Doc. Title: VE-MAG ScienceData Processing Description Issue: 1 
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Date : 04 April 2008 Page : 1 


VEX-MAG 
IWF – INTERNAL
Science Data Processing 
Description 


Issue 1 Rev. 3 
05 February 2009 

Author: M. Delva, W. Zambelli 
IWF Graz 
Schmiedlstrasse 6 
A-8042 Graz 
Phone: 
Fax: 
e-mail: 
+43(316)4120-553 
+43(316)4120-590 
magda,delva@oeaw.ac.at 


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CHANGE RECORD 


Issue Rev. Date Changed Para. Remarks 
1 0 11.10.2005 All 
1 1 07.06.2006 Par 4, 5 added Description 
V0 and V1 
of Data Calibration SW 
1 2 April 2008 Par 6, 7 added Description 
V2 and V3 
of Data Calibration SW 
1 3 Feb. 2009 "Purpose of this document" added, p.2
In Fig. 1.2.1 CODMAC levels indicated 
Relation to ESA archive CODMAC data-levels explained

PURPOSE OF THIS DOCUMENT
The purpose of this document is to describe the IWF - INTERNAL data 
processing pipeline of the RAW SENSOR data as received from the 
spacecraft, to a set of SCIENCE data which is corrected for KNOWN 
SENSOR EFFECTS, and called herein "calibrated" for internal reasons.

RELATION TO ESA ARCHIVE CODMAC DATA LEVEL DEFINITIONS
The outcome of the procedures "Science data Calibration" performed 
here leads to an IWF - INTERNAL set of ASCII files, containing a 
header which describes the processing done on the data, and the 
data itself.
The status of this IWF – INTERNAL science data-set in SC coordinates,
before the removal of the SC field effects, is equivalent to the ESA 
archive data level CODMAC 2; only the format is different. It is the 
DIRECT SOURCE for the ESA archive CODMAC level 2 data-set. 
The relationship to CODMAC levels is illustrated in Fig. 1.2.1


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TABLE OF CONTENTS 

1 INTRODUCTION 
5 

1.1 
Overview 5 

1.2 
Flow Diagram 5 

2 DATA PROCESSING 
6 

2.1 
File Name Generation 6 

3 VEX -MAG SCIENCE DATA TRANSFORMATION 
7 

3.1 
Raw to ASCII 7 

3.1.1 Input Files (in binary) 
7 

3.1.2 File Creation 
7 

3.1.3 On Board Time (OBT) Format 
7 

3.1.4 Output Files (in ASCII) 
8 

3.2 
Calibration and Transformation into S/C coordinates 10 

3.2.1 
Input Files (in ASCII, Sensor Coordinates and OBT from 
T0) 10 

3.2.2 
File Linking to one File per Sensor, per DataRate, per 
Orbit 10 

3.2.3 Offset Correction 
10 

3.2.4 Alignment Correction 
10 

3.2.5 Transformation into S/C Coordinates 
10 

3.2.6 Combination of MAGOS and MAGIS data to one file 11 

3.2.7 Compute UTC Time 
11 

3.2.8 Output Files (in ASCII, S/C coordinates and UTC) 11 

3.2.9 Header Part of the Calibrated Output File 
12 

3.3 
Correction of S/C – Field – Effects 12 

3.4 
Transformation to VSO Coordinate System 12 

4 DESCRIPTION OF CALIBRATION SW V0 (USED TILL MAY 13 2006) 
13 

4.1 
SCIENCE DATA CALIBRATION V0 13 

4.1.1 INPUT DATA 
13 

4.1.2 Transformation of on board time (OBT) to UTC: 13 

4.1.3 Correction for compensation range 
13 

4.1.4 Correction for orthogonality of the sensors 
13 

4.1.5 Correction to VEX S/C coordinate system 
14 

4.1.6 OUTPUT DATA 
14 

4.2 
HOUSEKEEPING DATA: 14 

5 DESCRIPTION OF CALIBRATION SW V1 (IN USE FROM MAY 14 2006) 
15 

5.1 
SCIENCE DATA CALIBRATION V1 15 

5.1.1 General differences from V0 to V1 
15 

5.1.2 Correction for MISALIGNMENT of the sensors 15 

5.1.3 
Correction for saturation effects/change of 
compensation range 15 

5.1.4 Correction for filter effects 
16 

5.1.5 OUTPUT DATA files 
16 

5.1.6 APPLICATION to dataset 
16 


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6 DESCRIPTION OF CALIBRATION SW V2 (IN USE FROM 24 JAN 2007) 

