WATCH: Cmdr. Hadfield’s son looks back on father’s time in space

While his dad defied gravity for the past five months, Evan Hadfield has been Canadian astronaut Chris Hadfield’s right hand man on land.

But by the end of the day Monday, his father will be back on Earth.  He’s due to land in Kazakhstan after 10:30 p.m. EDT.

Cmdr. Hadfield has done what no astronaut has done before, becoming an Internet sensation while floating in space during his term aboard the International Space Station (ISS).

He’s done everything from tweet pictures of almost every corner of the Earth to hand over control of the ISS in song.

The younger Hadfield, donning a moustache in honour of his father, admits the now-viral cover of David Bowie’s “Space Oddity,” posted to YouTube on Sunday, has been in the works since November, well before Cmdr. Hadfield blasted off to the ISS.

WATCH: Chris Hadfield sings David Bowie’s ‘Space Oddity’ in new music video

Believe it or not, building the astronaut’s social media stardom was only a small fraction of what he did in space, his son explained in a Skype interview with Global News.

“Dad works 18 hours a day every single day,” he said.

But his engagement with followers young and old is what has set Hadfield apart from his fellow astronauts. While he’s not the first one to use social media from space, Hadfield’s name has become known for his tweets from above.

Read more: The best of Canadian astronaut Chris Hadfield

“It requires a certain finesse,” said the junior Hadfield. But he admits it was very much a group effort.

It’s been a huge effort, involving a number of people, to help his father interact with students all over Canada and pique their interest in space and science.

“What I’m most proud of is the Canadian Space Agency’s capacity to react to what we’ve been doing and immediately change their system to fit what’s going on,” he said.

The Hadfields had a plan for what they wanted to accomplish during the commander’s time on board the ISS, but they didn’t anticipate how popular he would become. Hadfield said the CSA’s quick adaption to the situation was “amazing.”

He said he hopes they’ve made a difference in the way space programs operate and discuss space travel.

While Hadfield said he’s looking forward to some of the simpler things in life, such as the smell of a fresh cup of coffee, his adjustment to life on land will be as smooth a Soyuz spacecraft landing.

In other words, it’s not going to be the most splendid transition.

“He’s gonna land on Earth, he’s probably gonna vomit on himself, and then he’s going to pass out. That’s what happens when you come back from space.  You have to get used to gravity,” said the astronaut’s son.

And, yes, all of the details of Hadfield’s readjustment to life on Earth will probably be tweeted.

*With files from Stuart Greer