The data made available through this page has been updated. The most recent version of this data may be accessed through /product/map/current/

Product Name
I Maps (Individual Differencing Assemblies)
Coord. System
Projection Type
0.23°- 0.93° (frequency dependent)


Iterative algorithms are used to create skymaps from the calibrated differential time-ordered WMAP data for each of the ten differencing assemblies. Each pixel in a map represents a sky temperature for the bandpass appropriate to the differencing assembly. The CMB dipole has been removed and the zero point of each map has been set using a Galactic csc |b| model (see Bennett et al. below).

The data provided in each map consist of two fields for each pixel:

  • the thermodynamic temperature, in mK, and
  • the effective number of observations, N_obs.
Pixel noise can be evaluated from N_obs via sigma = sigma_0/sqrt(N_obs), where sigma_0 for each differencing assembly is listed in the following table:

Differencing Assembly K1 Ka1 Q1 Q2 V1 V2 W1 W2 W3 W4
sigma_0 (mK) 1.42366 1.44883 2.26677 2.15567 3.28789 2.93683 5.85196 6.53276 6.88032 6.72537

More details can be found in:

"First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations:
Data Processing and Systematic Errors Limits," Hinshaw, et al., 2003

"First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations:
Foreground Emission," Bennett, et al., 2003

"Producing Megapixel Cosmic Microwave Background Maps from Differential Radiometer Data," Wright, Hinshaw, and Bennett, ApJ Lett, 458, L53-L55, 1996

WMAP Explanatory Supplement

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