Categories: Astronomy

Why is James Webb Traveling to the Launch Site by Boat and not an Airplane?

The James Webb Space Telescope inside a cleanroom at NASA’s Johnson Space Center in Houston. Credit: NASA/JSC

The James Webb Space Telescope has faced a lot of questions during its arduous journey to completion. Some of the questions have been posed by concerned legislators, mindful of the limitations of the public purse as the telescope’s cost ballooned.

But the budget wrangling and the cost overruns are behind us now. The question that needs an answer is, why is it travelling to its launch site by boat and not airplane?

At this point in time, the ground-breaking space telescope has cost around 10 billion USD. That’s a lot of money. So whatever happens next for Webb, including its journey to the launch site in Kourou, French Guiana, will be focused on avoiding any damage or mishaps.

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The JWST is due to launch from Kourou in December. That’s 14 years past its initial launch date in 2007. Once in operation at the Sun-Earth L2 orbit, it’ll bring its power to bear on some of the most pressing issues in astronomy and cosmology. The Webb will look back in time to the formation of some of the earliest galaxies in the Universe. It’ll also examine the atmospheres of some potentially habitable exoplanets. Read about its science objectives here.

We’ve been waiting a long time for the JWST to become operational, but we have to wait a little longer. The next step in its journey is to the launch site at Kourou. Rather than flying the telescope to the launch site, NASA is transporting it by ship from Long Beach, California, down through the Panama Canal, then along the coast of South America to French Guiana.

As it turns out, flying the JWST to Kourou wasn’t an option.

It’s not that the telescope is too heavy for an aircraft. It’s more to do with the lay of the land near the Guiana Space Centre at Kourou. The Lockheed C5 Galaxy cargo aircraft can easily carry the telescope, it’s what happens when it lands that’s the problem.

The nearest airport to the Guiana Space Centre is the Cayenne Airport. But Cayenne is nearly 96 km (60 miles) down the coast from the launch site. And in that 96 km, there are several bridges that can’t support the telescope’s weight. So NASA is adding one more leg to the JWST’s epic journey: a sea voyage.

Whether by land, air, or sea, the JWST needs to be protected during its journey. It is, after all, a finely-engineered, expensive piece of equipment. So NASA has a special shipping container, just for space telescopes. It’s called the Space Telescope Transporter for Air, Road, and Sea (STTARS).

The Space Telescope for Air, Road, and Sea (STTARS) is a custom-designed container that holds the James Webb’s Optical Telescope and Integrated Science (OTIS) instrument module. In this image its being unloaded from a U.S. military C-5 Charlie aircraft at Los Angeles International Airport (LAX) on Feb. 2, 2018. Image: NASA/Chris Gunn

NASA designed STTARS to hold the Webb’s OTIS, or Optical Telescope and Integrated Science module. OTIS must be kept safe at all costs, and STTARS does just that. The container itself weighs nearly 75,000 kilograms (165,000 lbs) and controls the temperature and humidity to protect the JWST. It also helps isolate the telescope from the physical stresses of travel.

According to a report on Inverse, NASA isn’t releasing all the details of the James Webb’s ocean voyage. There’s some concern around piracy and other potential interference, so NASA’s not revealing the timing and exact course the ship will take. NASA has enlisted the US transportation Command to help assess the route for safety and other considerations, and it’s possible that a naval ship will provide some escort.

When the ship carrying STTARS and the JWST makes landfall in French Guiana, the journey isn’t over. It takes meticulous planning to transport the telescope to the launch facility, even though it’s only about one hour of travel to reach the Guiana Space Centre. Every road, intersection, and bridge must be fully analyzed before the valuable cargo can make the final Earth-bound leg of its journey.

The official poster for the James Webb Space Telescope. Image Credit: By NASA/JPL-Caltech – Public Domain.

Potholes are filled, trees are trimmed, and any and all hazards are examined. There are alternate contingency routes in case any problems or new hazards crop up. NASA planners will also designate safe havens along the route, in case the convoy needs to stop for repairs or some other, unforeseen reason. There’ll be a police escort, too.

While a typical tractor-trailer truck is about 15.2 meters (50 feet) long, STTARS is double that. That means it needs a very large turning radius. STTARS is also tall, so some traffic lights along the route will have to be removed while the convoy passes by. All of these considerations mean that STTARS can only travel between midnight and 6 AM. If it can’t complete the journey in that time, it’ll have to wait in one of the safe-havens until the next window.

When the journey is over, there’s still more work to be done. It’ll take 55 days just to prepare the JWST for launch. Everything must be tested to ensure there are no problems after the long journey. Then the telescope has to be configured to mate with the rocket. It’ll take a couple of weeks to fuel the spacecraft with the fuel it needs to hold its position at Sun-Earth L2. Then it’ll be attached to the Ariane 5 rocket, the same rocket family that launched other space telescopes like XMM-Newton, and the Herschel and Planck observatories.

Then, finally, after so many delays, the telescope will launch on December 18th.

After launch, the telescope will travel about 1.5 million km (930,000 mi) where it will enter into an unstable halo orbit at Sun-Earth L2. It’ll join a growing community of spacecraft there, including the ESA’s Gaia mission and NASA’s future Nancy Grace Roman Space Telescope (formerly WFIRST.)

Once there, it’ll take about 6 months to commission the telescope before science operations can begin. The JWST has a nominal mission length of five years, with an upper limit of ten years, dictated by the amount of propellant it carries.

There’s been so much written about the JWST’s long journey from concept to completion that it could fill a server farm. It’ll be a relief to finally be talking about its discoveries. If all goes well, and STTARS can get the Webb safely over the sea to Kourou, we’ll be one step closer to that day.

After launching on December 18th—fingers crossed— the spacecraft will take 30 days to reach Sun-Earth Lagrangian 2. Science operations should begin 6 months after that. Researchers are lined up to use their allotted time, so we can expect some results next summer, hopefully.