Satellite/Instrument    Observation dates    Wavelength ($\micron$)         Spatial resolution       
  ---------------------- ------------------- -------------------------- ------------------------------ --
  AKARI/FIS$^{a}$         2006 May–2007 Aug       65, 90, 140, 160       $\sim 60\arcsec$–90$\arcsec$  
  AKARI/IRC$^{b}$         2006 May–2007 Aug            9, 18                   $\sim 6\arcsec$         
  IRAS$^{c}$              1983 Feb–1983 Nov       12, 25, 60, 100              $\sim 5\arcmin$         
  COBE/DIRBE$^{d}$        1989 Dec–1990 Sep   1.25, 2.2, 3.5, 4.9, 12,      $\sim \timeform{0.7D}$     
                                               25, 60, 100, 140, 240                                   
  WISE$^{e}$              2010 Jan–2010 Aug       3.4, 4.6, 12, 22           $\sim 6$–12$\arcsec$      

  : Comparison of IR satellite survey observations (sky coverage $>90$%) at mid- and far-IR wavelengths.[]{data-label="tab:irsurveys"}

$^{a}$ @Doi15.\
$^{b}$ @Ishihara10.\
$^{c}$ Explanatory Supplement to the IRAS Sky Survey Atlas (http://irsa.ipac.caltech.edu/IRASdocs/issa.exp.sup/).\
$^{d}$ DIRBE Explanatory Supplement (http://lambda.gsfc.nasa.gov/product/cobe/dirbe\_exsup.cfm).\
$^{e}$ The fully cryogenic survey phase. @WISE12.

The observed far-IR sky brightness consists of the ZE, the integrated light from the Galactic components (stars and emission from the interstellar medium) and extragalactic emission. Since AKARI far-IR all-sky map data are processed mainly to study the Galactic and extragalactic objects, the ZE components in the released maps have been subtracted during data processing. As mentioned previously, although we tried to subtract the ZE from the AKARI far-IR data by applying the DIRBE ZE models [@Kelsall98; @Wright98; @Gorjian00], we found that there are discrepancies on small scales between the model estimates and 