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Cosmic Background Explorer

The Cosmic Background Explorer (COBE /ˈkoʊbi/ KOH-bee), also referred to as Explorer 66, was a NASA satellite dedicated to cosmology, which operated from 1989 to 1993. Its goals were to investigate the cosmic microwave background radiation (CMB or CMBR) of the universe and provide measurements that would help shape our understanding of the cosmos.

Names

Explorer 66

Cosmic microwave background Astronomy

NASA

1989-089A

20322

lambda.gsfc.nasa.gov/product/cobe

6 months (planned)
4 years, 1 month and 4 days (achieved)

Explorer LXVI

Cosmic Background Explorer

COBE

Goddard Space Flight Center

2,206 kg (4,863 lb) [1]

1,408 kg (3,104 lb) [2]

5.49 × 2.44 m (18.0 × 8.0 ft)

750 watts

18 November 1989, 14:34 UTC

Delta 5920-8 (Delta 189)

Vandenberg, SLC-2W

Douglas Aircraft Company

18 November 1989

23 December 1993

Geocentric orbit[3]

Sun-synchronous orbit

900 km (560 mi)

900 km (560 mi)

99.00°

103.00 minutes

COBE's measurements provided two key pieces of evidence that supported the Big Bang theory of the universe: that the CMB has a near-perfect black-body spectrum, and that it has very faint anisotropies. Two of COBE's principal investigators, George F. Smoot and John C. Mather, received the Nobel Prize in Physics in 2006 for their work on the project. According to the Nobel Prize committee, "the COBE project can also be regarded as the starting point for cosmology as a precision science".[4]


COBE was the second cosmic microwave background satellite, following RELIKT-1, and was followed by two more advanced spacecraft: the Wilkinson Microwave Anisotropy Probe (WMAP) operated from 2001 to 2010 and the Planck spacecraft from 2009 to 2013.

Mission[edit]

The purpose of the Cosmic Background Explorer (COBE) mission was to take precise measurements of the diffuse radiation between 1 micrometre and 1 cm (0.39 in) over the whole celestial sphere. The following quantities were measured: (1) the spectrum of the 3 K radiation over the range 100 micrometres to 1 cm (0.39 in) (2) the anisotropy of this radiation from 3 to 10 mm (0.39 in); and, (3) the spectrum and angular distribution of diffuse infrared background radiation at wavelengths from 1 to 300 micrometres.[5]

First, in 1981, two teams of astronomers, one led by David Wilkinson of and the other by Francesco Melchiorri of the University of Florence, simultaneously announced that they detected a quadrupole distribution of CMB using balloon-borne instruments. This finding would have been the detection of the black-body distribution of CMB that FIRAS on COBE was to measure. In particular, the Florence group claimed a detection of intermediate angular scale anisotropies at the level 100 microkelvins[14] in agreement with later measurements made by the BOOMERanG experiment. However, a number of other experiments attempted to duplicate their results and were unable to do so.[6]

Princeton University

Second, in 1987 a Japanese-American team led by and Paul Richards of University of California, Berkeley and Toshio Matsumoto of Nagoya University made an announcement that CMB was not that of a true black body.[15] In a sounding rocket experiment, they detected an excess brightness at 0.5 and 0.7 mm (0.028 in) wavelengths.

Andrew E. Lange

a minor planet named after the experiment.

9997 COBE

S150 Galactic X-Ray Mapping

Wilkinson Microwave Anisotropy Probe

WMAP

Arny, Thomas T. (2002). Explorations: An Introduction to Astronomy (3rd ed.). Dubuque, Iowa: McGraw-Hill.  978-0-07-241593-3.

ISBN

Liddle, A. R.; Lyth, D. H. (1993). "The Cold Dark Matter Density Perturbation". Physics Report — Review Section of Physics Letters. 231 (1–2): 1–105. :astro-ph/9303019. Bibcode:1993PhR...231....1L. doi:10.1016/0370-1573(93)90114-S. S2CID 119084975.

arXiv

Odenwald, S.; J. Newmark & G. Smoot (1998). "A study of external galaxies detected by the COBE Diffuse Infrared Background Experiment". Astrophysical Journal. 500 (2): 554–568. :astro-ph/9610238. Bibcode:1998ApJ...500..554O. doi:10.1086/305737. S2CID 18799050.

arXiv

Mather, John C.; Boslough, John (1996). . New York: BasicBooks. ISBN 0-465-01575-1.

The Very First Light: The True Inside Story of the Scientific Journey Back to the Dawn of the Universe

Smoot, George; Davidson, Keay (1993). Wrinkles in Time. New York: W. Morrow.  0-688-12330-9.

ISBN

WMAP

NASA's website on COBE

NASA informational video prior to COBE launch

by NASA's Solar System Exploration

COBE Mission Profile

showing the 600 km/s motion of the Earth relative to the cosmic background radiation

APOD picture of the COBE dipole

article from Scholarpedia

Cosmic Background Explorer