Measurement comparison contributes to space mission

Improving self-calibrating photodiode standards for environmental monitoring and European industry

Photonics and optics are exciting, rapidly evolving technologies of importance across industry, environment, health, medicine, energy, lighting and science. The photonic industry and standardisation organisations request miniaturised, cost-effective, integrated and self-calibrating measurement systems that cannot be provided by traditional methods. Recent developments exploiting Predictable Quantum Efficient Detectors (PQEDs) have demonstrated improved uncertainty of responsivity to 10 ppm and the proof-of-concept of an NMI-on-a-chip suitable for miniaturisation.

Metrology Partnership project Self-calibrating photodiodes for UV and exploitation of induced junction technology (22IEM06, S-CALe Up) is working to demonstrate exploitation of the new photodiodes as built-in standards in various applications and develop improved standard detectors for the UV range by exploiting new methods.

Measurement comparison

A PQED detector intercomparison was performed with the Laboratory for Atmospheric and Space Physics in Boulder Colorado. The consortium was working with the ground reference detector for the NASA Libera space mission. The Libera instrument is scheduled to be launched in 2027 and will record how much energy leaves our planet’s atmosphere on a day-by-day basis maintaining a decades long data record of observations from NASA’s suite of CERES (Clouds and the Earth’s Radiant Energy System) instruments. This data can provide crucial information about how the Earth system is evolving over time.

In addition, understanding fluctuations in solar radiation leaving Earth and its interactions with clouds, aerosols, and components of our atmosphere informs the foundational science needed to explore our universe – especially planetary bodies like the Moon and Mars.

Project coordinator Jarle Gran from JV, the Norwegian Metrology Service, said

‘We are very proud of the achievements in the project, where we have demonstrated that state-of-the-art radiometry is achieved over a wide spectral and dynamic range at room temperature. Exploiting PQEDs in radiometric measurements is a very convenient way of improving traceability as it operates in room temperature with very low noise, has a fairly low size and fits within many set-ups directly. Furthermore, its predictability ensures that the device is well suited to deploy traceability in current and future digitalised metrology systems in a wide range of applications.’

Dave Harber from LASP in Colorado said

‘This intercomparison was extremely valuable. The radiometric scale of the Libera instrument was established using our ground reference detector, a room temperature electrical substitution radiometer that obtains SI traceability through optical and electrical calibration of individual components. The intercomparison between our ground reference detector and the PQED detector provided an independent and direct path to SI traceability. This work both underpins the radiometric scale of Libera and lays the groundwork for future methods of ground calibration of spaceflight instruments.’

Video

The project consortium produced a video describing the work of S-CALe Up.

This Metrology Partnership project has received funding from the European Partnership on Metrology, co-financed by the European Union Horizon Europe Research and Innovation Programme and from the Participating States.

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