The goal of the TAFTS instrument is to improve our understanding of the role of water vapour and cirrus clouds in the regulation of the Earth's climate. It can do this by taking direct measurements of the properties of these atmospheric constituents whilst being flown on an aircraft.
The easiest way to envisage how TAFTS works is to consider it as belonging to two separate instrument groups each with different abilities. The first instrument group to which TAFTS belongs is the radiometer. A radiometer measures the amount of energy being emitted from an object within a certain spectral range. There are radiometers that are designed to detect and quantify the energy in the visible part of the spectrum, the region of the spectrum which we detect by eye. The second instrument group to which TAFTS belongs is the spectrometer group.A spectrometer is able to distinguish between slightly different parts within the spectrum, say blue from green from red.
Now if we were to combine the spectrometer properties with that of a visible radiometer we would be able to distinguish between looking at a cloud (white scene, even distribution of energy in the visible) and vegetation (where the energy distribution is biased towards the green).
TAFTS does not work in the visible, it works in what is refered to as the far infra-red but the principles stated above are also applicable here, i.e from the distribution of energy in the infra-red we are able to infer certain properties of the scene we are looking at. TAFTS is not unique, there are similar instruments which work in the infra-red but not quite in the same region. Hence, there is a lack of direct measurements of the properties of water vapour and cirrus cloud within this part of the spectrum. It turns out that this particular part of the spectrum is very important, water vapour has a considerable influence on the energy balance of the atmosphere (heating/cooling rates) just in this region.
Theorists trying to understand and model global warming effects across the globe require knowledge of the properties of the key constituents of the atmosphere. If these properties have not been measured directly then the properties themselves have to be modelled, a not very satisfactory solution. TAFTS has been designed to address the problem of this lack of data within the far-infrared, and along with other unique instrumentation around the globe improve the data set used in understanding global warming.