1. CAA Implementation Review ESTEC, 31 May - 1 June 2005
Cluster Active Archive Implementation for the ASPOC Instrument Klaus Torkar and Harald Jeszenszky
IWF/OAW Graz
CAA Implementation Review ESTEC, 31 May - 1 June 2005

2. Interface Control Document
Contents according to standard table
Introduction
Points of contact
Instrument description
Science objectives
Hardware overview
Data processing chain
Instrument data products
General conventions and considerations
Data product descriptions
IONS
IONC
STAT
CMDH
CAVEATS

3. Points of Contact
Institution: Space Research Institute Austrian Academy of Sciences Schmiedlstrasse Graz, Austria
People involved:
Name
Main Function
Klaus Torkar
Project lead, co-ordination, documentation
Harald Jeszenszky
Software development, testing, documentation
Gunter Laky
System management
Manfred Stachel
Operations, data production

4. Support for Plasma Electron Measurements
The objective for active spacecraft potential control is to minimise the disturbances of low-energy plasma measurements caused by high spacecraft potentials
Potentials in the Earth's magnetosphere often reach several tens of volts positive
Before ASPOC turn-on, low-energy electrons are accelerated by s/c potential to 40 eV.
After ASPOC turn-on, low-energy electron measurements improve (example of Cluster 4 PEACE-LEEA data)
point out 40 V potential before ASPOC turns on
June 12, 2002

5. Operating Principle
An ion beam is generated. Its current - typically 10 µA, up to 50 µA - shifts the equilibrium potential to a very low positive value
The new potential is nearly independent of plasma density

6. Ion Emitters
Ions are generated by field emission in liquid metal ion sources
Liquid Indium at T200C covering a needle is ionised in a strong electric field
4 emitters combined in one module with common high voltage of 5 to 9 kV
Active emitter requires heater, 0.5 W power
Protection cap with pyro actuator

7. Currents Total current is provided by the electrical supply
Up to 100% of the total current goes into the ion beam leaving the emitter
The difference between total current and outgoing beam current consists of the current to the extraction electrode and eventual leak paths
outgoing ion beam
extractor
leak
total

8. Instrument Modes
ITOT constant total current, utilised most of the time
IION constant beam current
FEFW feedback loop to maintain constant spacecraft potential measured by EFW
STDB standby, heater and high voltage off
HOTS hot standby, heater on, high voltage off
T&C test and commissioning
TECH technical mode
STARTUP warm-up of heater before beam ignition
outgoing ion beam
extractor
leak
total

9. Instrument Modes
ITOT constant total current, utilised most of the time
IION constant beam current
FEFW feedback loop to maintain constant spacecraft potential measured by EFW
STDB standby: heater and high voltage off
HOTS hot standby: heater on, high voltage off
T&C test and commissioning
TECH technical mode
STARTUP warm-up of heater before beam ignition
IION
FEFW

10. Onboard Software Features
Sampling time resolution 0.33 s, 0.5 s or 10.3 s
Digital resolution of monitors: 8-bit
Command execution timing: 1 command per 5.15 s
"Cleaning" of emitters: short (30-60 s) operation at higher current (50 µA) helps to keep the operating voltage low (see example).
Such high-current "pulses" were applied occasionally, either autonomously or pre-planned

11. Archive Software Features
Software works directly from Cluster raw data
Extension of PP/SP pipeline software: well tested
Data sets are split according to time resolution
Data are delivered in CEF
Both automated and manual caveat information

12. Quality Control
By visual inspection of plots designed for this purpose
By spot-checks of data products
Manual&automated consistency checks of products:
Correlation between ion current and spacecraft potential
Correlation between ion current and total current
Correlation between currents in the emitter system and the derived quality flag
Correlation between ion current data products at different time resolutions
Correlation between instrument status and ion emission
Anomalies due to processing lead to re-issue of data product after correction
Anomalies attributed to instrument performance lead to new caveat entry

13. Product Descriptions All metadata are listed
Mission Level: CL_CH_MISSION.ceh
Experiment Level: CL_CH_ASP_EXP.ceh
Observatory Level: Cn_CH_OBS.ceh (n=1...4)
Instrument Level: CL_CH_ASPOCn_INST.ceh (n=1...4)
Dataset Level:
All attributes of each variable are listed
FILENAME (n=1...4)
CONTENTS
Cn_CH_ASP_IONC_DATASET.ceh
Metadata for the dataset as a whole
Cn_CH_ASP_IONC_PARAMETER.ceh
Metadata for parameters inside the dataset

