Factors are:
Time - as in "how long since you started the colony". The older, the heavier the raids. Not that impactful though.
Visibility - for frequency/chance of ambushes, not severity.
Wealth of colony/caravan - the more your caravan is worth the harder the raids will be. If you got 3 dudes with shitty gear and not much loaded on the muffalos, you'll be fine. However I once trekked across the entire planet to reach the hidden ship and had 20 bionically enhanced colonists (people also count as wealth), about 90 dromedaries and a ton of expensive stuff loaded up. You can guess what the ambushes looked like... 90 raiders are no joke!
Last but not least: Difficulty - the harder the game, the harder the raids.
Time - as in "how long since you started the colony". The older, the heavier the raids. Not that impactful though.
Visibility - for frequency/chance of ambushes, not severity.
Wealth of colony/caravan - the more your caravan is worth the harder the raids will be. If you got 3 dudes with shitty gear and not much loaded on the muffalos, you'll be fine. However I once trekked across the entire planet to reach the hidden ship and had 20 bionically enhanced colonists (people also count as wealth), about 90 dromedaries and a ton of expensive stuff loaded up. You can guess what the ambushes looked like... 90 raiders are no joke!
Last but not least: Difficulty - the harder the game, the harder the raids.