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
Far-Sidelobe Maps
Coord. System
Spacecraft Coordinates
Projection Type
HEALPix, nested, res 7 (Nside=128)


Low resolution maps of the antenna gain response over 4pi steradians for each of the 10 WMAP differencing assemblies. While WMAP's optical system gain drops very rapidly when moving away from the main beam line-of-sight, the emission of the extended Galactic foreground can be 1000 times brighter than the fluctuations of the CMB and can cover very large solid angles. It is therefore extremely important to fully characterize the antenna gain response. The Far-Sidelobe Maps are based on compilations of data from the following sources:

  • GSFC anechoic chamber antenna range
  • Princeton outdoor antenna range
  • In-flight lunar data
  • Physical Optics Code theoretical predictions

The gain pattern is provided in spacecraft coordinates, such that the X axis is parallel to the plane of the radiators, -Z is the anti-sun direction of the spin axis, and Y is perpendicular to both. Gain is in dimensionless units, 4pi/(beam solid angle). Positive values refer to A-side pickup, and negative values to B-side pickup.

More details can be found in:

"First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations:
Characterization of the Far-Sidelobes", Barnes, et al., 2003

WMAP Explanatory Supplement

Back to Product Page

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