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The ICA and IMA experiments

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The ICA-IMA TC/TM data formats

and related software aspects.

Issue 1.3

2002-05-08 Hans Borg. IRF- Kiruna.

Document history.

Date

Issue

By

Changes

2002-04-07

Draft

HB

Composed and edited from several partial documents.

2002-04-20

1.2

HB

Added: Related documents.

Important NOTE for HK-data change.

Corrected standard header status bit.

2002-05-08

1.3

HB

Added: Mass order for table look up. Command status coding.

       
       
       

 

 

 

Related documents.

1) ICA – RPC : the Ion Composition Analyser in the Rosetta Plasma Consortium. O Norberg et. al.

Note: "The ICA –RPC: … should basically be applicable on the IMA - MU configuration"

2) ICA command description. Issue 1.5. H Borg.

3) IMA command description. Issue 1.4. H Borg.

4) CCSDS 120.0-B-1.

5) Basics of ICA/IMA embedded software. Issue: 1.3 H Borg

Table of contents.

  1. Scope.
  2. Terminology.
  3. Experiment basic operation.
  4. The commanding system.
    1. General.
    2. Detailed command list.
  5. Telemetry/Science modes.
    1. Telemetry modes.
    2. Data reduction modes general.
      1. Science data processing.
      2. Shadow and bad HV masking.
      3. Parameter orders.
    3. The data reduction modes.
      1. Minimum modes.
        1. Spectras only.
        2. Selected Ion species.
        3. Energy-Mass.
      2. Normal modes.
      3. High angular resolution modes.
      4. Energy-Mass modes.
    4. Special modes.
      1. Test mode.
      2. Calibration 1 mode.
      3. Calibration 2 mode.
      4. Fake mode.
      5. Idle mode.
      6. The 16-bit AD monitors.
      7. The switch bits.

5.5 The standard header.

5.6 Telemetry/Data reduction mode combinations.

 

6.0 Housekeeping data.

7.0 Special data characteristics.

7.1 The F8 code.

7.2 Data compressions.

7.2.1 Compressed data layout.

 

 

 

1.0 Scope.

As the ICA (RPC/Rosetta) and the IMA (Aspera/Mars Express) experiments are essentially the same this document treats both. Differences are explicitly noted. It only briefly describes the operation of the experiments.

It is assumed that the reader has a basic knowledge of the experiments.

The document tries to describe in some detail the tm data return from the experiments.

2.0 Terminology.

If not otherwise stated a byte denotes an 8-bit item and a word a 16-bit item. A nibble is a 4-bit item.

Bits are labeled in the power of 2, i.e. 0 (zero) is the least significant bit.

Precaution: ESA uses "octets" for an 8-bit item and "word" for a 16-bit item. ESA also uses 0 as the MS-bit (Mil Std. 1750 convention. Item size dependent).

F8 denotes an experiment 8-bit hybrid floating code used to reduce 32/16 bit parameters to 8 bits.

3.0 Experiment basic operation.

The basic operation consists of stepping through 32 or 96 energy HV deflection steps for each of 16 entrance HV deflection steps (polar angles). A complete cycle (scan) takes 64 seconds (32 levels) or 192 seconds (96 levels) respectively. The sampling time is 102.9 milliseconds. Each sample produces an imager matrix of 32 mass bins times 16 sectors (azimuth angles).

The data acquisition and transmission is synchronized to an acquisition (start) pulse. For ICA that pulse is received once per 32 seconds and for IMA once per 16 seconds.

All data to and from the experiment is transmitted over a serial 1355-link from/to a central unit that in turn interfaces to the spacecraft systems.

Each format starts with a 16-byte long standard header with a 3-byte long synchronization pattern.

Except for the header and some data in the special modes all data is by default converted to an 8-bit hybrid floating code (F8) followed by a loss less bit data compression.

Thus, most ICA-IMA data formats will float in the ESA telemetry packets. Some may, however, be synchronized (see §5.4).

For a more detailed description of the experiment see ICA – RPC : the Ion Composition Analyser in the Rosetta Plasma Consortium. (Norberg,O. et al.).

 

 

4.0 The commanding system.

4.1 General

With a few exceptions all experiment commands consists of a 16-bit word.

The word is subdivided into 4 nibbles n3-n0.

n3

n2

n1

n0

The commands are divided into 3(4) classes (types) as:

Type 3 n3 \ 0 n2,n1,n0 represents a 12-bit variable parameter.

Capacity: 15 sets. n3=1-15.

