Transcript The Freja charging study: A perspective five years later

ESA EJSM/JGO
Radio & Plasma Wave
Instrument
(RPWI)
Warsaw meeting
110110
Lennart Åhlén
Radio & Plasma Wave Instrument (RPWI) Principle Block diagram
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
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.
Main box mechanics
•Backplane with power distribution, analog and digital interfaces
•Board size: 20x15cm
•Connectors: Micro-D type
•Box : 21x16x12 cm.
•Distance between Boards: 20mm
RPWI Grounding block diagram
EMC.
MIL-STD-462D ECSS-E-ST-20-07C(31July2008)
RO-EST-RS-3001/EIDA
Conductive and radiation emission requirements
EMC requirements
1.
2.
3.
4.
5.
6.
Oscillator controlled DC/DC converters.
To minimize magnetic stray fields from DC/DC converter transformer and coil
toroid cores should be used.
Motor magnetic circuits should be balanced in order to minimize stray field
variations synchronic to the rotation.
Motor brushes should be filtered in order to minimize voltage and current spikes.
SCM and the flux gate magnetometer (MAG) sensors should be separated by a
minimum of 0.3 meter, and recommended 0.5 meter.
The MAG harness has to be placed at least 8 cm from the SCM sensor.
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
LP-PWI Bias control, LF wave analyzer and MIME
HFwave analyzer
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
RA-PWI, RWI and LP-PWI Preamplifiers
Lennart Åhlen
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 10^12 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)
MEMS pre-amplifier implementation
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.
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)
RA_PWI and RWI Preamplifier
FET follower or FET input negative feed back amplifier ?
•High distortion
•Limited output range
•Low power
•Simple
Specifications:
1kHz to 50MHz Bandwidth
+-1V input range
•Low distortion
•Medium power
•Complex
2 nV/sqr(Hz) noise
100mW power consumption
Amplifier from Tohoku University 100Hz to 50MHz 0.6W
RPWI EGSE Principle Block diagram
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.