COsmic Background Explorer (COBE)
Study the CMBR from Space with a Dedicated Satellite Mission
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Above the Atmosphere
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Long flight
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1-4 years in orbit
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unlike sub-orbital rockets - 15 minutes
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balloons - typically 5-10 hours
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flight duration allows cross checks
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they can throw out half of the data and still have a strong
signal
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worried about the effect of the moon?
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check out the data from the times when the moon is behind
the Earth
COBE
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Space mission with three experiments
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Far Infrared Absolute Spectrophotometer (FIRAS)
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Studies the CMBR Spectrum
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Cooled to 1.5K
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covers wavelength range from
= 0.1mm to
=
1.0cm
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Here's the FIRAS Spectrum:
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Berkeley-Nagoya "sub-mm excess" ruled out

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Differential Microwave Radiometer (DMR)
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measures difference in temperature between spots on
the sky separated by 60 degrees
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operates at 3 different wavelengths:
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= 3.3mm
(strong CMBR signal)
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= 5.7mm
(strong CMBR signal)
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= 9.5mm
(strong Galactic signal)
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helps to subtract Galaxy's contribution

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Diffuse Infrared Background Experiment (DIRBE)
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Here are some images of the DMR results:
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The anisotropy map
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the top panel is the "dipole" anisotropy due to the motion
of the Earth and Sun
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The middle panel has the "dipole" anisotropy subtracted and
is dominated by the Galaxy
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The bottom panel has the Galaxy subtracted.
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Here are the maps in the 3 different wavelengths:
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= 3.3mm
is 90 GHz
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= 5.7mm
is 53 GHz
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= 9.5mm
is 31.5 GHz (note the strong Galactic signal)
