|Paper title||How SI-Traceable Satellites may support the net zero agenda|
|Form of presentation||Poster|
SI-Traceable satellites (SITSat) provide highly accurate data with an unprecedented absolute calibration accuracy robustly tied to international system of units, the SI. This increased accuracy and SI traceability helps to improve the quality and trustworthiness of the measurements performed by the SITSat itself and those of others through in-orbit cross-calibration, enabling the prospect of litigation quality information. Such a system can have direct benefits for the net-zero agenda as it reduces the prospect of ambiguity and debate through the ability to understand and remove biases in a consistent and internationally acceptable manner, hereby creating harmonised interoperable virtual constellations of sensors to support decision-making and monitoring of climate change mitigation strategies accounting for emissions and sinks. The very high accuracy capabilities of SITSats can also provide a benchmark from which change can be monitored so that the intended success of our climate actions can be identified and quantified in as short a time as possible.
In this poster we consider how the ESA Traceable Radiometry Underpinning Terrestrial- and Helio- Studies (TRUTHS) mission can contribute to and investigate some of the benefits of the high calibration accuracy and hyperspectral nature of a mission like TRUTHS in relation to the climate emergency. TRUTHS is a climate mission, led by the UK Space Agency, which is being developed as part of the ESA Earth Watch programme to enable, amongst other things, in-flight calibration of Earth observation (EO) satellites. TRUTHS will establish an SI-Traceable reference in space with an unprecedent calibration accuracy of 0.3% (k=2), over the spectral range of 320 nm to 2400 nm at a ground spatial resolution of up to 50 m.
In particular, we look at how TRUTHS might help to anchor sensor measurements used to estimate sinks and sources of GHG emissions, including ocean and land biology, and track land use changes. We also explore how TRUTHS might help to constrain atmospheric measurements by improving the quality of ancillary information used in the retrievals e.g. aerosols, surface albedo, as well as bias removal in the sensor radiometric gains through in-orbit calibration, enabling harmonised constellations of satellites in support of the stocktake.
For the stocktake, as many GHG monitoring satellites have large field of views and also are anticipated to sit in a variety of orbits, we explore in some detail the impact of solar illumination and view angle on the calibration process. Here we evaluate how TRUTHS can estimate the bidirectional reflectance distribution function (BRDF) of the surface, particularly of typical desert calibration targets, and the impact on uncertainty.
Additionally, regardless of the main purpose of TRUTHS in this context as a ‘metrology laboratory in space’ and calibration reference, we also explore how TRUTHS itself can perform or at least contribute to some of the mitigation-related measurements. Even though the mission is not explicitly designed for many short-term climate action related activities, by virtue of being hyperspectral, of high accuracy and relatively high spatial resolution it can still make a positive contribution and improve spatial and temporal coverage of monitoring. As an example of such measurements, we chose the detection of methane point emitters (e.g. fossil fuel extraction and use facilities, agriculture facilities and landfills), one of the top priorities among the mitigation actions for the next decade.
In summary, the poster will explore the impact and contribution of a SITSat like TRUTHS to the climate action agenda through both direct observations and derived information, improvement of retrieval algorithms and interoperability and accuracy of existing sensors specifically designed for particular variables such as GHG satellites, those monitoring land and ocean biological properties serving as sinks and/or their impact on emissions. The climate emergency requires policy makers and society to have confidence in the information in order to pursue the necessary actions and this needs to be underpinned by data of rigorous and unchallengeable uncertainty.