Datacube Reconstruction from Detected Interferograms

The output of the instrument simulator FllnS is a set of FITS files where the interferograms corresponding to each baseline and to each FTS scan are stored for a given input sky datacube, Skyi . These FITS files also include fhe mefrology data for the FTS drive and pointing of the telescope, as well as all the information needed to calculate the baseline vector. 

Once the data has been loaded, if noise has been selected to be included in the simulation, the first step will be the noise reduction to increase the dynamic range (DR) and the signal to noise ratio (SNR). Next the reconstruction of the dirty datacube is achieved by extracting the spectral and spatial properties detailed below. To illustrate the data reduction process a master sky map is used. 

To run a FllnS simulation the first step is to select the instrument parameters which define the size of the sky grid. For a pseudo-realistic simulation, the baseline range 

The instrument parameters define the beam size. Setting up the spectrograph to work in the 25 00 p,m range (400-25 cm ), the minimum beam size is A9,ei = 2.097 arcsec and the spatial angular resolution A0i , = 0.086 arcsec. To prove the principles of interferometry, the astronomical sources on the sky grid must be positioned inside the beam. 

Three different types of sources are positioned in the sky grid a point source, a gaussian source and an elliptical source, as shown in Fig. 5.2 (left). 

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The datacube reconstruction from detected interferograms has been performed. Initial steps consist of the noise reduction and time domain interpolation when instrument errors have been included in the simulation. Once the data has been reduced, the dirty datacube is calculated in two steps first through Fourier transforming in the wavenumber domain and second through two dimensional Fourier transforming in the spatial domain. 

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