High-grade, Compact spectrometers for Earth observation from smallsats

The market for nano- and microsatellites is developing rapidly. There is a strong focus on 2D imaging of the Earth\u27s surface, with limited possibilities to obtain spectral information. More demanding applications, such as monitoring trace gases and aerosols, or water quality still require advanced spectral imaging instruments, which are large, heavy and expensive. In recent years TNO has investigated and developed different innovative designs to realize advanced spectrometers for space applications in a more compact and cost-effective manner. This offers multiple advantages: A compact instrument can be flown on a much smaller platform (nano- or microsatellite); a low-cost instrument opens up the possibility to fly multiple instruments in a satellite constellation, improving both global coverage and temporal sampling (e.g. multiple overpasses per day to study diurnal processes); in this way a constellation of low-cost instruments may provide added value to the larger scientific and operational satellite missions (e.g. the Copernicus Sentinel missions); and a small, lightweight spectrometer can easily be mounted on a high-altitude UAV (offering high spatial resolution). Moreover, a low-cost instrument may allow us to break through the \u27cost spiral\u27: lower cost will allow us to take more risk and thus progress faster. This may lead to a much faster development cycle than customary for current Earth-observation instruments. Finally, the TNO designs offer flexibility to tune the performance (spectral range, spectral resolution) of the spectrometer to a specific application. Thus, based on the same basic system design, these instruments offer a wide range of applications to a variety of clients, both inside and outside the scientific community using a quasi-recurrent instrument. In this presentation we will illustrate this innovative approach, using the most mature design of a hyperspectral imaging spectrometer (named \u27Tropolite\u27) as an example. Other, less developed, designs will be presented briefly. We will discuss the different design and manufacturing techniques that were used to realize these very compact and low-cost concepts. The first laboratory test results of a Tropolite breadboard will be presented and commented upon. Based on these test results the feasibility to use Tropolite for different applications (e.g. air quality, water quality, …) will be discussed further. Currently, efforts are being made to realize an in-orbit demonstration of Tropolite