‘TRUTHS’ satellite for robust climate monitoring to be decided in November 2019

Truths mission, © NPL

ESA members will decide on funding for satellite mission designed to monitor Earth’s climate explicitly tied to SI – a ‘metrology laboratory in space’

On 27 – 28 November member states of the European Space Agency (ESA) will decide on funding for a new satellite to monitor the Earth – TRUTHS. TRUTHS stands for ‘Traceable Radiometry Underpinning Terrestrial-and Helio-Studies’.

This small satellite, consisting of a hyperspectral imager that will measure the light coming from the Sun and that reflected by the Earth, has two main aims. First it will establish a benchmark of the state of the planet – 10 times more accurate than current observations – which will be used in climate modelling. Second it will be a ‘primary reference standard’ which will be able to calibrate other satellites from orbit, upgrading the existing fleet. If funded, this will be a world first for monitoring climate change effects. Not only is it expected to reduce the time taken to detect climate trends - and with that reduce the uncertainty in forecasts of the Earth’s temperature rise - but the data it collects will also be directly traceable to the SI, providing unprecedented rigour and trust.  

Development of this satellite has been supported through the work of three EU-funded EURAMET projects:

- European metrology for earth observation and climate (MetEOC, ENV04) – which supported the development of concepts of the on-board calibration system including the on-board cryogenic radiometer CSAR.

- Metrology for earth observation and climate (MetEOC2, ENV53) – which supported some of the build and test of the TRUTHS calibration system.

- Further metrology for earth observation and climate (MetEOC-3, 16ENV03) – which further developed on the work of the first two projects to improve the pre- and post-launch calibration and validation of other Earth viewing satellite sensors.


The projects have enabled many of the concepts that differentiate TRUTHS from other satellites to be evaluated and tested at early Technology Readiness Levels (TRL) helping to de-risk the concept and hopefully facilitate its funding in preparation for launch. All three projects have been coordinated by the lead scientist of TRUTHS Professor Nigel Fox of the National Physical Laboratory.

The disruptive ‘self-calibration’ of TRUTHS - directly to an in-space SI primary standard - mimics methods used on the ground for pre-flight calibration. TRUTHS exploits this concept further through its ability to not only anchor to SI, but also in many cases upgrade the performance of other satellites to ‘climate quality’. This climate and calibration observatory in space will herald a ‘new era’ of Earth Observation (EO). TRUTHS not only supports observations of climate but also many secondary commercial applications including those being pioneered by the emerging constellations of microsatellites.

Dr. Emma Woolliams, chair of the European Metrology Network for Climate and Ocean Observation said

'This mission illustrates the growing recognition of the critical importance of metrology to support climate observations. Many of the concepts that will be developed or enabled by this mission will also benefit a wide range of climate and ocean observations.'

This EMPIR project is co-funded by the European Union's Horizon 2020 research and innovation programme and the EMPIR Participating States.

This EMRP joint research project is part of EURAMET’s European Metrology Research Programme. The EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union.

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