Spectral Integrated Infrared Filter for the Martian Airborne Dust Sensor of the MetNet Space Mission

摘要

A micro-sensor for the characterization of airborne dust in the Martian atmosphere has been designed as a part of MetNet space Mission under strict conditions in mass (<45 g) and power (1 W). Basic physical properties of dust are still poorly known mainly because the usual instruments for dust characterization are located onboard on orbiters and are based on extinction measurements for the whole atmosphere. Conversely, the measuring principle of the proposed dust sensor (DS) is based the scattering properties of dust provided by local measurements on the surface. The sensor takes advantage of the strong dependence of the scattering wavelength in mid infrared (IR) with the particle size (micron-sized). The data retrieval algorithm is based on IR multispectral measurements. In order to provide the system with spectral resolution without increasing the mass increasing, a sensor based on the integration of different interference filters deposited onto different lines of a 32 × 32 elements PbSe array detector is proposed. This sensor provides, in addition to spectral resolution in the mid wavelength (2-5 microns) infrared (MWIR) band, further information about scattering geometric distribution for higher precision measurements. In order to study the optical properties of the DS and its behavior in the prescriptive spatial tests, a simpler version of it has been fabricated using two discrete detectors with a filter on each, which only provides spectral resolution. The fabricated microsensor is based in the same optical principles and uses similar detectors and filters than the proposed DS. It has met not only with all the tests for spatial qualification but also with the very strict conditions imposed by MetNet Mission in mass and power consumption, which are not found in typical spatial sensors.