SRTM below 60 deg, ASTER above?

Microwave Toolbox
#1

I’m using SNAP to operationally (every 12 hours) process Sentinel-1 images over a study area that intersects 60 deg latitude. My GPT scripts use the SRTM 3Sec data (see below). Is there some way to configure this GPT node to tell it to use SRTM 3Sec when available, and otherwise ASTER DEM saved locally in the auxdata (which, from reading other threads, seems to be the best alternative)?

The workflow has been working well for 90% of my analysis tiles, and I just now realized that for my two small subset areas above 60 deg don’t have any data yet… I hope there’s an elegant way to fix this. Any tips are appreciated!

<node id="Terrain-Correction">
    <operator>Terrain-Correction</operator>
    <sources>
      <sourceProduct refid="Calibration"/>
    </sources>
    <parameters class="com.bc.ceres.binding.dom.XppDomElement">
      <sourceBands>Gamma0_VV</sourceBands>
      <demName>SRTM 3Sec</demName>
      <externalDEMFile/>
      <externalDEMNoDataValue>0.0</externalDEMNoDataValue>
      <externalDEMApplyEGM>true</externalDEMApplyEGM>
      <demResamplingMethod>BILINEAR_INTERPOLATION</demResamplingMethod>
      <imgResamplingMethod>BILINEAR_INTERPOLATION</imgResamplingMethod>
      <pixelSpacingInMeter>10.0</pixelSpacingInMeter>
      <pixelSpacingInDegree>8.983152841195215E-5</pixelSpacingInDegree>
      <mapProjection>GEOGCS[&quot;WGS84(DD)&quot;, &#xd;
  DATUM[&quot;WGS84&quot;, &#xd;
    SPHEROID[&quot;WGS84&quot;, 6378137.0, 298.257223563]], &#xd;
  PRIMEM[&quot;Greenwich&quot;, 0.0], &#xd;
  UNIT[&quot;degree&quot;, 0.017453292519943295], &#xd;
  AXIS[&quot;Geodetic longitude&quot;, EAST], &#xd;
  AXIS[&quot;Geodetic latitude&quot;, NORTH]]</mapProjection>
      <alignToStandardGrid>false</alignToStandardGrid>
      <standardGridOriginX>0.0</standardGridOriginX>
      <standardGridOriginY>0.0</standardGridOriginY>
      <nodataValueAtSea>true</nodataValueAtSea>
      <saveDEM>false</saveDEM>
      <saveLatLon>true</saveLatLon>
      <saveIncidenceAngleFromEllipsoid>false</saveIncidenceAngleFromEllipsoid>
      <saveLocalIncidenceAngle>false</saveLocalIncidenceAngle>
      <saveProjectedLocalIncidenceAngle>false</saveProjectedLocalIncidenceAngle>
      <saveSelectedSourceBand>true</saveSelectedSourceBand>
      <outputComplex>false</outputComplex>
      <applyRadiometricNormalization>false</applyRadiometricNormalization>
      <saveSigmaNought>false</saveSigmaNought>
      <saveGammaNought>false</saveGammaNought>
      <saveBetaNought>false</saveBetaNought>
      <incidenceAngleForSigma0>Use projected local incidence angle from DEM</incidenceAngleForSigma0>
      <incidenceAngleForGamma0>Use projected local incidence angle from DEM</incidenceAngleForGamma0>
      <auxFile>Latest Auxiliary File</auxFile>
      <externalAuxFile/>
    </parameters>
  </node>