17 

6.1 SCIENCE DATA CALIBRATION V2 
17 

6.1.1 General differences from V1 to V2 17 
6.1.2 OUTPUT DATA files 17 
6.1.3 APPLICATION to dataset 
17 

7 DESCRIPTION OF CALIBRATION SW V3 (IN USE FROM 11 SEPT 2007) 

18 

7.1 SCIENCE DATA CALIBRATION V3 18 
7.1.1 Necessity of correction to V2: Problem in timing: 18 
7.1.2 Time-difference within MAG data-sets: 19 
7.1.3 General differences from V2 to V3 21 
7.1.4 OUTPUT DATA files 21 
7.1.5 APPLICATION to dataset 21 

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Introduction 

1.1 
Overview 
The task of the “Science Data Processing” process is to transform the binary science and 
the HK data from the sensor coordinate system into the PDS format in Venus Orbit 
Coordination System (VSO). 

a) 
The science data of the MAG instrument is transmitted to ground using the following 
two APIDs: 

• 
1644: MAGOS Science (binary in Sensor coordinates) 
· 1660: MAGIS Science (binary in Sensor coordinates) 
b) For the HK information the following 3 APIDs are reserved: 
• 
1620: DPU HK (binary) 
• 
1636: MAGOS HK (binary) 
· 1652: MAGIS HK(binary) 
c) The time information is given in the Time Correlation Packets, which can be 
downloaded from the DDS server. 
d) The Mission Phase information (Commissioning / Orbit number) TBD. 
Concerning the science data processing task only the temperature information from the 
MAGOS HK and the MAGIS HK are relevant. 

1.2 
Flow Diagram 
For the transformation of the raw data into VSO data several transformation steps must be 
performed. 

Science (binary) 


Science [B] 

RAW 
to 


Calibration, 
Transformation 
into S/C 
Coordinate 
Science Calib.[B] 

Science Calib.[B] 
HK (binary) ASCII HK (Temp/Volt) 

Correction 
S/C -Field -
Effects 
Calibration File 

S/C Attitude File 

Boom Alignment File 

S/C Position File 

Transformation 
to VSO 
Coordinates 
Science in VSO 
Fig. 1.2-1 Data Processing flow diagram 



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2 Data Processing 

2.1 File Name Generation 
The Filename is composed of the Sensor, the DataRate, the Mode, the DataLevel and the 
Time Information. 

Very important Notes: 

• 
The “RAW to ASCII” software packet uses the S/C Event Time (SCET) of the 
first vector to generate the file names. 
• 
The output files of the “Calibration and Transformation” software packet uses 
the measurement time in UTC of the first vector. 
FileName: Bs_CCYY-MM-DDTHH-MM-SS-sss_Mc_Dn_i_l.dat 


CCYYMMDD assigns the date 
HHMMSSsss assigns the time (milli sec. resolution) 
s assigns sensor (OS / IS) 
c assigns Mode(ST/C1/C2/C3/C4/C5/HK) 
n assigns DataRate (001Hz, 002Hz, 032Hz, 064Hz, 128Hz) 
I assigns counter (1 digit) (if a new file has to be generated within the same 


transmission frame) 
l assigns DataLevel 

Note: only capitals and numbers are allowed in the file name. 

Example for science file name: 
BOS_2005-10-11T22-12-45-788_MST_D032_2_RAW.dat 

Example for HK file name: 
BOS_2005-10-11T22-12-45-788_MHK_D032_0_RAW.dat 


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3 VEX -MAG Science Data Transformation 

3.1 Raw to ASCII 
The conversion from the binary raw file to the ASCII raw file is peformed by the SW packet 
“VEX MAG PacketValidator” (written by Gerhard Berghofer). 

3.1.1 Input Files (in binary) 
-MAGOS HK (1636.dat, in binary) 
-MAGIS HK (1652.dat, in binary) 
-MAGOS Science (1644.dat, in binary) 
-MAGIS Science (1660.dat, in binary) 


3.1.2 File Creation 
The file name generator uses the S/C Event Time (SCET in UTC). The SCET is afterwards 
not uses anymore and therefore not content of the output files. All internal time 
applications use the measurement time within the MAG telemetry packets. 

