The Freja charging study: A perspective five years later

1
ESA EJSM/JGORadio Plasma Wave
Instrument(RPWI)Kick-off meeting
091126Lennart Åhlén
2
Plasma waves
Electric fields Plasma measurements Conductivities
?B
Radio
3
Main box mechanics

• Backplane with power distribution, analog and
  digital interfaces
• Board size 20x15cm TBC
• Connectors Micro-D type
• Box 21x16x12 cm average 3.2mm wall thickness
  for Al.
• Distance between Boards 20mm

4
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 7W average 11W peak 100ms

Instrument interfaces

• Digital Differential
• Analog Single ended (TBC)

Satellite interfaces

• 2 Mbit SpaceWire
• Single ended (TBC)

5
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. lt 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

6
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)
7
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 3.6mm
• 2 kg extra mass needed for 8mm box protection
• Action
• Calculations of internal box radiation levels

Radiation facilities in Uppsala

• Co60 1 to 10 Rad / min Free of charge
• Electrons 7.5 to 15 MeV high dose rate 500
  Euro/h
• Protons 20 to 180 MeV 150 Rad/min 500Euro/h
• Protons max 6MeV low dose rate 100Euro/h
• Heavy Ions

8
(No Transcript)
9
(No Transcript)
10
(No Transcript)
11
(No Transcript)
12
Low and high frequency analyzers Lennart Åhlen
Scientists dream receiver
A downgrade is needed for the JGO receivers.
13
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.
• 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?

14
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 _at_ 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 _at_ 10kHz bandwidth
  

• Measurement range 70dB to 120dB _at_ 10kHz
  bandwidth
• Dynamic range 70dB to 100dB _at_ 10kHz
  bandwidth

15
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
  mixer-based heterodyne receivers.
• Signal processing FFT, I/Q, Filter bank,
  Wavelets, PFT,

Principle of under sampling
16
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

17
(No Transcript)
18
RA-PWI, RWI and LP-PWI Preamplifiers Lennart
Åhlen
19
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 109 input resistance
• 1nA 1uA Current Bias range
• 16 nV/sqr(Hz) noise
• Density
• DC to 10kHz bandwidth
• 10pA to 1uA input current range
• -100V Voltage Bias range

Mission heritage. Viking E-field /
Density Rosetta E-field / Density Freja
E-field / Density Cluster E-field /
Density Astrid E-field / Density Swarm
Density Cassini Density
New development Find new low noise Rad hard
operational amplifiers Develop a MEMS chip
including nano-switches and amplifiers
20
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
21
Low Voltage Power Supply (LVPS)
Göran Olsson Royal Institute of Technology
(KTH) Space and Plasma Physics
22
LVPS IN RPWI JGO
LFA AM
8V / -8V
3.3V
1.8V
LVPS-A
SCM
8V / -8V
3.3V
SCM PREAMP
1.8V
8V
3.3V
DPU
-8V
1.8V
3.3V
CEB BACKPLANE
LVPS CONTROL MONITORING
1.8V
LP-PWI
8V / -8V
3.3V
LP-PWI Preamps
1.8V
LVPS-B TBD
8V / -8V
RWI RA-PWI HFA
3.3V
RWI Preamps
1.8V
RA-PWI Preamp
Clock, Control, Data and Emergency Power-Off, A
B
23
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

24
LVPS Block Diagram
Voltage And Current Monitors (4)
1.8, 3.3 V
From SC 28V
CEB BPLN
DC/DC Converter A
DPU
Common-Mode Filter
1.8, 3.3 V
DC/DC Converter B
From SC 28V
Power Switches (9 Instruments)
Voltage and Current Monitors (24)
Common-Mode Filter
1.8, 3.3, 8 V
Common Bus

• 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

Housekeeping
From SCM Thermistor
Controller A FPGA
CDPU-A Ctrl Clock, Command, Data, EPO
Controller B FPGA
25
DC/DC Converter A/B
Secondary
Primary
Shielded
Shielded
Main Transformer
Input 27- 36 V
First Stage
Second Stage
Outputs 1.8 V, 1.1 A 3.3 V, 1.1 A 8 V, 350
mA -8 V, 300 mA
Pulse-Width Modulator Forward Converter 420 kHz
EMI Filter
Synchronous Rectifiers
13-14 V DC

• Inrush current limiter

Output Filters
Transformer Driver
-
Switchmode Regulator Controller
50mO

Internal 15 V

• Regulated input voltage to Transformer Driver
• Current positive feedback Counterbalances losses
  in driver transistors, transformer and
  rectifiers.

• Primary to Secondary Isolation
• Double Shielding

• Full-Wave Rectification

• LC Pi Filters

• Push-Pull
• Full-Wave
• 210 kHz

• No Feedback from Secondary

Two-stage Conversion Excellent input and load
regulation Low noise Low output
cross-regulation
Slightly lower efficiency
26
Digital Controller A/B
Power Switch Control (9)
FPGA
3.3 V Linear Regulators 1.5 V 2.5 V
HK Control (ADC, Mux, Gain Switch)
DC/DC A/B

• Instrument Power Control
• Housekeeping Control with Storage and Readout
• Overcurrent Tripping, limits under software
  control
• IVM Actel ProASIC3 A3P250
• FM Actel RTSX72

LVDS
CDPU A/B
Housekeeping ADC Data

• 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

27
Design Heritage

1. 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.
2. 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 co-delivered
dummy load board
28
(No Transcript)
29
RPWI DPU

• Walter Puccio
• Reine Gill

30
CPU 32-bit Sparc V8

• Aeroflex/Gaisler RTAX Actel 24MHz LEON3-FT
• 0.5-0.3W _at_24MHz
• 20 MIPS and 4 MFLOPS
• 3 x Spacewire links
• CQFP 352 or CCGA 624 (Actel RTAX 2000S)
• 300kRad, Fault
• Aeroflex/Gaisler UT699 ASIC 66MHz LEON3-FT
• 4.0W _at_66MHz (?)
• 52.8 MIPS 11 MFLOP
• 4x Spacewire links
• CQFP 352 or BGA 484 (32g)
• 300kRad
• ATMEL RH ASIC 100MHz LEON2-FT
• 1.0W _at_100MHz
• 86 MIPS and 23 MFLOPS
• MQFPF 256 or MCGA 349 (9g)
• 300kRad

31
CPU Memory
Analog Monitoring Power CTRL
Spacewire link to S/C 2Mbit/s
8-12 MByte SRAM (EDAC)
Actel RTAX
LEON2FT or LEON3FT
64MByte FLASH
20-86 MIPS 4-23 MFLOP
4KB Boot PROM
Serial links with simple protocol to instrument
FPGAs
32
Algorithm dataflow, decimation and processing
Instrument ADCs raw data
Instrument FPGAs with optional data processing
and decimation
Serial links
DPU FPGA with optional data processing and
decimation
CPU with optional data processing and decimation
Spacewire to S/C
33
RTOS

• RTEMS (preferable)
• Proven flight software on LEON CPUs
• Multi-tasking
• Interupt driven (no scheduling)
• Very small footprint
• RT Linux
• Multi-tasking
• Open source

34
Mission heritage

• Viking (software)
• Freja (sensor, hardware and software)
• Cassini (sensor, hardware and software)
• Astrid 12 (sensor, hardware and software)
• Munin (S/C, sensor, hardware and software)
• Rosetta (sensor, hardware and software)
• Swarm (sensor, hardware and software)
• RTEMS on LEON2
• BepiColombo (sensor, hardware)