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Follow the Sun ... but do it small scale

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“Follow the Sun” is a much-heard motto in atmospheric research. Sunlight is crucial to study the composition of the atmosphere with optical spectrometers. Over the past two decades, BIRA-IASB engineers have designed, built, and used different types of solar trackers. It is time now to retire the first-generation trackers. A second-generation mini solar tracker is ready to take over. It is much more compact and better equipped to withstand the harsh weather conditions it will have to operate in.
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Following the Sun – crucial in atmospheric research

To study the composition of the atmosphere by means of an optical spectrometer, sunlight is essential. The longer one can keep track of the Sun, the more information one will collect, and the more efficient instrumentation becomes.

Spectrometers operating from the surface of the Earth therefore benefit from having a system mounted at their optical apertures, that is capable to capture sunlight from early morning until just before dawn. A solar tracker in other words.

Over the past 20 years BIRA-IASB has designed, built and operated different solar trackers. These first-generation trackers will now be replaced by more robust and more flexible mini solar trackers.

First-generation solar trackers

The solar trackers that were built between 2000 and 2020 by the Engineering department of BIRA-IASB are fully operational mechanical, electronic and electrical systems, in which a set of two mirrors (one azimuthal and one elevation) are controlled. The trackers work autonomously and can be remotely controlled as well.

The trackers were (and still are) mostly used in combination with BIRA-IASB’s infrared Fourier-transform spectrometers (FTIR), that perform high-precision measurements of the atmospheric composition (especially of methane), in the frame of calibration campaigns of the NDACC and TCCON networks.

These first-generation solar trackers of BIRA-IASB have been used amongst others:

  • on Reunion Island,
  • in Brazil,
  • in India,
  • in Congo
  • at our own Space Pole in Brussels

Operating a moving system day-in day-out in challenging conditions (high and low temperatures, humid and salty air near the sea) is not straightforward. Throughout the years improvements have been carried out to the existing concept.

Nevertheless, in 2020 it was decided to perform an extensive redesign. Technological evolution goes on and the first-generation solar trackers were really due for a thorough update.

There comes the mini solar tracker

The mechanical structure and the drive electronics of the original solar tracker was refined into a much smaller, versatile, autonomous, robust second-generation mini solar tracker.

More reliable rotation stages were incorporated to control the tracking mirrors. The housing was restyled and equipped with better joints so that humidity and salt will no longer be an issue.

The experience acquired with the first-generation trackers was now fully exploited to reshape the control electronics completely, again in view of increasing robustness and flexibility. Also, the embedded software, that programs the mirrors for their chase after the Sun, was rewritten in more versatile and readable Python code.

The mini solar tracker will still be the ideal companion of BIRA-IASB’s infrared Fourier-transform spectrometers but can now also be coupled to other instrumentation. At this time the possibility is studied to couple the mini solar tracker to the SEMPAS spectrometer that will be installed on a windmill in the North Sea from where it will measure and monitor emissions of passing ships.

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First-generation solar tracker at the Space Pole in Brussels
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Computer Aided Design (CAD) drawing of the mini solar tracker – (right) finished mini solar tracker on the workbench in the mechanical workshop at BIRA-IASB
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Finished mini solar tracker on the workbench in the mechanical workshop at BIRA-IASB
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