To turn my earlier question on its head, how would you go about sorting lamp decoys from actual ships, assuming this is possible?
I don't know if there is a way around it or not. It depends on the implementation.
Hmm, using GMT's numbers from earlier, I got a 4 gigawatt energy source being detectable from around 1 AU for a 1 second exposure by the New Horizons telescope, and a 60 megawatt source being detectable from around 17.5 million km. Of course this is "we're sure we've got something but it's a dot of light". Spectroscopy would require something on the order of thousands of kilometers, which ... would probably require a grid density that doesn't seem realistically feasible.
The New Horizons LORRI telescope has an aperture diameter of 208 mm, which gives us an aperture of 3.3979e-2 m². A sphere with radius of 1 AU (149.598e9 m) has a surface area of 7.0307e22 m². To get 100 pJ in one second requires the power coming into the aperture to be 100 pW, and at 1 AU, this requires a source power of 206.91 terawatts,
and that's in the visual band. By your figs, not even Project Daedalus pumps out this power, and that's over the entire spectrum
in which it's radiating. Ralph is even smaller arpeture, 6 cm (60 mm), so it's not going to be any better.
Furthermore, with the LORRI telescope, you have a pixel resolution of 4.94 µrad. At 1 AU, 4.94 µrad corresponds to 369.5 kilometers. Its field of view, on the other hand, is 0.29 degrees squared (1024 x 1024 px²), which corresponds at that distance to a grid 378,300 km x 378,300 km. A ship of similar engine parameters as Project Daedalus can spend 38 seconds thrusting and still remain within one pixel of your resolution if its mass is greater than a tenth that of Daedalus. Unless you know that mass, you don't know if this was 2 km/s delta-V or 0.2 km/s delta-V or even 20 km/s delta-V. In a day's time, it could've gone anywhere from 17,280 km (same view) to 1,728,000 km (four views over). (Actually, we can go all the way down to zero, but let's ignore that.) This gives you approximately 65 frames to scan after a day to catch another burn (58% chance of catching it). After two days between burns, 263 frames (14.5%); three days, 589 frames (6.45%). That assumes that shift to the new field is instantaneous. If not — if it takes a second or longer to acquire a new field to start observing, then the chances go way down.
But even if you're lucky enough to catch the burn, you only have the ship's proper motion (if you were lucky enough to get the triangulation first off — see below). Even if you deduce the exhaust velocity, you can't detect the radial velocity of the craft because the velocity of the exhaust washes any difference out, even if you assume that the exhaust is moving the same velocity as last time. So by the second burn, you only have the proper motion of the ship (but not radial velocity) and the radial velocity of the exhaust (but not proper motion). Dispite what Dr. John Shilling says, while you do have the mass flow (a scalar), you only have one component
of the exhaust velocity (a vector), and therefore only one component of the thrust (also a vector). Any mathematician can tell you this problem is unidentified.
Triangulation? Forget it. First, you have to contact another post and tell them that you need its help. But then you have to figure out if the other post is free or if it's observing something else that's interesting, so you have to wait for its reply. Assuming that you get a reply in the affirmative, you then have to tell the other post where to look. That's a three step communication which means that over the burn, light has to go three ways. This means that your partner has to be within 3.8 million km (~13 light-seconds), otherwise the burn disappears before the second post can draw bead on it. Of course, that assumes you know where the next bead needs to be. If it's not, your partner will have to scan along your own line of sight until you acquire the interesting object. The preceding are predicating on the posts catching the burn promptly. If it has to look for the next burn, then there will be less time to triangulate even if it's caught.
I'm going to leave things there for you to mull over.
What I mean is this. You know where the enemy bases are. To get away from the immediate vicinity of these bases on a practical timescale the enemy ships will have to do burns, and these burns if detected will allow the courses to be tracked.
See above. If the staging area is far enough away, not only will you have trouble detecting the burn and not be boggled by a billion and one other things that could distract you (unless it's a torchship), for short burns you will not be able to determine its trajectory during the burn with any reasonable accuracy. You'll have the mass flow and (maybe) the radial component of the exhaust velocity, but nothing else. That's not nearly enough to determine a trajectory, and especially not in a solar system.
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