Optical expertise for space

Optimisation of detector systems for science in space

Designing optics for space therefore means searching for an optimal design: one that fits within limits and can do as much science as possible.

Each space instrument for astronomy and Earth observation is therefore custom designed for a specific wavelength range and specific scientific purpose.

For instance, the detection system that has been measuring methane on the TROPOMI instrument since 2017 cannot be ‘just adapted’ for TANGO, which will also measure methane, but in more detail. TROPOMI carries a hefty cooling system, which helps prevent contamination, and which will never fit within the space and development budget of the small TANGO satellite. So we are again providing new customisation.

Testing optical systems for science in space

Once all the elements of an instrument are determined, extensive tests follow to see what happens to the signal. Experts devise precise tests for demonstrators and final flight models that precisely mimic conditions in space. For example, they subject instruments to an ultra-high vacuum and all kinds of extreme temperatures.

Examples of this extensive important test work include the test campaigns for SRON’s SPEXone spectropolarimeter for studying aerosols from the NASA PACE satellite. And SRON’s space simulator for testing the cameras for ESA’s PLATO telescope for the study of exoplanets.

Because optics scientists have control over the signal entering the instrument during tests in a lab, they can test the instrument properly. They know the instrument inside out and examine whether the result of the test measurement matches what you would expect with this incoming signal AND this instrument. At the end of this process, the instrument (part) is calibrated and ready for flight.

Optical systems for space design, testing and validation

SRON’s optics experts design, test and calibrate new and existing optical instruments. This way, the instrument only measures what it is supposed to measure, and thus the measurements are reliable. Optics experts always know exactly all the peculiarities of a measuring instrument. When harvesting and processing measurement data, they can also correct exactly for these peculiarities. So they get good quality data for scientific use.

Peculiarities they want to know are, for example, whether unwanted light also falls on a detector, causing a false signal. How much of the signal entering the instrument also reaches the detector? Is some amount of signal also lost before it reaches a detector? Is the signal different when the instrument does not operate in light, but completely in darkness?

Using and calibrating space instruments

After launch, scientific operations can begin. But optics experts must also regularly monitor the health of an instrument to ensure that the data continues to meet the high standards set before launch.

During their lifetime, instruments on satellite missions always deteriorate somewhat, due to harsh radiation conditions in space. So you always want to be sure that all the features you see in the scientific data say something about the measured source, and are not due to the declining health of the instrument.

You can notice deterioration by periodically looking at light signals that we know exactly. For example, a built-in LED, sun or moonlight, well-documented nearby stars, or even remote desert areas on Earth can be used as benchmarks to check whether instruments are in the right state.

The optical expertise at SRON, where extreme conditions, extreme temperatures, extreme demands and extreme reliability are everyday fare, plays a vital role in scientific advances in space research. These experts ensure that instruments are well designed, well tested and well maintained.