<?xml version="1.0" encoding="UTF-8"?>
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  <Version>2.3.1</Version>
  <Instrument>
    <ResourceID>spase://CNES/Instrument/CDPP-AMDA/Solar_Orbiter/PAS</ResourceID>
    <ResourceHeader>
      <ResourceName>PAS</ResourceName>
      <AlternateName>Proton-Alpha Sensor</AlternateName>
      <ReleaseDate>2018-10-27T18:45:12Z</ReleaseDate>
      <Description>The Proton-Alpha Sensor (PAS) is designed to continuously determine the 3D 
distribution functions of the dominant ions of the solar wind, from 200 eV to 20 KeV, 
without mass and charge selection. In practice, this concerns mostly the proton and alfa 
populations. These measurements are used to calculate the density, speed, pressure 
and temperature tensors of the main component of the solar wind.

At full resolution, PAS measures the 3D ion distribution function, in the form of arrays of 
96 energies, 11  azimuth angles and 9 elevation angles, in about ~1 second. The 
energy and the angle of elevation are selected by imposing different high voltages to 
the electrodes of the deflection system and the electrostatic analyzer. The 11 azimuthal 
angles correspond to the 11 detectors of the instrument (channeltron’).

In ‘burst‘ mode, the measurement rate can reach up to 20 Hz. The phase space 
sampling is then reduced, for example by 24 energies and 5 deflections, which allows 
to increase the time cadence of distribution functions measurements. An algorithm 
(peak tracking procedure) is used to select the peak of the distribution and to center 
sampling around this peak.

The different types of sampling are programmed in the form of cyclograms. They define 
the operation of the instrument over periods of several days. In normal mode, the 
functions are measured every 4 s with, every 300 s, a short burst mode of 9 s 
(SnapShot). ‘Long’ burst mode is also acquired every day, consisting in 300 s of 
continuous sampling at high cadence. The sampling frequency during burst or 
snapshots is generally of 4 distributions / s (4 Hz analysis).</Description>
      <Acknowledgement></Acknowledgement>
      <Contact>
        <PersonID>spase://SMWG/Person/Philippe.Louarn</PersonID>
        <Role>PrincipalInvestigator</Role>
      </Contact> 
      <Contact>
        <PersonID>spase://CNES/Person/Andrei.Fedorov</PersonID>
        <Role>TechnicalContact</Role>
      </Contact>       
      <InformationURL>
        <Name></Name>
        <URL></URL>
      </InformationURL>   
    </ResourceHeader>
    <InstrumentType>ParticleDetector</InstrumentType>
    <InvestigationName>SWA</InvestigationName>
    <ObservatoryID>spase://CNES/Observatory/CDPP-AMDA/SolO</ObservatoryID>
  </Instrument>
</Spase>