

‘Truths’ is an acronym* but it helps with the publicity. The satellite ‘will be sensitive to light in the visible and near-infrared part of the electromagnetic spectrum’.

[*Traceable Radiometry Underpinning Terrestrial- and Helio- Studies]

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The UK is going to lead a space mission to get an absolute measurement of the light reflected off Earth’s surface, reports BBC Science.

The information will be used to calibrate the observations of other satellites, allowing their data to be compared more easily.

Called Truths, the new spacecraft was approved for development by European Space Agency member states in November.

Proponents of the mission expect its data to help reduce the uncertainty in projections of future climate change.

Scientists and engineers met on Tuesday to begin planning the project. Industry representatives from Britain, Switzerland, Greece, the Czech Republic and Romania gathered at Esa’s technical centre in Harwell, Oxfordshire.

The agency has allocated €32.4m (£27.7m) for the initial design phase, with the scientific lead on the mission to be taken by Britain’s National Physical Laboratory.

NPL is the UK’s “keeper of standards”. It holds references for the kilogram, the metre, the second and all other units used in the international system (SI) of measurement.

The lab is the place you go, for example, if you want a precise description of the intensity of a light source – something it’s able to gauge using a device called a cryogenic radiometer.

And the aim of the Truths mission is to get one of these instruments into orbit.

Working in tandem with a hyperspectral camera, the radiometer will make a detailed map of the sunlight reflected off Earth’s surface – off its deserts, snowfields, forests and oceans.

The map should be of such exquisite quality that it’s expected to become the standard reference against which all other imaging spacecraft will want to adjust and correct their own observations.

This ought to make it a much simpler task to compare the pictures from different satellites, not just from those missions flying today but also from the ones that have long since been retired and whose data now sits in archives.

Full report here.