The Freja charging study: A perspective five years later

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ESA EJSM/JGORadio Plasma Wave
Instrument(RPWI)Warsaw meeting 110110Lennart
Åhlén
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Radio Plasma Wave Instrument (RPWI) Principle
Block diagram
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Power consumption
  Xilinx, mW (100) Actel, mW (100) On time Xilinx, mW Actel, mW
LP-PWI (preamp) 400 400 0,8 320 320
SCM (preamp) 400 400 0,8 320 320
RWI (preamp) 300 300 0,5 150 150
RA-PWI (preamp) 200 200 0,1 20 20
MLA (preamp) 300 300 0,05 15 15
MIME (drivers) 800 800 0,1 80 80
Bias MIME 1200 1500 0,8 960 1200
LF 1000 2000 0,8 800 1600
MF 1000 1500 0,25 250 375
HF 1700 1700 0,5 850 850
DPU 2800 1000 1 2800 1000
Total 10100 10100   6565 5930
With 85 DCDC 11918 11918   7747 6997
Mass 6.8kg Harness 1kg
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Cosmic Vision Instrumentation ASIC
The activity will be kicked off 17th of September
with a Spanish consortium involving Arquimea,
CSIC, UPC and the University Carlos III.
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Main box mechanics
HF
MF
LF
LP-PWI MIME
DPU
DC/DC Converter

• Backplane with power distribution, analog and
  digital interfaces
• Board size 20x15cm
• Connectors Micro-D type
• Box 21x16x12 cm.
• Distance between Boards 20mm

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RPWI Grounding block diagram
EMC. MIL-STD-462D ECSS-E-ST-20-07C(31July2008) R
O-EST-RS-3001/EIDA
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Conductive and radiation emission requirements
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EMC requirements

• Oscillator controlled DC/DC converters.
• 2. To minimize magnetic stray fields from
  DC/DC converter transformer and coil
• toroid cores should be used.
• 3. Motor magnetic circuits should be balanced
  in order to minimize stray field
• variations synchronic to the rotation.
• 4. Motor brushes should be filtered in order
  to minimize voltage and current spikes.
• 5. SCM and the flux gate magnetometer (MAG)
  sensors should be separated by a
• minimum of 0.3 meter, and recommended 0.5
  meter.
• 6. The MAG harness has to be placed at least
  8 cm from the SCM sensor.

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Radiation protection

• Spot shielding should be used for all S/C
  external electronics
• Box and spot shielding should be used for the
  RPWI Box
• Use of Rad Hard components
• Box shielding 10mm
• 2 kg extra mass needed for 8mm box protection
• 3kg allocated by ESA for radiation shielding of
  RPWI
• Action
• Calculations of internal box radiation levels
  using GEANT 4

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LP-PWI Bias control, LF wave analyzer and MIME
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HFwave analyzer
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• WHY Should we use the ESA ASICs ?
• They are guarantied Rad hard
• ESA will do the paper work
• ESA will pay for the qualification
• We will save mass (up to 650g)
• We may save power that can be used for signal
  processing
• We may save money
• We can convert saved mass into antenna length
• If they are not delivered in time we blame ESA
  for the delay

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RA-PWI, RWI and LP-PWI Preamplifiers Lennart
Åhlen
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LP_PWI Preamplifier

• Specifications
• Switchable E-field / Density
• 100mW power consumption
• 500kRad Radiation hardend
• Positive feed back current generator
• E-field
• DC-300Hz -100V input range
• DC to 3MHz small signal bandwidth
• Better than 1012 input resistance
• 1nA 100nA Current Bias range
• 16 nV/sqr(Hz) noise
• Density
• DC to 10kHz bandwidth
• 10pA to 100uA input current range
• -100V Voltage Bias range

New development Find new low noise Rad hard
operational amplifiers Develop a MEMS chip
including nano-switches and amplifiers MEMS
amplifier 10x10x1mm total mass 4x30g (4x250g)
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MEMS pre-amplifier implementation
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• Conclusions
• Each single requirement is hard to meet, and
  combined it is more or less impossible to build a
  component that meet all requirements (voltage,
  leakage current, temperature and size).
• Lowest leakage current is reached with own-built
  reed-relay (fA or pA)
• Smallest size is reached by MEMS-based switch,
  (100 um)
• pA leakage is easier to reach at lower voltage.
• Reed relays In test and measurement,
  particularly in integrated-circuit (IC) testers
  and wafer testers, with parallel high switch
  point counts, leakage current becomes a real
  problem. Reed relays designed to handle fast
  digital pulses will exhibit extremely low leakage
  currents in the order of 0.1 pA or less. No other
  technology currently offers anything close to
  this combination.
• To manufacture reed switches 5mm or less in a
  stable manner is difficult.
• Alternative system approach is to use 2 boxes
  one with thick radiation shield for small and
  radiation sensitive components and one with less
  shielding, if reed relays are enough radiation
  tolerant.

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Alternative system approach.
Radiation protected area for sensitive
components, with thick Al capping (solid state
relay)
Area for less sensitive components (low leakage
reed relay)
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RA_PWI and RWI Preamplifier
FET follower or FET input negative feed back
amplifier ?

• High distortion
• Limited output range
• Low power
• Simple

• Low distortion
• Medium power
• Complex

Specifications 1kHz to 50MHz Bandwidth 2
nV/sqr(Hz) noise -1V input range 100mW power
consumption Amplifier from Tohoku University
100Hz to 50MHz 0.6W
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RPWI EGSE Principle Block diagram
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ESA INTERNAL REVIEW RECOMMENDATIONS COMMENTS ON
ELECTRONICS

• System
• We have to look into single point failure areas
  in the system design.
• It looks like the magnetic requirements will
  govern the system grounding
• concept and we urgently have to find a way to
  prevent that to happen.
• Instrument
• ESA just reminds us of the pre- amplifier
  radiation environment, which we have under
  control. However, ESA needs to give the
  specifications how to test parts.
• Mass and power impact on fall back options need
  to be estimated.
• The thermal environment for the pre-amplifiers
  and the boom mechanisms need to be identified.