Leareth wobbled on the last occasion but he's expecting it this time. 

He opens his mind to Cayaldwin again, to get a second view on his targeting. It takes a moment after that for him to clear his thoughts enough to try the Gate, though; he's still pretty emotional about seeing Velgarth from space. Grief and anger, for everyone who's lived and died in the last two thousand years, for the damage done, for the gambles he lost, and the magnitude of the stakes. But not despair; it only feeds a bedrock-solid determination, never to die never to give up to try again and again as long as it takes - 

Leareth folds all of that away, again, along with the memory of a tower against the sky, and his mind is still again, and then he builds a Gate-terminus, deftly and efficiently, and aims the search again, not at a specific place-memory this time, but here on Velgarth's map, and where the distance-between-planes is just so...

The Gate comes up.

The robot goes off, explores, comes back.

Leareth dismantles the Gate and pulls (some of) the energy spent on it back into his reserves. 

And? 

It was, as hoped for, deep underwater. It has pressure readings. 

Is it a level of pressure that people can survive? Or that the shuttles can withstand, if he makes a Gate big enough to fly them through? 

Humans cannot survive that! The shuttles will be fine, and some of the Andalites have morphs that can handle it.

Nod. They can head back, and Leareth will rest for a few candlemarks and then be able to do their first test Gate to Earth, underwater, and get some sensor readings that will hopefully help confirm whether it is Earth. 

(He's also mulling over a modification to his physical shields that would protect against pressure extremes in both directions, just in case of Gate-mishaps.) 

The ship is not really supposed to be in and out of atmosphere anywhere like this frequently, so the engineers are being kept very busy. 

Leareth doesn't think they'll need to do any more trips like that; he didn't think about whether it was hard on the ship, sorry.

He asks if they can find a map of Earth's oceans for him, to help target, and then heads back to his conference-room to check in with his people preparing up north and then take a nap. 

He can get a three-dimensional projection of Earth that shows the oceans (Earth has lots of oceans) and marks where they know Yeerks to be operating though of course the Yeerks should be assumed to be everywhere.

Leareth lets Cayaldwin ride along, again, it'll make it much easier to do a post-mortem on his mistake if he lands in the wrong place. 

He spends quite a while narrowing down on it, holding the three-dimensional image of Earth in his mind alongside the felt-sense of planar distance that matches what he remembers from Velgarth. It's both 'further'-feeling but also less tiring, somehow, anchoring an inter-world Gate between two gravity wells. 

He points the spell very firmly at a point in the ocean, and builds the other threshold, and raises it. Gate to Earth! Hopefully undetectable even from the surface, let alone to a ship in orbit! 

Off the robot goes! This time they're sending two, one that will hang out just outside the Gate and receive signals from the other one, so the other one can travel much farther without a totally uninformative result if it's unable to find its way back.

Leareth grits his teeth a little and settles in to hold the Gate for as long as possible. 

Nayoki, hovering, can slip into rapport with him and feed him extra node-energy. 

In which case Leareth can hold his tiny Gate for a full half-candlemark, at the cost of a reaction-headache when he's done. 

The one robot makes for the surface.

It takes it a while, but it's up before the half candlemark is up, and sends back its readings on the air. It does not make it back down through the Gate, but that was planned for; it will instead go to the bottom of the ocean to die, and shouldn't present much exposure risk.

Leareth takes a minute to close his eyes and rub his temples, then examines the readings, not that he can interpret them all that much. 

The Andalites can! There are pollutants in the air like from a civilization burning its oil, which is promising, Earth is at about that tech level. The air will be breathable to Andalites and humans, which is another good sign, they really cannot overemphasize how implausible it is that in this case they landed on a human-habitable planet but not the one they were aiming for, usually if you're wrong the planet's just uninhabitable. They have water samples, too, and will scan them for traces of plastics and pharmacologically complex compounds that humans know how to make on Earth but not how to responsibly unmake. 

After about ten minutes they're pretty sure this is Earth.

That's such good news! 

Hmm, the last tests Leareth wants to do won't involve the ship leaving atmosphere, but might involve moving it. He can test underwater Gates over at Lake Evendim, and check whether their sensors pick anything up at various depths, both when they're right there at the surface and when they're on the nearest land point. Even if the Yeerks do have surface sensors, Leareth figures they almost certainly don't have them stationed every few miles in the entire ocean. 

The Andalites are so delighted at this progress and are more than happy to get their ship off the ground for more tests. They are practically skipping across the grass as they arrange it.

It's faster progress than Leareth initially guessed by about an order of five. Then again, he wasn't taking into account having Cayaldwin and the other engineers. 

With the ship right over part of Lake Evendim, Leareth does a small Gate from a shielded records-cache fifty miles away, to a hundred yards below the surface. Can they sense anything? 

With the sensors turned up to their maximum sensitivity they get a blip which they tell him they'd be inclined to assume was random noise.

What about for a brief but much larger Gate, enough to fit a shuttle through? 

Louder! They wouldn't necessarily assume it was random noise though they wouldn't guess it was a direct-to-planet hyperspace jump since no one can do that.

And if the ship is instead twenty miles away at the shore?