Christophe Coudrain

Experimental results from an airborne static Fourier transform imaging spectrometer

A high étendue static Fourier transform spectral imager has been developed for airborne use. This imaging spectrometer, based on a Michelson interferometer with rooftop mirrors, is compact and robust and benefits from a high collection efficiency. Experimental airborne images were acquired in the visible domain. The processing chain to convert raw images to hyperspectral data is described, and airborne spectral images are presented. These experimental results show that the spectral resolution is close to the one expected, but also that the signal to noise ratio is limited by various phenomena (jitter, elevation fluctuations, and one parasitic image). We discuss the origin of those limitations and suggest solutions to circumvent them.

SYSIPHE system: a state of the art airborne hyperspectral imaging system: initial results from the first airborne campaign

SYSIPHE is an airborne hyperspectral imaging system, result of a cooperation between France (Onera and DGA) and Norway (NEO and FFI). It is a unique system by its spatial sampling -0.5m with a 500m swath at a ground height of 2000m- combined with its wide spectral coverage -from 0.4μm to 11.5μm in the atmospheric transmission bands. Its infrared component, named SIELETERS, consists in two high étendue imaging static Fourier transform spectrometers, one for the midwave infrared and one for the longwave infrared. These two imaging spectrometers are closely similar in design, since both are made of a Michelson interferometer, a refractive imaging system, and a large IRFPA (1016x440 pixels). Moreover, both are cryogenically cooled and mounted on their own stabilization platform which allows the line of sight to be controlled and recorded. These data are useful to reconstruct and to georeference the spectral image from the raw interferometric images. The visible and shortwave infrared component, named Hyspex ODIN-1024, consists of two spectrographs for VNIR and SWIR based on transmissive gratings. These share a common fore-optics and a common slit, to ensure perfect registration between the VNIR and the SWIR images. The spectral resolution varies from 5nm in the visible to 6nm in the shortwave infrared. In addition, the STAD, the post processing and archiving system, is developed to provide spectral reflectance and temperature products (SRT products) from calibrated georeferenced and inter-band registered spectral images at the sensor level acquired and pre-processed by SIELETERS and Hyspex ODIN-1024 systems.

SYSIPHE: the new-generation airborne remote sensing system

The SYSIPHE system is the state of the art airborne hyperspectral imaging system developed in European cooperation. With a unique wide spectral range and a fine spatial resolution, its aim is to validate and quantify the information potential of hyperspectral imaging in military, security and environment applications. The first section of the paper recalls the objectives of the project. The second one describes the sensors, their implementation onboard the platform and the data processing chain. The last section gives illustrations on the work in progress.

SYSIPHE: focus on SIELETERS, the medium and longwave infrared spectral imaging instrument

Sysiphe is an airborne hyperspectral imaging system, result of a cooperation between France (Onera and DGA) and Norway (NEO and FFI). It is a unique system by its spatial sampling -0.5m with a 500m swath at a ground height of 2000m- combined with its wide spectral coverage -from 0.4μm to 11.5μm in the atmospheric transmission bands. Its infrared component, named Sieleters, consists in two high étendue imaging static Fourier transform spectrometers, one for the midwave infrared and one for the longwave infrared. These two imaging spectrometers have very close design, since both are made of a Michelson interferometer, a refractive imaging system, and a large IRFPA (1016x440 pixels). Moreover, both are cryogenic and mounted on their own stabilization platform which allows at once to actively control and independently measure the line of sigh. These data are useful to reconstruct and to georeference the spectral image from the raw interferometric images. Sysiphe first flight occurred in September, 2013.

Noise sources in imaging static Fourier transform spectrometers

Abstract. Imaging static Fourier transform spectrometers are well-adapted instruments for remote sensing. However, the path from the raw images to the spectral images is quite long, thus multiplying the potential noise sources. In this article, we propose to review these perturbation sources. We first recall how detector or photon noise on the interferogram affects the estimated spectrum. Then, we focus on inhomogeneities of the focal plane array. Although these inhomogeneities are deterministic, they generate noise when they are ill-corrected. Finally, we describe defects due to errors that may occur during the image processing step. We also give some avenues to limit the impact of these noises.

System design of an airborne infrared measurement system

Onera has designed and developed an scientific airborne infrared measurement system. This system is constituted of a supervisor computer and two scientific instruments (a cryogenic IR multiband camera and a cryogenic IR spectro-radiometer). This article presents the different elements of the system and focuses on the design of the cryogenic IR camera. The IR camera design involves instrument control, data acquisition, IRIG time stamping, target acquisition and tracking. This article highlights also the communication design using two Ethernet networks linking the elements of the experimental measurement chain.

Compact hyperspectral camera in the mid-infrared for small UAVs

Hyperspectral imaging from small unmanned aerial vehicles (UAVs) arouses a growing interest, as well for military applications as for civilian applications like agriculture management, pollution monitoring or mining. This paper establishes a quick state of the art of cameras of which the capabilities in small-UAVs embedded campaigns have been demonstrated. We also introduce a novel compact hyperspectral camera operating in mid-infrared spectral range embeddable on small UAVs. This camera combines birefringent interferometer for size reduction and cooled imaging optics for a better signal noise ratio. The design of a first prototype and first results from a ground-based measurement campaign, of which the goal was an optical concept validation, is also discussed. Finally, we present the design modifications for the small-UAVs-embeddable version.

Results from the first flight campaign of Sieleters, an airborne infrared Imaging Fourier Transform Spectrometer

Sieleters is an airborne MWIR and LWIR imaging Fourier Transform Spectrometer developed at Onera. The first flight campaign was led at the end of 2013. Experimental results are presented, including a comparison with simulated data.

SYSIPHE, airborne hyperspectral system: Focus on the SIELETERS thermal hyperspectral imaging instrument

The SYSIPHE system is the state of the art airborne hyperspectral imaging system developed in European cooperation. With a unique wide spectral range and a fine spatial resolution, its aim is to validate and quantify the information potential of hyperspectral imaging in military, security and environment applications. The first section of the paper recalls the architecture of the project. The second one describes the SIELETERS sensors, their implementation onboard the platform and the data processing chain. The last section gives illustrations on the work in progress.

Sieleters, an airbone Imaging Static Fourier Transform Spectrometer: design and preliminary laboratory results

Sieleters is an airborne hyperspectral imager, composed of two cryogenic instruments (MWIR and LWIR), both based on a static interferometer. Its first flight is expected for June, 2013. We present design details and preliminary laboratory results.