Designed in frame of the Artes 5.2 program ITAR free extended temperature fine sunsensor and intended to be the first small fine sunsensor to be capable of surviving the temperature excursions and radiation exposure experienced when mounted on extendable solar panels of geostationary telecom satellites, The BiSon74-ET-RH is intended to be a unique sensor, providing a cost effective and highly reliable solution to some issues already known for years.

Fine sun sensor - BiSon74-ET-RH Engineering model (ITAR free, extended temperature)

BiSon74-ET-RH Engineering model

In stowed configuration, solar panels quite often obscure the field of view of sunsensors thus hampering effective attitude acquisition during the Launch and Early Orbit Phase (LEOP) of many missions. Mounting a sunsensor on the solar panel until now was not feasible because no generally available sunsensor could handle the temperature ranges associated with this application. In Safe mode operation, the reliability of the solution is of utmost importance, and adding a sunsensor to the solar panel is the most direct and reliable way to measure the orientation of the solar panel. This is why Lens R&D (with support of ESA) is developing and qualifying an extended temperature sunsensor who’s temperature range allows for application at even the most demanding positions on a satellite, be it thin mechanical brackets or solar panels.

Today (23th of November 2016) we received 12 EM units produced in two different configurations for which 2*3 will be submitted to a compact but highly stressing qualification program.

The units have received their standard factory tests (10 thermal shocks from -55C to +125C according to MIL-STD-883 Method 1010B and PIND testing according to MIL-STD-883 Method 2020A which constitutes 3 periods of 20g sine and 12*1000g shocks) without any failure and are currently being calibrated.

The with ESA agreed upon test program consists of:

  1. calibration
  2. 12 thermal vacuum cycles -125C..+125C to demonstrate the capability to survive on ground testing
  3. calibration
  4. 30g sine and 38.9g random testing in all 3 axis to show launch load compatibility
  5. calibration
  6. 3500g pyroshock testing in all three axis (3 shocks per axis) to show the ability to withstand the expected separation shock
  7. calibration.

This test program is expected to be sufficient to convince potential customers we can survive on ground testing and launch.

The tests needed to show the resistance to a large number of wide range thermal cycles is still under discussion as this depends on the actual mission type targeted.

The current mission profile targeted is a long duration (20 years) geostationary profile where the satellite will go into a long eclipses (causing low temperatures) for only a couple of days per year.

More recent telecom missions however seem to focus on 1100 to 1300km altitudes with high radiation loading, many thermal cycles but not such low temperatures.

How to handle this will be decided at a later stage when the above testprogram has been completed successfully.

Completion of the current test program is expected by the end of 2016 if we can manage to limit the duration of the thermal vacuum cycles. Due to the large temperature range to be covered, each cycle could take a considerable time to complete. This is why we start on a Friday, so we can have a better estimation next week on how long the entire cycling process will take.