In many 'a space odyssey novels', the main characters are those directly involved in the space mission. This could include a young and ambitious astronaut who is on his first big mission. There might also be an older, more experienced astronaut who serves as a mentor. Additionally, there could be a communications specialist who is crucial for keeping in touch with Earth. These characters often have different personalities and goals, which create the drama and the story as they face the challenges of space exploration.
Typically, there is a scientist or an explorer type of character. They are the ones with the knowledge and the drive to understand the mysteries of space. There may also be a captain or a leader figure among the group of astronauts, who is responsible for making decisions during the space odyssey. And sometimes, there could be an AI or a computer system that is also a sort of 'character' in the story, which interacts with the human characters in interesting ways.