A new science file is generated if 

· a Mode change occurred 
· a Range change occurred 
· a DataRate change occurred 
· the time interval between two science packets is not within a certain limit 
(manually adjustable) 
There are only two HK files for each orbit; one for MAGOS and one for MAGIS. The 
generation interval of the HK packets has to be estimated by the S/C clock OBT time 
stamps. 

3.1.3 On Board Time (OBT) Format 
The format of the time stamp within the MAG TM packets is a 32 bit (unsigned) binary 
second counter (coarse time) and a 16 bit (unsigned) binary Tic counter (fine time). The 
Tic counter counts not in milliseconds but in 1 / 65535 [s]. 

32 bit Second Counter 16 bit Tics Counter 
(Coarse Time) (Fine Time) 

Fig. 3.1-1 Time Format of the MAG OBT. 
The Time Stamp Format within the ASCII Raw files is given in DDDD-HH:MM:SS.ttttt 


DDDD number of days (4 digits) 
HH hour (2 digits) 
MM minute of the day (2 digits) 
SS second of the day (2 digits) 
ttttt Tics (5 digits) (counter from 0…65535) 


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3.1.4 Output Files (in ASCII) 
-MAGOS HK (in ASCII) 
-MAGIS HK (in ASCII) 
-MAGOS Science (in ASCII) 
-MAGIS Science (in ASCII) 

NOTE: The number of science output files depends from the number of Mode changes; 
Range change, DataRate changes and the gap between the time stamps of the vectors 
(see 3.1.2). For one Venus orbit there are at least 5 science output files for each sensor 
foreseen. (1Hz, 32Hz, 128Hz, 32Hz, 1Hz). Please not that there can be more output files 
and that the number of files can be different for each sensor. 

3.1.4.1 Science File 
The science file contains the “Header” part and the “Science Data” part. 

a) Header Part 

#File = Name 
#Sensor= OS / IS 
#Mode = Std / Cal1 / Cal2 / Cal3 / Cal4 / Cal5 / HK 
#DataRate = 1Hz / 2Hz / 32Hz / 64Hz /128Hz 
#Range = 32nT / 64nT / 128nT / 256nT / 512nT/ 1024nT /…/ 8192nT 
#MissionPhase = Com1 / Com2 / Orbit 1 / Orbit 2 / …. 
#CoordinateSystem = SensorCoordinates / SCCoordinates / VSOCoordinates 
#DataLevel = RAW 
#CompensationBx = xxxx nT 
#CompensationBy = xxxx nT 
#CompensationBz = xxxx nT 
#StartTime = DDDD-HH:MM:SS.ttttt (S/C clock OBT from T0) 
#StopTime = DDDD-HH:MM:SS.ttttt (S/C clock OBT from T0) 
#TimeInterval = DDDD-HH:MM:SS. ttttt (StopTime-StartTime) 
#DataLines = xxxxxx 
#FirstFrameTime = CCYY-MM-DDTHH:MM:SS.ssssss (SCET of first TM Packet ) 
#LastFrameTime = CCYY-MM-DDTHH:MM:SS.ssssss (SCET of last TM Packet) 
#Columns: OBT Bx By Bz 

b) Science Data Part 

1. column: Time string (OBT) (DDDD-HH:MM:SS.ttttt) 
2. column: Bx (x.ppp) 
3. column: By (x.ppp) 
4. column: Bz (x.ppp) 
3.1.4.2 HK File 
The HK file contains the “Header” part and the “HK Data” part. 

a) Header Part 


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#File = Name 
#Sensor= OS / IS 
#Mode = Std / Cal1 / Cal2 / Cal3 / Cal4 / Cal5 / HK 
#DataRate = 1Hz / 2Hz / 32Hz / 64Hz /128Hz 
#Range = 32nT / 64nT / 128nT / 256nT / 512nT/ 1024nT /…/ 8192nT 
#MissionPhase = Commisioning1 / Commisioning2 / Orbit 1 / Orbit 2 / …. 
#DataLevel = RAW 
#StartTime = DDDD-HH:MM:SS.ttttt (S/C clock OBT from T0) 
#StopTime = DDDD-HH:MM:SS.ttttt (S/C clock OBT from T0) 
#TimeInterval = DDDD-HH:MM:SS.ttttt (StopTime-StartTime) 
#DataLines = xxxxxx 
#FirstFrameTime = CCYY-MM-DDTHH:MM:SS.ssssss (SCET of first TM Packet) 
#LastFrameTime = CCYY-MM-DDTHH:MM:SS.ssssss (SCET of last TM Packet) 
#Columns: OBT Temp1 Temp2 Temp E +5Vd +8Vd 

