He had studied space engineering at university and always been interested in it but hadn't really considered it a credible career path. Then he discovered there was a small satellite company just down the road in Guildford.
What he found at SSTL appealed immediately.
“I liked that it was small and rogue and defiant,” says Calem. “We could afford to be more innovative and move faster. I had a lot to learn… but there was a vast wealth of knowledge and experience around me.”
Calem joined SSTL's Mechanisms team and, over the years that followed, designed almost every type of mechanism we use - from deployment and separation systems to imager and pointing mechanisms.
Several started with a blank sheet of paper and went on to become flight hardware.
There is still something special, he says, about unboxing a piece of hardware that until then has existed only as a design on a screen.
“They're often beautifully machined and intricately detailed – like little sculptures. And the first time a mechanism moves, in a deployment test or when you first power a motor, is pretty cool.”
One of those is the S-band Antenna Pointing Mechanism for Lunar Pathfinder – giving Calem a rather unusual relationship with the Moon.
“When I look up at the Moon now, I think that something I designed, built and tested by hand will soon be up there.”
Today, Calem has moved from Mechanisms into Product Management, taking the experience gained developing individual products and applying it at spacecraft level.
It's quite a progression for someone who once wasn't convinced that space could be a career at all.