14. Products Part 1 IONC: Ion beam current with 0.5 s resolution
PARAMETER_TYPE = "Data"
PARENT_DATASET_ID = "C3_CP_ASP_IONC"
ENTITY = "Ion"
PROPERTY = "Current"
FLUCTUATIONS = "Waveform"
CATDESC = "Cluster C3 Ion emission current, 0.5s resolution"
UNITS = "uA"
SI_CONVERSION = "1.0E-6>A"
VALUE_TYPE = FLOAT
SIGNIFICANT_DIGITS = 6
FILLVAL = -1E+30
FIELDNAM = "Ion Emission Current"
SCALETYP = "Linear"
LABLAXIS = "Ion Current"
DEPEND_0 = "time_tags__C3_CP_ASP_IONC"
LABEL_1 = ""
PARAMETER_CAVEATS = "*C3_CQ_ASP_IONC_"
QUALITY = "0"
IONS: Ion current snapshot with s resolution
8.25 s every s - to check for any current fluctuations

15. Products Part 2 STAT: Instrument status at 5.15 s (10.3 s) resolution:
Operating mode, emitter start-up status, emitter cleaning
Explains deviations from nominal beam current
Emitter ID and emitter module ID
Emitters show individual characteristics and performance
Anomaly flags
Contain the reason of an anomaly, e.g. no ignition
Ion beam energy
Total ion source current
Heater current
Heater voltage
Temperature of the ion source module
Raw spacecraft potential received from EFW through inter-experiment link
Timing differs from EFW data product

16. Products Part 3
CMDH: Command history with time stamps of on-board execution
TC execution time
TC counter
TC code
TC mnemonic
TC description
TC parameter
IONC, IONS, STAT, and CMDH will be delivered as daily files

17. Products Part 4 - Caveat Files
For Instrument Caveats, there will be one file per spacecraft, containing span-valid entries (valid between instrument mode changes)
Each record in the caveat files contains a textual description and quality parameters
Quality is understood here as quality of the spacecraft potential control, as expected from the ion current and its stability in time.
Time span (driven by mode change, e.g., ion beam on or off, emitter change and resulting quality variations)
Mean quality during time span
Minimum quality during time span
Maximum quality during time span
Comment (textual description associated with the average quality flag)

18. Itotal  20 µA AND Ibeam/Itotal  0.50
Quality Levels
Quality is derived from the ion current, its deviation from the set value, and temporal variations
Quality Flag
Current Conditions
Ion Emission Quality 1
Ibeam/Itotal > 0.97
Excellent 2
0.92 < Ibeam/Itotal  0.97
Good, almost completely stable 3
0.75 < Ibeam/Itotal  0.92
Moderate fluctuations 4
0.30 < Ibeam/Itotal  0.75
Substantial fluctuations 5
0.00 < Ibeam/Itotal  0.30
Severe variations 8
Itotal  20 µA AND Ibeam/Itotal  0.50
Cleaning 9
Ibeam = 0.0
No emission

19. Quality Levels - Example
Beam current
Total current
Quality

20. Global Instrument Caveats
Information is provided in the INSTRUMENT_CAVEATS parameter of the instrument level metadata (filename: CL_CH_ASPOCn_INST.ceh with n=1...4)
This parameter contains fewer entries than the previously described, automated caveats.
Each entry is typically valid for time spans between one day and a few months, and characterizes particular issues of the instrument performance or status in this period.
Examples given on next slide

21. Examples of Caveat Entries
For ASPOC 2
: Almost flawless operation, except for a minor deviation from 100% efficiency around 09:00 UT
: Short dropouts of the ion current of the order of 1 µA below the nominal value occur occasionally; one dropout is 4 µA deep.
: Short dropouts of the ion current of the order of 1 µA below the nominal value occur occasionally.
: At 21:53, a cleaning operation using 20 and 30 µA reduced the operating voltage.
: Short dropouts of the ion current of the order of 1-2 µA become more frequent.
: At 17:17 and 20:55 there are short total drop-outs of the ion current; smaller dropouts (1-2 µA) become frequent; the efficiency drops to ca. 90% at 17:39 UT.
: Emitter cleaning using 20 µA is attempted, but emitter voltage exceeds threshold before the 30 µA level is reached.
: Emitter cleaning operation using 20 µA.

22. Other Products & Status
Validation and browsing software
ASPOC Users Manual
Status
Test data for period January-June 2001 submitted
ICD Issue 1.1 submitted
Future deliveries according to agreed schedule
Generation of caveat information drives schedule