The commentator tells us in the NO PLACETO HIDE script that Dr. John Robinson, Professor of Astrophysics at the University ofTaos is heading the expedition. It also claims he is a Westerner of 40 years of age.

RELUCTANT STOWAWAY script -- wide set, intelligent eyes. His brilliance does not offset his humanity. He is very human and caring. John went to school with a boy whose father owned a carnival. The boy taught him how to do the old shell game trick (THE CURSE OF COUSIN SMITH).

The unaired pilot claims John was Professor of AstroPhysics at the University of Stellar Dynamics.  John also played football in college (THE DEADLY GAMES OF GAMMA SIX) and somewhere along the way learned masterful fencing techniques (SPACE DESTRUCTORS, THE CHALLENGE).

He and Maureen discussed bringing the kids along with them and wondered if they had the right (WELCOME STRANGER).  John may be haunted by their decision (FOLLOW THE LEADER).  He tells Will his battles are fought in the lab, not the ring in DEADLY GAMES OF GAMMA SIX.

He can put Don in his place (THE HUNGRY SEA), tolerate Smith up to a point more than Don can, but when Smith goes overboard (SPACE CIRCUS, THE KEEPER, DEADLY GAMES - where John tells Smith he is reaching the end of his patience), John wants to beat him to a pulp .. which he never does.

John often plays referee to Smith and Don's usual verbal and almost physical fights in many episodes.  John has an open mind but not as open as Maureen's.  John also makes mistakes (A CHANGE OFSPACE, THE HUNGRY SEA), becomes irritable and exhausted (SPACE CIRCUS), and can sometimes snap at the others (FORBIDDEN WORLD - in a comment to Maureen, Don in INVADERS FROM THE 5TH DIMENSION and THE MECHANICAL MEN, THE OASIS when Judy blames the drought, Will in A CHANGE OF SPACE, and Judy again when she sticks up for Smith in MUTINY IN SPACE and THE MECHANICAL MEN). 

John, however, proves he cares deeply for all aboard his spaceship.  He has tried to save them all many times (giving himself up in A VISIT TO A HOSTILE PLANET and fought an army of cyborgs in SPACE DESTRUCTORS), stuck up for each member risking his life several times over (Judy and Don in VISIT TO HADES; Don in THE LOST CIVILIZATION and TRIP THROUGH THE ROBOT, Will in THE CHALLENGE and TRIP THROUGH THE ROBOT; Penny in MY FRIEND MR. NOBODY and THE PROMISED PLANET; Judy in ATTACK OF THE MONSTER PLANTS and ONE OF OUR DOGS IS MISSING; risked his life space walking to try to bring the spacecast Robot back in CONDEMNED OFSPACE; Maureen, Judy, and Penny in TWO WEEKS IN SPACE.

John also sticks up for Smith when he has to -- HIS MAJESTY SMITH, THE PHANTOM FAMILY). He also has a human side, giving water to Tybo in THE GREAT VEGETABLE REBELLION and in the same episode, calling Penny's idea that plants could feel the pain in the atmosphere of this planet sensitive and caring.