Experimental Astronomy

, Volume 35, Issue 3, pp 527–559

Integral wide-field spectroscopy in astronomy: the Imaging FTS solution

  • J. P. Maillard
  • L. Drissen
  • F. Grandmont
  • S. Thibault
Original Article

DOI: 10.1007/s10686-013-9330-9

Cite this article as:
Maillard, J., Drissen, L., Grandmont, F. et al. Exp Astron (2013) 35: 527. doi:10.1007/s10686-013-9330-9


Long-slit grating spectrometers in scanning mode and Fabry–Perot interferometers as tunable filters are commonly used to perform integral wide-field spectroscopy on extended astrophysical objects as HII regions and nearby galaxies. The goal of this paper is to demonstrate, by comparison, through a thorough review of the imaging Fourier transform spectrometer (IFTS) properties, that this instrument represents another interesting solution. After a brief recall of the performances, regarding FOV and spectral resolution, of the grating spectrometer, without and with integral field units (IFU), and of the imaging Fabry–Perot, it is demonstrated that for an IFTS the product of the maximum resolution R by the entrance beam étendue U is equal to \(2.6\,N\times S_I\) with \(N\,\times \,N\) the number of pixels of the detector array and S\(_I\) the area of the interferometer beamsplitter. As a consequence, the IFTS offers the most flexible choice of field size and spectral resolution, up to high values for both parameters. It also presents on a wide field an important multichannel advantage in comparison to integral field grating spectrometers, even with multiple IFUs. To complete, the few astronomical IFTSs, built behind ground-based telescopes and in space, for the visible range up to the sub-millimetric domain, are presented. Through two wide-field IFTS projects, one in the visible, the other one in the mid-infrared, the question is addressed of the practical FOV and resolution limits, set by the optical design of the instrument, which can be achieved. Within the 0.3 to \(\sim \)2.5 \(\upmu\)m domain, a Michelson interferometer with wide-field diopric collimators provides the easiest solution. This design is illustrated by a \(11^{\prime}\times 11^{\prime}\)-field IFTS in the 0.35–0.90 \(\upmu\)m range around an off-axis interferometer, called SITELLE, proposed for the 3.6-m CFH Telescope. At longer wavelengths, an all-mirror optics is required, as studied for a spaceborne IFTS, H2EX, for the 8–29 \(\upmu\)m range, a \(20^{\prime} \times 20^{\prime}\) field, and a high resolution of \(\simeq 3\times 10^4\) at 10 \(\upmu\)m. To comply with these characteristics, the interferometer is designed with cat’s eye retroreflectors. In the same domain and up to the far infrared, if the instrument aims only at a low spectral resolution (few thousands) and a smaller field (few arcmins\(^2\)), roof-top or corner cube mirrors, as for the IFTS SPIRE on the Herschel space telescope, are usable. At last, perspectives are opened, behind an ELT in the visible and the near infrared with the SITELLE optical combination, in the 2–5 \(\upmu\)m on the Antarctic plateau or in space up to longer wavelengths, with the H2EX design, to provide the missing capability of global high spectral resolution studies of extended sources, from comets to distant galaxy clusters.


Instrumentation Spectroscopy Star formation Gas kinematics ISM 

Copyright information

© Springer Science+Business Media Dordrecht 2013

Authors and Affiliations

  • J. P. Maillard
    • 1
  • L. Drissen
    • 2
  • F. Grandmont
    • 3
  • S. Thibault
    • 4
  1. 1.Institut d’Astrophysique de Paris, UMR7095 CNRSUniversite Pierre & Marie CurieParisFrance
  2. 2.Département de Physique, de Génie physique et d’Optique, Centre de Recherche en Astrophysique du QuébecUniversité LavalQuébecCanada
  3. 3.ABB BomemQuébecCanada
  4. 4.Département de Physique, Génie physique et Optique, Pavillon d’optique-photoniqueUniversité LavalQuébecCanada