How come the Shield Gate cannot shield itself?

Question

In Rogue One, the Rebel Alliance was successful at their attempt to disrupt the deflector shield covering Scarif by destroying the Shield Gate. This allowed them to transmit radio messages to the fleet around the orbit. I see two major problems about this plot;

1. If the deflector shield was generated by the Shield Gate itself (which is strongly suggested as the Gate's destruction allowed the transmission to be made) why can't the Gate cover itself with the deflector shield? As the shield itself is there to prevent any unauthorized entry to the atmosphere, It should be able to hold even -lets say- an Imperial Star Destroyer crashing down on it. I don't think it would require much energy as the station itself is minuscule compared to the planet.

2. If the shield was generated by other means, destruction of the Shield Gate would have caused the whole planet to be sealed completely, covering even the only hole that can be punched in by the Shield Gate, effectively preventing the message to be transmitted by the devised plan.

I know Rogue One is not a movie trying to be very realistic, but is there any explanation that I've missed for how the Shield Gate can be destroyed in such a way as it happened in the movie or is it just a logical flaw in the script?

Answer 1

The way the shield and the gate are depicted in the film, I think its strongly implied that the gate's ability to actually be a gate (i.e. to open and close a hole in the planetary shield) relies on it being amidst the shield, as opposed to underneath it.

For such a high traffic facility, this presumably provides much better security overall than a shield like the one the Rebel Alliance used on Hoth, which had to be taken down entirely each time a ship went through.

Assuming the planetary shield is much stronger than the shields that typically protect battlestations and ships in Star Wars, I think we also have to assume that it can't be projected as "casually" — that there are certain limitations in shape, direction of projection, and so on, that prevent a similar shield from covering the station.

The station does have a shield that's significantly stronger than the shielding on an Imperial Star Destroyer, as evidenced by the Alliance fleet being able to damage the Destroyers with conventional weaponry but being relatively ineffectual against the gate itself for most of the battle.

From this I would conclude that the shielding on the gate was as good as they were able to make it — or perhaps more importantly, as good as they felt it needed to be made. You could also ask why they didn't have ten Star Destroyers guarding it instead of only two. :)

Answer 2

Bear in mind also that Scarif was a top secret installation. If it was guarded by half of the imperial fleet, that would have raised too much suspicion. A shielded single orbital space station was deemed the most effective way of controlling planetary traffic. Add that to the utter domination of the Empire as well, there was no need for any other defense mechanism.

It would take a lot of firepower to take it down and until we see it in Rogue One there was no attempt of any significant large scale attack (you saw how the rebel alliance council voted "It's too great a risk"). So I can answer both Question 1 and 2 at the same time:
The Shield Gate is in fact heavily shielded and it is the generator also. Multiple kinetic (particle) and laser (energy) attacks were attempted (either as a deliberate attack or an accidental crash etc...) and none of them made a dent in the shield. However the sustained assault finalized by the crashing of aforementioned destroyer into the space station was ultimately enough force to overwhelm the shields.