Experience with COTS components on ADPMS unit (PROBA satellites)

Agenda

1 Company Introduction
2 ADPMS Introduction
3 Why COTS?
4 Examples
5 Conclusion

Company Introduction

• Founded in 1969 as product developer
• Space activities started in 1983
• Delivered 100+ systems and sub-systems for manned space stations, satellites and interplanetary missions
• Acquired by the QinetiQ group (UK) in 2005
• 170 highly educated specialists employed
• 2 sites in Belgium
• 450m2 cleanroom

QinetiQ Space Ground Station

• Located in Belgium, Redu
• ESA satellite ground station
• Jointly operated with SES Astra

QinetiQ Space

• Located in Belgium, Kruibeke
• Offices: 3.742 m2, Warehouses: 1.200 m2
• 2 Class 100.000 cleanrooms

ADPMS Introduction

• ADPMS : Advanced Data and Power Management System
  • Dual lane computer and power system
  • Modular digital boards
  • Intended for platform computer

• Onboard computer for Proba satellites
  • Design started in 2000
  • Flight heritage on Proba-2 and Proba-V (16 combined years in orbit)
  • Flight units ready for Proba-3
  • Spin-off used on IXV

• Parts Usage
  • General class 3 level parts
  • About 20 different types of commercial COTS parts used on a total almost 300 parts
  • Design predates the ECSS-Q-ST-60-13C

Why COTS?

• Because of functional reasons (No suitable FM equivalent available)
  • However market and availability evolves
    • Several components could now be replaced by MIL / ECSS / Hi-rel parts
  • But, unless replacement is size/function compatible, risk of change is considered too high
    • Very dense PCBs prevent updating without complete redesign
    • Loss of flight heritage / qualification
    • excellent performance of most COTS parts in space

• NOT because of cost reasons
  • Component parts cost is lower however
    • Upscreening costs
    • Parts approval flow (repeated for each project)
    • Radiation testing when applicable
    • Solder qualification
    • (relifing)

• • Difficult to assess total cost at start of project
    • Accumulated cost of PAD discussions and extra tests over consecutive projects
    • Obsolescence, manufacturer changes or batch variability (no long term assurance)

• Design concept
  • cPCI compliant modular boards and backplane with rear-IO
    • Multiple types of cPCI connectors

• PCB space constraints
  • Decoupling of CCGA /MCGA devices
    • 0402 ceramic capacitors
    • Large value / small size ceramics
  • Qualified parts too large to accommodate
    • SOT23 plastic package dual schottky diode

• Functionality and performance
  • Memories required for LEON processor
    • Commercial SRAM and FLASH
  • Low power analog housekeeping
    • ADC, OPAMP and instrumentation amplifier

Design concept : cPCI connectors

• Part selection and Qualification
  • Initially parts from Tyco were selected with Sn/Pb leads
  • For each FM lot a press-fit qualification campaign was required
  • Extensive Lot acceptance testing, structural analysis performed
• Lessons learned
  • Standard PCB manufacturing with hot-oil reflow finish not ideal for press-fit mounting due to tolerance restrictions.
  • Due to obsolescence change required to other manufacturer (Harting)
    • Different tolerances and small dimension differences caused damaged connectors and pins
    • Same type of connector but internal construction is significantly different between manufacturers.
• Current status
  • cPCI equivalent connectors for space are available but limited choice and no reliable intermateability with other brands can be warranted.

PCB space constraints : Ceramic capacitors

• Part selection and upscreening
  • Commercial “Hi-rel” 0402, 0805 and 1206 caps from Kemet
    • Procured with traceability from authorized distributor
    • Manufacturer test level “C”
    • SnPb finish
• Lessons learned
  • Solder qualification and operational performance successful
  • Lifetime issues, solderability decreases
    • Solderability failed in reusing previous flight lot, new procurement required
    • Sourcing new SnPb COTS parts difficult with increased lead time (non standard product)
•  Current status
  • 0402 size capacitors are now available from European space-qualified manufacturers
    • High lead time and considerable higher cost than MIL CDR types
    • Used in new designs requiring class 3 or better.

PCB space constraints : SOT23 plastic package dual schottky diode

• Part selection
  • Multiple small signal schottky diodes required on small space
  • Space qualified single diodes available but FM package too large
  • Initial part from ON-semi selected
•  Lessons learned
  • Obsolete ON-Semi Flight batch failed 7-year relifing
    • Same BAS40-04 component from Infineon selected as replacement
  • Solder qualification required for all new batches of plastic parts
    • No issues for the older On-Semi part
    • Initial solder qualification of Infineon part failed due to difference in lead
  • Obsolescence and differences between commercial parts resulted in an unexpected cost and delay.
• Current status
  • Still a need for small diode packages
  • New designs with no COTS use more PCB area for same configuration

Functionality and performance : Memories

• Part selection and upscreening
  • Components were selected because some radiation data was already available
  • COTS memories have a short market lifetime. Large number was purchased. FM assembly uses only a few but quantities for upscreening and testing are significant.
  • Solder qualification required on each lot of plastic parts
  • Radiation test cost is extensive
    • Total dose testing
    • Single event latchup testing
    • Single event effects testing (SEU, SEFI)
    • In some cases proton SEE testing was required (sensitive part)
• Lessons learned
  • Combining all test costs the memories become the most expensive parts
  • Quick obsolescence and short lifespan of non hermetic plastic parts is a project risk and eventually limits the time a design can be reused.
  • Beware of variations in a “single lot” COTS parts
• Current status
  • For new projects external qualified devices (e.g. 3D-plus) are preferred

Functionality and performance : Analog Frontend

• Part selection and upscreening
  • Core is a radhard RTAX FPGA
  • Power conditioning with radhard parts
  • Critical parts for analog acquisition however are all COTS
    • Low speed ADC with SPI interface
    • Opamp
    • Instrumentation amplifier
    • Several high precision resistor divider arrays
• Lessons learned
  • To date no degradation is notable on the DAM housekeeping telemetry on both the Proba-2 and Proba-V satellites
  • No SEFI detected over the years for the ADC
• Current status
  • Qualified devices available on the market

Conclusion

• COTS can be successfully used in space
• Risk of obsolescence
• Significant differences between batches and manufacturers
• Upscreening costs per part are very high for small series

COTS comes with a COST