A REMUS 6000 underwater vehicle is brought back aboard the research vessel Alucia during this spring's search for Air France Flight 447 off Brazil. Sylvain Pascaud/WHOI
The Alucia, a renovated French research ship, left the port of Suape, Brazil, in late March with one purpose: succeed where its team of scientists and engineers had previously failed.
On June 1, 2009, Air France Flight 447 took off from Rio de Janeiro en route to Paris with 228 passengers and crew. Approximately 350 miles off the coast of Brazil, the Airbus 330 — widely thought to be one of the safest planes in the world — crashed into the Atlantic Ocean, killing all aboard.
In the first 18 months since the plane disappeared, there had been three failed attempts to find it and things were getting desperate. The French government and Air France wanted answers. But more than answers, the families of the victims wanted closure.
The French aviation accident investigation agency partnered with experts from Woods Hole Oceanographic Institution. Even though WHOI came up short on a previous attempt, the French felt confident they were the right team for the job. "We made some great maps and proved to ourselves we could work in that terrain," said Dr. David Gallo, special projects coordinator at WHOI. With an average depth of two miles and terrain more rugged than the Rocky Mountains, the Alps or the Grand Canyon, it was a difficult search, Gallo said.
A circle was drawn around the plane's last known point, establishing an area of about 5,000 square nautical miles. WHOI searched the northwest portion of the circle on its first attempt in spring of 2010. This time, they were to map the entire circle at an estimated cost of $3 million. "If you centered it in Massachusetts you could get almost all of New England in the area," said Mike Purcell, senior engineer at WHOI.
The Alucia carried food and supplies for a 30-day voyage, along with three REMUS 6000s — underwater autonomous vehicles — capable of mapping the ocean floor at depths of 6,000 meters using side scan sonar.
Purcell and his team of 14 relaxed for two and a half days as the boat steamed out to the site. When the boat arrived Purcell described the scene as "chaotic." "Everyone was working, we were running three vehicles at once, the scene on the Alucia was crazy for four days until everyone settled in and adjusted to the pace," Purcell said.
The team made the decision to start their search at the center of where they believed the plane had entered the water, near the Mid-Atlantic Ridge — a rugged tectonic plate boundary. The plan was to run two 12-hour shifts and have three REMUS vehicles in the water at a time.
On the eighth day of their mission, a REMUS vehicle surfaced with side scan data of an unusually flat space that was the right size for a debris field, Purcell said. To confirm that side-scan sonar data was the wreckage of Air France Flight 447 meant another vehicle had to be fitted with a camera and travel almost three miles underwater to photograph the area. Purcell and his team had worked on this project for a year and a half. In 16 hours, they would know if their search was over.
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REMUS — or Remote Environmental Monitoring Units — were developed by scientists and engineers at Woods Hole Oceanographic Institution. Founded in 1930, WHOI has made important discoveries ranging from new forms of marine life to the final resting place of the Titanic.
"We are the best in the world and we have a really good system to make sure that's the case," said Dr. David Ross, scientist emeritus and 40-year veteran of WHOI. "We have the technology, the ships, and the tradition of doing these things."
The original REMUS 100 was a five-foot-long missile-like vehicle that weighed about 80 pounds and could reach depths between 300 and 400 feet. It has been used to support environmental studies and to provide mine detection in the Persian Gulf.
Hydroid Inc. was formed in 2001 by WHOI engineers with the REMUS 100 as the foundation of its business. The REMUS technology was transferred from to Hydroid through a law that provides universities, among others, with ownership of intellectual property funded by the U.S. government.
The small size of the REMUS 100 was an asset, but also a weakness. It was compact and easily portable, but not did not have the payload to travel deeper and conduct more complex missions. "The sensors that are used to explore the ocean are big and they take a lot of power so you cannot fit all the advanced sensors in something this small," Hydroid president Chris von Alt said. "That's why the REMUS 600 was invented, for the more advanced sensors and more energy for longer missions."
The abilities of these underwater vehicles for scientific and military purposes made Hydroid a valuable company. It was purchased by a Norwegian tech company in 2008 for $80 million.
Each REMUS vehicle is slightly bigger than its predecessor, providing a larger payload and capable of reaching greater depths. The newest model, the REMUS 6000, weighs 1,900 pounds and is 12.6 feet long. It can dive almost five miles underwater with a 22-hour battery life.
It was this machine experts from WHOI used in their search for Air France 447.
As REMUS vehicles get bigger, their potential capabilities increase. "Through sensors and transmitting, it can measure anything you can come up with," Ross said. "We are limited by our imagination right now."
There are no joysticks or piloting of these vehicles. An operator uploads a mission for the AUV to follow. When the vehicle reaches its depth, side-scan sonar pings out both sides of the vehicle, painting a swath; it maps similar to the way people mow their lawn. The vehicle goes back and forth across the ocean floor, making sure it leaves no uncovered space. When it completes the mission, it surfaces at a predetermined point, von Alt said. "We use the same software, same skills, same training programs, so if you can run this vehicle, you can run that vehicle," von Alt said.
To prevent a collision with a natural barrier or an underwater mine, these vehicles have a device that allows them to remain a certain distance from the ocean floor. The vehicle rises with the ocean floor. A sensor sends the vehicle information, allowing it to adjust its heading to stay on course through water currents.
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The 16-hour wait was a time of quiet energy. Purcell's team was aware of the progress but there was little talk of the potential discovery. The French were notified of the side-scan sonar data but, given the false reports and bad press, there was a need for secrecy. "They were pretty big on keeping it a secret, we didn't share it with the whole boat," Purcell said. "If they said something, they wanted it to be accurate."
The 16 hours had passed and the REMUS surfaced. But the answers were just out of their grasp. "The vehicle was supposed to be up at 11 a.m., but we had the worst weather out there, with a squall and winds blowing 30 miles an hour and the waves were coming up," Purcell said. "We actually let it sit out there for a couple of hours while we waited for things to calm down."
For the team, 18 months was a long time to wait — 16 hours was a long time to wait — but the two hours the REMUS vehicle sat in the ocean while riding out the storm may have been the most difficult of all. "The recovery time is the most dangerous part for the vehicles," Purcell said. "You always have this risk of a moving ship and a moving vehicle and it could hit the propeller." The weather subsided and the team was able to successfully recover the vehicle.
It took several hours to upload the 16,000 pictures the REMUS carried, but within 45 minutes, the first pictures of the airliner's landing gear lit up the computer screens aboard the Alucia. "Next to the day my kids were born, hearing Mike's voice on the telephone telling me we had found it was one of the happiest days of my life," Gallo said.
Since the discovery of the airliner on the ocean floor, the remains of more than 100 victims have been recovered. The cockpit voice recorder and flight data recorder have been retrieved and analyzed by investigators. French authorities announced Monday that a report will be released on Friday with new findings into the cause of the crash.
When the team from WHOI went searching for the plane the first time, they docked after 30 days to refuel and gather supplies. "I thought they would break for a few days and rest on shore," Gallo said. "These people were so committed that they left the next day.
"This had been something we had worked on for 18 months, and to know that we had helped air safety for years to come and provided those families a sense of closure was a tremendous feeling."