Novel in which a derelict ship is observed entering the solar system, leading to an alien invasion

Question

I'm looking for a book from the '90s or maybe the early 2000s. The plot is as follows:

A ship is observed entering solar system. Another ship is sent to intercept and checks the derelict ship that is empty, having only a ring inside, similar to Stargate.

The ship lands somewhere in the North or South Pole and from the ship - the ring was a portal - a massive invasion starts. The aliens control enormous numbers of biological creatures (insectoids and so on) to conquer the Earth.

The story is of the main character (in the USA) that tries to arrive at a launch site to leave the Earth with a shuttle. It fails (the Earth is conquered) and goes to a secret location inside a mountain, where some sort of cryogenic installation may be used hoping that will escape in stasis.

The novel ends quite grimly... while entering in stasis pod a stone eating worm ener in location...

What I can tell is that the name of the author was of German origin and the novel isn't any of the ones proposed as answers to a similar question: "Novel about rendezvous with alien ship travelling through the solar system"

Answer 1

May be the Charity series by Wolfgang Hohlbein.

I can't find a summary on english, but the german one for the first book describes a mission to an empty space ship that lands at the north pole and the alien invasion.

Am 4. März 1998 geschieht das Unfaßbare: An den Grenzen des Sonnensystems taucht ein außerirdisches Raumschiff auf. Das rätselhafte Schiff scheint völlig leer zu sein - bis es am Nordpol landet und die Invasion beginnt. Eine Frau aber nimmt den Kampf gegen die außerirdischen Invasoren auf: Charity Laird, die beste Raumpilotin der US Space Force.

On March 4th, 1998 the unbelievable happened: An extraterrestrial spaceship appeared at the borders of the solar system. The mysterious ship appears to be completely empty - until it lands at the North Pole and the invasion begins. But a woman takes up the fight against the extraterrestrial invaders: Charity Laird, the best space pilot in the US Space Force.

For the second book it states that the protagonist awakens in 2055 from cold sleep.

In einem unterirdischen Bunker erwacht Charity Laird, die jüngste und beste Raumpilotin der US Space Force, aus dem Kälteschlaf.

In an underground bunker, Charity Laird, the youngest and best space pilot in the US Space Force, awakens from hibernation.

Found here.

I couldn't find if the books were translated to english.

Edit: I found the book and it fits the description. Some of the aliens are described as spider like monsters, the book ends with the protagonist in a bunker under the Rocky Mountains trying to reach a space ship to escape but gets into (experimental) cold sleep instead. They're even attacked by giant worms that borrowed through the mountain (although that doesn't happen at the very end but a bit before that).