+8Va -8Va 

b) HK Data: 

1. column: Time string (OBT) (DDDD-HH:MM:SS.ttttt) 
2. column: Sensor Temp. 1 (xxx.pp) 
3. column: Sensor Temp. 2 (xxx.pp) 
4. column: Sensor Electronic Temp (xxx.pp) 
5.column: +5V Digital (x.pp) 
6.column: +8V Digital (x.pp) 
7.column: +8V Analog (x.pp) 
8.column: -8V Analog (x.pp) 

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3.2 Calibration and Transformation into S/C coordinates 
3.2.1 Input Files (in ASCII, Sensor Coordinates and OBT from T0) 
-MAGOS HK (ASCII) 
-MAGIS HK (ASCII) 
-MAGOS Science (ASCII, in Sensor coordinates) 
-MAGIS Science (ASCII, in Sensor coordinates) 
-Time correlation Packets (download from DDS Server) 
-Mission Phase Information (TBD) 
3.2.2 File Linking to one File per Sensor, per DataRate, per Orbit 

In this procedure all science data input files of the same sensor and the same DataRate of 
one orbit are linked together. Also the temperature information from the HK files is linked 
to this science data. 

3.2.3 Offset Correction 
The offset correction is done by subtracting the offset vector from each collected science 
vector. This offset is caused by the sensor itself and by the sensor electronic. The offset 
correction is done separately for each sensor. 

The default offset vector is set to O = (0; 0; 0) 

3.2.4 Alignment Correction 
The alignment correction is the transformation of the science data from the non orthogonal 
sensor coordinate system to an orthogonal coordinate system. To transform the science 
data into an orthogonal system each vector has to be multiplied by the Alignment Rotation 
Matrix. This correction is done separately for each sensor. 

.
. 
. 
.


.
. 
. 
.


100 


The default Alignment Rotation Matrix is set to =


A 


010 


001


.


.


3.2.5 Transformation into S/C Coordinates 
It is important that the data of both sensors has the same direction. To satisfy this 
requirement the data of both sensors is transformed into the S/C coordinate system. Each 
vector has to be multiplied by the S/C Coordinates Rotation Matrix. This transformation is 
done separately for each sensor. 

.
. 
. 
.


.
. 
. 
.


100 


The default Alignment Rotation Matrix is set to =


B 


010 


001


.


.



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3.2.6 Combination of MAGOS and MAGIS data to one file 
Here the science data of one orbit and of the same DataRate of MAGOS and MAGIS are 
combined together. 

3.2.7 Compute UTC Time 
In this procedure the time stamp of the science frames in transformed into a UTC time 
using the “Time correlation Packets”. 
The Output Format is CCYY-MM-DDTHH:MM:SS.sss 


CC century (2 digits) 
YY year (2 digits) 
MM month (2 digits) 
DD day (2 digits) 
HH hour (2 digits) 
MM minute of the day (2 digits) 
SS second of the day (2 digits) 
sss milliseconds (3 digits) 


3.2.8 Output Files (in ASCII, S/C coordinates and UTC) 
There is one file per mode, per orbit containg the calibrated data of both sensors. 

-Science 1Hz (ASCII, in S/C coordinates and UTC) 
-Science 2Hz (ASCII, in S/C coordinates and UTC) 
-Science 32Hz (ASCII, in S/C coordinates and UTC) 
-Science 64Hz (ASCII, in S/C coordinates and UTC) 
-Science 128Hz (ASCII, in S/C coordinates and UTC) 


Each science file contains the calibrated science data in S/C coordinates of MAGOS and 
MAGIS. Also the temperature of both sensors is given in these files. 


