-------- Original Message --------
 On January 25, 2018 5:45 PM, Kelly St. Clair <xxxxxx@efn.org> wrote:

>
> It's very very hard to lose an object proceeding on a zero-acceleration
> course in deep space, particularly when you can observe it directly with
> any decent telescope/EMS array.  Especially when that object is worth
> millions of credits to someone.

What are the rules for detecting deep space objects in Traveller? The sensor range rules seem to handle out to S=12 (30 light minutes) but I'm not clear how to follow the rules to build a sensor system that would allow detections out at several light-weeks.

It's also hard to reconcile real world astronomy with Traveller rules. In our TL8 world, tracking an interstellar object much larger than a typical Traveller ship - 1I/'Oumuamua - which would be about 20,000 Dtons in Traveller terms, the tracking was all via telescope and after only a couple of months was no longer detectable by any ground based telescope and is too small and distant to be imaged by interplanetary radar (goldstone and acerabo), and it is still well within the inner solar system. Issues with proposed intercept missions included the error ellipse of the trajectory getting high enough that once lost, the volume of space to search in would be too high for an intercept mission to accomplish prior to the anticipated intercept.

Knowledge of Halley's Comet's exact return date is impossible, and will be until we start to get the first new observations when it is inbound on its return visit, because its behavior at aphelion will have substantial impact on the return time.

Detecting and tracking Voyager 1 (via radio) is not trivial now, and it is also far closer than what a rescue mission would have to deal with and 70 meter radio telescopes are available for the task and the object tracked has a parabolic antenna aimed directly at the receiver.

And, of course, there's a huge difference between TL8 and TL15, but Traveller rules really don't seem to cover deep space detection, so I think it's natural to take cues from real world astronomy.

This is well within the bounds of referee discretion, but I suspect that it would be easier to lose an object proceeding on a zero-acceleration course in deep space, first because objects are never at zero acceleration and second because the actual course will be very hard to know to the precision necessary for a redetection. I think, anyway.