Type 2 n3=0 n2\ 0 n1,n0 represents an 8-bit variable parameter.

Capacity: 15 sets. n2=1-15.

Type 1/0 n3=n2=0 n1,n0 is dynamically used for variable length parameters like

4-bit, 1-bit or no parameter commands.

Capacity: 256 sets. n1,n0=0-255.

Note: The combined command words = 0xFFFF or 0x0000 are not used for safety.

The basic experiment internal interpretation of the 16-bit word is given below (§4.2).

For further details about commanding, see ICA/IMA Command Description. Issue 1.4. (H Borg).

 

 

    1. Detailed command list.

The list below gives all the commands in terms of a short description, type, fixed part, parameter mask, acceptable parameter range and when applicable the default value. Note that this is the internal interpretation.

Prm: below stands for parameter. A "-" below indicates not applicable or not defined.

Short description

Type

Fixed part

Prm. mask

Prm. range

Default

Main +28 volt switch

1/0

0x0002

0x0001

0-1

0

Opto +28 volt switch

1/0

0x0004

0x0001

0-1

0

Mcp +28 volt switch

1/0

0x0006

0x0001

0-1

0

Post acc. HV switch

1/0

0x0008

0x0001

0-1

1

Grid LV switch

1/0

0x000A

0x0001

0-1

1

Entrance HV switch

1/0

0x000C

0x0001

0-1

1

Deflection LV switch

1/0

0x000E

0x0001

0-1

1

Deflection HV switch

1/0

0x0010

0x0001

0-1

1

Direct command switch

1/0

0x0012

0x0001

0-1

0

Watch dog enable/disable

1/0

0x0014

0x0001

0-1

1

Gas pressure HV control. ICAonly

1/0

0x0016

0x0001

0-1

0

Thruster firing HV control. ICA only

1/0

0x0018

0x0001

0-1

0

Compression enable/disable

1/0

0x001C

0x0001

0-1

1

Alternating post acc. enb/dis

1/0

0x001E

0x0001

0-1

0

Post acc. level high/low

1/0

0x0020

0x0001

0-1

1

Auto reduction change enb/dis

1/0

0x0022

0x0001

0-1

1

Shadow masking enb/dis

1/0

0x0024

0x0001

0-1

1

Bad HV masking enb/dis

1/0

0x0026

0x0001

0-1

1

Next command direct

1/0

0x0040

-

-

-

Energy deflection stepping

1/0

0x0041

-

-

-

Entrance deflection stepping

1/0

0x0042

-

-

-

Release V-cal format

1/0

0x0043

-

-

-

Activate debugger. Bench only

1/0

0x0046

-

-

-

Gas-HV timeout test. ICA only

1/0

0x0047

-

-

-

Trigger machine error. Bench only

1/0

0x0048

-

-

-

Test Watch dog reset.

1/0

0x004A

-

-

-

Empty TM fifo

1/0

0x004B

-

-

-

Flush TM fifo

1/0

0x004C

-

-

-

Boot PROM

1/0

0x004D

-

-

-

Imager test

1/0

0x004E

-

-

-

Dummy command

1/0

0x004F

-

-

-

           

Boot EEPROM incl. Context

1/0

0x00B0

0x000F

0-15

-

Set imager test pattern

1/0

0x00C0

0x000F

0-15

-

Boot EEPROM excl. Context

1/0

0x00D0

0x000F

0-15

-

Set ICA/IMA SID number

1/0

0x00E0

0x000F

0-5/0-6

5

Set EEPROM default boot section

1/0

0x00F0

0x000F

0-15

0

 

 

Short description

Type

Fixed part

Prm. mask

Prm. range

Default

Set energy deflection level

2

0x0100

0x00FF

0-95

-

Set entrance deflection level

2

0x0200

0x00FF

0-15

-

Set ICA/IMA solar wind start index

2

0x0300

0x00FF

0-64

0/24

Set Gas pressure low level. ICA only

2

0x0400

0x00FF

0-255

0x16

Set Gas pressure high level. ICA only

2

0x0500

0x00FF

0-255

0x15

Set data reduction mode

2

0x0A00

0x00FF

0-39

0

Reprog. all EEPROM sections *)

2

0x0C00

0x00FF

0-16

-

Reprog. EEPROM section *)

2

0x0D00

0x00FF

0-255

-

           

