Cosmic Background Explorer/DMR

Product Name
Pixelized Differential Data
Coord. System
Projection Type
COBE Quad Cube


The calibrated differential antenna temperature (DT) and the number of observations are given for each combination of sky positions observed simultaneously by a DMR horn pair. The data (temperature in "horn 1" minus temperature in "horn 2") are sorted according to the COBE sky map pixel number seen by horn 1, and sub-sorted by the horn 2 pixel number. The observations are made with a 7 degree beam and presented in 2.8 degree pixels. The pixelization scheme is described in a FITS file called dmr_firas_skymap_info.fits.

All differential temperatures for a given pixel pair are combined, after correcting for known systematic errors and subtracting a nominal dipole to minimize pixel gradient effects, into four moment sums, specifically the sums of DT, (DT)^2, (DT)^3, and (DT)^4. The Pixelized Differential Data are presented in FITS files formatted as described in the DMR Explanatory Supplement. There are six Pixelized Differential Data files corresponding to two independent DMR channels at each of three frequencies: 31.5, 53, and 90 GHz. The Pixelized Differential Data Sets describe observations made during the same four-year period as the Sky Maps (see above).

The 4-year Pixelized Differential Data files are online, but be aware that each file is about 40 MB in size. If you would prefer not to download these files over the Web, they may be ordered either on CD-ROM or tape through the NSSDC's Coordinated Request and User Support Office.

The 2-Year data sets and documents, which have been superseded by 4-year products, are available on request.

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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