Someone flings a few asteroids at you.

Lets say they use special engines that attach to the asteroid and accelerate it to a great speed.

then they detonate a controlled explosion break them up into thousands of peices big enough to not burn up in your atmosphere. But more importantly, to shred all of your space infrastructure.

Lets say the asteroids are also being escorted by a few hundred ships. Ready to intercept your ships, and torpedoes.

This fleet of rock and spaceship is constantly accelerating toward your planet and not planning to flip and burn to slow down.

The escort fleet will miss your planet, while their payload hits.

EDIT: more info I forgot to include

Good questions! I should have included this info.

You see the attack coming for almost a week. Evacuation starts as soon as the threat is seen.

You have access to a fleet that easily outnumbers the escort. As well any planetary defense measure you can think of that these people presumably would have thought of.

Tech is very very beyond earth. Thousands of years. But, In my setting im not doing ftl, gravity manipulation, warp drives. Its pretty hard sci fi.

How would you (realistically, no gravity manipulation) defend against this?

Note: I already have a solution to this that I thought of, so I'm not trying to get people to write my plot for me. I just want to bounce this off of some more people to see if they come up with something I missed.