The third pillar of Federation is the Survey Service, analogous to the Scouts of Traveller but without the courier functions. These are the guys who get the first opportunity to learn how all the best ways new world can kill you. They are the silent Service, not interacting much with the Patrol or Trade. They operate at the fringe of the Federation or more commonly beyond it.
The major duty of the Survey is t explore and chart new worlds. After a thorough preliminary survey a new world is classified and its trade rights are put up for auction. There is some bias in this as the auctions usually take place on Terra or the Core Worlds while Free Traders work the fringe. Likewise the pricing of choice worlds is completely beyond that of your average Free Trader.
The Survey charts courses in hyperspace. While this can be done by anyone competent in astrogation there are risks involved. New coordinates are approximate and the wrong calculations with proven coordinates can end your voyage and your career. Survey ships are built very tough with this in mind. They feature armor, compartmentalization and more redundancy than a clone trooper reunion. Their crews can survive most crashes or mishaps that don't disintegrate the ship immediately.
It can be assumed that the dangers the Survey faces would make even the most hardened Free Traders take pause. They are exposed to any unknown toxins or pathogens a world presents. They make the first contact and evaluation of local intelligent life, far more dangerous than pathogens (you can't get a vaccination against a blaster bolt or sword thrust). While the most deadly worlds are never put up for trade auctions that is only after teams from Survey visited them and lost a few people learning about the local food chain from the inside.
Every ship has a navigation book. Yes book, Andre Norton was writing this stuff in the fifties. these days you could call it a tablet. The navigation books are monitored very carefully by the Patrol. Without a book you can't chart a FTL course. When a ship is decommissioned its book is destroyed. Of course smugglers and pirates find ways to steal, copy or cobble together their own books. One wonders how many of these pirate books are created by Survey personnel either under bribe or duress. In any case though the Patrol monitors these books the Survey is responsible for providing new data for them.
Charting star is the primary duty of the Survey. In a setting where an aging freighter (the Solar Queen by name) can travel halfway around the galaxy in six months there are hundreds of millions of stars. Obviously Survey can visit every one. They must stick to the one with known planetary systems and a high probability of life bearing worlds.
Some of the duties of monitoring trade missions to aliens worlds must fall to the Survey since they have the most experience with contact and xenopsychology. Even though they are not as heavily armed and equipped for war as the Patrol they have serious firepower. For one thing as mentioned their ships are the toughest in the Federation. For another thing they have no problem calling the Patrol if they get in over their heads. Many pirates and outlaws will cease operations and lay low while a Survey vessel is close.
Survey may be the most overworked Service. The data they provide Free Traders is very incomplete in a number of stories. In one case they missed a semi-sentient race that was already practicing limited agriculture and had planted some fields! While the Patrol handles the interdiction of Forerunner sites the Survey may be tasked with their research.
As overworked as they are the Survey never leaves a ship behind. Any missing Survey ships become a top priority for a sector wide search. All other activities are put on hold until the search bears results or is reluctantly called off.
Sometimes the results are not what anyone would want, a derelict tumbling out of hyperspace, dead lights glowing a forlorn pale blue. the unknown claims another crew and the would be rescuers can only shepherd the dead vessel into the nearest sun before turning away and back to their endless exploration.