ABOUT LAMBDA

South Pole Collaboration Data Products at LAMBDA

The South Pole Collaboration made measurements of the CMB temperature at six frequencies from 0.82 to 7.5 GHz.


southpole image

South Pole Collaboration

  • Measurements at six frequencies (0.82, 1.47, 2.0, 2.5, 3.8, 7.5 GHz) of the absolute difference
    of antenna temperature ΔT between the sky at the zenith and a black body at Liquid Helium temperature.
  • Measurements of the atmospheric emission by a 90 GHz dedicated radiometer.
  • Ground and Sun screens.
  • Galactic, atmospheric, ground and sun signals measured by drift and zenith scans.
  • Blend of extragalactic radio sources by (log N – log S) data in literature.
  • TCMB = Tblack body + ΔT – Tgal - Texg - Tatm - Tground
  • Black Body. <1 GHz: coaxial dummy load in a commercial LHe dewar; >1 GHz: Eccosorb in a 70 cm diameter LHe dewar.
  • Corrugated horns: pyramidal at ν ≤ 3 GHz, conical at ν > 3 GHz, steerable between zenith (sky) and nadir (cold load) directions.
  • Site : 1.6 km from the Amundsen Scott Base at South Pole (2820 m altitude, atm pressure : 524 ± 2 Hg mm).
    Observation during local summer (December-January).
  • Participating institutions : Physics Dept – University of Milano – Italy - LBL – Berkeley (CA) - USA.

(see Antarctic Journal Review 1991, XXVI, 286 and Review 1993, XXVIII 306)


Radiometer properties

Frequency
(GHz)
Rx Type Antenna Beam
(HPBW)
Receiver
noise (K)
Cold Load
eff. temp.
(a)
0.82 Differential
(Dicke switch)
Heterodyne
Corrugated
pyramidal
horn
18° x 23° 55±2 9.69±0.42
(b)
1.47 Total power Corrugated
pyramidal
horn
30° x 27° 53.5±0.04 3.854±0.023
(c)
2.0 Total power Corrugated
pyramidal
horn
20° x 23° 118±4 3.855±0.040
(c)
2.5 Differential
(Dicke switch)
Heterodyne
Corrugated
pyramidal
horn
18° x 23° 31±2 11.84±0.55
(b)
3.8 Direct RF
gain total
power
Corrugated
conical
horn
16° 84±1 3.762±0.019
(c)
7.5 Direct RF
gain total
power
Corrugated
conical
horn
20°±2° 234±3 3.671±0.023
(c)
90(d) Differential
(Dicke switch)
Heterodyne
Corrugated
conical
horn
7.5° x 7.5° 1530±20 n/a

(a) Liquid Helium boiling temperature (3.842±0.002) K
(b) Coaxial dummy load
(c) Eccosorb absorber
(d) Used as atmospheric monitor in 1989 campaign


Components of the Antenna temperatures at the zenith (typical values)

Frequency
(GHz)
Antenna
Temperature
(K)
Atmosphere
Contribution
(K)
Ground
Contribution
(K)
Sun
Contribution
(K)
Galactic
Contribution
(K)
Blend of
Extragalactic
Radiosources
(K)
0.820 ref. 1 6.7±1.5 0.90±0.35 0.03±0.05 0.08±0.08 2.67±0.33 0.34±0.07
1.47 ref. 2 and 4 3.971±0.096 1.08±0.08 0.06±0.03 <0.01 0.82±0.19 Modelled inside the galactic component
2.0 ref. 3 and 4 3.95±0.05 1.07±0.07 0.05±0.04 <0.01 0.33±0.10 <0.03
2.5 ref. 1 3.73±0.15 1.155±0.300 0.03±0.05 0.000±0.005 0.118±0.025 0.016±0.005
3.8 ref. 5 3.653±0.008 1.109±0.004 0.006±0.008 <0.001 0.055±0.015 Modelled inside the galactic component
7.5 ref. 6 3.544±0.045 1.222±0.064 0.022±0.015 0.008±0.004 0.007±0.004 negligible
90 ref. 7 n/a 8.4 – 10.3 0.030 <0.001 <0.001 <0.001

Summary of results

Frequency (GHz) TCMB(a) (K) Laboratory
0.82 2.7±1.6 Milano, Ref.1
1.47 2.26±0.20 Berkeley Ref. 2 and 4
2.0 2.55±0.14 Berkeley Ref. 3 and 4
2.5 2.50±0.34 Milano Ref. 1
3.8 2.64±0.07 Berkeley Ref. 5
7.5 2.69±0.07 Berkeley Ref. 6

(a) Thermodynamic Temperature

(1) Sironi G. et al., 1991, ApJ 378, 550, ADS
(2) Bensadoun M. et al, 1993 ApJ 409,1, ADS
(3) Bersanelli M. et al., 1994, ApJ 424, 517, ADS
(4) Bersanelli M. et al. 1995, Astro. Lett. and Communications 32, 7, ADS
(5) De Amici G. et al., 1991, ApJ 381, 341, ADS
(6) Levin S. et al., 1992, ApJ 396, 3 ADS
(7) Bersanelli et al. 1995, ApJ 448, 8, ADS

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