>, <code>"red"</code>,
<code>"nir"</code>, <code>"swir1"</code>, <code>"swir2"</code>, <code>"panchromatic"</code>,
<code>"cirrus"</code>, <code>"tirs1"</code>, or <code>"tirs2"</code>.  For Landsat-7 data,
this may be one of <code>"blue"</code>, <code>"green"</code>, <code>"red"</code>,
<code>"nir"</code>, <code>"swir1"</code>, <code>"tirs1"</code>, <code>"tirs2"</code>,
<code>"swir2"</code>, or <code>"panchromatic"</code>.  For Landsat data prior to
Landsat-7, this may be one of <code>"blue"</code>, <code