Was Dr. Gero aware of Freezer?

[Malek86]

In the manga it's said that the Cell project wasn't actually supervised by Dr. Gero himself, but by his computer, which pretty much kept doing all the work after he abandoned the research. Also, the doctor says that they didn't follow Goku anymore after the battle with Vegeta.

I would assume, then, that Dr. Gero didn't know of Freezer, nor that he and Cold had arrived on Earth and were threatening to destroy the whole planet. If he did, he might have sent some androids (assuming he had any available) to deal with them.

Or perhaps, he knew thanks to a power radar (we know he could build them), but also saw that Goku was returning and so felt that he didn't need to bother himself?

Granted, if he were indeed following the scene with a power radar, wouldn't he have also noticed the surge in power when Goku became super saiyan?

[dbgtFO]

This is a no brainer. As you yourself said, he didn't follow Goku's adventures on Namek, which should be enough to conclude that he was left in the dark about any new foe encountered on Namek.

[Piccolo Daimao]

Yeah, if the research was abandoned after the battle with Vegeta, and only the computer supervised and continued the Cell project (thus, recording Freeza, King Cold and Super Saiyan data) after Dr. Gero gave up on it, then Gero wouldn't have known anything about Freeza.

However, it's probably safe to assume that he knew they were travelling to Namek, because when Goku asked him if he tracked them on Namek, Gero didn't act surprised or confused and just replied that they didn't need to because they had all the data required to make calculated predictions on their power growth.

I'm wondering if Gero knew about the Zenkais. Probably, since it was only Super Saiyan that he was surprised by, and seemed to have a problem with. He clearly didn't seem worried about base Goku's strength when he met him - only Super Saiyan, which he said would still be enough for #19 to handle, so he was probably counting on #19 being able to absorb Goku's ki before he got too damaged. In fact, I think he even mentions something like this.

Here are some relevant quotes:

Chapter 339 (DBZ 145), P12.5
Context: speaking to Goku and co.
No.20: “You can’t defeat us.”

Chapter 340 (DBZ 146), P14.1
Context: after Goku transforms into a Super Saiyan
No.20: “However, this isn’t anything great enough to give us reason to fear. It’s still within a level which even No.19 is more than capable of defeating, and naturally that goes for myself as well…”

[Fox666]

so he was probably counting on #19 being able to absorb Goku's ki before he got too damaged.

Nah, I think he just overestimated. He probably also didn't expected that Piccolo would actually be stronger than him too.

[Piccolo Daimao]

so he was probably counting on #19 being able to absorb Goku's ki before he got too damaged.

Nah, I think he just overestimated. He probably also didn't expected that Piccolo would actually be stronger than him too.

I don't know whether or not it's the same in the original, but I have Viz's Dragon Ball Z Volume 13 here with me. While SSj Goku is smacking around #19, #20 says this:

No. 20: ...A problem. This increase is so far above what the data projected that at this rate, #19's energy will run dry before he's able to absorb Son Goku's power

Of course, #20 overestimated Goku's power. But I think that, judging by his initial attitude and the above quote, he originally thought that while Goku may've been stronger than #19, it wasn't a big enough difference for #19 to not be able to absorb Goku's power. However, the fact that Goku's power was so far above what Gero originally thought meant that he was worried #19's energy will run dry before he'd be able to absorb Goku's power.

With Piccolo, Gero underestimated him because he was suppressing his power. Perhaps a similar thing to what Goku was doing when he fought the Ginyu Force: rapidly heightening his ki in the brief bursts of attack, so instantaneously that power sensors can't pick it up.

[Malek86]

This is a no brainer. As you yourself said, he didn't follow Goku's adventures on Namek, which should be enough to conclude that he was left in the dark about any new foe encountered on Namek.

Yes, of course. But what I mean is, was he at least aware that two super-powerful aliens had landed on Earth a year after Goku had left for Namek? If so, what was he counting on doing?

To be frank, it's not like it would be the first time. We know he was actively spying on Goku during the fight with Vegeta... and yet, if Goku hadn't won that fight, all of his work would have gone to waste. We could assume something similar when Piccolo Daimao announced he was taking over the planet, but maybe in that case he just felt safe in hiding in his laboratory. However, for all he knew, Vegeta was going to entirely raze the planet and then sell it to the best offerer.

Is it possible that Dr. Gero always had a few cyborgs ready just in case somebody was gonna mess with him? I certainly can't imagine him as the savior of the Earth, but if no other warrior was left, I don't think he was just gonna welcome their new alien overlords.

[Super Saiyan Turlast x4]

I don't think he was aware of Freeza and Cold's arrival. If he was, then he wouldn't have been so clueless about Super Saiyan and Trunks. When he first saw Trunks, he wondered who he was and why he had no data on him.

As for having Androids ready in case of an attack, it's possible. While it's stated that he disposed of all the previous Androids up to #15, it's possible that he kept a few around for awhile before doing so. In fact, while the 3 Androids before #16 had issues, they were close to being finished, I believe, so he probably decided to keep at least one in reserve for a little while before moving onto the next experimental model.

If Goku lost the battle to Vegeta, I could see Gero unleashing whatever Android he had done at the time to start destroying the world. I think world domination was at least a #2 goal for Gero, while beating Goku was obviously #1 for him.