Development of LabVIEW based data acquisition unit for Compact photometer for terrestrial and planetary emissions

The study of atmospheric emissions like Airglow, Aurora etc, are essential to understand the theory and behavior of atmosphere. The Compact Airglow photometer (CAP) is one of the Fabry-Perot (FP) etalon based optical instruments which is capable of detecting the faint airglow emissions from sky in the presence of bright background light (which may be Sun or moon light). This is achieved by capturing the circular fringes of the required emissions, formed by the Fabry-Perot (FP) etalon as images along with the background using a Charge Coupled Device (CCD). The paper purports to the development of data acquisition unit for Compact photometer for terrestrial and planetary emissions using LabVIEW Software. The data acquisition unit interfaces CCD with any personal computer. The system is capable of subtracting the dark noise from each CCD frame (obtained at every 100 ms minimum) and integrating them for the desired time. It is also capable of selecting and counting the photons falling on two rectangular portions at any region in the CCD image plane separately. For each wavelength, two regions, one with fringe (Signal + Background) and other without fringe (Background alone) have been identified. Subtraction of the latter from the former will give the intensities of the airglow emissions at desired wavelengths (signal).