Data Set Overview
    =================
 
This data set is composed of data produced during the descent to Titan on
January 14 2005 from the ACP instrument (Engineering data) and also from
the GCMS instrument (Science data) which analyses the gaseous products from
ACP.
 
Only the channel B data is archived (no data has been recovered by Cassini
on channel A).
 
The raw data in binary format is not archived in this data set. It has been
processed to calibrated (engineering) data by means of the transfer
functions described in the ACP Software User Manual. This calibrated data
is presented hereafter.
 
The ACP engineering data:
 
It includes all the temperatures, pressure, references voltages, DC/DC
converter voltages, mechanisms position sensors, and  is sorted in the four
following data files :
 
1)ACP_OVEN_V1_0.LBL/ACP_OVEN_V1_0.TAB:
 
Oven group parameters which monitor the heating and transfer phase
performance including (columns title): UTC time, ACP internal sampling
time, oven temperature, oven wall temperature,oven pressure, and
electrovalves V1, V2, VT status.
 
2)ACP_PUMP_V1_0.LBL/ACP_PUMP_V1_0.TAB:
 
Pump group parameters which monitor the pump performance including (columns
title): UTC time, ACP internal sampling time, pump temperature, pump
current, pump speed.
 
3)ACP_TEMP_V1_0.LBL/ACP_TEMP_V1_0.TAB:
 
Temperatures group parameters including (columns title): UTC time,  ACP
internal sampling time, temperatures; electronics, base plate, cold
junction, electrovalves VT & V2.
 
4)ACP_VOLT_V1_0.LBL/ACP_VOLT_V1_0.TAB:
 
Voltages group parameters including (columns title): UTC time, ACP internal
sampling time, DC/DC converter voltages (+ 5V , +15V , -15V), calibration &
reference voltages (Rcal, RO, TCgnd, Vref1/2/3).
 
 
The documentation includes the ACP EAICD, The GCMS EAICD, the ACP on board
software user manual, the ACP & GCMS ESA SP-1177 publications, and  the ACP
& GCMS Nature publications.
 
 
The ACP science data :
 
The GCMS analyses samples from the ACP.  The Data Products that are
referencing the ACP are provided to the ACP Science team, and are analyzed
by them.
 
The ACP products are sampled at determined times during the descent
directly by the GCMS Ion source 2  dedicated to ACP  (IS 2), and by the
combination of the GC & ion sources 3/4/5 (GC-IS 3/4/5).
 
This dataset  contains the calibrated data of the ACP data products
analysed by the GCMS. The same dataset is archived by the GCMS team.
 
For more information refer to the GCMS DATASET\DATASET.CAT.
 
The GCMS Stage 2 ACP data is converted from raw counts per integration
period to counts per second and corrected for the counter overflow
condition where this can be determined to have happened.  Stage 3
processing corrects this data for pulse pile-up, counter dead-time and
other known counting system (error) conditions. These errors can become
significant where the count value is large.
 
The files are all of the valid data from MS Ion Source #2 (the ACP data)
plus the Ion Sources #3 & 4 data for Sample #3, the ACP injection to the GC
Columns attached to Ion Sources #3 & 4.  As the Ion Source #5 did not work
during the descent, the IS5 data files are not included.
 
These files are in column aligned comma delimited ASCII TEXT format as
required by the PSA/PDS for archiving.
 
The overall structure of this dataset is:
 
It contains the data Table files, the Label files associated with the Table
files plus the Format files referred to in the Label files.
The LBL file gives information on the file.
The FMT file gives information on the columns.
 
 
The ACP data consists of one GC data product, 6 stage 1 mass scan products,
and 6 stage 2 and 6 stage 3 mass scan products.
 
Stage 1 Processed Data: Scripts that call programs convert *.archive to
 *.dat files; sort data into smaller files
Stage 2 Processed Data: Break into smaller files, convert units, add
 headers and comments
Stage 3 Processed Data: Lengthy processing, plotting, comparing to
 calibration (pre & post encounter)
 
 
IS2_Smpl1_Stg2: Ion source 2 (MS) data at 75 eV ionization energy and unit
mass resolution for ACP sample #1 in counts per second.
IS2_Smpl2_Stg2: Ion source 2 (MS) data at 75 eV ionization energy and unit
mass resolution for ACP sample #2 in counts per second.
Note - Programmed low IE data is present in this block of data and not
marked between times 10:18:49 - 10:19:01.
IS2_Smpl5_Stg2: Ion source 2 (MS) data at 75 eV ionization energy and unit
mass resolution for ACP sample #5 in counts per second.
Note - Programmed low IE data is present in this block of data and not
marked between times 10:52:48 - 10:52:55.
 
IS2_Stg1:                  Ion source 2 (ACP) full scans
(mass range: 2 - 141) at unit resolution and 25 eV ionization energy.
IS2_Stg2:                  Ion source 2 (ACP) full scans
(mass range: 2 - 141) at unit resolution and 25 eV ionization energy.
 
IS2_Smpl1_Stg2: Ion source 2 (MS) data at 25 eV ionization energy and unit
mass resolution for ACP sample #1 in counts per second.
IS2_Smpl2_Stg2: Ion source 2 (MS) data at 25 eV ionization energy and unit
mass resolution for ACP sample #2 in counts per second.
IS2_Smpl3_Stg2: Ion source 2 (MS) data at 75 eV ionization energy and unit
mass resolution for ACP sample #3 in counts per second.
IS2_Smpl4_Stg2: Ion source 2 (MS) data at 75 eV ionization energy and unit
mass resolution for ACP sample #4 in counts per second.
IS2_Smpl5_Stg2: Ion source 2 (MS) data at 25 eV ionization energy and unit
mass resolution for ACP sample #5 in counts per second.
IS2_Smpl6_Stg2: Ion source 2 (MS) data at 75 eV ionization energy and unit
mass resolution for ACP sample #6 in counts per second.
 
IS3_GC1_Smpl3_Stg2: Ion Source 3 (Column 1) data at 75 eV ionization energy
 and unit mass resolution for ACP Sample #3 as counts per second.  Time
 relative to the injection has been determined and added to the file.
IS4_GC2_Smpl3_Stg2: Ion Source 4 (Column 2) data at 75 eV ionization energy
 and unit mass resolution for ACP Sample #3 as counts per second.  Time
 relative to the injection has been determined and added to the file.
 
IS3_Smpl3_Stg2: IS3 (GC Column 1) sample 3 mass scans at unit resolution
and 75 eV ionization energy.
IS4_Smpl3_Stg2: IS4 (GC Column 2) sample 3 mass scans at unit resolution
and 75 eV ionization energy.
 
 
The first results from the ACP data have been published in NATURE2005.
 
There is no specialized software required to view the ACP data products,
and no software is provided or archived to do so.
 
Review
======
 
      The Huygens data sets were reviewed in two steps:
      (1) a review of the Experimenter-to-archive-ICD, in 2004.
      (2) a review of the data sets, in 2006.
      Procedures and details of this process can be obtained from
      the ESA archive team:
 
      Olivier Witasse or Joe Zender
      ESA ESTEC
      Keplerlaan 1
      2200 AG Noordwijk
      The Netherlands
      Olivier.Witasse@esa.int or Joe.Zender@esa.int
 
     This data set was reviewed by Nathalie Boudin and Heidi L.K. Manning.

N/A