UNSC WARNING: This document, Thetis-class Survey Ship, is property of the UNSC and is Classified [NOVEMBER BLACK], protected under Office of Naval Intelligence Security Protocol 1A. Disclosure of its contents to, or access or alteration by, personnel with a clearance level lower than GAMMA THREE is an offense punishable by court(s) martial and imprisonment or execution for treasonous acts. Failure to disclose confirmed or suspected breaches of security will be treated as complicity, and is punishable by dishonourable discharge and/or imprisonment.
Lieutenant Commander Michael Pomare, Office of Naval Intelligence, UNSCDF Navy
ONI Seal 1

UNSC Thetis-Class Stellar/Planetary Survey Ship
Production information

Sierra Space Systems/Reyes-McLees Naval Shipyards


Survey Ship





Technical specifications






Maximum speed (atmosphere)


Engine unit(s)

CC32/Sierra Fusion Reactor

Slipspace Drive

Shaw-Fujikawa Translight Engine

Slipspace velocity

2.625 lightyears per day

  • Stealth ablative coating
  • Titanium-A battleplate
Sensor systems
  • ELF-X Radar
Navigation system

14 x OPHELIA Slipstream navigational computers


3 x 50mm point defence autocannons



Minimum crew


Year introduced


  • stellar and planetary survey (civilian)
  • Electronic Warfare Support
  • Electronic Attack
  • Electronic Protection

Human-Covenant War


UNSC Navy (Office of Naval Intelligence, Prowler Corps)


Slipspace is often chaotic, and travelling point-to-point between two well-known and much-used locations is difficult enough. In order to locate new habitable star systems, however, a survey ship must travel to a point that has not been used, and the coordinates and calculations for which have never been made before. Few starships are equipped to make a journey into the unknown, and those that can are few and far between. Corvettes, Frigates and Prowlers are able to make short jumps, and carry limited mapping equipment, but their pathfinding abilities pale in comparison to specialised survey ships, such as the Thetis-class survey ship.

The Thetis’ are dedicated to making highly accurate slipspace transitions to unknown locations, using powerful sensory equipment to map out the system, use powerful computers to assemble a virtual map of the planets, satellites, asteroids, and other local bodies and assemble a working model of the orbits and rotations for future reference, and then return to UNSC space. A second ship jumps in-system, using the data gathered by the first, and establishes safety zones, areas where slipstream transition is possible without the interference of gravitational forces, and drops marker buoys to permanently mark these zones for future travel. Onboard AI’s calculate possible inter-system routes between planetary bodies, and designates the safest and most efficient ones for use. This data is instrumental in UNSC ship movements – once the system has been fully mapped out, travel becomes significantly safer and more efficient, and routes are permanently logged in UNSC navigational databanks for future use.

After the initial surveys are completed, the ships are able to analyse the planets and planetoids in the system, assessing them in terms of habitability, cataloguing them in the colonial database, and assigning designations. These designations may be arbitrary, or take its name from distinguishing features of the planet – they may not even be final. Harvest, for example, acquired its name after it had become an agricultural hub world. Others may take their names from places on Earth or the other Inner Colonies, such as Minorca, taking its name from an island in the Mediterranean. Survey ship captains often get the right to name a planet, and while some are changed later to appeal more to colonists, most names are retained, at least in some capacity.

When the Covenant attacked Harvest, all colonial survey missions were immediately cancelled, for fear of stumbling upon a Covenant world or battlegroup. In response, the Office of Naval Intelligence purchased seven survey ships from the Department of Colonial Affairs, retrofitting them with rudimentary point-defence systems and robust stealth systems, commissioning them as pathfinder ships to search out Covenant-controlled worlds, listen in on Covenant communications, and overall provide as much intelligence on an enemy that was technologically centuries ahead of humanity, previously unknown, and extremely aggressive, as possible, making it the first Prowler class commissioned after 2525, followed by the IX-991 prototype in 2549. More of the ships were purchased or built specifically for ONI, and the UNSC Navy’s stealth fleet encompassed more than ninety ships by 2531, all dedicated to improving the UNSC’s ability to fight the Covenant. A small number remained in civilian use, though with military escorts, and colonial surveying continued until 2536 when the last of the Outer Colonies fell – after that, colonisation was banned completely by the UNSC, and the last of the ships were quickly snapped up by ONI cheaply.


  • “I guess they’re not your usual ship. For one thing, they’re almost totally automated – only a skeleton crew to control the ship. For another, they have huge spaces for storing computing gear. They need to for all the calculations and mapping they do.”
  • “People think slipspace jumps are proportionate to speed – they’re wrong. Its proportional to time. A Thetis-class ship takes twenty minutes to make the calculations needed, checking and rechecking them for improved accuracy, calculating and taking into account any variable. Their jumps take just as long as a regular ship, but the payoff is that they’re 300% more accurate. Its all about the hardware.”
  • “The UNSC Huginn used to scout for the DCA – now it works for ONI. Its not the first acquisition from the civilian fleet, but its definitely one of the best.”
  • “Most ships make separate calculations for a jump in-system and a jump out-system. The Thetis’s make those calculations at the same time – they aren’t really designed to move around much in realspace, since distance doesn’t really matter to their sensors.”
  • “I remember at Delta Pavonis, when the rest of the fleet had retreated to regroup, the UNSC Muninn stayed in orbit, providing intel for us groundpounders. It was found and blown out of the sky – but they helped us hold out for the rest of the fleet. God bless them.”