Meson guns are treated as indirect fire, but is more accurate than barrelled artillery. The entire indirect fire procedure is time-delayed and rather inaccurate, you can easily be off target by 500 m in the first round.
They have no stated maximum range, but a Striker battlefield is only a few km across so that does not say much.
They are always indirect fire weapons, with the implied inaccuracy that entails.
For something like a Striker play field, the range would certainly be "unlimited", simply because the nominal range of these things is in the 1000's of kilometers.
The reasons for inaccuracy in indirect fire is two fold. First, is simply bad spotting and range finding. The Forward Observer gets the range wrong. Second, is the inherent inaccuracy of an unguided ballistic projectile that's subject to the whims of the environment, plus the error rate of a mechanical device firing it (variances in powder charge, friction and how it affects velocity from the tube, etc.).
Neither of these would apply to a TL 15 battlefield.
Meson artillery nominally requires an FO, so in that sense the gun does not have LOS on the target. But, beyond that, it's a light speed weapon, and it's, literally, aimed at the target. It points through the mountain, through the trees, through the planetary crust and oceans if it has to aim at the target.
The targeting is going to be based solely on the precision of the delta between the designated target, as recorded by the FO, and the placement of the mount. We'd picture that as being done through some global reference point. The mount position needs to be precisely located. Then the FO needs to be, finally the FO needs a reliable way to measure from it's position to that of the target.
I don't think anyone foresees problem with the FO having some kind of binoculars with inbuilt GPS, inertial navigation/internal compass, and a laser range finder. With a useful range of 10-20km. (You know, like this:
http://www.celestron.com/browse-sho...0-binocular-with-gps,-digital-compass-reticle)
We have B-1 bombers flying loitering missions waiting for calls of close air support. With JDAM munitions, the FO of the ground force GPS pings the target, forwards that through combat operations, and the bomb is configured on the fly for this specific sortie. The B-1 the executes the attack, plopping a precision 1000lb bomb on top of a particularly stubborn target. It then goes back to patrolling.
This is not the old days of artillery firing smoke and the FO walking the fire in to the target. There's no need to do that with precision munitions, especially with something like a Meson gun (ESPECIALLY something with a 100m burst radius, you know the old saying "horseshoes, hand grenades, atom bombs, and 100m burst meson blasts").
So, yes, Mesons are "indirect fire", but even a trained spotter with a Mk 1 Eyeball should be able to take a simple bearing and guesstimate to within 100-200m, much less a pair of $200 TL 8 binoculars ordered from Amazon.
The only rules in a Traveller product that I ever saw for this specific thing said treat it as a HG2/MegaTrav spacecraft hit but ignore every result except a Weapon or Sensor hit.
Do you get the bonus DM for the planet being a REALLY BIG target size?
There is some reference to it in MT:Arrival Vengeance, though not hard rules...
Any more details than that?