Transcript The Freja charging study: A perspective five years later

ESA EJSM/JGO
Radio & Plasma Wave
Instrument
(RPWI)
Prag meeting
100218
Lennart Åhlén
Plasma waves
Electric fields
Plasma measurements
Conductivities
B
Radio
Main box mechanics
•Backplane with power distribution, analog and digital interfaces
•Board size: 20x15cm TBC
•Connectors: Micro-D type
•Box : 21x16x12 cm average 4.7mm wall thickness for Al.
•Distance between Boards: 20mm
Power
Voltages:
+3.3V Digital interface supply
+1.8V Digital DPU and FPGA core supply
+-8V Analog
•Software current limiters (msec turn off at latch up)
•Common ground for all voltages
•Only one ground in the backplane
•Total power: 6.6W average 10W peak (100ms)
Instrument interfaces
• Digital: Differential
• Analog: Single ended (TBC)
Satellite interfaces
• 2 Mbit SpaceWire
• Single ended (TBC)
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 4.7mm
•1.1 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
Generic Instrument
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)
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 Grounding block diagram
EMC Actions.
Define acceptable satellite RE and CE levels for the
frequency range DC to 45 MHz.
MIL-STD-462D ECSS-E-ST-20-07C(31July2008)
Develop the RPWI EMC requirements for the S/C by interaction during S/C design
Experimenter EMC requirements
1.
All spacecraft surfaces exposed to the plasma environment shall be sufficiently
conductive and grounded. < 5 kohm/sq
2. Small surfaces differential charging potential shall not exceed +-10 V, assuming a
plasma current of 5 nA/cm2
3. The S/C structure shall not be used as return path for power and signals except for
sensor signals to avoid common impedance coupling and magnetic disturbances.
4. Isolated receivers and balanced differential signals should be used as subsystem
signal interfaces.
5. All active wires shall be twisted with its return wire and loops on circuit boards
should be minimize to reduce magnetic disturbances.
6. The spacecraft system shall use a Distributed Single Point Grounding.
7. Secondary power shall be grounded to structure only once in each unit / experiment.
8. Cable shields shall be grounded to structure ground at both ends. Shields shall not be
used as the return path for signal or power.
9. Non-magnetic materials shall be used wherever possible.The use of ferro-magnetics
shall be avoided wherever possible.
10. It is recommended to use crystal oscillator controlled DC/DC converters
Low Voltage Power Supply (LVPS)
Göran Olsson
Royal Institute of Technology (KTH)
Space and Plasma Physics
+8V
-8V
3.3V
1.8V
CEB BACKPLANE
LVPS CONTROL & MONITORING
LVPS-B TBD
LVPS-A
LVPS IN RPWI JGO
+8V / -8V
3.3V
1.8V
LFA + AM
+8V / -8V
3.3V
1.8V
SCM
3.3V
1.8V
+8V / -8V
3.3V
1.8V
+8V / -8V
3.3V
1.8V
SCM PREAMP
DPU
LP-PWI
RWI RA-PWI
HFA
Clock, Control, Data and Emergency Power-Off, A + B
LP-PWI Preamps
RWI Preamps
RA-PWI Preamp
LVPS Requirements
Functional:
•DC power to all RPWI instruments:
•
±8V +3.3V, +1.8 V from 25-36 V input, nominal total power output: ~10 W
•CEB Form Fit:
•
PCB Dimensions 200x 150 x 1.6 mm
•
Component height 12 mm upper side, 3 mm lower side
•
Backplane connector 160 pin, 3 row Airborn WG series
•
Mass 300 g
•Primary to secondary isolation
•Temperature range: -30 °C to +50 °C operating
•Redundant DC/DC converters and digital controllers TBD
•Power Switching: 5 instruments having two to four supply voltages
•Voltage and Current Monitoring
•Overcurrent Tripping; Limits under software control
•Temperature Monitoring: DC/DC converter and SCM sensor
Performance:
•No-load Power (Including DC/DC converter, controller, monitoring and switches): 1.1 W
•Differential Efficiency: 82%
•Output Deviation: ±5% from nominal including all effects
•Output Ripple: < 5 mVrms
LVPS Block Diagram
1.8, 3.3 V
From
SC
28V
Common-Mode
Filter
From
SC
28V
Common-Mode
Filter
DPU
Voltage
And
Current
Monitors
(4)
DC/DC Converter A
1.8, 3.3 V
•Redundant TBD DC/DC Converters and
Controllers chained with the DPU
•Unused chain is a cold spare
•Common power bus for all instruments.
Design to minimize risk of single point
failures here.
•What if both chain A and B are powered?
Must be survivable, but no functional
requirement. - No mutual interlock
implemented. Subject of further study.
