Mr. MacCallum is a Paragon co-founder. Mr. MacCallum was the Principal Investigator on four microgravity experiments on the US Space Shuttle, the Russian Mir Orbital Station and International Space Station using Paragon’s Autonomous Biological Systems, and has supported numerous other biological experiments on the Space Shuttle and International Space Station. The four-month Mir experiments produced the first animals to have completed their life cycle in microgravity and the first aquatic plants to be grown in space. Mr. MacCallum is a co-designer and patent holder for the Autonomous Biological System. He was the design lead for the Jet Propulsion Lab Mars Greenhouse Experiment Module (GEM) payload, and Mars GEM payload ECLSS. He is presently involved in the design of life support and thermal control systems for commercial manned suborbital spacecraft, a novel Mars space suit portable life support system technology funded by NASA, as well as hazardous environment life support technology development for the US Navy divers in which he is the test diver.

Mr. MacCallum was a member of the first two-year mission living and working inside Biosphere 2, a three-acre materially closed ecological system, containing seven biomes, which supported the life of the eight human inhabitants. It was designed for research applicable to environmental management on Earth and the development of human life support for space.

He was responsible for the design, implementation and operation of the atmosphere and water management systems as well as the self-contained paperless analytical laboratories for Biosphere 2 and its Research and Development Center. He has been granted a patent for his design of the Biosphere 2 air sampling and analysis system. Mr. MacCallum has been involved in numerous analytic efforts including a Soviet BioSatellite project and a marine microbial sampling project. Mr. MacCallum also served as Safety Officer and Assistant Medical Officer on the Biosphere 2 Resident Research Team. He has published numerous papers resulting from his work at Biosphere 2, on space related issues, medical issues and on the experience of living and working in an Isolated Confined Environment.

Mr. MacCallum has worked at every level of command on a research vessel, sailing to over 40 ports and over 30,000 miles around the world. Training in Singapore, he became certified as a Dive Controller and Advanced Open Water Diving Instructor. He served as Dive Master for a project to reintroduce two captive dolphins to the wild, ship salvage operations, and specimen collecting expeditions in every ocean and most of the world's seas.