Timothy J. Pearson

Senior Research Scientist, Radio Astronomy

Cahill Center for Astronomy and Astrophysics
Mail Code 249-17
California Institute of Technology
Pasadena, California 91125

e-mail: tjp at astro.caltech.edu

Current projects

C-Band All Sky Survey (C-BASS)

I am the U.S. PI for C-BASS, an international project to image the whole sky at a wavelength of six centimeters (a frequency of 5 GHz), measuring both the brightness and the polarization of the sky, using telescopes at the Owens Valley Radio Observatory and in South Africa. The main uses of this survey will be to help us make better images of the cosmic microwave background (CMB) and to study diffuse radiation from our Galaxy.

Monitoring Fermi blazars

Using the 40 meter telescope at the Owens Valley Radio Observatory, we are making observations in support of the Fermi Gamma-ray Space Telescope, launched in 2008. The 40m telescope is monitoring more than 1800 blazars at 15 GHz about twice per week. We are commissioning a new receiver, KuPol, to monitor both total intensity and linear polarization.


RoboPol a specialized photopolarimeter mounted on the 1.3m telescope at the Skinakas Observatory in Crete. It is used for monitoring the optical linear polarization of more than 100 gamma-ray bright blazars, to probe the jet structure, composition, magnetic fields, and emission mechanisms. RoboPol is also used to map the magnetic field in interstellar clouds.


PASIPHAE (Polar-Areas Stellar-Imaging in Polarization High-Accuracy Experiment) aims to map, with unprecedented accuracy, the polarization of millions of stars at areas of the sky away from the Galactic plane, in both the Northern and the Southern hemispheres. Combined with stellar distances provided by ESA’s Gaia mission, this data will allow us, for the very first time, to construct a tomographic map of the Galactic magnetic field. Our ultimate goal: to clear the path towards the detection of the imprint of inflation on primordial light. The experiment is set to take place at the Skinakas Observatory, Crete, and the South African Astronomical Observatory in Sutherland, South Africa.

The CO Mapping Array Pathfinder (COMAP)

The CO Mapping Array Pathfinder (COMAP) will open a new window on both the Epoch of Reionization (EoR) and the epoch of galaxy assembly by using carbon monoxide (CO) lines to trace the distribution of star-forming galaxies in both epochs. Phase I of COMAP comprises a 10-m telescope, located at the Owens Valley Radio Observatory (OVRO), equipped with a 19-pixel spectrometer array that will map a total of 10 square degrees of sky in the frequency range 30-34 GHz, with spectral resolution R~800. This band will be sensitive to CO(1-0) in the redshift slice z = 2.4-2.8 and to CO(2-1) in the redshift slice z = 5.8-6.7.

Completed projects

The Planck satellite

The ESA/NASA Planck mission, launched on May 14, 2009, has measured the anistropies in the cosmic microwave background (CMB) over a broad range of radio and far-infrared wavelengths, and to an unprecedented accuracy. Planck addresses many fundamental questions about the early history and evolution of our universe. I was part of the U.S. Planck team, centered at the Jet Propulsion Laboratory.

The Cosmic Background Imager (CBI)

The Cosmic Background Imager (CBI) was a special-purpose radio telescope designed to study the cosmic microwave background radiation from the early universe. It was located at an altitude of 5080 m (16,700 feet) in the Chilean Andes at the Chajnantor Observatory.

The Q/U Imaging Experiment (QUIET)

The Q/U Imaging ExperimenT (QUIET) employed coherent receivers at 43 GHz and 94 GHz, operating on the Chajnantor plateau in the Atacama Desert in Chile (at the same site as CBI), to measure the anisotropy in the polarization of the cosmic microwave background. QUIET placed stringent upper limits on the B modes from primordial gravitational waves.

The Caltech Continuum Backend (CCB) for the NRAO Green Bank Telescope

The CCB is a sensitive, wideband backend designed for use with the GBT Ka-band (26-40 GHz) receiver. It provides a carefully optimized radio frequency (RF) detector circuits and the capability to beamswitch the receiver rapidly to suppress instrumental gain fluctuations. The backend digitizes and records the signals from the broad-band continuum detectors, generates phase-switching signals for the front-end, and demodulates the phase switch. It was designed and constructed at Caltech.



I am the author of the PGPLOT Graphics Subroutine Library, a Fortran- or C-callable, device-independent graphics package for making simple scientific graphs. It is intended for making graphical images of publication quality with minimum effort on the part of the user. Although it dates from the 1980s and has been largely superseded by more modern tools, it continues to be used by many astronomers and other scientists throughout the world.



Other activities

I am a member of the Editorial Board of Monthly Notices of the Royal Astronomical Society (MNRAS).

From 2011 to 2016 I was a member of the Committee on Radio Frequencies (CORF) of the National Academies of Sciences, Engineering, and Medicine. In November 2015 we published the Second Edition of the Handbook of Frequency Allocations and Spectrum Protection for Scientific Uses (DOI: 10.17226/21774). The handbook is available to download as a free PDF and can be purchased as a hard copy. Earlier I served on the Academies' Committee on Scientific Uses of the Radio Spectrum, which wrote a report on Spectrum Management for Science in the 21st Century (DOI: 10.17226/12800).

2020 November 20