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3.2.9 Header Part of the Calibrated Output File 
#File = Name 

#Sensor = MAGOS and MAGIS 

#Mode = Std / Cal1 / Cal2 / Cal3 / Cal4 / Cal5 / HK 

#DataRate = 1Hz / 2Hz / 32Hz / 64Hz /128Hz 

#Range = 32nT / 64nT / 128nT / 256nT / 512nT/ 1024nT /…/ 8192nT 

#MissionPhase = Com1 / Com2 / Orbit 1 / Orbit 2 / …. 

#CoordinateSystem = SCCoordinates 

#DataLevel = Calibrated 

#StartTime (UTC) = CCYY-MM-DDTHH:MM:SS.sss 

#StopTime (UTC) = CCYY-MM-DDTHH:MM:SS.sss 

#TimeInterval = DDDDTHH:MM:SS.sss (StopTime-StartTime) 

#DataLines = xxxxxx 

#FirstFrameTime = CCYY-MM-DDTHH:MM:SS.ssssss (SCET of first TM Packet) 

#LastFrameTime = CCYY-MM-DDTHH:MM:SS.ssssss (SCET of last TM Packet) 

#Columns: UTC Bx/OS By/OS Bz/OS BT/OS Bx/IS By/IS Bz/IS BT/IS TempOS 
TempIS 

3.2.9.1 Science Part of the Calibrated Oputput File 
1. column: Time string (UTC) (CCYY-MM-DDTHH:MM:SS.sss) 
2. column: Bx / OS (x.ppp) [nT] 
3. column: By / OS (x.ppp) [nT] 
4. column: Bz / OS (x.ppp) [nT] 
5. column: BT / OS (x.ppp) [nT] 
6. column: Bx / IS (x.ppp) [nT] 
7. column: By / IS (x.ppp) [nT] 
8. column: Bz / IS (x.ppp) [nT] 
9. column: BT / IS (x.ppp) [nT] 
10 column: TempOS (x.ppp) [°C] 
11. column: TempIS (x.ppp) [°C] 
3.3 Correction of S/C – Field – Effects 
This task will be performed by our colleges from slowakia. 

3.4 Transformation to VSO Coordinate System 
To transform the corrected science data into the VSO coordinate system the attitude and 
position files of the S/C are necessary. 
TBD. 



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4 Description of Calibration SW V0 (used till May 13 2006) 

The SW –package V0 corrects for the following effects in the data: 

4.1 SCIENCE DATA CALIBRATION V0 
4.1.1 INPUT DATA 
The Calibration SW uses the RAWASCII files for the SCIENCE data and for the 
housekeeping data. 

4.1.2 Transformation of on board time (OBT) to UTC: 
This is done using the SPICE SCLK-files from 

JPL/NAIF-server: 
naif.jpl.nasa.gov 
username: anonymous 
passwd: anonymous 


remote dir: /pub/naif/VEX/kernels/sc 

Get the latest file with filetype= VEX_060515_STEP.TSC 
Here, “060515” is the data of issue of the file; be sure to always use the LATEST fileversion!! 


4.1.3 Correction for compensation range 
The values of the compensation are added to the values on the raw files. 

4.1.4 Correction for orthogonality of the sensors 
The correction for orthogonality is done INDEPENDENT from the sensor-temperature 
-> DEFAULT CALIBRATION. 

The following matrices are applied to the vector-components. 
From 


Doc. Title: VEX-MAG FM Instrument CalibrationIssue: 1 
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Date : 19.10.05 Page : 6 


%-----------------------------------------------Matrix_
OS_ortho_row1 = [ 1 0 0 ]; 
Matrix_OS_ortho_row2 = [ -0.00369 1 0 ]; 
Matrix_OS_ortho_row3 = [-0.00109 0.00259 1 ]; 
% 
Matrix_IS_ortho_row1 = [ 1 0 0 ]; 
Matrix_IS_ortho_row2 = [ 0.00778 1 0 ]; 
Matrix_IS_ortho_row3 = [-0.00372 0.00384 1 ]; 


The elements of the mis-alignment matrices above correspond with the following mis



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alignment angles within the sensors: 

Axis ma angles [°] delta90°[°] 

OS-YX 89.79 -0.21 
OS-ZX 89.94 -0.06 
OS-ZY 90.15 0.15 
IS-YX 90.45 0.45 
IS-ZX 89.79 -0.21 
IS-ZY 90.22 0.22 

Tab. 4-1 Mis-alignment angles 
%-----------------------------------------------------------


