Mission objectives

Space-based calibration of data gathering satellites

Whilst there is no doubt that the Earth's climate is changing and near-global consensus that mankind is playing a major role, the timescale and nature of our impact remains uncertain. Assessments of climate change depend on data collected over decades so that small, often subtle, changes are reliably detected.

This figure from SITSCOS Workshop Report, published in 2022, shows that there is a large discrepancy between the SI-traceable calibration uncertainty of current satellite sensors and climate change observation requirements for essential climate variables derived from those sensors. TRUTHS' unprecedented accuracy will provide major improvements in these critical requirements enabling us to detect climate trends in the shortest possible timeframe, limited only by natural variability.

The Intergovernmental Panel on Climate Change (IPCC) has highlighted the uncertainty in the ensemble of climate models, which forecast a range of potential further temperature rises of the Earth, from 0.5°C to 5°C by 2100. Many Earth Observation satellites are used to provide inputs and developments to these models. However, for effective policy making and the development of global initiatives, which will help address changes in the Earth’s temperature, there must be complete confidence in the data which underpins decision making. TRUTHS will provide and enable, through other satellites, highly accurate and trusted climate records to help constrain the uncertainties in the predictions of climate models.

This will be achieved through the two primary objectives of the TRUTHS mission:

1. Climate benchmarking through high-accuracy direct hyperspectral measurements of the Earth’s incoming and outgoing radiation to enhance our ability to estimate the Earth’s radiation budget by an order of magnitude, enabling detection of climate signals in the shortest possible time.
2. To establish a ‘gold-standard’ reference dataset against which to cross-calibrate other sensors, facilitating an upgrade to the performance of the global Earth observing system to ensure interoperability and robust anchoring to an SI reference in space.

As the first satellite to host a primary standard cryogenic radiometer, TRUTHS will be unique in establishing SI-traceability in-orbit. Global, hyperspectral measurements of both the incoming solar and reflected radiation with unprecedented accuracy will increase our ability to estimate the Earth’s radiation budget by an order of magnitude and act as a ‘gold-standard’ calibration reference for other EO missions. In this way, TRUTHS will improve the accuracy, reliability and integrity of EO data.

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TRUTHS

SI traceability in-flight

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Mission development