Enabling SI-Traceable Calibration for Small Satellite Missions
The National Physical Laboratory (NPL) and the Science and Technology Facilities Council's (STFC) RAL Space have combined expertise to build a new national centre – the Small Satellite Calibration Facility (SSCF) – for calibrating visible and thermal infrared instruments on small, cube, and nano satellites.
With well-established, world-class facilities for pre-launch testing and calibration of satellite technology, NPL and RAL Space have a long track record of SI-traceable calibration of space instrumentation including the CNES/UKSA MicroCarb mission and the Copernicus Sentinel missions. The Small Satellite Calibration Facility merges the calibration capabilities of NPL in the ultra-violet, visible and short-wave infrared (UV-SWIR) with RAL Space in the thermal infrared (IR), providing a resident facility at the Harwell Space Campus that offers an agile calibration service to support companies developing instrumentation for small satellite missions.
Calibrating small satellites is essential to ensure the accuracy, reliability, and scientific value of their data. Proper calibration guarantees traceability to international standards, enabling interoperability with other missions and consistency across datasets. For missions aligned with the goals of the European Space Agency (ESA), such as supporting Copernicus Sentinel missions, calibration is key to ensuring that data products are credible, comparable, and fit for international collaboration and policy-making.
As part of the SSCF, NPL manages the traceable radiometric calibration in the UV-SWIR. Building on the knowledge gained from the development of NPL’s STAR-cc-OGSE, this facility utilises much of the same science & engineering to enable quick turnaround, affordable access to radiometric calibration of small satellite payload instruments.
The STAR-cc-OGSE facility at NPL
The SSCF system combines the design of the radiometric calibration setup from STAR-cc-OGSE with a novel SI-traceable reference detector and a 1 kHz pulsed tuneable laser. This enables radiometric calibration measurements from 320 nm to 2500 nm with both monochromatic and broadband sources. The sequence of images below show how the SSCF can scan through the visible spectrum using monochromatic radiation.
Small Satellite Calibration Facility offers a range of characterisations including:
- Absolute spectral response
- Linearity
- Polarisation sensitivity
- Spectral response function
- Stray light
- Spectral calibration
Small Satellite Calibration Facility Radiometric Specifications:
| Monochromatic spectral range |
320 nm – 2500 nm |
| Monochromatic radiance |
0.04 – 2.10 W m-2 sr-1 |
| Monochromatic tuning resolution |
< 0.01 nm |
| Monochromatic wavelength accuracy |
< 0.03 nm |
| Broadband spectral range |
300 nm – 2500 nm @ TCCT = 3080 K |
| Broadband radiance |
2.0 W m-2 sr-1 nm-1 (@1000 nm) |
| Polarisation extinction ratio |
40 dB |
| Reference detector absolute radiance calibration uncertainty |
< 0.5 % (k=1) |
A member of the SSCF NPL team setting up the facility at RAL Space
For enquiries about the facility and to speak to a member of the team please email.
Hear from the experts working on the facility here:
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