A Question of Mass: Accounting for all the Dust in the Crab Nebula with
  the Deepest Far Infrared Maps
  Supernovae represent significant sources of dust in the interstellar medium.
In this work, deep far-infrared (FIR) observations of the Crab Nebula are
studied to provide a new and reliable constraint on the amount of dust present
in this supernova remnant. Deep exposures between 70 and 500 $\mu$m taken by
PACS and SPIRE instruments on-board the Herschel Space Telescope, compiling all
observations of the nebula including PACS observing mode calibration, are
refined using advanced processing techniques, thus providing the most accurate
data ever generated by Herschel on the object. We carefully find the intrinsic
flux of each image by masking the source and creating a 2D polynomial fit to
deduce the background emission. After subtracting the estimated non-thermal
synchrotron component, two modified blackbodies were found to best fit the
remaining infrared continuum, the cold component with T$_c$ = 8.3 $\pm$ 3.0 K
and M$_d$ = 0.27 $\pm$ 0.05 M$_{\odot}$ and the warmer component with T$_w$ =
27.2 $\pm$ 1.3 K and M$_d$ = (1.3 $\pm$ 0.4) $\times$10$^{-3}$ M$_{\odot}$.
