The water leak that nearly drowned a spacewalking astronaut last summer started a week earlier but was misdiagnosed by NASA officials who were reluctant to report serious problems, an investigation has found.

The National Aeronautics and Space Administration released Wednesday the findings of a panel set up to review the life-threatening incident of last July 16, when Italian astronaut Luca Parmitano had to abort a spacewalk outside the International Space Station (ISS) because water filled the upper part of his helmet.

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NASA didn’t terminate the outing more promptly, the report said, because ground controllers were initially more concerned with the water interacting with anti-fog chemicals on the helmet visor and stinging the spacewalker’s eyes – a problem that happened to Canadian astronaut Chris Hadfield in 2001.

There was, in fact, a major leak and Major Parmitano, an Italian Air Force test pilot, had to find his way back to the airlock despite being blinded by water covering his ears, eyes and nose. Afterward, 1.5 litres of water was found from his helmet.

“Given the limited volume of the helmet and the behaviour of the water, this condition was life-threatening,” the 222-page investigation report says.

The report reveals that there had been a leak in a previous spacewalk on July 9 that was not dealt with properly because the spacesuit’s drinking bag was wrongly blamed.

“This event was not properly investigated, which could have prevented placing a crew member at risk a week later,” ISS Chief Engineer Chris Hansen, who chaired the five-member investigation board, told reporters during a teleconference on Wednesday.

He said the probe found that the ISS program was too focused on trying to maximize the time the crew spent on orbital experiments, while at the same time ground officials were reluctant to investigate engineering problems further.

“The flight control team [had a] perception that the anomaly-reporting process was a bit resource-intensive and there were some schedule pressure. It made them reluctant to invoke it,” he said.

As a result, the ground team was all too willing to agree with the space station crew’s initial assessment that the drinking bag was to blame when leaking began on July 9.

In fact, the leak was caused by particles that plugged a fan pump separator in the suit’s life-support system. The contaminants clogged holes, causing water to back up and migrate into the helmet.

Given what little was known at the time, the report praised Major Parmitano’s performance. “[His] calm demeanour in the face of his helmet filling with water possibly saved his life.”

On that day, Major Parmitano and U.S. Navy Commander Chris Cassidy were supposed to conduct a six-hour spacewalk to rig jumper cables for the future arrival of a Russian lab module.

About 44 minutes into the spacewalk, Major Parmitano felt some wetness behind his head.

“It’s hard to tell but it feels like a lot of water,” he radioed flight control in Houston.

“Where is the water coming from? It’s too much,” he said a few minutes later. “It’s in my eyes.”

In a blog post afterward, Major Parmitano wrote that he was blinded and could get back to the airlock only by tugging on his safety tether lines.

“My ability to see – already compromised by the water – completely vanishes, making my eyes useless; but worse than that, the water covers my nose – a really awful sensation that I make worse by my vain attempts to move the water by shaking my head.

“By now, the upper part of the helmet is full of water and I can’t even be sure that the next time I breathe I will fill my lungs with air and not liquid.”

Of all the spacewalking issues the ISS program has faced until now, Mr. Hansen said, “this is probably the most serious one we’ve encountered.”