COsmic Background Explorer (COBE)

• Figures borrowed from:  COBE Home Page

Study the CMBR from Space with a Dedicated Satellite Mission

• Above the Atmosphere
• No H₂O vapor problems
• Long flight
• 1-4 years in orbit
• unlike sub-orbital rockets - 15 minutes
• balloons - typically 5-10 hours
• flight duration allows cross checks
• they can throw out half of the data and still have a strong signal
• worried about the effect of the moon?
• check out the data from the times when the moon is behind the Earth

COBE

• Space mission with three experiments
• Far Infrared Absolute Spectrophotometer (FIRAS)
• Studies the CMBR Spectrum
• Cooled to 1.5K
• covers wavelength range from = 0.1mm to  = 1.0cm

• Here's the FIRAS Spectrum:
• Berkeley-Nagoya "sub-mm excess" ruled out

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

• Diffuse Infrared Background Experiment (DIRBE)
• we won't cover this much
• Here are some images of the DMR results:
• The anisotropy map
• the top panel is the "dipole" anisotropy due to the motion of the Earth and Sun
• The middle panel has the "dipole" anisotropy subtracted and is dominated by the Galaxy
• The bottom panel has the Galaxy subtracted.

 
• Here are the maps in the 3 different wavelengths:
• = 3.3mm is 90 GHz
• = 5.7mm is 53 GHz
• = 9.5mm is 31.5 GHz (note the strong Galactic signal)