Set ICA/IMA Opto reference

3

0x1000

0x0FFF

0-7

0/6

Set ICA/IMA Mcp reference

3

0x2000

0x0FFF

0-15

0/13

Set ICA/IMA Grid reference

3

0x3000

0x0FFF

0-7

0/7

Set ICA/IMA post acc. low reference

3

0x4000

0x0FFF

0-7

0/4

Set ICA/IMA post acc. high reference

3

0x5000

0x0FFF

0-7

0/7

Set energy defl. LV reference

3

0x6000

0x0FFF

0-4095

-

Set energy defl. HV reference

3

0x7000

0x0FFF

0-4095

-

Set entrance defl. HV reference

3

0x8000

0x0FFF

0-4095

-

Set noise reduction level

3

0x9000

0x0FFF

0-4095

0

Set ICA/IMA Fifo low (min) water mark

3

0xA000

0x0FFF

0-4095

40/20

Set ICA/IMA Fifo high (max) water mark

3

0xB000

0x0FFF

0-4095

80/40

Set ICA/IMA Fifo force water mark

3

0xC000

0x0FFF

0-4095

120/60

Set ICA/IMA Fifo clear water mark

3

0xD000

0x0FFF

0-4095

320/320

Set IMA Tm scaling factor. IMA only

3

0xE000

0x0FFF

0-4095

180

Start command (combined)

3

0xF000

0x0FFF

0-4095

-

*) Requires a second word reading 0xFEED (security lock key).

 

5.0 Telemetry/Science modes.

5.1 Telemetry modes.

The experiments have to their disposal a number of telemetry modes (here named Sid, Science ID). The Sid defines the TM rate available. The Sid numbers below are the internal ICA-IMA numbers that is also used in commanding. Note that direct (near real time) TM is mostly not available. The TM data is buffered onboard the S/C. The TM rate below then describes the reasonable amount to create to stay within the buffer allowance allocated for the planned S/C session before tapping to a ground S/C tracking station.

Telemetry modes (Sid+HK).

Sid

Mnemonic

Exp. Pkt. size in bytes

ICA rate

IMA rate

0

Min (Minimum)

618

5.15 bps

10.3 bps

1

Nrm (Normal)

2478

103.25 bps

206.5 bps

2

Bst (Burst)

4092

1023 bps

2046 bps

3

Cal (Calibration)

1074

268.5 bps

537 bps

4

Spc (Special)

3198

799.5 bps

1599 bps

5

Tst (Test)

600

75 bps

150 bps

6

Ima (Ima)

3996 *

NA

3996 bps

HK

Housekeeping

24

6 bps

12 bps

*) For IMA 2 such packets are sent every acquisition period.

5.2 Data reduction modes general.

The H/W operation of the experiment is always the same but for the 32 or 96 energy level step modes. The number of energy levels is strictly tied to the science mode selected. The experiment produces too much data to be transmitted (~ 80 000 bps). The parametric space measured are 32 mass bins (not true M/q) for 16 azimuths, 16 polar angles and 96 (32) energy levels. To cope with the high production rate versus the available Tm rate capacity the data is first reduced by integrations in the measured parametric space. The resulting (32/16 bit parameters) are then converted to a hybrid 8 bit floating code (F8). The size of the data set (format) is after this mostly still too big. The data therefore passed via a loss less bit compression routine before feeding it to the tm output FIFO.

The tm FIFO can take a certain backlog of data due to its size. The backlog is watched by low and high watermarks. When appropriate, the S/W will change the reduction scheme such as to stay (on average) within the allocated tm rate. Thus the watermarks are scaled against the current telemetry mode. A more detailed description is given in § 5.2.1

5.2.1 Science data processing.

The data is read from the imager memory, shadow masked and fed to a data reduction module. The reduction is performed by integrations in the parametric space mass*azimuth*energy*polar-angles. When a full data set is acquired a 32/16 bit to a hybrid 8 bit floating code further reduces the data. The resulting data set is then compressed by a loss less method and fed to the telemetry FIFO for transmission. The TM-FIFO can take a certain backlog with respect to the current TM-rate (SID). The size of the compressed data will vary due to the characteristics of the actual data. For the Normal and Burst modes the TM-FIFO filling is controlled by analyzing the data set size with respect to the TM-FIFO filling and the actual TM-rate. When appropriate, a feedback is made to the reduction module to change the reduction scheme. The TM-FIFO filling is guided by watermarks. For the Minimum modes that create several data sets during the duration of a format, the reduction is fixed but instead the number of sets to transmit is adjusted to match, on the average, the TM-rate (SID).

