OBC Tests

Cubesat, February 19, 2020

In the near future CubeSats will be used extensively for missions far outside of Earth’s protective magnetic field. The accumulated radiation dose the satellites must endure in such missions is significantly higher than when “only” orbiting Earth in LEO. One of the major objectives of CLIMB is to identify software and hardware means to endure increased radiation levels. At the same time, those means must remain within the limited financial scope of CubeSats. Such considerations were already part of the design of PEGASUS , our first satellite. As the results indicate, those efforts were already rather successful (see IAC paper).

However, CLIMB will endure a significant high radiation rate than PEGASUS due to its higher orbit and exposure in the Van Allen Belt.  In order to ensure CLIMB’s safe operation throughout the mission, we rely on similar techniques as applied in PEGASUS but also on ground testing of the hardware performance in an increased radiation environment.

The subject of the first of (many) such tests, were two identical versions of the OBC developed for CLIMB. In the radiation facility at Seibersdorf Laboratories (see picture provided by Seibersdorf Laboratories), the OBC was exposed to an accumulated dose of a little bit more than 50 krad (at 3Gy/hour) – a dose, which corresponds roughly to 2.5 years in LEO.

During the nearly one week-long test, both OBCs were operating continuously, executing complex calculations, requesting data from all internal sensors, writing to and reading from storage amongst other things. This allowed us to continuously monitor the performance of all the OBC components and correlate the performance directly with the measured accumulated radiation dose.

The detailed analysis of the test is still ongoing. However, as a preliminary result one can summarize that both OBCs survived the test well. Very important is that we did not observe any impact whatsoever on the main microprocessor. We lost some analog temperature sensors and some components showed a higher current draw but otherwise both OBCs performed very well until the end of the test. This test has shown that the general concept of the OBC is valid for an increased radiation environment for extended time.

This is a really a BIG success for us. Many thanks to our colleagues at Seibersdorf Laboratories! A Big Thank You also to Andreas and Robert who prepared this test over the Christmas holidays.