CT SENSORS
BTW: LBB2
very explicitly spells out detection ranges and the reductions for ships 'maintaining complete silence' - and that stars and planets can completely conceal a ship. It also provides tracking limits of 3 light seconds (6/1000ths of an AU). See Detection rules, LBB2 pg 32 (in Reprint edition).
I never did elaborate on this when I responded earlier.
If you read pg. 32, it's incomplete. Detection range is there. And, how far a detected ship can be tracked is there, after the ship is detected.
But, how do you detect a ship?
If you make a throw, then what's the throw? What skill is used?
No skill fits the bill adequately. Some argue that Navigation skill should be used for ship's sensors. Others argue that Computer skill should be used. And, there are other arguments for skills that obviously use sensors, like Gunnery, Recon, and Survey (those last two from LBB4 and LBB6).
A "Sensors" skill never did enter the game officially, though I believe I've seen it in supplementary articles, or as part of an adventure, or by a third party publisher like DGP. (Sensors did become an official skill in MT.)
Then, there's the 1977 version of the rules (what most people think of Book 2 is the 1981 second edition). Those first edition LBB2 rules are supposed to be a bit different than what we see in 1981 LBB2. I've always wondered if those rules contained throws for detection that have since been dropped from the game.
Judges Guild published a magazine called Pegasus, and in one of that mag's issues, there was a neat, early, article written about Traveller starships. A new Program was included called Detection which improves ship's sensors (and that supports the idea that Computer should be used for any sensor throws). But, we can hardly consider a neat rule from a third-party magazine article to be official.
So, really, CT sensors are left with the question: We know the range of ship sensors, but how do we detect other craft.
The prevailing thought on this is that every ship within detection range is detected--that it is darn right impossible to hide in space*. Therefore, no sensor skills is needed. The GM just tells the players about everything in detection range. And, this actually works well for the RPG because, if you're mapping space combat, you don't have to hide anything. You put your ships on the map and fight out the space combat.
I wanted to include this in Book 9 because I think it worthy of illumination.
*EDIT: GMs are free to create special dramatic situations, though...of course. Pirates swinging around a moon. A SDB hiding in a gas giant. Ship's sensors delivering false echos due to sun spots. A ship hiding in the magnetic pole of a planet, or a ship rigged for silent running. This would all be up to the GM on how to handle any detection.
99.99% of the time, ship's have transponders that broadcast their position. It's probably illegal to shut these puppies down. A favorite pirate tactic is mostly likely using a false transponder--a poorly armed trader turns out to be a fully armed corsair. Plus, power, heat, light...all these things give a ship away in vacum. It must be extremely hard to hide, indeed.
But of so true of pretty much any government throughout the ages! 