The automatic data reduction change and data compression can be disabled by commands. It affects

both Minimum and Normal/Burst modes.

Principle data flow.

Normal/Burst mode Minimum mode

 

5.2.2 Shadow and bad HV masking.

It is just the fact that the anticipated field of view of the experiments is not clean. Due to the mounting there are other S/C obstacles in the field of view. The current S/W has built in tables to simply clear out (set to 0) imager sectors that are more or less obscured. This has a two-folded motivation.

  1. A clear knowledge of what data is included (partly obscured may give "funny" effects).
  2. Zeroing out may (not for sure) give a better compression efficiency.

Like wise, due to HV limitations (capacity or accuracy) all polar angles cannot be reached for all energies. They are treated as for shadowed sectors above.

 

5.2.3 Parameter orders.

Apart from the Special modes, Science data are always delivered as a matrix mass*azimuth*energy*polar, where mass (the first) is the fastest varying one.

For masses above or equal to 8, the integration is simply done by adding adjacent mass bins. E.g. 8 mass bins integrate them 4 by 4 from the 32 available.

Note that the Imager addressing is such that the heavier masses comes first and the lighter ones

last.

For masses below 8 (i.e.<= 6), the mass bins are integrated according to lookup tables and supposed to represent true M/q. The transmission order of the M/q masses is defined by the lookup tables.

The mass order for ICA is:

and for IMA: H+ >O+ O+ He+ He++ O++

If less than 6 masses, masses at the end are skipped.

Azimuth, energy and polar angles always come in the same order.

5.3 The data modes.

The data modes are divided into 5 groups: Min, Nrm, Har, Exm and Special.

5.3.1 The minimum modes.

The duration of the Minimum mode data formats is 16 minutes.

Mode

Index

Masses

Azimuth angles

Energies

Polar angles

Max sets

Idle *

0

 

Void

1

 

Mspo

2

2

1

32

1

15

Void

3

 

Msis

4

6

1

96

1

5

Mexm

5

32

1

96

1

5

Void

6

 

Void

7

 

*) The Idle mode produces no scientific data and is described under the Special modes.

5.3.1.1 Minimum spectra only (Mspo).

The energy deflection is stepped through 32 levels starting at the solar wind start index.

For each scan all data for the two masses protons and alpha (table look up) are integrated over the sunward facing sectors. This produces a maximum of 15 sets of 2 masses * 32 E-levels spectra. As many as can be fitted (on the average to stay within the TM capacity) in the current SID block size are transmitted.

Layout: 1 header

n 2*32 spectra (Compressed F8)

5.3.1.2 Minimum selected ion species (Msis).

The energy deflection is stepped through all 96 levels for each of the 16 entrance steps.

For each scan all data for 6 selected ion species (table look up) are integrated over all angles (azimuth and polar). This produces a maximum of 5 sets of 6 masses * 96 E-levels spectra. As many as can be fitted (on the average to stay within the TM capacity) in the current SID block size are transmitted.

Layout: 1 header

n 6*96 spectra (Compressed F8)

 

5.3.1.3 Minimum energy-mass matrix (Mexm).

The energy deflection is stepped through all 96 levels for each of the 16 entrance steps.

For each scan all data for 32 mass bins are integrated over all angles (azimuth and polar). This produces a maximum of 5 sets of 32 mass-bins * 96 E-levels spectra. As many as can be fitted (on the average to stay within the TM capacity) in the current SID block size are transmitted.

Layout: 1 header

n 32*96 spectra (Compressed F8)

 

5.3.2 The normal modes (Nrm).

The duration of the Normal mode format is 192 seconds.

The energy deflection is stepped through all 96 steps for each of the 16 entrance steps.

The normal mode (group) is subjected to an automatic change of the data reduction scheme (if enabled) in order to adapt to the current TM capacity (SID).

The order of the reduced data matrix is always Mass-Azimuth-Energy-Polar with Mass being the fastest varying index. The masses are integrated by means of energy dependent lookup tables.

The reduction scheme.

Mode

Index

Masses

Azimuth angles

Energies

Polar angles

Nrm-0

8

6

16

96

16

Nrm-1

9

6

16

96

8

Nrm-2

10

6

16

96

4

Nrm-3

11

6

16

96

2

Nrm-4

12

6

8

96

2

Nrm-5

13

6

4

96

2

Nrm-6

14

3

4

96

2

Nrm-7

15

3

4

96

1

Layout: 1 header

1 data set (Compressed F8)

 

5.3.3 The burst high angular resolution modes (Har).

The duration of the burst high angular resolution mode format is 192 seconds.

