There is a long history of research on the CMB at Princeton starting with Bob Dicke, Jim Peebles, Peter Roll, and Dave Wilkinson on the spectrum and Partridge and Wilkinson on the first targeted search for the anisotropy. Over the years, members of the Gravity Group have played major rolls in many of the leading CMB measurements including COBE (Dave Wilkinson), Boomerang (Bill Jones), and Planck (Bill Jones and Jo Dunkley) in addition to the following that I've had a major role in, as always working with colleagues and students. A relatively up-to-date plot of power spectra from multiple groups is here.

The Simons Observatory (SO). We built one of the Small Aperture Telescopes (SAT) that will search for primordial gravitational waves ("B-modes"). It was shipped to Chile in Aug 2023. Our SAT observes at 90 and 150 GHz through a cooled spinning half wave plate. At the heart of the receiver are seven focal plane modules. Each module has 430 feeds with a total of 1720 optical detectors. There are 7 modules cooled to below 100 mK.

The Atacama B-mode Search (ABS) was aimed at measuring the gravitational radiation left over from the Big Bang. Complementing ACT/ACTPol, it observed with an angular resolution of 0.5 degrees. ABS demonstrated the use of a continuously spinning HWP to "see through" atmospheric fluctuations and demonstrated NIST's polarization sensitive detectors. The data are available through Lambda.

The Atacama Cosmology Telescope (ACT/ACTPol/Advanced ACTPol). ACT was a 6 m telescope at the same site Toco and MINT. It stopped operations in 2022 to make way, in part, for SO.  The three generations of camera have led to every increasing sensitivity. Some of the highlights include high-ell measurements with greater sensitivity than Planck, first measurement of intrinsic CMB lensing, first measurement of the kSZ effect, measurement of more SZ cluster than all previous surveys combined (as of 2023), discovery of the most massive and X-ray luminous high redshift object known, dubbed "El Gordo." ACT is gearing up to make observation of the polarized CMB. The data are available through Lambda.

The Wilkinson Microwave Anisotropy Probe was a partnership between Princeton and NASA/GSFC with collaborators at Chicago, UBC, Brown, and UCLA. It produced the observational evidence for all elements of the current standard model of cosmology. Much of the instrument was designed and built at Princeton and the Princeton team played a large role in the data analysis. The satellite is named in honor of Prof. Wilkinson, a leader in experimental cosmology and a faculty member in the Physics Department until his death in 2002. The data are available through Lambda. The Princeton group's first proposal is here.

MINT, This was a four element compact heterogeneous 150 GHz interferometer based on the Kerr-Pan SIS mixers. It observed from Chile.

Toco. We put the QMAP balloon gondola on a Nike-AJAX trailer and converted the LHe-cooled cryostat to a GM cooler and took it to Chile. We learned about the site from Tony Readhead through Tom Herbig, a Princeton postdoc. Tony would go on to situate CBI there. This was the first CMB experiment in the altiplano. At 17,000 feet the sky was transparent enough for our 150 GHz mixers to work. We measured the position of the first peak which, when combined with LSS and H0, showed the universe is geometrically flat. See also a full description and the location of the first peak, and a mention in the NYT.

QMAP. To map the high-ell fall from the first CMB peak we saw with SK, we needed greater resolution. We tried this with SIS mixers, along with HEMTs, on a balloon as the Saskatoon atmosphere was too opaque at 150 GHz. We couldn't control the mixers well enough to get reliable data but made high S/N maps of the CMB and independently confirmed the SK results.  The data are available through Lambda.

Saskatoon (SK). This was a series of experiments done over three seasons from Saskatoon, SK at a site pioneered by Norm Jarosik, Peter Timbie, and Dave Wilkinson. The instrument was based on HEMT amplifiers designed by NRAO's Marian Pospieszalski. Many of the techniques we learned informed the design of WMAP. An independent analysis was done by Dick Bond and colleagues.

FIRS was my thesis experiment under the mentorship of Stephan Meyer. It had three flights, October 1988, October 1989, and May 1990. It used bolometers operating at 240 mK to observe at 168, 260, 474, and 675 GHz. In the first flight we showed that dust emission does not have a  \nu² emissivity, which is expected when the grain is much smaller than the wavelength.  The second flight confirmed the COBE/DMR discovery of the anisotropy. An independent analysis was done by Dick Bond.

I've also participated in MSAM, TopHat, and IAC/Bartol.