<?xml version="1.0" encoding="UTF-8"?>
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  <Version>2.2.6</Version>
  <Instrument>
    <ResourceID>spase://CDPP/Instrument/AMDA/MGS/PROXY</ResourceID>
    <ResourceHeader>
      <ResourceName>Proxy</ResourceName>

      <AlternateName>IMF clock angle MGS Proxy</AlternateName>

      <ReleaseDate>2009-05-20T21:10:13Z</ReleaseDate>

      <Description>Draping direction is calculated on an orbit-by-obit basis using MGS data from time periods when the spacecraft 
        was above 50-60 N planetary latitude on the Martian dayside. We use this small latitude range in an attempt to minimize 
        the contaminating effects of crustal magnetic fields, which are weakest in this latitude band. 
        Draping direction is reported as the median azimuth angle from each orbit, with 0° pointing locally Eastward from 
        the spacecraft, and 90° pointing locally Northward.</Description>

      <Contact>      

        <PersonID>spase://CDPP/Person/David.Brain</PersonID>
        <Role>TechnicalContact</Role>

      </Contact>

      <InformationURL>
        <Name>MGS Proxy webpage</Name>
        <URL>http://sprg.ssl.berkeley.edu/~brain/proxies/drapingdirxn.html</URL>
      </InformationURL>   

    </ResourceHeader>

    <InstrumentType>Magnetometer</InstrumentType>
    <InvestigationName>MAG/ER</InvestigationName>
    <ObservatoryID>spase://CDPP/Observatory/AMDA/MGS</ObservatoryID> 
    <Caveats>* IMF direction can change on any timescale, from seconds to minutes to hours to days. 
      Therefore, determination of the direction of the ambient magnetic field between 50-60 N latitude on the dayside may
      not provide a reliable indication of the IMF direction over an entire MGS 2-hour orbital period. 
      Please use appropriate caution when using the information on this page.
      
      * We do not believe that IMF draping direction is accurate to more than ~90o, due to contributions 
      of ionospheric current-generated magnetic fields to the ambient field measured at 400 km altitudes by MGS. 
      Further, anti-solar "weathervaning" of the ambient magnetic field is observed more prominently for one set of IMF directions (dawnward upstream IMF).
      
      * Keep in mind that Mars "rocks" back and forth with respect to the Sun over the course of a single year, and therefore the 
      azimuth angle (which is defined relative to the planetary rotation axis) rocks back and forth by as much as 25o as well.
      
      * I use only publicly available MGS data, since those data have been fully calibrated. Therefore, the timeseries will 
      usually be several months "behind" the current date. You can always email me to see whether the page is as up-to-date as possible.
    </Caveats>

  </Instrument>
</Spase>