The Venus Emissivity Mapper (VEM) - Design

VEM is designed as a multispectral push broom imager to map the surface emissivity using six spectral bands in five atmospheric windows of the atmosphere and eight spectral bands for calibration and detection of near- surface water vapor. It leverages a proven measurement technique pioneered by VIRTIS on Venus Express (VEX). It also incorporates lessons learned from VIRTIS to achieve greatly improved sensitivity and spectral and spatial coverage. 

A filter array (rather than a grating) provides wavelength stability (band-center and widthscatter) about 5 times more stable and maximizes signal to the focal-plane array (FPA). A two-stage baffle decreases scattered light and improves sensitivity. Use of an highly integrated InGaAs detector with 1280 x 768 pixels including an thermal electric cooler (TEC) eliminates the need for cryogenic cooling. The thermal stabilization ensures the high Signal to Noise Ratio for measurements in the wavelength range between 0,8µm and 1,6µm. A turntable window protects the optical entrance against contamination during the aerobreaking phase when VERITAS enters the atmosphere of VENUS. The telecentric optics image the spectral lines on the detector which is thermally stabilized to ensure a high signal to noise ratio. Electronics drives and supply the system. An onboard processing unit installed with on-board software controls the components and provides data processing and compression.