VenSpec-H is a spectrometer working in the infrared spectral range. It is composed of:

• a warm section that contains the main base plate and the overall cover of the instrument;
• a cooled optical bench (also called “the cold section”) mounted inside the warm section (warm and cold section form together the main instrument);
• an electronic box (separated from the main instrument)

The warm base plate interfaces to the S/C deck by means of 3 kinematic mounts. It carries the cold section. The warm section contains the instrument entrance (nadir aperture). In front of the cold section a first part of the band selector is mounted, a filter wheel with 4 filters and associated optics. At the exit of the cold section a detector-cooler assembly is mounted with its proximity electronics. A shutter mechanism is foreseen to close off the instrument aperture and to protect the instrument during aerobraking. The optical bench (cold section) contains a cooled spectrometer.  The entrance of the cold section is a rectangular slit that is part of a filter-slit-assembly. The image of the slit is projected on the spectrometer. The filter on the filter-slit-assembly consists of an upper and a lower zone that and is part of the band selection of the instrument, together with the filters in the filter wheel (hence, the band selector is partly in the warm, partly in the cold section). Filters and slit are deposited together on a carrier substrate. The spectrometer consists further of a parabolic mirror (rendering the incoming light parallel), a free form corrector plate (correcting the aberrations of the parabolic mirror), an echelle grating (spectral diffraction of the light), a detector optics unit (collimating the diffracted light on the detector). The optical path contains a number of folding mirrors to reduce the size of the spectrometer section.

The optical bench (cold section) contains a cooled spectrometer.  The entrance of the cold section is a rectangular slit that is part of a filter-slit-assembly. The image of the slit is projected on the spectrometer. The filter on the filter-slit-assembly consists of an upper and a lower zone that and is part of the band selection of the instrument, together with the filters in the filter wheel (hence, the band selector is partly in the warm, partly in the cold section). Filters and slit are deposited together on a carrier substrate. The spectrometer consists further of a parabolic mirror (rendering the incoming light parallel), a free form corrector plate (correcting the aberrations of the parabolic mirror), an echelle grating (spectral diffraction of the light), a detector optics unit (collimating the diffracted light on the detector). The optical path contains a number of folding mirrors to reduce the size of the spectrometer section.

The cold section is cooled down by means of a cold section radiator to -45 °C. The warm baseplate is kept at approximately 0 °C by means of a warm section radiator.

The detector is an Integrated Dewar Detector-Cooler Assembly (IDDCA). The dewar window sits in the exit aperture of the cold section. The Focal Plane Array (FPA) is located a bit further in the focal plane of the detector optics. The FPA is cooled by means of a cryocooler.

The VenSpec-H electronics (lodged in a dedicated unit and mounted separately to the S/C deck) consist of a channel control unit (CCC), a motor driver unit (MOD) that drives the filter wheel driver, the cryocooler and the shutter, and a Detector control unit (DEC) that interfaces with the detector and its proximity electronics (DEP). The VenSpec-H electronics interface with the Central Control Unit (CCU) and Power Supply Unit (PSU) of the VenSpec-suite. It contains a so called sub-PSU that receives primary power from the central VenSpec-PSU and provides secondary power to the VenSpec-H instrument.