H. Fragner1, P. Beck2, A. Dielacher1, A. Hörmer3, O. Koudelka3, C. Tscherne2, M. Wenger3, M. Wind2
1 RUAG Space GmbH, Stachegasse 16, 1120 Vienna, Austria
2 Seibersdorf Labor GmbH, Forschungszentrum Seibersdorf, 2444 Seibersdorf, Austria
3 Graz University of Technology, IKS, Inffeldgasse 12, Graz 8010, Austria
As announced last year  in the frame of the RADHARD Symposium, the consortium RUAG Space GmbH, TU Graz and Seibersdorf Laboratories have now finalized the Phase B study of a CubeSat mission by conducting a successful PDR under supervision of ESA.
Within this Phase B study the platform and the payload design was substantially advanced. The platform consists of several COTS components which have been selected in the preliminary design phase. Most of them have flight heritage from other missions with exception of the horizon detector used for attitude determination. The need for such a detector became evident due to the requirements put on the mission by the passive reflectometer and its operation during eclipse. The detector is currently developed by GomSpace and will provide in combination with the magnetometers the required determination accuracy.
The implementation of the passive reflectometer payload has been significantly advanced and the SW and firmware is in a shape to accurately predict the reflection points and to set up the PACO FPGA with the correct parameters. The implemented earth model allows distinguishing between sea and land surface and also includes a height mapping.
The original plan for the dosimeter was to measure the TID by means of RADFETs. In the course of the Phase B study the idea for the dosimeter has been substantially advanced and the design baseline of the dosimeter now foresees two different sensors for TID measurements: The RADFET and the relatively new floating gate dosimeter (FGDOS). Both sensors will be available on board of PRETTY in an unshielded and a shielded configuration. The comparison of the measurement results under real space radiation environment will allow valuable insights in the characteristics of these two measurement devices.
Another improvement of the dosimeter is the implementation of a LET spectrometer, which allows characterizing the radiation environment based on histograms obtained by counting SEE occurrences within a certain amplitude range. The LET spectrometer sensor is a single PIN diode, which will have a certain angular dependency of the LET by a single particle due to geometry of the p-n barrier. Extensive simulations have been performed in order to characterize this angular dependency and trade it off against other concepts, e.g. dual sensor geometry.
 H. Fragner, P. Beck, A. Dielacher, O. Koudelka, C. Tscherne, M. Wenger, M. Wind, „PRETTY: Passive Reﬂectometry based on the Interferometric Method and Dosimetry Measurements”, RADHARD Symposium 2018, www.seibersdorf-laboratories.at/en/radhard/archive/2018-radhard-symposium, ISBN (Print) 978-3-902780-12-6, ISBN (Ebook) 978-3-902780-13-3, Editor: Peter Beck, Seibersdorf Labor GmbH, 2444 Seibersdorf, Austria, Publisher: Seibersdorf Laboratories Publishing, Austria, April 2018.
The Phase B study for the PRETTY mission has been funded by ESA GSTP Programme. The according Phase A study was funded by ASAP/FFG.