The exploration / colonization of space and nearby planets presents several challenges. Among these are lower gravity, lower pressure and exposure to both solar, and cosmic radiation -- each of which raise significant doubts about manned exploration. One strategy to address these challenges would be to "cyborg up" our explorers (Isaac Arthur) presumably replacing vulnerable human systems with mechanical alternatives.
What three biological systems would you prioritize for replacement (more than three systems is acceptable as long as they are prioritized)? What would you replace them with?
Technological advances such as mind machine interfaces, nannites capable of repairing light tissue damage are available.
You have power generation / batteries to match the strength of a
recruit fresh from boot camp for at least a day. The power generation / battery does not give off large amounts of dangerous radiation.
Materials should be reasonably conventional. That is: Adamantium no. Titanium yes. Composite yes. Diamond yes.
Your cyborg's mission package is generic. In other words your cyborg rebuild is meant to explore Mercury, Mars, the asteroid belt... changing out only minimal components (Venus could be considered a special case.