Somehow the Satellite 2 is available well before I unlocked the rocket silo. This skips the 4k science required for the tech! I think it happened during the on_configuration_changed step.

Additionally, when playing with Space Exploration, the default satellite is lowered to 100 space science, but the satellite 2 remains 4k.

Thanks for reporting.
It is just caused by setting always available for testing, but stupidly not setting back after that... Nothing to do with script. The release as fix 0.17.12 will wait a bit, after also solving the "satellite 4k problem".

As a first glance, SE reduced the vanilla satellite from 1k to 100. So it looks straightforward to scale satellite 2 with a factor of 0.1.
BUT I have to think of the tech cost of my own tech at the same time. Simple scaling like above will make my tech 10 times harder to achieve as well. My current tech costs are (finely) adjusted to be streamlined with vanilla tech costs.

To make things more complicated, most of my advanced tech require both space and alien science packs with the same amount (like all vanilla infinite tech). So it is not the issue of just factoring space science packs but excluding alien science packs. It would be a nightmare to readjust all these tech cost, according to separate factors.

So my questions are:
1. Does SE scale every tech requiring space science?
2. Or does SE intend to create a new balance so every tech is 10 times harder to research?
3. Or does SE replace the vanilla set of satellite and science pack tech?
I am not playing SE (my laptop gets very hot to run that), so I am not sure if SE provides other means to obtain space science packs, or what they do with vanilla tech and modded tech. I will wait for your answers to decide what I can do with this.

PS: In the worst case, if things are too complicated and I finally give up on readjusting for a new compatibility balance... You can always uncheck the option "Enable satellite series" in this mod, to remove the new satellites.

Space Exploration makes science packs directly craftable. The vanilla tech costs are fine. The emphasis is shifted instead to getting labs (and science packs) into space where they can be consumed.

Satellites serve a different purpose in SE. I'm not fully sure of what they can do, but the first one launched unlocks a moon and effectively infinite radar coverage. The 100 science is secondary so I'm not sure if 400 science for your Satellite 2 would be helpful given the cost.

Alright, so it sounds adjusting astronomical satellite 2 to 400 space science packs will NOT fit any purposes, both for cost-usefulness and modified role of satellites.
So I guess I will just leave the satellite 2 untouched, and leave players to toggle the option "Enable satellite series" on/off, according to your taste.

I have just released 0.17.12, fixing the availability of the new satellites.