The energy deflection is stepped through all 96 steps for each of the 16 entrance steps.

The burst high angular resolution mode (group) is subjected to an automatic change of the data reduction scheme (if enabled) in order to adapt to the current TM capacity (SID).

The order of the reduced data matrix is always Mass-Azimuth-Energy-Polar with Mass being the fastest varying index.

The reduction scheme.

Mode

Index

Masses

Azimuth angles

Energies

Polar angles

Har-0

16

16

16

96

16

Har-1

17

16

16

96

8

Har-2

18

16

16

96

4

Har-3

19

8

16

96

4

Har-4

20

4

16

96

4

Har-5

21

2

16

96

4

Har-6

22

2

8

96

4

Har-7

23

2

8

96

2

Layout: 1 header

1 data set (Compressed F8)

5.3.4 The burst energy-mass matrix modes (Exm).

The duration of the burst energy-mass matrix mode format is 192 seconds.

The energy deflection is stepped through all 96 steps for each of the 16 entrance steps.

The burst energy-mass matrix mode (group) is subjected to an automatic change of the data reduction scheme (if enabled) in order to adapt to the current TM capacity (SID).

The order of the reduced data matrix is always Mass-Azimuth-Energy-Polar with Mass being the fastest varying index.

The reduction scheme.

Mode

Index

Masses

Azimuth angles

Energies

Polar angles

Exm-0

24

32

16

96

16

Exm-1

25

32

16

96

8

Exm-2

26

32

16

96

4

Exm-3

27

32

16

96

2

Exm-4

28

32

8

96

2

Exm-5

29

32

4

96

2

Exm-6

30

32

2

96

2

Exm-7

31

32

2

96

1

Layout: 1 header

1 data set (Compressed F8)

 

5.4 The special modes.

The special modes are mainly aimed for ground testing and calibration, but may well be used also when in orbit. Typically "Test" for commissioning.

As opposed to the science modes, the special modes do not allow any Tm FIFO backlogging.

The Test and the Cal1 mode will be synchronized to the ESA packets provided they run in combination with the Telemetry modes Tst and Cal respectively. The Fake mode is always synchronized to the ESA packets.

Mode

Index

Content

Test

32

H/W close information and an Imager snapshot

Cal1

33

HV information and one Imager in 16-bit uncompressed words

Cal2

34

HV information and 96 Imagers (one per Energy level) in compressed F8

Fake

35

An incremental (by one) 16-bit counter in 16-bit uncompressed words

Void

36

 

Void

37

 

Void

38

 

Void

39

 

 

5.4.1 The test mode (Test).

The test mode delivers "hard ware close" information and do not contain any compressed data. It is 600 bytes long and will be synchronized to the ESA TM packets if SID=Tst (ICA-IMA nr 5) is used.

It contains the following data:

Byte offset

Length in bytes

Bits

Content

0

16

 

Standard header. See §5.4.6

16

2

 

Command word 0 return

18

2

 

Command word 1 return

20

20

 

10 16-bit AD monitor values. See &5.4.7

40

1

 

Void

41

1

 

Nos. 1355-link forced resets

42

1

 

Nos. 1355-link resets seen

43

1

 

Nos. 1355-link credit failures

44

2

15-10

9-8

7-4

3-0

EEPROM programming result

Reprogramming counter

Failure bits

Destination EEP section

Source EEP section

46

1

 

Nos. Watch dog resets

47

1

 

Nos. machine error resets

48

1

 

Void

49

3

 

48-bits S/W switch status. See §5.4.8

52

1

 

Noise reduction level

53

1

 

The gas pressure as seen from ROSINA. ICA only

54

2

15

14-12

11-0

Copy from HK format

Direct command switch

Pacc. low reference level

Energy deflection HV reference

56

2

15

14-12

11-0

Copy from HK format

Tm overflow flag

Pacc. high reference level

Energy deflection LV reference

58

2

15

14-12

11-0

Copy from HK format

Pacc. current level (high=1 or low=0).

Grid LV reference

Entrance HV reference

60

2

 

CPU fault register

62

2

 

CPU fault address

64

1

 

Gas pressure low level. ICA only

65

1

 

Gas pressure high level. ICA only

66

2

 

CPU BIT result

68

2

 

Current program version running

70

1

 

Nos. sample overruns

71

1

 

Nos. sweep overruns

72

1

 

Nos. post overruns

73

1

 

Void

74

2

 

+28V monitor.

