Straylight
CSL has a long experience in straylight design, analysis and testing of a lot of different optical space and non-space systems.
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traylight is a topic covering a lot of different skills. It starts from genius designs and new ideas in manufacturing and testing.It adresses complex modeling and measurements of coating reflectivity or BSDF. To close the loop, CSL developed unique facilities to test the manufactured systme. Last but not least, innovative image handling methods are used to reduce the residual straylight to an acceptable level are also developed. CSL straylight expertise covers a large number of topics. Straylight concerns are different for systems operating in the Xrays than in the Infra Red, for astronomical telescope than for Earth Observation satellites, for instrument working on ground that in space. Since the 80’s CSL has been involved in stray light design and testing. For example, CSL worked on the Phase B of VEGETATION for studying the pre-flight calibration methods and defining the OGSE requirements. CSL has later been involved in the straylight issues of PROBA V with a complete novel approach.
CSL can offer a complete straylight :
- Review of customer’s specifications
- Straylight analyis
- Straylight baffle and baffling
- Straylight testing
- Stray-light calibration
- Test result correlations and analysis
- Straylight reduction by data handling
Design capabilities
The exact position of the vanes in the baffle were optimized with the goal of first level scattering reduction with ad hoc methods. Validation is carried out with ray-tracing simulations as well as experimentally.
Straylight analysis
Straylight analysis is used to validate the design in terms of stray-light level. In addition, the analysis can later be correlated with test results. Correlation between model and in orbit data up to 10-13 has been achieved.
Straylight Facility
CSL developed a straylight facility for In Field and Out of Field of View straylight characterization of small Earth observation satellites. The first tested satellite was PROBA V (a small Belgian satellite, succesor of the SPOT VGT on SPOT missions).
Straylight testing
Other missions as SOLO HI and SOLO/WISPR for NASA were also tested with this facility. The facility is designed for in-field and far field straylight characterization: intensities dynamic range up to 108:1 for in-field and up to 1010:1 for far field straylight in the visible to SWIR spectral ranges. The test results demonstrate that the stray light performance of both PROBA V and the test facility are excellent and are in line with the model predictions.
Straylight data handling
When the stray-light level of an instrument is not acceptable, numerical methods can be used to reduce it below what hardware can achieve. CSL devleops stray-light post-processing correction methods, which combines software with stray-light characterization. Such algorithms are expected to become more and more frequent in space missions.
