Comments on: Help the author with her research: Infrared technology and other survey methods

By: Glennnn

Glennnn — Tue, 13 Jul 2010 14:51:52 +0000

Interesting comments above- lots of intelligence !
Just a few comments.
A survey would mean some kind of map. All maps are started from some reference-point, called a “bench mark” for standard Terrestrial mapping, that is essentialy the zero-point of the map. Someplace would stick out in their initial survey that would be designated as the initial starting point for the map, from which all coordinates would follow. Their hand-helds might have a mostly blank map of the planet (that would be constantly updated) but the region they were interested in would be reduced to workable coordinates for speed and ease of use.
From orbit with their cameras, (and more than likely a lens that in effect would be the size of the ship) they would have the resolution be able to see almost anything. People would be the easiest, because they leave trails and marks wherever they go. Any settlement would be surrounded by clearings for housing, roads, refuse and the other signs of habitation like smoke, factories, radio-stations would be easy to see. But if there has been a war or some kind of disaster people and their signs might be more hidden. Their analysis would show perhaps old cities but the people would have taken refuge in more strategic locations, like underground, and be much more difficult to observe.

By: Hans Lemurson

Hans Lemurson — Mon, 18 Jan 2010 07:27:58 +0000

6 months later…still some input!!!
Given that they are still on the surface and still want to scan things from orbit, it should still be reasonably useful.

Military spy-satelites TODAY can read the license plate off of a car. Given the amount of technological advancement in this story, I’m certain that a good scanner would be able to read a book over your shoulder from orbit. The ship, simply put, has an aerial view of everything going on on the ground. With the optics necessary to examine stellar objects, you could easily turn them planet-side and get a mighty-fine view of the surface.

So in summary, you are in NO danger at all of exceeding reasonable surface-detection capabilities given what you may or may not want for the plot. Geostationary orbit is at an altitude of 36,000km which is less than 1/10th the distance of the moon, and our ground-based telescopes can get a pretty darned good picture of that. For futuristic telescopes IN SPACE!!!(R), you should certainly be able to detect people walking about on the surface…assuming you knew where to look. Which they do.

By: Galaxion | 104

Galaxion | 104 — Thu, 30 Jul 2009 02:07:51 +0000

[...] I wanted to mention that the “Help me out with survey methods” blog post is still going strong! All the contributions have been fascinating and helpful. I know [...]

By: Galaxion | 096

Galaxion | 096 — Thu, 30 Jul 2009 02:06:34 +0000

[...] long note!–I wanted to give a shout-out of thanks to all of you who’ve chimed in on the discussion about survey technologies! It’s been very helpful, and a source of all sorts of new ideas. Posted on March 24, 2009 [...]

By: Galaxion | 095

Galaxion | 095 — Thu, 30 Jul 2009 02:06:09 +0000

[...] Remember that blog entry I posted a few months back about parsecs? Well, I’ve got another topic for all you smart folks to help me out with, if you’re willing. Let’s talk about… orbital survey technology! [...]

By: Ben

Ben — Mon, 11 May 2009 05:36:55 +0000

Better references>

http://en.wikipedia.org/wiki/Spectrum_analysis

http://en.wikipedia.org/wiki/Photo-ionization_detector

By: Ben

Ben — Mon, 11 May 2009 05:24:17 +0000

In A Nut Shell>

Using the entire range of the electromagnetic spectrum from very low frequency (VLF) right through to Ultra violet you can interrogate just about anything as long as you have the ability to understand the information that is returned by your equipment. You see different wavelengths react differently to different matter. This includes the characteristic of certain frequencies to penetrate/conduct for miles through matter aswell.
See also GasChromatoghraphy http://en.wikipedia.org/wiki/Gas_chromatography

(Electronics tech married to a forensic scientist)

By: Aaron

Aaron — Thu, 07 May 2009 19:10:38 +0000

In terms of what they will not know:
Orbital technologies that can detect a human on the surface are pretty likely, but this is in terms of detecting that there is something where the human is. This is not the same as detecting that there is a human there, much less which human it is. The useful dramatic limitation is that technologies that can distinguish one moving blob of hot water a meter in diameter (not a bad model for a human without any material tech on their person) from another (say a deer) are much harder. The more human like things there are in the landscape, and the more human like they are, the harder the problem becomes.
Finding a human that you know is there in a snow field is easy. Finding a human you don’t know is there is in a geothermal area is less easy. Noticing a human in a forest full of deer would be hard, Noticing a human that you did not already know was there in a building full of apes that are playing with bits of metal left over from an extinct civilization could be impossible.

By: Baris

Baris — Thu, 07 May 2009 13:46:46 +0000

Oh, and if you need ‘technobabblish’ words that are not made up, here are a couple for you:

Hot electron bolometers
Superconducting transition edge bolometers/sensors (That even makes a decent acronym: STES )

By: Baris

Baris — Thu, 07 May 2009 13:41:34 +0000

You might wish to look into terahertz sensing (using waaay far infrared, i.e. sub-micron infrared wavelengths). There are, as of yet, no good sensors (beyond wide range bolometers) in this range, but a lot of research is going on about both coherently creating and detecting terahertz radiation. There were Science and Nature articles on the topic a couple of years ago. Google Terahertz sensing and skim through.

One point to note is that detecting the presence of a signal and detecting its wavelength (i.e., color) are very different concepts (check the difference between ‘bolometers’ and other semiconductor based infrared sensors). Also, detecting a signal does not immediately imply that you can get an ‘image’. For an image, you need many sensors and be able to light them up separately. But given a good terahertz sensor and a bit of sci-fi, that wouldn’t be a problem.