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It remains unclear if Virgin Galactic’s business model — or any space tourism business — can be made into a successful and sustainable money-making enterprise. But Virgin Galactic executives have acknowledged for years that its success or failure will hinge on whether or not the company convinces the general public that the trip can be not just safe, but worth the hefty per-seat price tag.

However, NASA and SpaceX officials at Florida’s Kennedy Space Center, the launch site for the mission,

Musk issued a brief series of tweets overnight, stating that he had “mild sniffles,” a “cough” and “slight fever” for the past few days. He added that he is expecting to get the results of a PCR test — which are known to be more accurate than the type of rapid test Musk said he took— within 24 hours.

Meanwhile, Musk’s tweets echoed across the country to Kennedy Space Center in Florida, where four astronauts are preparing to ride into space aboard a SpaceX Crew Dragon capsule on Sunday.

NASA chief Jim Bridenstine, who was scheduled to conduct a routine press conference Friday morning, told reporters who asked about Musk’s tweets that, per NASA policies, Musk should be in quarantine and SpaceX would be attempting to determine who might have come into contact with Musk.

On Friday evening, during another routine press briefing, NASA and SpaceX officials at Kennedy Space Center said the contact tracing was largely complete, and they determined no one who is essential to this weekend’s mission was at risk of exposure to Covid-19.

The astronauts, according to NASA’s deputy manager of flight operations Norm Knight, are almost certainly not at risk.

The space agency has regularly tested anyone who has been in close proximity to the crew. Even before the pandemic, NASA astronauts have abide by pre-flight quarantine rules to ensure they don’t take an illness into space, where viruses and bacteria could rapidly spread among crew members packed onto a spacecraft. NASA has also implemented stricter measures in response to Covid-19.

For two weeks prior to launch, the astronauts have been in “hard quarantine,” meaning they’re “totally isolated” and are unable to be in close proximity to anyone outside of the launch team, even their families, Knight said.

And Musk, he added, will not be allowed into NASA facilities on launch day.

“It’s restricted access,” he said. “It doesn’t matter if you’re Elon Musk or Jim Bridenstine… if any [of NASA’s Covid-19 protocols] have been compromised, then we’re not going to let you near the crew. And again, it’s to protect the overall mission.”

It’s not clear if Musk had been planning to attend the launch in Florida, though he is frequently seen at SpaceX’s launch control at the Kennedy Space Center during important SpaceX missions.

SpaceX’s head of human spaceflight programs, Benji Reed, said that SpaceX’s mission control center in Hawthorne, California is abiding by strict health and safety rules. Employees who serve critical roles in the launch process have been taking tests, undergoing temperature screenings, and quarantining to assure their health ahead of this weekend’s mission.

Reed also urged members of the public not to disregard Covid-19 if they choose to watch the launch from the ground in Florida this weekend.

“We know that everybody’s very excited about launch and very excited about recovery and human spaceflight in general,” Reed said. “We certainly do ask that everybody’s who’s involved, If you come out to watch the launch…please wear your masks and and follow social distancing guidelines. Do the right things there to keep everybody safe.”

The mission is slated to take off Sunday at 7:27 pm ET. The original launch date was Saturday evening, but officials delayed that earlier today due to unfavorable weather conditions, NASA and SpaceX officials said.

Why Musk’s tests may have been wrong

Musk said on Twitter that all four tests he took on Thursday were rapid tests, or “antigen tests,” conducted by the same nurse at the same facility. He alleged in his late-night tweets that something “extremely bogus” was going on, echoing months of earlier tweets in which Musk has expressed doubt about Covid-19’s threat. He also previously shared a YouTube video that was later removed for containing misinformation about the virus.

In a recent interview with journalist Kara Swisher, Musk doubled down on his skepticism, saying he would not take a Covid-19 vaccine when it becomes available and insisted that stay-at-home orders designed to thwart the virus’s spread did more harm than good.

In fact, medical professionals are well aware that rapid antigen tests can be inaccurate and generate false negative or, more rarely, false positive results.

PCR tests, on the other hand, can take a day or more to return results but are far more accurate.

That’s because PCR tests search for signs of the Covid-19 virus’s genetic material, while antigen tests search for one of the viral proteins, or a small trace of the virus’s presence. And though both types of tests rely on a nasal swab, PCR tests require complicated specialized labs and trained technicians to conduct. That’s why in the early days of the pandemic, PCR tests were heavily backlogged, sometimes taking more than a week to return results. The antigen tests were expected to provide a quicker — albeit less accurate — picture of how the novel coronavirus was spreading throughout the United States.

Musk also called out the company that manufactured the antigen tests he took on Thursday, New Jersey-based medical technology company BD (BDX).

Jessica Offerjost, a BD communications manager, responded in an emailed statement to CNN Business, saying the company is “aware of the tweet and are reaching out to learn more consistent with our quality management process.”

“While the scientific community agrees that no diagnostic test is perfect, we stand behind the quality, utility and science of our system,” the statement reads. “There are many factors that could lead to a discordant result…As we clearly state in our instructions for use, negative results should be considered in the context of a patient’s specific situation and confirmed with a molecular PCR assay if necessary for patient management.”

Virgin Galactic said Monday that it no longer plans to conduct a key test flight of its spacecraft this week because of a surge in new Covid-19 cases and resulting related restrictions in New Mexico, home to the company’s glitzy spaceport.