- This article is about the ComStar organization. For the sourcebook, see Explorer Corps (sourcebook).
The ComStar Explorer Service or Explorer Corps was formed by Primus Adrienne Sims in 2959 to publicly chart and catalog the worlds beyond the Periphery, but covertly to locate lost Star League caches and Kerensky's lost Exodus fleet for ComStar's benefit. In 2982 the ECV Fortitude and Discovery set out on a 1,600 light year trip to the Orion Nebula.
Motivated by visions of previous Primuses referring to the space outside the borders of the Inner Sphere as the only true threat to ComStar, Sims requested funding for the branch based on the mystery of the Exodus fleet and the threat to ComStar's position and technological superiority if the fleet ever returned.
Using long range scout JumpShips such as the Magellan and lightly armed DropShips to investigate old Star League naval charts, the Corps traveled in every direction to re-establish contact with lost and forgotten worlds and locate old SLDF era caches. Most of the contacts on inhabited worlds was diplomatic and cool, while some were outright hostile, with response to ComStar's mystical ways and technology as mixed as the Inner Sphere without the threat of an Interdiction to cow people into line. If locating a former abandoned SLDF cache or base of value, the Corps either stripped its resources for return to the Inner Sphere, or restored it to operation. (One such base was the Columbus facility, which the Corps discovered in 3023.) While some of the lesser or stripped finds were reported to the Inner Sphere governments, the Explorer Corps retained many for the use of ComStar operations in the Periphery, some of which were used in the Jolly Roger Affair.
Prophetically, Primus Sims' fears of destruction from beyond came true not in spite of but because of the Explorer Corps, when in 3048 the Explorer Corps vessel Outbound Light found the Clan Smoke Jaguar world of Huntress, their arrival giving ammunition to Crusader Clans to launch Operation REVIVAL, the Clan Invasion of the Inner Sphere.
With the threat of the Clans, the majority of Explorer Corps resources were directed to locating the Clan Homeworlds, but ComStar's covert agents had more success finally pin-pointing their location. After the Great Refusal, Explorer Corps vessels have returned to the goal of pure exploration and making contact with long-lost Periphery colonies.
In the Jihad, the Corps was decapitated by the Blakists destruction of their headquarters of Columbus and Fort Cameron, on Tukayyid. It remains unknown what part the remains of the Corps played during the Jihad.
In 3095 many of the Explorer Corps' duties were augmented by the actions of Interstellar Expeditions, due to the reduced funding available for the Corps. In fact many former members of the Explorer Corps joined Interstellar Expeditions full-time. In addition, the remaining Explorer Corps personnel served as advisers to other private exploration groups, and in some cases, a source of equipment as the Corps sold off its assets. Despite this, the Explorer Corps found a new purpose after the Jihad: Finding The Hidden worlds and any surviving remnants of the Word of Blake. This was a duty they took seriously, and had in fact engaged in combat with other exploration groups who stood in their way.
Of the hundreds or maybe thousands of missions launched by the corps, only some are known, particularly three who ended with disasters:
- Outbound Light mission: The Merchant-class JumpShip Outbound Light was a ComStar Explorer Corps vessel (alternatively described as a ROM exploration vessel)
- Under mission command of ROM Precentor Arabella Bradford and with the ships under the command of Precentor Vincent Dupont, the Outbound Light departed from Bone-Norman in June 3046 on a standard three-year exploratory survey carrying two DropShips, the Union-class Knox and the Buccaneer-class Golden Hind. It was manned by a crew of 46 across all ships, plus a standard seven-person Explorer Corps survey team. After a relatively uneventful voyage, the Outbound Light jumped on 27 September 3048 into what was believed to be an unknown G7V star system. Instead, they stumbled upon the Clan Smoke Jaguar capital of Huntress. On Smoke Jaguar Khan Leo Showers' orders, the Explorer Corps vessels were engaged and impounded by OmniFighters from the Smoke Jaguar Comitatus-class vessel High Guard before they could attempt to escape. The crews were detained and subjected to interrogation (including the use of mind-control drugs) for several days, revealing considerable information about the current state of the Inner Sphere's political scene and the apparent goals of the major powers. This ship somehow accomplished the objective of the Explorer Corps (finding Kerensky's army), but in any other aspect, the results of this expedition were catastrophic: the information extracted from the ship and his crew was of high importance for the clans, and when presenting this information to the Grand Council, the Jaguars managed to scare the other clans into believing that there was a (false) threat of imminent attack from the Inner Sphere, precipitating the beginning of Operation REVIVAL—the Clan invasion of the Inner Sphere. 
