System Survey Equipment

[DerekL1963]

2 hours ago, radonek said:

Also, since you are probably especially interested in habitable planets, you take measurements of star energy output to establish borders of Goldilocks zone.

Only if you presume the place is free of races that are no longer bound to planetary surfaces.

[kerbiloid]

57 minutes ago, DerekL1963 said:

Only if you presume the place is free of races that are no longer bound to planetary surfaces.

It's ok, such races will find you first.

[radonek]

6 hours ago, radonek said:

…Or, if you have precise star maps, you can construct image of what starfield at target system should look like, and then look for objects that do not belong. …

A gave this more thought and it is probably way to go. If this is not first expedition, and previous ones were able to relay back their observations, you should have very precise star maps at hand. And most false positives should be easy to detect through simple matching of magnitude, frequency or spectra. Visible (here is the rub) local objects like planets will stand out, with a bit of automation you should be able to identify them as fast as you can swing a telescope around.
 

4 hours ago, DerekL1963 said:

Only if you presume the place is free of races that are no longer bound to planetary surfaces.

This go without saying. Technological civilization is almost by definition active and very obvious source of all kinds of radiation. If you imagine OP scenario in our solar system, arriving expedition  can spend weeks or months mapping all planets and their moons and asteroid fields and comets and what not. But they would need just a few minutes and simple antenna with primitive frequency analyzer to find Jupiter and Earth.
 

[Shpaget]

9 hours ago, Stargate525 said:

The massive array would be at the home system. Because of how the FTL works, going back isn't an option; you're in the system, and you either spend the time and resources to build back, or you die.

Galileo also knew where Jupiter was in relation to himself. This thing doesn't know where it's sitting in the system.

That's not what you said in OP.

Yes, Galileo knew where Jupiter was, but so woul you after about 15 seconds it would take you to scan the entire sky with a wide field IR camera.

[YNM]

An IR / Visible all-sky survey for a few days/weeks with automated blink comparator (or some digital counterpart) plus a spectrograph. That's all you need.

Edited November 3, 2016 by YNM

[magnemoe]

11 hours ago, Stargate525 said:

The massive array would be at the home system. Because of how the FTL works, going back isn't an option; you're in the system, and you either spend the time and resources to build back, or you die.

Galileo also knew where Jupiter was in relation to himself. This thing doesn't know where it's sitting in the system.

My idea was mostly to do an general survey finding interesting habitable planets, even with most FTL systems this would be more efficient as you move outward. If returning is hard its far more important. 

[Stargate525]

Thanks a ton for the all the input guys. This is basically what I've got sketched out -

-Ship arrives with a predicted starfield map, does a full circular visual image to correlate and identify anomalies and any planets visible.
-Locates and pings the system's sun for distance within the system.
-Visual anomalies / visual planets are scanned with radar/radio telescope arrays to determine distance and emissions spectra.
-Probes are fired at 3-5 more promising targets for closer scan and insertion into orbit around the body. Their telemetry is used to more accurately triangulate position, and their flight time is used to observe and map orbital parameters.
-Ship selects most promising candidate and plots intercept course.

...Did I miss anything?

[Shpaget]

No pinging.

You would need stupidly powerful radars and would wait hours for data. Simple triangulation from probes is faster and more accurate.

[radonek]

15 hours ago, Stargate525 said:

...Did I miss anything?

IMO you missed almost everything. I mean, look at orbital science platforms or space probes of today - they are packed with all kinds of experiments. I am sure that professional astronomer could talk your ears off with everything of interest that can be measured. Its more question of what your crew is after and what kind of equipment they bring (which is why I did not ventured there). Few thing that come to mind:

• Visible light, obviously. Hubble-sized mirror can get you lots of surface features. Even if you do not see alien cities, you can for instance make statistics of surface cratering to determine possible geological activity, cloud cover can hint at atmospheric circulation etc.
• Infrared camera was already mentioned. But think about it some more - if you point it at earth, what will it show? Coldness of stratosphere, warm oceans, hot volcanoes, air currents in troposphere? It is not just snapping nice pictures, there is serious science to this.
• Same thing goes about spectrography. Volcanism, photosynthesis, industrial production - it's there if you know what to look for.
• Magnetic field. Planets without one are vulnerable to cosmic radiation and smaller ones may have trouble holding onto their atmospheres.
• Just about anything you can measure about central star to determine its age, composition, and what not. At minimum, you should know wavelength at which most radiation is produced, because that is what possible local life will tune it's photoreceptors for (modulated by atmosphere).
• Once you get close, gravimetry can hint at subsurface features.
• If you are looking for signs of life, you better measure everything you can and look for irregularities. Thermodynamicaly unstable weather patterns, reactive gases in atmosphere, this kind of stuff. For example, if you pointed sensors at early earth from afar, you may not be able to see oceans teeming with microorganisms. But presence of free oxygen in atmosphere is a strong hint of life, since oxygen does not last long if left to its own devices. Similar disturbances can be pointers to some other, unknown forms of life.