ESA GNC Conference Papers Repository
In-orbit earth observation experiences of GHGsat-D
The Greenhouse Gas Satellite (GHGSat-D) is a successful high fidelity micro-satellite developed in partnership with GHGSat Inc. and built by the Space Flight Laboratory (SFL). GHGSat-D was launched on 21 June 2016 with the primary objective of specifically measuring carbon dioxide and methane emissions from industrial facilities. GHGSat-D was demonstrated to be a robust and reliable small-satellite platform for Earth observation. The satellite has a mass of less than 20kg and was designed on SFL's low-cost and high-performance Earth observation bus. For its size, this bus boasts not only high communication and power throughput, but also Earth observation guidance and navigation technologies to autonomously target terrestrial locations with minimal operator input. Subsequent to in-orbit calibration, target sites were observed daily at accuracies of up to 0.3° by effecting the Attitude Control System (ACS) to autonomously pan through regions of high-interest including, but not limited to, those in the oil and gas, mining and power generation sectors. This autonomous panning is achieved by intelligently handling ACS sensor/actuator telemetry, using this telemetry to predict satellite states, constructing panning trajectories on-the-fly and commanding the actuators to regulate the trajectories in real time. An advanced miniature hyperspectral short wave infrared (SWIR) spectrometer is used as the primary instrument to monitor greenhouse gas emission sources, while a visible and near-infrared camera measures clouds and aerosols to enhance retrievals from the SWIR. The pairing of the ACS, and the onboard spectrometer and visible and near-infrared camera allows repeatable visual identification of sites at spatial resolution of less than 50m and high spectral resolution. Altogether, GHGSat-D is able to accurately monitor greenhouse and air quality gases at a fraction of the cost of comparable alternatives. This paper describes the in-orbit experiences and successful results of the GHGSat-D ACS as learned through design, commissioning, imaging and daily operations, even under the constraints of cost and an ambitious schedule.