— Mike Massimino is launching on his third, or maybe his fourth, mission — sort of.

Massimino's first two missions were as a NASA astronaut aboard the space shuttle. He launched twice to service the Hubble Space Telescope (his second mission was the final flight to upgrade the orbiting observatory in 2009).

His third mission, if one counts it, was as a fictional version of himself on the CBS sitcom, "The Big Bang Theory." (He told the show's producers three things were needed for it to be a mission: a crew patch and a crew portrait, which he got, and a spaceflight, which in the context of the TV show had him launching to the International Space Station with Howard Wolowitz [Simon Helberg].)

His current "mission" is of a different type. But, he says, it shares similarities with his prior trips into space.

On Tuesday (Oct 4), Massimino is launching his first book, "Spaceman: An Astronaut's Unlikely Journey to Unlock the Secrets of the Universe" (Crown Archetype).

"This is kind of like another mission," Massimino explained in an interview with collectSPACE, "trying to come out with a really good space book, a really good memoir, that can show people what it is like not giving up and pursuing your dream, how gratifying it is to have a sense of purpose and being a service to others and just how cool space is."

"I think we did that. I am happy with the way it turned out."

A NASA astronaut from 1996 to 2014, Massimino logged almost 24 days in orbit, including 30 hours spacewalking to repair the Hubble. In "Spaceman," he recounts growing up in Long Island, New York, and being inspired by the Apollo 11 moon landing to attend college (at Columbia University, where today he is a professor of engineering).

Massimino's path to becoming an astronaut wasn't always clear, literally, as he struggled to meet NASA's perquisites by overcoming a problem with his eyesight. As he recounts in the book, his perseverance paid off and he was able to accomplish his life's dream.

"It's been quite a challenge and a lot of work," Massimino said about writing his autobiography. "I feel like this is my third launch into space. There are a lot of similarities to it, being an astronaut and being an author."

For example, he couldn't do it without the help of his team ("my agent, my co-writer, manager, editor"), and it required a similar attention to detail.

"Just like a [mission's] flight plan, you want to make sure your plan for the book is good and that you haven't missed anything in the edits. It is all accurate, truthful and good," he stated.

Further, just like his other missions, Massimino found that sharing his story was something he found rewarding.

"It was fun, exciting," he said, continuing the comparison, "and hopefully less dangerous."

Massimino's spaceflight experience came to its climax on May 17, 2009, when a stuck handrail came between him and a critical repair to a science instrument on the Hubble Telescope. After exhausting what seemed like every other option, he ultimately had to use brute force to physically rip the aluminum bar off its last fastener.

Massimino describes the unprecedented action, and the still-complicated repair that came after it, in the book. The instrument that he helped to restore, the Space Telescope Imaging Spectrograph, or STIS, was recently at the center of NASA's announcement of evidence for water plumes on Jupiter's moon Europa.

"[In "Spaceman"], I talk about how that repair almost didn't work," Massimino said. "It was a cool spacewalk, but the reason we were doing it was to get this instrument working again and in the hands of the astronomers so they could make these sort of discoveries."

(As for the infamous handrail, Massimino said it became the subject of an engineering study at the Goddard Space Flight Center in Maryland, rather than becoming part of his mementos. "I tell my students if you really want something in life, you need to steal it," he joked. "I didn't steal it.")

To promote "Spaceman," Massimino is launching Tuesday on a multi-city and country book tour. He's also spent days signing thousands of tipped-in pages and adhesive plates to accompany the books ordered online.

"The way I figure it, if someone is willing to pay to buy my book, the least I can do is sign it," he said.

And even that experience paralleled his earlier missions.

"Signing autographs in preparation for a mission is just like this," Massimino stated. "We'd get hundreds of lithographs that we'd have to sign. The difference was that when we did that, I was part of a crew and seven people would need to sign them, so we'd each take a chunk and at the end of the week trade them to the next guy."

"And that's sort of what like this is, but it's only me signing them," he said.

"Spaceman: An Astronaut's Unlikely Journey to Unlock the Secrets of the Universe" by Mike Massimino was released by Crown Archetype on Tuesday, Oct. 4, 2016.