EChO, a space mission for exoplanets exploration, is considered the next step for planetary atmospheres
characterization. It will be a dedicated observatory to uncover a large selected sample of planets spanning a
wide range of masses (from gas giants to super-Earths) and orbital temperatures (from hot to habitable). All
targets move around stars of spectral types F, G, K, and M. EChO will provide an unprecedented view of the
atmospheres of planets in the solar neighbourhood.
The consortium formed by various institutions of different countries is proposing an integrated
spectrometer payload for EChO covering the wavelength interval 0.4 to 16 µm. This instrument is subdivided
into 4 channels: a visible channel, which includes a fine guidance system (FGS) and a VIS spectrometer, a
near infrared channel (SWiR), a middle infrared channel (MWiR), and a long wave infrared module (LWiR).
In addition, it contains a common set of optics spectrally dividing the wavelength coverage and injecting the
combined light of parent stars and their exoplanets into the different channels. The proposed payload meets all
of the key performance requirements detailed in the ESA call for proposals as well as all scientific goals.
EChO payload will be based on different spectrometers covering the spectral range mentioned above.
Among them, SWiR spectrometer will work from 2.45 microns to 5.45 microns. In this paper, the optical and
mechanical designs of the SWiR channel instrument, including the evolution of the different trades followed
and the current identification of critical points, are reported on.