b, is a shorter burn performed before the sunshield deployment is scheduled to start. The final maneuver, MCC-2, performed 29 days after launch, is designed to insert Webb into the optimum orbit around L2.
Astronomie
JWST :
Préparation déploiement protection solaire
Forward Sunshield Pallet
The Forward Unitized Pallet Structure (UPS).�This step begins the Sunshield deployment phase.
Nominal Event Time: Launch + 3 days
The UPS supports and carries the five folded sunshield membranes. Prior to this, the spacecraft is maneuvered to provide warmer temperatures on the forward UPS and various heaters are activated to warm key deployment components. Key release devices are activated. Various electronics and software are configured prior to support the UPS motions, which are driven by a motor. This step represents the start of the Sunshield deployment phase and the start of all major deployments.
Astronomie
JWST :
Le voile de protection solaire
https://drive.google.com/file/d/1LEJ7RbNKDX0YPlwmu9vhoFZs9zAybV3h/view?usp=sharing
Astronomie
JWST :
Le voile de protection solaire
Pour que JWST puisse détecter la lumière infrarouge des objets faibles, le télescope et les instruments scientifiques doivent être refroidis à ~ 40 K (soit environ -233°C). Ce refroidissement est effectué passivement par un pare-soleil gigantesque.
Le pare-soleil est un système en forme de losange de 5 couches d’un film polyimide enduit d’aluminium appelé kapton. Les dimensions de chaque couche sont d’environ 21 m de long et 14 m de large. Chaque couche successive du pare-soleil est plus froide que celle ci-dessous. La chaleur rayonne entre les couches.
Astronomie
JWST :
Le voile de protection solaire
Le pare-soleil sépare le télescope en un côté chaud et exposé au soleil (les modèles thermiques montrent que la température maximale de la couche la plus externe est de 383K ou 110°C), et un côté froid (avec la couche la plus froide ayant une température minimale modélisée de 36K ou environ -237°C). Le pare-soleil à cinq couches empêche la lumière du soleil d’interférer avec les instruments sensibles du télescope
Son objectif est d’isoler le télescope et les instruments scientifiques de 99,9999 % de l’énergie du Soleil, de la Terre, de la Lune et du module de service qui lui restera face au Soleil et donc atteindra une température d’environ 85°C. Seul l’instrument MIRI (Mid InfraRed Instrument),aura besoin d’un système de refroidissement supplémentaire.
MIRI doit être refroidi à une température de -266°C, soit plus de 30 degrés de moins que les autres instruments de l’observatoire Webb. MIRI est donc doté d’un « "cryorefroidisseur" » , un réfrigérateur sophistiqué spatial équipé de pompes et de compresseurs répartis dans l’ensemble du cryorefroidisseur pour le refroidir et maintenir sa température à un niveau optimal.
Astronomie
JWST :
Suite déploiement protection solaire
Aft Sunshield Pallet
The Aft Unitized Pallet Structure (UPS)
Nominal Event Time: Launch + 3 days
The UPS supports and carries the five folded sunshield membranes. Prior to this, the spacecraft will have been maneuvered to provide warmer temperatures on the forward UPS and various heaters have been activated to warm key deployment components. Key release devices have been activated. Various electronics and software have also been configured prior to support the UPS motions, which are driven by a motor.
Astronomie
JWST :
Déploiement du support du télescope
DTA Deployment
Deployable Tower Assembly (DTA)
Nominal Event Time: Launch + 4 days
The Deployable Tower Assembly (DTA) is deployed. The tower extends 1.22 meters. This movement/distance provides needed separation between the spacecraft and telescope to allow for better thermal isolation and to allow room for the sunshield membranes to unfold. Prior to this, several release devices will have been activated, and various heaters, software, and electronics have been configured to support deployments. This deployment motion is driven by a motor.
Astronomie
JWST :
Déploiement de cache de stabilisation (pour éviter le vent solaire)
Aft Momentum Flap
Nominal Event Time: Launch + 5 days
The Aft Momentum Flap is used to help offset some of the solar pressure that impinges on the large sunshield. Use of the momentum flap helps to minimize fuel usage during the mission. After releasing hold-down devices, a spring drives the rotation of the aft flap to its final position.
Astronomie
JWST :
Ouverture de la protection du voile
Sunshield Covers Release
Nominal Event Time: Launch + 5 days
This operation releases and rolls up the protective membrane cover. The sunshield release cover has been protecting the membranes during ground and launch activities. Release devices are electrically activated to release the covers.
Astronomie
JWST :
Déploiement du voile de protection solaire
Sunshield PORT Mid-Boom
The Left/Port (+J2) Sunshield Boom Deployment
Nominal Event Time: Launch + 6 days
The Port +J2 Mid-boom deployment steps include the completion of the sunshield cover roll up, the deployments team then extends the +J2 mid-boom along with the +J2 side of the five membranes. This operation is a motor-driven deployment.
Astronomie
JWST :
Déploiement du voile de protection solaire
Sunshield STARBOARD Mid-Boom
The Right/Starboard (-J2) Sunshield Boom Deployment
The Starboard (-J2) Mid-boom deployment steps include the completion of the sunshield cover roll up, the deployments team then extends the -J2 mid-boom along with the -J2 side of the five sunshield membranes. This operation is a motor driven deployment.
Astronomie
JWST :
Mise en tension du voile de protection solaire
Sunshield Layer Tensioning Ongoing
Nominal Event Time: Launch + 9 days
This operation is a multi-step two-day activity which completes the final membrane releases, as well as tensioning the five layers of the sunshield.