•1.8 V is regulated to 1.5 V locally on each
subsystem
•Power switches have turn-on ramping
•Emergency Power-Off
DC/DC Converter B
1.8, 3.3, ±8 V
Common Bus
Power
Switches
(9
Instruments)
Voltage
and
Current
Monitors
(24)
CEB
BPLN
Housekeeping
From SCM Thermistor
Controller A
FPGA
CDPU-A Ctrl: Clock, Command, Data, EPO
Controller B
FPGA
DC/DC Converter A/B
Second Stage
Pulse-Width
Modulator
‘Forward’
Converter
13-14 V DC
420 kHz
Switchmode
Regulator
Controller
50mΩ
+
Shielded
Outputs:
+1.8 V, 1.1 A
+3.3 V, 1.1 A
+8 V, 350 mA
Output Filters
•Inrush current limiter
First Stage
Secondary
Main
Transformer
Synchronous
Rectifiers
EMI
Filter
Shielded
Transformer Driver
Input: 2736 V
Primary
-8 V, 300 mA
Internal:
±15 V
•Regulated input voltage to Transformer
Driver
•Current positive feedback:
Counterbalances losses in driver
transistors, transformer and rectifiers.
•Full-Wave
•Primary to
Secondary
Isolation
•210 kHz
•Double Shielding
•Push-Pull
Two-stage Conversion:
Excellent input and load regulation
Low noise
Low output cross-regulation
Slightly lower efficiency
•Full-Wave
Rectification
•LC Pi Filters
•No Feedback from Secondary
DC/DC A/B
Digital Controller A/B
3.3 V
Linear
Regulators:
1.5 V
CDPU A/B
2.5 V
LVDS
FPGA
Power Switch Control (9)
HK Control (ADC, Mux, Gain Switch)
•Instrument Power Control
•Housekeeping Control with Storage
and Readout
•Overcurrent Tripping, limits under
software control
•IVM: Actel ProASIC3 A3P250
Housekeeping ADC Data
•FM: Actel RTSX72
•System clock derived from the CDPU interface clock: 1.048
MHz
•If three consecutive samples (~15 ms) exceed the limit ► All
voltages turned off for the affected instrument
Design Heritage
1.
2.
DC/DC Converter, Housekeeping System and Stepper Motor Controller for EMMA, a plasma
payload on the Swedish Astrid-2 satellite, launched December 10, 1998. Dimensions 177 x 134
x 16 mm. DC/DC design power 10 W. COTS components. This design has many features in
common with the MMS LVPS.
DC/DC Converter for SPEDE, a plasma payload on the SMART-1 ESA Lunar Orbiter, launched
2003. Dimensions 71 x 44 x 11 mm. Design power is a mere 1.2 W.
Impacted on the Moon as planned on September 3,
2006.
LVPS IVM on the UNH lab bench with codelivered dummy load board
Mass
Antennas/Sensors
Circuit board Main Box
Width
21cm
Depth
15cm
SCM
650
Card mass/cm¨2
0.7
SCM Harness
480
Number of cadrs
6
Preamp
100
LP-PWI
1800
Box mass
Material density
Card mass
Box thickness
1000g
2.8
1449g
4.7mm
meter
LP-PWI Harness
375
Preamp
200
RWI
g/m
4
120
15
25
3
40
3
28
1400
Box surface
1191cm^2
RWI Harness
120
Total Box Mass
3000g
RWI Preamp
100
RA-PWI
200
Harness mass
1059g
RA-PWI Harness
84
Preamp mass
600g
RA-PWI Preamp
200
Sensor mass
4050g
Sensor + Box+Preamp
7650g
Total
8709g
Low and high frequency analyzers
Lennart Åhlen
Scientists dream receiver
A downgrade is needed for the JGO receivers.
TDA: Development of FPGA algorithms for digital analyzers to obtain high
dynamic measurement range
JGO Scientists dream receiver
A downgrade is needed for the JGO receivers.
Dynamic range: The ratio of the specified maximum signal level capability of a
system to its noise level in a record of continues sampled data.
What is required to fulfill the JGO since objective?
Questions to be answered by the RPWI scientists.
1.
2.
3.
4.
5.
Ranges and overlap for the low and high frequency receivers?
Wave-form capture?
Low and High frequency data coverage?
Number of parallel data channels?
Type of on-board data analyzes?
Low frequency receiver
• Signal processing: FFT, I/Q, Filter bank, Wavelets, PFT,
• Buffer memory for wave form capture and Burst data.
• Dynamic range: 80dB to ~120dB @ 100Hz bandwidth
High frequency receiver
• Burst data signal processing: FFT, I/Q, Filter bank, Wavelets, PFT,
• Buffer memory for wave form capture and Burst data.
• Dynamic range: 70dB to ~100dB @ 10kHz bandwidth
• Measurement range: 70dB to ~120dB @ 10kHz bandwidth
• Dynamic range:
70dB to ~100dB @ 10kHz bandwidth
Under sampling high frequency receiver
• All
high speed ADCs has a higher analog bandwidth
than the maximum sampling rate.
•This makes it possible to build HF digital receivers by
use of under-sampling.
•Under-sampling design approach is replacing mixerbased heterodyne receivers.
•Signal processing: FFT, I/Q, Filter bank, Wavelets,
PFT,
Principle of under sampling
Dual 1 0 -1 I/Q Mixer including SH
•Conventional mixer using high speed analog switches.
Antenna impedance measurements
•Net work analyzer S11 type measurements
•Impedance antenna to plasma vs. frequency
•Useful for side-by-side antenna comparisons