Product Name


The Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE 2) measures the absolute temperature of the cosmic microwave background and astrophysical foregrounds at frequencies from 3 to 90 GHz. Differential radiometers compare the sky intensity to a full-aperture blackbody calibrator maintained within a few mK of the sky temperature. Careful control of the instrumental signature establishes the zero level of the sky maps to an accuracy of several mK (see Table 3 of Fixsen et al. 2011).

The delivered files contain sky maps from the 2006 flight of the ARCADE 2 instrument. Each FITS file 'arc2_fffff_v19.fits' consists of a sky map in Galactic coordinates with units K thermodynamic temperature. The string "fffff" denotes thecenter frequency in MHz, so for example file arc2_9720_v19.fits contains the sky map from the 9720 MHz channel. There are two channels at 29500 MHz with different beam widths. File arc2_29500s_v19.fits has a 4 deg FWHM beam width while file arc2_29500_v19.fits has the same 11.6 deg beam width as all of the other maps.

Each file contains a map in a binary FITS extension; this extension contains two fields:

  • TEMPERATURE contains the absolute sky intensity in units K thermodynamic temperature for each pixel. The CMB dipole has been removed from the maps, but no other Galactic or cosmological source has been removed.
  • N_OBS contains the number of observations within each pixel. Each observation corresponds to 0.5 seconds integration time. Table 2 of Singal et al 2011 lists the corresponding white noise amplitude for each map.

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A service of the HEASARC and of the Astrophysics Science Division at NASA/GSFC
Goddard Space Flight Center, National Aeronautics and Space Administration
HEASARC Director: Dr. Alan P. Smale
LAMBDA Director: Dr. Eric R. Switzer
NASA Official: Dr. Eric R. Switzer
Web Curator: Mr. Michael R. Greason