After initial sunshield deployments of the forward and aft UPS (which carry the fully folded sunshield), followed by the port and starboard mid-booms (which support and initially unfold all 5 layers of the sunshield together), each layer is successively tensioned.
Astronomie
JWST :
Déploiement du miroir secondaire
Secondary Mirror Deployment Begins
This step begins the Secondary Mirror deployment phase.
Nominal Event Time: New Date: Launch+11 days - Wednesday 1/5/22
The deployments team begins planning and operations for the deployment of the Secondary Mirror Support Structure (SMSS) from its stowed/launch position into its operational position. Webb's secondary mirror is at the end of this structure. As it is deployed, its long booms will swing the secondary mirror out in front of the primary mirror. The secondary mirror plays an important role in reflecting the light from the primary mirror to where the instruments sit, behind the primary mirror.
Astronomie
JWST :
Déploiement refroidisseur instruments
Aft Deployed Instrument Radiator
Aft Deployed Instrument Radiator (ADIR)
Nominal Event Time: Launch + 12 days
This activity releases the last of four launch locks that holds the Aft Deployed Instrument Radiator (ADIR) in its launch configuration. Releasing the last device allows springs to drive the ADIR into its final deployed position. The first three launch locks were released just after launch to prevent any unwanted strain in the system as the ADIR and telescope cools.
Astronomie
JWST :
Déploiement cotés miroir primaire
Port Primary Mirror Wing Begins
This step begins the Primary Mirror deployment phase.
Nominal Event Time: Launch + 13 days
The deployments team begins planning and operations for the deployment of the left/port (+V2) primary mirror wing from its stowed/launch position into its operational position. This operation deploys and latches the +V2 wing of the primary mirror. Each wing holds three of the 18 mirror segments. This is a motor-driven deployment.
Astronomie
JWST :
Fin déploiement miroir primaire
Port Primary Mirror Wing Complete
The Port Primary Mirror Wing is fully deployed and latched.
Nominal Event Time: Launch + 13 days
The left/port (+V2) wing of the primary mirror is fully deployed and latched. Each wing holds three of the 18 mirror segments. This is a motor-driven deployment.
Astronomie
JWST :
Positionnement de autres miroirs
Starboard Primary Mirror Wing Begins
Nominal Event Time: Launch + 14 days
Status: Future.
The deployments team begins planning and operations to deploy the right/starboard (-V2) wing of the primary mirror from its stowed/launch position into its operational position. Each wing holds 3 of the 18 mirror segments. This is a motor driven deployment.
Astronomie
JWST :
Déploiements terminés !
WEBB IS FULLY DEPLOYED!
Nominal Event Time: Launch + 14 days
Status: Future.
It will continue to travel to the second Lagrange point (L2) for another two weeks, at which point it will enter a large orbit around the L2 point. The following five months will be used to cool the telescope to operating temperature, fine-tune the mirror alignment, and calibrate the instruments.
Astronomie
JWST :
Test de chaque segment du miroir
Individual Mirror Segment Movements
Nominal Event Time: Launch + 15 days
Status: Future.
This operation is a multi-day multi-step activity to activate and move each of its 18 primary mirror segments (which are adjustable) out of their launch configuration.
The primary mirror segments and secondary mirror are moved by six actuators that are attached to the back of each mirror piece. The primary mirror segments also have an additional actuator at its center that adjusts its curvature. The telescope's tertiary mirror remains stationary.
Astronomie
JWST :
Début insertion L2
IL2 Insertion Burn
Mid Course Correction Burn (MCC2) - Begins L2 Insertion
Nominal Event Time: Launch + 26 days
A series of activities to plan and execute MCC2 - the insertion burn for Webb's L2 orbit. MCC2 corrects any residual trajectory errors and adjusts the final L2 orbit.
The James Webb Space Telescope is launched on a direct path to an orbit around the second Sun-Earth Lagrange Point (L2), but it needs to make its own mid-course thrust correction maneuvers to get there. This is by design, because if Webb gets too much thrust from the Ariane rocket, it can’t turn around to thrust back toward Earth because that would directly expose its telescope optics and structure to the Sun, overheating them and aborting the science mission before it can even begin. Therefore, Webb gets an intentional slight under-burn from the Ariane and uses its own small thrusters and on-board propellant to make up the difference.
There are three mid-course correction (MCC) maneuvers: MCC-1a, MCC-1b, and MCC-2. This final burn, MCC-2, which inserts Webb into its L2 halo orbit.
Astronomie
JWST :
En orbite autour de L2
WEBB IS ORBITING L2
Orbit Insertion Complete. �Webb is Orbiting L2 in a HALO Orbit.
Nominal Event Time: Launch + 29.5 days
Webb is now orbiting L2. Telescope deployment is complete. Ongoing cooldown and instrument turn-on continue. The telescope and scientific instruments started to cool rapidly in the shade of the sunshield once it was deployed, but it will take several weeks for them to cool all the way down and reach stable temperatures. This cooldown will be carefully controlled with strategically-placed electric heater strips. The remaining five months of commissioning will be all about aligning the optics and calibrating the scientific instruments.
Astronomie
JWST :
Les instruments
L’optique arrière (troisième miroir)
Le module scientifique ISIM
FGS pour le pointage des cibles du JWST
NIRSpec
NIRISS
NIRCam
MIRI
Astronomie
JWST :
La suite :
Astronomie
JWST :
A construire ?