4.1.5 Correction to VEX S/C coordinate system 
MAGIS is always MASTER, MAGOS is always SLAVE. 

§ 
MAGIS is aligned with the VEX S/C coordiante system 
§ 
MAGOS: 
-Before boom deploýment, MAGOS is not aligend to the VEX S/C coordinate 
system: 


boomdeployment time: UTC 
Deploy_time = 2005-11-18T17-07 


the following matrix transformation is applied on the MAGOS data: 

Matrix_OS2IS_row1 = 0.041876 0 -0.999123 
Matrix_OS2IS_row2 = 0 1 0 
Matrix_OS2IS_row3 = 0.999123 0 0.041876 


-After boom-deployment time, the MAGOS data are in VEX S/C cosys and 
NO correction is performed. 

4.1.6 OUTPUT DATA 
Calibrated files are generated, default is one file per day of year or per orbit (for the 
S/C in the final orbit) 

4.2 HOUSEKEEPING DATA: 
For the housekeeping data, only the times are transformed from OBT to UTC. 


The RAW HK files are attached to each other, to build: default one file per day of year 
or per orbit (for the S/C in the final orbit) 
Only the OBT is transformed to UTC. 



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5 Description of Calibration SW V1 (in use from May 14 2006) 

5.1 SCIENCE DATA CALIBRATION V1 
5.1.1 
General differences from V0 to V1 
The V1 version corrects for ALL the SENSOR ARTEFACTS in the data, known until 1 
June 2006 by the VEX-MAG team. 
The science Science Data Calibration V1 is different from V0 in the following points: 
1) The orthogonality-correction was done WRONGLY in V0 due to a SW error; 
however, the orthogonality matrices are correct. 
V1 now does the transformation in a correct way!! 
2) Correction for MISALIGNMENT of the sensors is applied 
3) Correction for saturation effects in the data is applied (data are flagged) 
4) Correction for filter effects in the data is applied (data are skipped) 


5.1.2 Correction for MISALIGNMENT of the sensors 
MAGIS is the master, MAGOS is the slave: 

% MATRIX for ALIGNING OS to IS Sensorcosystem 
%---------------------------------------------------% 
rotate OS about Zos back to Xis over angle alfa 


Align_OS2IS_row1 = 1.0 0.028 0.0 
Align_OS2IS_row2 = -0.028 1.0 0.0 
Align_OS2IS_row3 = 0.0 0.0 1.0 


5.1.3 Correction for saturation effects/change of compensation range 
Automatic change of the compensation range occurs only, if a minimum number of 
subsequent vector components are in saturation: 
The saturated data-values are detected BEFORE the compensation range correction 
is performed. 


Saturation treshold value: 520 nT; larger components are FLAGGED. 

For the different datarates, the following number of vectors are required to trigger a 
change of the compensation range (of at least 4.5 nT) 

1Hz: 
1*64samples 
(X=1 
volles 
frame) 
2Hz: 
1*64samples 
(X=1 
full 
frame) 
32Hz: 
5*64samples 
(X=5 
full 
frames) 



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64Hz: 
10*64samples 
(X=10 
full 
frames) 
128 
Hz: 
20*64samples 
(X=20 
full 
frames) 


The saturated values/blocks are detected automatically and the values are FLAGGED. 

Beforer each block of saturated values, a fixed number of vectors is to be flagged 
additionally, depending on the datarate: 

[ 1, 2, 32, 64, 128]; % DATA-rates in Hz 
[15, 15, 20, 20, 20]; % nr. of previous samples to be 
ADDITIONALLY flagged 

5.1.4 Correction for filter effects 
Filter effects occurr atin the data of BOTH sensors at each: 
§ 
Change of data-rate at one of the sensors 
§ 
Change of compensation range at one of the sensors 


The filter effect generates in the first data-sets NON-REAL variations in the data until 
the filter is in good action 
Therefore, at each switch on of the filter, a fixed number of lines is to be skipped in 
the data: 

DEFAULT: 15 data-lines are skipped, (same value for all data – rates) 

5.1.5 OUTPUT DATA files 
Output calibrated files of V1 now have the version extension: 

_1_SCC 

The HEADER description in the file contains the line: 

#DataLevel = V1-CALIBRATED 

5.1.6 APPLICATION to dataset 
The Calibration V1 was applied to all data from START of the mission and initial 
switch-on of MAG: 

i.e. for all data after 
2005-11-20T00-00-32 

till 

2007-01-11 


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Date : 04 April 2008 Page :17 


6 Description of Calibration SW V2 (in use from 24 Jan 2007) 

6.1 SCIENCE DATA CALIBRATION V2 
6.1.1 General differences from V1 to V2 
The V2 FLAGS more data-lines before and after a saturation block. 