76

2

 

Fifo low water mark (Fmin)

78

2

 

Fifo high water mark (Fmax)

80

2

 

Fifo force limit (Ffrc)

82

2

 

Fifo clear limit (Fclr)

84

2

 

IMA Tm scaling factor. IMA only

86

1

7-6

5-3

2-0

Image memory test result

Test counter.

Memory half 1 test result

Memory half 0 test result

87

1

 

E-level for Image snapshot

88

512

 

Imager snapshot in F8 code

 

 

5.4.2 The calibration-1 mode (Cal1).

The calibration-1 mode is specially designed for Imager calibration. It is 1074 bytes long and will be synchronized to the ESA TM packets if SID=Cal (ICA-IMA nr 3) is used.

Byte offset

Length in bytes

Bits

Content

0

16

 

Standard header. See §5.4.6

16

2

 

The digital deflection HV reference

18

2

 

The digital deflection LV reference

20

2

 

The digital entrance HV reference

22

1

7-4

3-0

The Opto. HV digital reference

The Mcp. HV digital reference

23

1

7-4

3-0

The digital Post acc. HV reference

The Grid LV digital reference

24

20

 

10 16-bit AD monitors. See §5.4.7

44

2

 

+28V monitor

46

1

 

Entrance angle index

47

1

 

Energy level index

48

2

 

Void

50

1024

 

Full Imager in 16-bit words

 

 

5.4.3 The calibration-2 mode (Cal2).

The calibration-2 mode is specially designed for Imager calibration. It delivers Imagers for a full 96

E-level sweep. The data is in compressed F8 code.

Byte offset

Length in bytes

Bits

Content

0

16

 

Standard header. See §5.4.6

16

2

 

The digital deflection HV reference

18

2

 

The digital deflection LV reference

20

2

 

The digital entrance HV reference

22

1

7-4

3-0

The Opto. HV digital reference

The Mcp. HV digital reference

23

1

7-4

3-0

The digital Post acc. HV reference

The Grid LV digital reference

24

20

 

10 16-bit AD monitors. See §5.4.7

44

2

 

+28V monitor

46

1

 

Entrance angle index

47

1

 

Energy level index

48

2

 

Void

50

nn

 

96 energy levels of full Imager in compressed F8

 

 

5.4.4 The faked data mode (Fake).

The Fake mode is specially designed to test the 1355-link for transmissions from the experiment to the PIU/MAIN-unit. It simply delivers a header followed by a word sequential counter as uncompressed data. It automatically adjusts the data size to match the current SID and will therefore always be synchronized to the ESA TM packets. Except for the header missing data can easily be detected.

Layout: 1 header.

An incremental counter to fill the current Sid packet.

5.4.5 The Idle mode.

The mode index refers it to the Minimum group, but may as well be regarded as a special mode.

This mode does not produce any science data.

The Idle mode may be entered in two ways.

1) By command.

If entered by command the Opto and Mcp HV are regulated down to 0 reference, but the +28V Main switch stays ON. Also all science tm output are inhibited. Data in the tm FIFO are kept for later transmission. Commanding the experiment into the idle mode opens up for memory management activities (patch, dump or check).

2) Automatic (ICA only).

The experiment will enter Idle mode if the gas pressure as delivered by ROSINA excides a predefined upper limit or the experiment receives a thruster fire warning. When entered this way the +28V main switch to the HV supplies is switched off. Data in the tm FIFO, however, will continue to be transmitted.

 

 

5.4.6 The 16-bit AD monitors.

The AD monitors are stored in the following order.

Byte offset

Length in bytes

Content

Linear calibration

0

2

Opto. HV

TBD

2

2

Mcp. HV

TBD

4

2

Upper entrance HV

TBD

6

2

Lower entrance HV

TBD

8

2

Post acceleration HV

TBD

10

2

Energy deflection HV

TBD

12

2

Energy deflection LV

TBD

14

2

Sensor unit temperature

TBD

16

2

Grid LV

TBD

18

2

DPU temperature

TBD

 

 

5.4.7 The switch status bits.

The switch bits are coded as 0=Off and 1=On.

