ABOUT LAMBDA

White Mountain Collaboration Data Products at LAMBDA

The White Mountain Collaboration made measurements of the CMB temperature at five frequencies from 2.5 to 90 GHz.


white mnt image

White Mountain Observations

  • Measurements of the absolute difference ΔT between the antenna temperatures of the sky at the zenith (antenna upward) and a black body at Liquid Helium temperature (antenna downward) at five frequencies: 2.5 , 4.75, 10, 33 and 90 GHz.
  • Heterodyne radiometers can be moved along a rail and set above a black body source (optically thick Eccosorb target covered by Liquid Helium at ambient pressure in a 70 cm diameter dewar)
  • Geometrically scaled, corrugated horns tiltable between zenith (sky) and nadir (cold load) directions. When looking down the horn circular mouth can be attached to the dewar mouth
  • Atmospheric and galactic foregrounds measured by zenith and drift scans
  • A separate 9.4 GHz radiometer entirely dedicated to simultaneous studies of the atmospheric emission
  • Observations from University of California White Mt. Research Station (3800 m altitude)
  • Participating institutions

    2.5 GHz : Physics Dept. – University of Milano – Italy
    4.75 GHz : Istituto TESRE – CNR – Bologna – Italy
    9.4 GHz : Haverford College - Haverford (Pa) – USA
    10 GHz : LBL – Berkeley (Ca) – USA
    33 GHz : LBL – Berkeley (Ca) – USA
    90 GHz : LBL – Berkeley (Ca) – USA
    ---- : Physics Dept. – University of Padova - Italy

(see Smoot, G.F. et al. 1983, Phys.Rev.Lett. 51, 1099 ADS, and Smoot, G.F. et al. 1985, Ap.J., 291, L23 ADS)


Radiometer properties

Frequency
(GHz)
System bandwidth
(GHz)
Antenna Half-power beam
width (deg)
System noise
(K/Hz1/2)
Laboratory
(Ref)
2.5 0.160 12.5 0.2 Milano (1)
4.75 0.160 12.5 0.1 Bologna (2)
9.4(*) 1 12.6 0.1 Haverford (3,4)
10.0 0.910 12.5 0.05 Berkeley (5)
33.0 1 7.5 0.08 Berkeley (6)
90.0 2 7.5 0.1 Berkeley (7)

(*) entirely dedicated to study the atmospheric emission

(1) Sironi G. and Bonelli G., 1986, ApJ, 311, 418
(2) Mandolesi N. et al 1986, Ap.J. 310, 561
(3) Partridge R.B. et al., 1984, Phys.Rev. D, 29, 2683
(4) Danese L. and Partridge R.B., 1989, ApJ 342, 604
(5) Kogut A. et al., 1988, ApJ, 325, 1
(6) De Amici G. et al., 1985, ApJ , 298, 210
(7) Witebsky C. et al., 1986, ApJ, 310, 145


Antenna Temperature of Cold Load and its components

Frequency
(GHz)
Eccosorb (o)
(mK)
Windows + gas
(mK)
Dewar walls
(mK)
Reflected signals
(mK)
Total
(mK)
2.5 3716±4 4±2 1209±210 (a)
1458±120 (b)
70±25 (a)
340±50 (b)
4999±212 (a)
5518±130 (b)
4.75 3663±4 5±2 8±7 40±30 (a)
6±4 (b)
3716±31 (a)
3682±10 (b)
10 3541±4 5±2 9±5 7±4 3562±10
33 3039±4 4±2 5±5 20±6 3068±9
90 2020±4 18±3 10±10 35±35 2083±37

(o) Eccosorb/Liquid Helium physical temperature 3776±4 mK,
(a) 1982 value,
(b) 1983 value


Measurements (representative values)

Frequency
(GHz)
TA,load
(mK)
ΔT
(sky-load)
(mK)
ΔToffset
(mK)
Tground
(mK)
Tatmosphere
(mK)
TGalaxy
(mK)
Year
2.5 4999±212
5518±130
-1401±100
-1557±58
(a)
(a)
12±10
6±10
950±50
950±50
148±30
200±30
1982
1983
4.75 3716±31
3682±10
940±80
-45±13
960±160
0±20
30±10
20±20
1000±100
997±70
40±30
35±25
1982
1983
9.4 --
--
--
--
--
--
30±10
8±5
1030±30
103±30
<30±10
<10±5
1982
1983
10 3562±10 57±4
43±7
0±40
0±30
0±3
0±3
930±160
1200±130
3±3
4±2
1982
1983
33 3068±9 3860±40
3540±30
-100±50
-30±30
1±1
1±1
4850±140
4530±90
1±1
1±1
1982
1983
90 2083±17 11340±60
8780±37
0±300
10±9
1±1
1±1
12600±590
9870±90
0±1
0±1
1982
1983

(a)included in TA,load


Final results

Frequency
(GHz)
Number of
observations
CMB antenna
temperature
(K)
CMB thermodynamic
temperature
(K)
Combined 1982
and 1983 results
(K)
2.5 6
18
2.48±0.14
2.81±0.07
2.54±0.14
2.87±0.07
2.79±0.15
Ref.1
4.75 5
38
2.63±0.21
2.59±0.08
2.73±0.22
2.70±0.07
2.70±0.07
Ref.2
10 82
59
2.43±0.12
2.40±0.14
2.66±0.12
2.63±0.14
2.65±0.09
Ref.5
33 21
32
2.10±0.20
2.09±0.13
2.82±0.21
2.81±0.14
2.81±0.12
Ref.6
90 29
49
1.00±0.57
0.99±0.09
2.58±0.79
2.57±0.12
2.57±0.12
Ref.7

For Columns 2-4, the first row is for 1982 data and the second row is for 1983 data.

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