Monthly Archives: December 2014

BiSon 6 measurement results coming in

For the last couple of months, two Bison 6 sunsensors have been put to test on a real tracker.
The tracker which is located at the Fraunhofer ISE in Freiburg.
Because this tracker is controlled with a sunsensor that has a quite high albedo sensitivity at the end of the day there are quite significant deviations form the nominal pointing.
These deviations are measured with a black photon sunsensor (red line) which has a very high accuracy but is far to expensive to be considered for per tracker applications.

The Bison 6 sunsensor (cost optimised for per tracker application) readings follow the Black Photon quite accurately for the majority of time, one of the Bison’s has the patented additional straylight mitigation included (blue line) and performs markedly better than the other as can be seen in the enclosed graph.

It should be noted that these measurements are only from one typical day and further data analyses will have to be performed, but the measurements seem to show to us that the Bison sunsensors fall in the category almost as good but a lot more affordable.

For further information please contact Lens R&D

radiation testing on BiSon64 photodiodes is progressing nicely

Radiation testing on the dedicated four quadrant photodiodes specifically produced for the BiSon64 sunsensors is progressing nicely with very good results.
On 26th of November 2014 the preliminary results where presented at the CNES radiation workshop in Toulouse.
Even after 560krad of Co-60 radiation no measureable degradation was found on the quantum efficiency and only a marginal increase in darkcurrent was noted.
Although the tests will continue until the final goal of 1Mrad is reached, the measurements already show that the diodes used are very radiation tolerant and the Bison 64 sunsensors are therefore suited for even the most demanding applications.
Earlier test up to 10^16 1MeV electrons already showed good radiation tolerance, but this is now confirmed for total dose.
It should be noted that the test where performed on non protected diodes (no cover glass mounted) and the Bison 64 sunsensors provide approximately 1mm equivalent shielding in the front (650um sapphire) and 3mm aluminium on the other sides, thus rendering the sensors suitable for long duration GEO or MEO missions.

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