Bit

Content

Type

0

Mcp. +28V

H/W

1

Opto. +28V

H/W

2

Main +28V

H/W

3

Post acceleration HV

S/W

4

Grid LV

S/W

5

Entrance HV

S/W

6

Energy deflection LV

S/W

7

Energy deflection HV

S/W

8

Direct command

S/W

9

Watchdog

H/W

10

Gas HV control

S/W ICA only

11

Thruster firing HV control

S/W ICA only

12

Void

 

13

Compression

S/W

14

Alternating post acceleration

S/W

15

Post acceleration level

S/W.

Not really a switch

16

Auto reduction changes

S/W

17

Shadow masking

S/W

18

Bad HV masking

S/W

19

Void

 

20

Void

 

21

Void

 

22

Test flag

S/W

23

Internal. Not commandable

 

 

 

5.5 The standard header.

Each data format starts with a standard header containing the following information

Byte offset

Length in bytes

Bits

Content

0

3

 

Sync. Pattern. 0xE3 0x31 0xCA

3

1

7-6

5-0

Unit (1=ICA 2=IMA)

Mode (index)

4

1

 

Experiment data format counter (Edf)

5

1

7

6

5

4

3-0

HV ramping in progress

Tm Fifo emptied

Checksum 0 failure

Checksum 1 failure

Number of sets in Minimum modes

6

1

7

6

5

4

3-0

Compression switch

Auto reduction change switch

Alternating post acceleration switch

Post acceleration level

Test pattern

7

1

 

Fifo filling. Number of 6-byte packets in F8

8

1

7

6

5

4-0

Post processing overrun

Sweep processing overrun

Sample processing overrun

PROM(0)/EEPROM section(1-16) loaded

9

1

7

6-0

Reset due to Watchdog or Machine error.

Solar wind energy start index

10

3

 

Format start time in units of 31.25 msec. *

13

1

7

6

5-4

Bad HV masking switch

Shadow masking switch

Void

13

3

19-0

Format length in words

*) As the Format start time only consists of 24 bits, the MSB part should be taken from the ESA packet time. The 24 bits covers about 6 days.

 

 

5.6 Telemetry/Data reduction mode combinations.

In principle any Data reduction mode can be combined with any Telemetry mode. All combinations will, however, not optimize the use of the telemetry capacity. There are no precautions or restrictions built into the S/W to refuse some combinations. In the worst case (like a burst mode in the Minimum Sid) no science data at all will be delivered due to Tm FIFO clearing, provided the Auto reduction change is enabled.

The table below gives the anticipated combinations. Other combinations may, however, be used as a result of experiences from in orbit operation. Likewise the Fifo controlling limits may be trimmed.

Telemetry mode

Data reduction modes

Minimum (0)

Minimum modes

Normal (1)

Normal modes

Burst (2)

Burst modes (Har, Exm)

Calibration (3)

Calibration 1. Tailored

Special (4)

Calibration 2

Test (5)

Test. Tailored

Ima (6). IMA only

Burst modes (Har, Exm)

The Fake and Idle modes are applicable in all Telemetry modes.

 

 

 

6.0 The Housekeeping format.

The housekeeping format consists of 24 bytes delivered once per acquisition period. This rate is independent of the current Telemetry mode (Sid) in effect.

The ICA-IMA housekeeping format contains the following parameters:

Byte offset

Length in bytes

Bits

Content

0

1

7-2

1-0

Current data reduction mode. For index see &4.3 & 4.4

Last command status where:

0=Ok 1=Parameter out of range

2=Invalid 3=Erroneous Opcode

1

1

 

HV switch status. The first 8 switches. See §5.4.7

2

1

7

6-4

3

2

1

0

The new command received toggle bit

The current Sid number

Post acceleration mode (Fixed/Alternating).

+28V Main HV present *

+28V Opto HV present *

+28V Mcp HV present *

3

1

 

Fifo filling in terms of internal packets (words/3) in F8

4

2

 

The first word command return.

6

1

 

The Opto. HV monitor

7

1

 

The Mcp. HV monitor

8

1

 

The Energy deflection HV monitor

9

1

 

The Energy deflection LV monitor

10

1

 

The Post acceleration HV monitor

11

1

 

The Grid LV monitor

12

1

 

The Sensor unit temperature

13

1

 

The DPU Temperature

14

2

15

14-12

11-0

The direct command switch

Post acceleration low level reference

Energy deflection HV reference

16

2

15

14-12

11-0

Tm Fifo overflow

Post acceleration high level reference

Energy deflection LV reference

18

2

15

14-12

11-8

Post acceleration level (high or low)

Grid LV reference

Entrance HV reference

20

2

15-13

12-9

8-0

Opto. HV default reference

Mcp. HV default reference

Entrance upper HV monitor

22

2

15-13

12-9

8-0

Opto. HV current reference

Mcp. HV current reference

Entrance lower HV monitor

*) For an explanation of the present status, See ICA/IMA Command Description Issue 1.4.

