Kurt Feltenberger wrote:
 > Mostly traffic to and from the world, though the sensors
 > would have the resolution to discern large structures on the surface.

If the idea is to watch ships go to and fro, they will be able to see
surface features to a reasonable resolution.

Hubble (2.4m diameter aperture) has angular resolution of 0.1
arcseconds, which is 1m at ~20,600km in near infrared wavelengths.

Half this, 50 milliarcsec, is achievable by 10m telescopes with adaptive
optics (e.g. the Keck). So 1m at ~41,000km with visible wavelengths.

1 milliarcsec resolution implies a 100m diameter aperture using visible
light. So 1m at ~2.06 million km.

To get to Greg Nokes':
 > A light hour or three out and you should be able to count
 > the gnats that are around the cook stove.

1 light hour is 1.08x10e9 km, or 7.2AU.
Counting gnats (~1mm resolution for earthly versions) around the stove
from this range implies a very, very large aperture even with grav focusing.

Or very, very large gnats.

Kurt again:
 > The goal is to watch the entire planet, thus one ship at a standoff
 > distance and that's pretty much "stationary" with regards to the
 > planet's revolving on its axis.

What's stopping the bad guys from 'hiding behind the planet' in this
situation?

Look up Lissajous orbits; you could use unpowered sensor drones to get
full planetary surveillance while the mother ship orbits a Lagrange point.

and Kurt again:
 > For this scenario, the ship is adequately stealthy
 > and the technology is up to the task assigned.

We've been trying to work out what the latter task is.
So pardon our uncertainty about what "adequate stealth" means in this
context.

Using FFS1 and 2:
At TL 13, a 100 displacement ton drone with a 100m diameter passive EMS
and 1 level of electromagnetic masking has the following capabilities:

Sensitivity 14.5: 100 displacement ton sphere detection range 160
million km, resolution 0.2m at 50,000km.
Visible/reflected Signature: -0.5 for area (1000m^2), -0.5 for masking = -1
IR Signature: -1 when not manoeuvring (6MW), -0.5 manoeuvring (36MW), -1
for masking = -2/-1.5

This vessel is not detectable by active sensors at orbital (5000+km)
ranges. There's a small chance of detection with passive sensors
(sensitivity - range band >1) at whatever range.

Rob O'Connor