Varied Assisting Utilities and Regional Defense system
A main force field around the colony proper with four sub-shield generators and a targeting system based on the direction of enemy fire from when it hit the field to its origin that could be used to provide tactical information to the deployed heavy troops, armors and craft.
The Guard Carrier was the most popular ship for merchant vessels to hire with its sub-shield generators that could protect multiple skiffs and transports in red-alert situations, placing the cargo ships in these designated spaces reduced the load of calculations needed for the system and defensive drones to intercept missile and rail-gun fire, the designated spaces also provided a link-up system allowing the Guard carrier to provide the jump coordinates though not the FTL propulsion to the vessels as of yet.
So with a few alterations the most popular Guard ship design became the popular Guard Colony design attracting many clients and became a factor in convincing companies that colonizing was a safe investment.
The soil here had a high amount of iron in it making iron dust the biggest industry on Luno until the second generation colonists were tracking what appeared to be intricate veins of iron but instead found the only native plant of Luno that surrounded its seeds in cotton like iron mesh.
The colonists went to work harvesting to supplement the already booming iron industry to make a tidy sum from the backbreaking labor that could wear down a man's hands the favorite working song was an old old song with a bit of an alteration 'Swing low sweet carrier'.

The colony defenses of Luno sported a mechanical iron wall perimeter from when this moon was contested and four large heavy-metal artillery guns that had never been toppled through the sieges.
The infantry burst forth from the four gates of the colony carrying portable shield generator kits, and armed with our finest phase rifles. What militia force we had were trained well and took positions in the marked areas to await armored reinforcements.
We didn't know what we were facing so we raised the old iron defenses and primitive monitoring making a circle around the GUARD to try and create an outer perimeter, we were desperate to at least get a look at what had escaped our patrols around the planet.
The small moon Luno had been receiving terraforming treatments for some time and had reached a phase where the atmosphere was thick with vapor water and charged particles from space that had penetrated the small magnetic field of luno.
When they appeared out of the mist decked out in limbs augmented with weapons and the fronts of their bodies covered in armor we opened fire.
Our infantry was deployed evenly along the defenses but the enemy only skirmished with us testing our defenses and not leaving any dead behind. It was a hard hit not to be able to see any of their casualties and to make it worse we had entered a time of uneasy quiet as the enemy likely gathered their forces outside our sensor range for a concentrated assault.
We knew they were coming at any direction but we had the ace up our sleeve, Tanks. Stationed below the colony in the underground motorized quick-deployment system were rows of tanks ready to reinforce any position.
*BOOM* The defenses were rocked and a gaping hole appeared in the perimeter and out of the mist came ranks straight out of a bazaar; humanoid bodies with legs replaced to sport wheels and spheres with phasers for hands, faces more computer then flesh and metal cage exoskeletons for ribs.
They charged heel and wheeling towards the opening, but a section of earth fell away to reveal a tank bearing an anti-personal flame nozzle taking position behind the opening and let loose the breathe of hell upon the enemy and they fled not bothering to take the charred remains of the fallen.
Cries of joy were heard along the defenses, then shouts from the opposite front, enemy with silent hovering vehicles had tried to sneak past the eastern perimeter but were repelled by the mounted defenses in the GUARD.
Military engineers and a tank technician kit were called for to look at the broken wall and refill the gas on the anti-personal tank.
"We have to pull the tank back, it's shield alone couldn't extinguish the kind of power they used to make this hole. Bring up an infantry unit with a heavy-shield kit and set them to guard. Pray they run out of batteries before we do."

The heavy-shield had to be brought by hover cart, assembly was done exquisitely and it bolted itself into the rock. The soldiers watched as they popped a fresh battery into the hold and the hum of power vibrating the air was a soothing sensation.
Only just in time did they manage to erect the field, as the *BOOM* came again and disintegrated dirt and charred enemy corpses before being absorbed by the heavy-shield field.
It popped out a white hot battery bright enough to blind anyone looking right at it, almost onto the foot of the engineer.
Eyes went wide as the battery lay there and burnt away dust on the ground while the disciplined team quickly brings in another battery, big enough it needs two or three men to lift while the heavy shield vents acquired heat into the air.
*BOOM* *BOOM* *BOOM*

The iron defenses opened to form a great gap a storm of red hot shrapnel that knocked down several squad of levies the heavy-shield picked up shrapnel trying to enter switching to a neutralizing momentum field pushing back foreign objects until they fall harmlessly down like a rain on the helmets of the operators, it initially rocked back and forth with force even mounted in the solid rock.
The enemy was on the move again rushing towards the gap reinforced with walkers mounted with cannons steaming from recent use. The levies opened fire and this time the infantry joined in as well, in response to the situation command sent in an anti-personal armor squad and an anti-armor armor squad bearing the short range flame nozzle and heavy metal cannons respectively.
A contingent of militia forces went forward to the gap to support the tanks for the regular's rifle fire could thin the tide but if any got through they could not be allowed to sabotage the armors. Usually this task could not be given to militia but morale and discipline were high in a Guard colony so when a few stragglers were approaching the gap they discharged their phasers without hesitation.
The Anti-Personnel armors burned away the enemy corpses before they could be dragged of or used for cover and the Anti-Armor Artillery Armors took up position behind them and let loose a volley into the walker ranks.
The heavy metal shots were made of very dense exotic metals and had been known to flip over armors that were near the impacting blast and so the walkers were crippled as their joints shattered and hulls burst circles of broken metal appeared on the field.
Command feared that the enemy might be able to make cover out of those circles or even drag it back to their camp to recycle resources so we would burn the circles on a drive-by and their own fuel would ignite to finish the job, volunteers were needed for this mission and wounded levies and militia were the first to step forward inside the colony was their families and this enemy had offered no terms.
Wounded were strapped to the anti-personnel tanks while a truck would carry the men all volunteers were given air masks, fire retardant armor and heavy metal shot-cannons for crowd control.
The suicide mission squad went out the west gate and would zigzag to reach as many broken walker circles as possible setting a blaze and igniting the fuel of the walker wrecks.

The field was hell. Whatever fueled the walkers burned hot and fierce and the moisture in the air was steaming us alive. It affected our weapons making them dangerously hot this could cost us dearly but with the field still burning they weren't pressing the attack and perhaps their artillery is also in danger of overheating.
This lapse in the fighting was just what we needed as Gerris the Guard cruiser that was tasked with patrolling this sector was on its way! It was possible the evacuation could come under fire from a cloaked vessel so we had to be prepared to evade fire.
When the Gerris arrived the flames had begun to die down and everyone pulled back to get on board. Supplies on board, designs and blueprints for Luno machines uploaded the ship launched with all the colonists and Guard soldiers boarding Gerris to rendevue with other survivors of this sudden invasion.
Of course we couldn't just leave the Luno Colony to them, while most moons have cooled Luno is large enough and young enough to have a hot core allowing us to use the No Man's Planet Bomb.
The iron defenses were turning pushing, the No Man's Planet Bomb deep into the earth and when it got deep enough it would detonate and trigger such a violent release from volcanoes that the planet would be rendered unihabitable and the atmosphere filled with ash, no construct would be able to stand on the planet as the tectonics jerk and shift for years to compensate for the sudden change.
Maybe in the future we could return to Luno and reclaim what was ours.