Important NOTE. Byte 2, bit 3 was intended to be the HV safety plug status (HV enabled/disabled). This status had to be taken out for technical reasons. The bit is now used to indicate the post acceleration mode of operation (Fixed or Alternating).

 

7.0 Special data characteristics.

The experiment uses some special tools to handle data. They are briefly described below.

7.1 The F8 code.

In order to reduce the number of bits to transmit, the S/W normally converts 32/16 bit items into a hybrid 8-bit floating code. The maximum capacity is numbers up to 507903. If greater (32-bits only) the number is set to the maximum. It is regarded as a hybrid due to the fact that numbers less or equal to 32 are transmitted as integers. The layout is:

where Exp is the Exponent and Man the Mantissa. Numbers less or equal to 32 are used as is, that is they will be coded as 0x00 – 0x20. If greater the real mantissa part will be used with the MSB stripped of (always a one, not transmitted) and the next four MSB bits set into "Man". The Exp part will be the real exponent adjusted for the new bias (32) and set into Exp.

This is a simple C routine to unpack the F8 coded data:

int unpack_f 8(int acc)

{ int exp;

exp=(acc >> 4) & 0x0F;

if(exp > 1)

{ acc=(acc & 0x0F) | 0x10;

acc=acc << (exp-1);

}

return acc;

}

 

 

7.2 Data compression.

The ICA-IMA compression consists of two functional parts: a preprocessor and an adaptive entropy coder.

The preprocessor first converts a 16 or 32 bit word to a hybrid floating 8-bit byte (F8-code). It then uses the delayed predictor technique (to calculate d ’s) for the mapping process.

The bit compression uses Rice’s adaptive coding (CCSDS 121.0-B-1). From above (F8-code) the implemented compression software works with 8 bit length data only (Types=0-7).

 

7.2.1 Compressed data layout.

The compressed data layout consists of records subdivided into blocks. With exception for type 0, sub 1 each record holds compressed data for 128 bytes. The layout is a variant of the CCSDS 121.0-B-1 recommendation.

The differences are:

1) A Record always starts with a record length in bytes and if required a bit padding field at

the end to ensure whole bytes. This way the next record may me located (except for some

special situations) if the decompression fails in a record.

2) The order of Fundamental sequences (Fs) and Split bits (Sb) are Fs+Sb,Fs+Sb….. instead

of Fs,Fs…. ,Sb,Sb… Again if a decompression fails in a block, the already decompressed

bytes may be correct. This also allows for short blocks, short records at the end of a fully

compressed data area.

3) The number of zero run blocks is given as a fixed binary 3 bit field instead of a Fs code.

4) The type 0 second extension (sub=1) do not use the CCDS one. Instead a special zero run

record is introduced for the ICA-IMA experiments. The reason is that both experiment

have large areas in shadow. When in shadow all data are zeroed out giving rise to long

sequences of records with zero run blocks. Instead of counting zero run blocks, zero run

records are counted. Example record: 0x03,0x00,0x17 would decompress to 128*8=1024

bytes of 0x00.

For details see CCSDS-121.0-B-1.

 

Record.

Length

Reference

Block 0

Block 1

……..

Block N

Pad

Block (Type 0.0).

Type = 0

Sub=0

Block count-1

Block (Type 0.1).

Type = 0

Sub=1

Record count-1

Block (Type 1-6).

Type=1-6

Fs0+Sb0

Fs1+Sb1

………

FsN+SbN

Block (Type 7).

Type = 7

Byte 0

Byte 1

………

Byte N

Fields

Name

Bits

Short description

Length

8

The total length in bytes of the record

Reference

8

The uncompressed reference value for the record

Block

Variable

A block of bits holding compressed data for 16 bytes *)

Pad

Variable

Bit padding to ensure whole bytes for a record

Type

3

The compression type (0-7)

Sub

1

The type 0 subtype extension (0-1)

Block count-1

3

Number of zero run blocks –1

Record count-1

4

Number of zero run records – 1

FsN+SbN

Variable

The Fundamental sequence + the Split bits for byte N

Byte

8

Un uncompressed byte

*) Block 0 only holds data for 15 bytes. The Reference gives the 16:th byte.

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