How to find a planet with high SOL value?

Solution 1:

Looking at the wiki - Polo hands out blueprint rewards as you complete milestones.

One such set of milestone is for Extreme Survival - where you need to spend time on extreme hazard planets (you can spend the time in a cave or building). There appears to be some confusion on the matter, but the milestone seems to be cumulative (the counter only resets on player death, and so you accumulate as you spend time on each hazardous planet you visit).

However, it seems that for the Polo rewards, the effect is not cumulative - so you have to spend over 20 Sols (5 hours) on a single extreme hazard planet before you can unlock all blueprints rewarded for survival.