Question: What is the infrared system used to study?
About the article "Astronomy", section "Infrared astronomy".

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An infrared countermeasure (IRCM) is a device designed to protect aircraft from infrared homing ("heat seeking") missiles by confusing the missiles' infrared guidance system so that they will miss their target. 
Infrared cleaning works by collecting an infrared channel from the scan at the same time as the visible colour channels (red, green, and blue).
This is done by using a light source that also produces infrared radiation, and having a fourth row of sensors on the linear CCD sensor.
Photographic film is mostly transparent to infrared radiation (no matter what the visible image contains) but dust and scratches aren't, so they show up in the IR channel.
This information can then be used to automatically remove the appearance of dust and scratches in the visible channels and replace them with something similar to their surroundings.
A major limitation of this technique is that it can only be used on dye-based (color and chromogenic black-and-white) films; the image-forming silver particles in most black-and-white film stocks are opaque to infrared radiation.
Scanner manufacturers usually have their own name attached to this technique.
Kodak developed Digital ICE at their Austin development centre, and is licensed by Epson, Nikon, Microtek and some others.
Canon developed its own FARE (Film Automatic Retouching and Enhancement) system.
LaserSoft Imaging is developing the iSRD Dust and Scratch Removal, on which among others Plustek is relying. 
Directional Infrared Counter Measures (DIRCM) is a system produced by Elbit Systems, Northrop Grumman, ITT Corporation, Selex ES and BAE Systems to protect aircraft from infrared homing ("heat seeking") man-portable missiles.
It is a lightweight, compact system designed to provide mission-vulnerable aircraft with increased protection from common battlefield threats.
It is more advanced than conventional infrared countermeasures.
The term DIRCM is used as a generic term to describe any infrared countermeasure system that tracks and directs energy toward the threat. 
Infrared cleaning is a technique used to remove the effects of dust and scratches on images scanned from film; many modern scanners incorporate this feature.
It works by scanning the film with infrared light; the dyes in typical color film emulsions are transparent to infrared light, but dust and scratches are not, and block infrared; scanner software can use the visible and infrared information to detect scratches and process the image to much reduce their visibility, considering their position, size, shape, and surroundings.
Scanner manufacturers usually have their own name attached to this technique.
For example, Epson, Nikon, Microtek, and others use Digital ICE, while Canon uses its own system FARE (Film Automatic Retouching and Enhancement system).
Plustek uses LaserSoft Imaging iSRD.
Some independent software developers design infrared cleaning tools. 
Infrared spectroscopy (IR spectroscopy) is the spectroscopy that deals with the infrared region of the electromagnetic spectrum, that is light with a longer wavelength and lower frequency than visible light.
It covers a range of techniques, mostly based on absorption spectroscopy.
As with all spectroscopic techniques, it can be used to identify and study chemicals.
A common laboratory instrument that uses this technique is a Fourier transform infrared (FTIR) spectrometer.
The infrared portion of the electromagnetic spectrum is usually divided into three regions; the near-, mid- and far- infrared, named for their relation to the visible spectrum.
The higher-energy near-IR, approximately 14000–4000 cm−1 (0.8–2.5 μm wavelength) can excite overtone or harmonic vibrations.
The mid-infrared, approximately 4000–400 cm−1 (2.5–25 μm) may be used to study the fundamental vibrations and associated rotational-vibrational structure.
The far-infrared, approximately 400–10 cm−1 (25–1000 μm), lying adjacent to the microwave region, has low energy and may be used for rotational spectroscopy.
The names and classifications of these subregions are conventions, and are only loosely based on the relative molecular or electromagnetic properties.