PYTHEAS - A MULTICHANNEL FABRY-PEROT SPECTROMETER FOR ASTRONOMICAL IMAGING

To achieve true 3D imaging spectroscopy in a wide spectral bandwidth w ith a high spectral resolution, we propose a new way of using the Fabr y-Perot (FP) interferometer. As in a cross dispersion technique, we si multaneously observe all the interference orders which are separated b y a grating. We have at the same time the m elements of a Fabry Perot' s channelled spectrum. After the scan of only one free spectral range of the FP, with a finesse F, we obtain the data of M = mF spectral ele ments. In order to achieve high spatial resolution imaging, we sample the field of view with a bidimensional micro-lens array, located at th e entrance of this spectrometer. The optical design uses a field/pupil inversion, so that spectral and spatial information become independen t. The high spectral resolution of the FP interferometer (Delta lambda /lambda = 410(4)) in the wide bandwidth of the grating (Delta lambda = 100 nm) is well adapted to study absorption lines. For example across a globular cluster we have estimated a limited magnitude of 17 at a s ignal to noise ratio of 10 using a four hour integration sequence with a 3.60 m telescope.