Beforer each block of saturated values, a fixed number of vectors is to be flagged 
additionally, depending on the datarate: 

[ 1, 2, 32, 64, 128]; % DATA-rates 
[30, 20, 20, 20, 20]; % nr. of previous samples to be ADDITIONALLY 
flagged 

6.1.2 OUTPUT DATA files 
Output calibrated files of V2 now have the version extension: 

_2_SCC 

The HEADER description in the file contains the line: 

#DataLevel = V2-CALIBRATED 

6.1.3 APPLICATION to dataset 
The Calibration V2 was applied to all data from ARRIVAL of the SC at Venus: 

i.e. for all data after 
2006-04-12T07-56-08 

till 

2007-09-01 


Doc. Title: VE-MAG ScienceData Processing Description Issue: 1 
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Date : 04 April 2008 Page :18 


7 Description of Calibration SW V3 (in use from 11 Sept 2007) 

7.1 SCIENCE DATA CALIBRATION V3 
7.1.1 Necessity of correction to V2: Problem in timing: 
A time-daly due to filtering was detected in the V2 calibration (and is existent also in all 
previous versions): 

Problem detected through comparison with ASPERA data: 
VEXMAG (1Hz data, 4 sec averaged data) seems to lag ~ 6 secs behind ASPERAdata 


Example: 
VEXMAG (4 sec averaged data from 1Hz data) lag ~ 6 secs behind ASPERA-data 



Fig. 1 Timely comparison ASPERA -MAG 



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7.1.2 Time-difference within MAG data-sets: 
MAG Problem: 
There is a ~ 6 secs TIME_DIFFERENCE between MAG 32 Hz and MAG 1 Hz datasets 
(see example in following figure). 


Onboard: 


MAG instrument samples normally with 128 Hz: 
In normal solar wind mode (22 hrs per orbit) : 
ALL data are digitally down-filtered to a 1 Hz data-rate 
In 32 Hz data –rate mode (1hr before and after pericenter): 
ALL data are digitally down-filtered to a 1 Hz data-rate. 
(and also 2 mins of data in 128 HZ around pericenter) 

On ground: 

To get a FULL orbit with 1 Hz data-rate, we digitally down-filter the 32 Hz data to 1Hz; so 
for all files with 32 Hz data-rate, we have the same data-set also in 1Hz. 

The FIR digital filter used on ground is exactly the same as the one onboard. 

The effect of the FIR filtering from 32Hz to 1 Hz causes a specific event in the data-set to 
be seen after the filtering at a time ~ 6 SECS later in the 1Hz data than in the 32Hz data. 

Conclusion: 

There is always a CONSTANT ~ 6 secs time-difference between the MAG 32Hz data-set 
and the MAG 1Hz data-set, due to digital filtering, where the 1Hz data are lagging behind 
the 32Hz data., see MAG example in Fig. below. 


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Example: same MAG data-set in 32Hz resp. 1Hz: time-diff ~ 6 secs. 



Fig. 2 MAG timely comparison 32Hz data (top 4 panels) to 1 Hz data (lower 4 panels) 



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7.1.3 General differences from V2 to V3 
Time-difference is corrected, i.e. all UTC times in V3 files are diminished by ~ 6 secs. 
This results in NEW start times of the daily files and some data-lines being attributed now to the 
PREVIOUS day. 


7.1.4 OUTPUT DATA files 
Output calibrated files of V2 now have the version extension: 

_3_SCC 

The HEADER description in the file contains the line: 

#DataLevel = V3-CALIBRATED 

7.1.5 APPLICATION to dataset 
The Calibration V3 was applied to all data from ARRIVAL of the SC at Venus: 

i.e. for all data after 
2006-04-12T07-56-08 

till present 

2008-04-04.