- The fate of the crew of the Outbound Light and its DropShips is unknown. Initial ComStar reports from the early days of the Clan invasion indicated that the crew and ships had been returned to ComStar, supplying vital intel on the Clan way of life, though with their memories and databanks of the route taken to Huntress wiped, but such reports turned out to be false. Only the seven member survey team was returned to ComStar; the other members of the expedition were not returned and no information about them has become available. The members of the survey team all exhibited heavy psychological scarring after their time with the Smoke Jaguars.
- According to Explorer Corps doctrine at that time, the crew did not file a predetermined route along which it would travel, allowing the crew the freedom to change their route should any promising leads develop. While this allowed them to stumble upon Huntress, it also made it virtually impossible for ComStar to discover the route the Outbound Light took in order to locate the Clan Homeworlds.
- Pivot Prime mission: This mission represents multiple missions launched by the Explorer Corps after the Battle of Tukayyid. These were combat missions, with the purpose of locating the Clan Homeworlds for a later attack. This one, occurring in 3056, was on the verge of success.
- The mission, with a single Scout class JumpShip, carried a full mercenary company, called Meredith's Marauders, under the command of Captain Briant Foster. The entire mission was apparently commanded by Capiscol Purdon, and the ship discovered a system named Pivot, part of the Exodus Road, which housed an HPG station. The Dropship detached from the Scout and landed on Pivot, where they defeated the HPG station garrison of Clan Smoke Jaguar solahma warriors, and seized the station.
- However, this mission was doomed from the very beginning: a Clan Smoke Jaguar JumpShip arrived in-system soon after they landed, en route to Huntress, and while two DropShips and their fighters attacked the Scout and captured it, six Smoke Jaguar warriors, piloting Inner Sphere 'Mechs, attacked the HPG station. They were outnumbered 2 to 1, and most of them were killed in the fight, but the mercenaries were crushed and defeated in turn, with Foster having been killed and Purdon captured.
- Ironically, the commanding officer of the Smoke Jaguar forces was then-Star Captain Trent, who had agreed in secret to provide the Exodus Road to ComStar. Working with his bondswoman, the ROM agent Judith Faber, they were mapping the Exodus Road and the victory on Pivot was the opportunity for both of them to return to the Inner Sphere, where Trent would defect from his Clan, hand over the navigational data to ComStar and, in doing so, provided key information for the eventual launch of Operation SERPENT.
- Cambridge disaster: In 3054, a Explorer JumpShip materialized in the system known as Cambridge, in the middle of a Clan Jade Falcon fleet base. The JumpShip, DropShips and their crews, including a good portion of the mercenary unit O'Gordon's Rifles, their command element and battalion leader, Jules O'Gordon were killed.
Coreward Operations Area
- HQ: Columbus, Deep Periphery
- Commander: Precentor Padraig O Bhaoil
- Deputy: Tai-sa Haruka Otanashi
- Spinward Exploration Theater: Precentor Lane West
- Anti-Spinward Exploration Theater: Precentor Morgan Coby
Spinward Operations Area
- HQ: Baliggora, Outworlds Alliance
- Commander: Precentor Ingrid Snorrisdottir
- Deputy: Precentor Albert McMahon
- Coreward Exploration Theater: Precentor Carmen Nesfield
- Rimward Exploration Theater: Demi-Precentor Wu-Fei Tang
Rimward Operations Area
- HQ: Hellespont, Taurian Concordat
- Commander: Precentor Saskia Dinelli
- Deputy: Demi-Precentor Alain Crosier
- Spinward Exploration Theater: Demi-Precentor Simon Bland
- Anti-Spinward Exploration Theater: Demi- Precentor Lisle von Radoslov
Anti-Spinward Operations Area
- HQ: Halifax, Lyran Alliance
- Commander: Precentor Natalia Croft
- Deputy: Precentor Jinny Blanks
- Coreward Exploration Theater: Precentor Chalngura Jahau
- Rimward Exploration Theater: Demi-Precentor Karol Stanislav
- The Clans: Warriors of Kerensky, p. 31
- Interstellar Players 3: Interstellar Expeditions, p. 24
- Jihad Final Reckoning p. 46
- Interstellar Players 3: Interstellar Expeditions, p. 11
- Interstellar Players 3: Interstellar Expeditions, p. 14
- Interstellar Players 3: Interstellar Expeditions, p. 31
- Interstellar Players 3: Interstellar Expeditions, p. 89
- Jade Falcon Sourcebook, p. 19 "The Go Vote"
- Jade Falcon Sourcebook, p. 5 "ComStar Classified Report Sanctum Level Clearance BLP-613-DTC"
- The Clans: Warriors of Kerensky, p. 17
- Explorer Corps, p. 9 "Overview - The Clan Wars - Outbound Light"
- Wolf Clan Sourcebook, p. 25 "History of the Clans - Golden Century - Crusader's Call - Invasion"
- ComStar, p. 65
- Mercenaries Supplemental Update p. 92
- Explorer Corps (sourcebook), p. 13, "Explorer Corps Operation Command Roster"