So you are going to gather intelligence on every deep meson site?
So this world has no counter intelligence forces either.
What's your concept of intelligence gathering? There are multiple strands and by exploiting all of them an attack should be able to build up a fairly complete picture of defenses, what is missed should be picked up by reconnaissance from the attacker's fleet. And yes that includes when ships start exploding due to meson fire,
But you have to understand that a complete intelligence picture is only built up slowly by exploiting every source. Analysts not field agents do most of the work. Trawl the System Government's budget, see where their spending went during the construction period for the DMG sites, estimate how many, how big and where they are, follow up with field agents confirming sensor and site locations. Do this type of analysis and follow-up on every strand you can to build "the big picture".
For an idea of how such intelligence gathering might work in the search for DMGs look to Earths Cold War era and how both the US and USSR tracked each others nuclear programs. Of course there is no such thing as perfect intelligence, both sides got estimates of the other sides capabilities wildly wrong in the 50's.
There's also the HUMINT route. Turn someone inside the Deep Meson Site command structure and have him pass you a map or a crew roster. Bribe the MegaCorp that supplied the meson guns with a juicy contract.
And of course there are counter intelligence forces but that doesn't checkmate intelligence operations it only makes them more difficult and then only if the counter intelligence agency is efficient.
A TL15 high pop world can have how many meson guns? One hundred, one thousand? Which will only fire on you after you have fired on them?
Any fleet coming within range of planetary meson guns is going to lose a lot of ships very quickly
Actually I have no idea how many DMGs a TL15 high pop world could have. How many depends on the perceived threats, the local budget, the military culture, even the amount of suitable rock strata to build the aiming chambers in.
The point is you don't launch any invasion before you know as much about your target as possible.
Any Admiral that sends his fleet steaming into orbit and range of any suspected defenses is an idiot and should be shot on the bridge. Fleets are made up of many assets. Keep your major assets, the capital ships and the troop/assault transports, back and send in your expendable assets. Drones, strike fighters, commando teams. Send in an old cruiser on autopilot to trawl for fire. Do everything possible to clear a safe path for your invasion forces.
Part of any invasion plan is a "defense suppression plan" which draws together all the knowledge of what and where the defenses are and assigns the proper assets to neutralize or suppress them.
My original point bears restating, invasions are a slow methodical process in which the attacker prepares in order to insure victory.
As to landing combine harvesters - it was a bit flippant but no world is just going to neatly package resources for an invader to come and take.
Turn it round.
You are the ruler of a high pop TL15 world - how do you defend your world?
Ah but you see they do "neatly package" the things you might want. Assume your invasion force is designed to have as small a logistical tail as possible (a smart thing to do if your logistical tail stretches over parsecs). Equip and design it to require very little resupply and to be able to exploit resources it captures.
Requiring little resupply: As I mentioned make your force Fusion+ powered. All you need for fuel in water. F+ plants can power energy based weapons like lasers or power equipment to provide H2 (for larger PP or as ammo for Plasma and Fusion guns) and O2 (for life support). Most F+ units contain enough fuel for a year. Make more reliable and survivable equipment (build it better so that it doesnt break down or wear out during normal campaign use so you don't have to carry or ship in a replacement).
Exploiting resources: Most armies provide their motorized troops with stirrup pumps to siphon petrol or gas from wrecked or abandoned vehicles. Armies equipped with the same weapons systems can exploit captured ammunition (note this is why many armies use many different calibers). Traveller assumes a high amount of commonality between worlds and equipment to facilitate trade between worlds so is it not likely that generic power cells for a particular weapon will be interchangeable or more likely that both sides in a conflict buy their weapons from the same handful of MegaCorps?
Other neatly packaged resources include food. I'm not talking about feeding an invading space army by raiding your local Walmart I'm going one or two steps back up the distribution chain to the warehouses that contain the food products in bulk before they are distributed. Of course in planning you must assume this is only supplemental as any good defender will be prepared to torch such stocks in a scorched earth policy.
There are other resources that the invader can exploit too. Communications infrastructure for example. I've already said capture the starport and spaceports, but use the road and rail systems too. Take a leaf out of the alien invader's playbook from Independence Day and take over the defender's satellite and media infrastructure.
The idea is don't haul things along with you if they can be found, captured and exploited on the target world. To make use of the combine harvester example, if you really need them and you know the enemy has their own, send commandos to capture these vital to the war effort combine harvesters (but I'd bring a contingency harvester along just in case a smart defender sabotages all his harvesters befor I can get them, but that still reduces the number I have to bring).
I'll plan a defense of a high pop TL15 world in my next post
