Webb telescope powered for flight, ready to be lifted to the top of the launcher – Spaceflight Now


The James Webb Space Telescope is loaded with toxic thrusters by technicians wearing self-contained protective suits. Credit: ESA / CNES / Arianespace / P. Piron

A crane from the Guyana Space Center in South America will hoist the nearly $ 10 billion James Webb Space Telescope more than 15 floors above the ground of a rocket assembly hangar this weekend to position the observatory above its Ariane 5 launcher for take off later this month.

The delicate operation, completed to perfection before the 111 previous Ariane 5 missions, will take most of the day on Saturday. If all goes well, engineers will get their hands on Webb for the last time on Sunday before locking up the 35-foot (10.66-meter) observatory inside the Swiss-made Ariane 5 payload fairing. Monday.

“The next big step will be this Saturday, and we will integrate the observatory on the launcher,” said Thierry Wilmart, mission director for the Webb launch at Arianespace, the commercial operator of Ariane 5. “It will, of course, be , a major and sensitive operation, so basically we have a full review with the spacecraft project to review the whole operation, all the stages. “

The James Webb Space Telescope is a joint program between NASA, the European Space Agency and the Canadian Space Agency. NASA, the lead partner, developed Webb’s spacecraft bus, heat shield, and the telescope itself, the largest ever sent to space. NASA was also responsible for part of Webb’s infrared instrumentation set.

ESA is launching an Ariane 5 rocket and has provided other elements of the instruments to collect reams of data from the cosmos. Canada provided parts of instruments and a guidance sensor to keep Webb pointed at his celestial targets.

A quarter of a century in the making, Webb is now less than two weeks away from Earth, bound for a gravitationally stable region known as L2, a Lagrange point a million miles away. The new space observatory will see farther into the universe and further in time than the Hubble Space Telescope, gathering images of the first galaxies after the Big Bang more than 13 billion years ago.

Webb will also study star formation and measure the composition of the atmosphere of planets around other stars.

Webb’s connection to its European launcher follows nearly two months of stand-alone processing with the observatory since arriving at the Kourou spaceport in French Guiana in October. Engineers verified that the observatory survived the trip to French Guiana from its factory in California, then mated Webb with the adapter ring that will attach to the top of the Ariane 5 upper stage.

During this stage of Webb’s preparations, a clamp band that connects the spacecraft to the payload adapter unexpectedly opened, sending a vibration throughout the observatory. Engineers re-tested parts of the spacecraft to make sure it had not been damaged in the incident, and then gave the go-ahead to load propellants into the spacecraft from November 25.

Illustration of the James Webb Space Telescope inside the payload fairing of its Ariane 5 rocket. Credit: ArianeGroup

Working inside Arianespace’s satellite readiness facility, technicians wearing self-contained protective suits loaded toxic hydrazine fuel and dinitrogen tetroxide propellants into tanks at the observatory base. The load consisted of 661 pounds (301 kilograms) of liquid propellant – 369 pounds (168 kilograms) of fuel and 292 pounds (133 kilograms) of oxidizer.

The propellants will power the mission’s 20 rocket boosters.

Four of the small engines – a main thruster and redundant in two nacelles – will consume fuel and oxidant for the main course correction maneuvers. Webb has eight other thruster modules, each with two small hydrazine-powered motors to push the observatory with a single pound of thrust, providing pointing control in concert with rotating reaction wheels inside the spacecraft.

The fuel loading system was disconnected from Webb on December 3, according to NASA.

Technicians also loaded pressurized helium into the spacecraft, then placed Webb in a temperature-controlled transport transporter for a road trip a few miles northwest of the Ariane rocket final assembly building. 5 – known in French as Batiment d’Assemblage Final, or BAF – on Tuesday evening.

The Ariane 5 rocket, made up of its cryogenic central stage powered by hydrogen, two solid rocket boosters and an upper stage, was built inside the launcher integration building of the Guyana Space Center from the November 6. Teams transferred the rocket, without Webb and its payload shroud, to the final assembly building on its vertical launch table on November 29, setting the stage for the observatory’s arrival after refueling.

With Webb now set to meet his trip to space, the launch campaign is now in the “combined operations” phase leading up to the mission’s target takeoff date of December 22.

Lifting an expensive and one-of-a-kind spacecraft above the Ariane 5 vertical rocket is “always a sensitive operation,” Wilmart said. Most Ariane 5 payloads are valued at a few hundred million dollars. A few, like ESA’s interplanetary science missions, cost more than $ 1 billion.

Webb will be the most expensive space science mission ever.

“We’re avoiding moving the spacecraft with the crane as much as possible, which means the next time we do that is for launcher integration,” Wilmart said this week in a phone interview with Spaceflight. Now.

The Ariane 5 rocket that will launch the James Webb Space Telescope was transported from its integration building to the final assembly building on November 29 at the Guyana Space Center. Credit: ESA / CNES / Arianespace / P. Baudon

Once Webb is attached to the top of the Ariane 5 rocket on Saturday, ground crews will remove the last protective covers from the thrusters and other parts of the spacecraft on Sunday. After removing the red “remove before flight” elements, teams will give the go-ahead to encapsulate Webb inside the 17.7-foot (5.4-meter) diameter nose cone of the Ariane 5 rocket.

“Once on the launcher, we want to encapsulate as quickly as possible,” Wilmart said. “We do not want to have too long a duration with the observatory on the launcher without the fairing because after the encapsulation, it will be under the fairing with the adequate ventilation and the protection of the fairing vis-à-vis the environment.

“So we all agreed to go there (quickly) for three days… That’s mainly because of that (will) have these three major operations over three consecutive days.”

“From Monday afternoon, the observatory will no longer be visible,” Wilmart said.

Webb will fill the front fairing of Ariane 5, one of the largest payload shrouds of any operational rocket. When a crane lowers the fairing above Webb, some parts of the observatory will only have 8 inches of free space, according to Daniel de Chambure, acting head of the Ariane 5 rocket adaptation program to the ‘ESA.

A laser alignment system will ensure the encapsulation goes smoothly, Wilmart said.

With Webb encapsulated in the fairing, officials in French Guiana will focus on a launch dress rehearsal on December 15, including the spacecraft, launch vehicle, and range safety teams. Next Friday, December 17, officials will meet for a launch readiness review to discuss the status of all Ariane 5 deployment systems from the final assembly building to the ELA launch pad. -3.

Wilmart said the Arianespace and NASA teams have two calendar days for the launch date of December 22, which is itself four days behind a previous target date. The four-day slip allowed engineers to retest the components on Webb after the payload adapter crash last month.

If all goes according to plan, officials will take two days off next weekend to rest before the final push to launch.

The Ariane 5 is expected to exit the final assembly building for the 2.7 km trip to the ELA-3 launch pad on December 20. It will roll on its mobile launch platform along the railroad tracks, pulled by a diesel engine – motorized tug.

The half-day countdown will begin at the end of December 21 and will continue with the loading of cryogenic liquid hydrogen and liquid oxygen propellants into the Ariane 5 before dawn on December 22. Webb has a 30-minute launch window that opens at 7:20 a.m. EST (1220 GMT; 9:20 a.m. PST).

Ariane 5 will launch Webb approximately half an hour after launch, sending Webb on its journey to Lagrange point L2. Then began a series of decisive deployments to configure Webb for scientific operations.

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Follow Stephen Clark on Twitter: @ StephenClark1.


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