POLAR Time Line
- 1993
With advice from Dave Wilkinson and support of some notable theorists,
Peter Timbie and grad students Khurram Farooqui and Grant Wilson propose to the NSF to build a correlation polarimeter to search for CMB polarization at their institution of Brown University. The hope is to improve existing upper limits by at least a factor of 10.
- 1993-1995
Brendan Crill, Brian Keating and others play around with a simple correlation polarimeter.
Brendan Crill writes his senior thesis on the topic. A simplified
radiometer is designed using only a feed-horn, OMT and 2 HEMTS (no magic tee).
Senior theses also came from Melvin Phua, who built the earliest
prototype, and Julia Steinberger, who modelled the effects of
galactic foreground contamination.
- 1995-1996
Brian Keating continues polarization work on both theoretical and experimental fronts, for his graduate work at Brown University under Peter Timbie.
His work with Alexander Polnarev explores the effects of recombination and reionization on the polarization characteristics of the CMB.
Joshua Gundersen begins working on the project as well, as a post-doctoral researcher, and designs the Ka-band feed horn.
- 1997
The Brown group moves to the University of Wisconsin-Madison, in search
of better cheese, beer and ice cream.
Brian Keating shifts the POLAR project into high gear, and soon many important
pieces of hardware are constructed, such as the dewar and feed horn. Preliminary radiometer testing and calibration is performed.
Chris O'Dell joins the group as a graduate student, and Nathan Stebor joins
as an undergraduate. Lucio Piccirillo comes to Wisconsin from the Bartol Research
Institute, and also begins pitching in.
- 1998-1999
The long haul of constructing POLAR continues, and the group learns many important lessons in the design and construction of a microwave polarimeter.
At long last, POLAR appears ready for operation, and is deployed to its new home
in Pine Bluff, Wisconsin, and the Pine Bluff Observatory (PBO). PBO is a small astronomical installation run by the University of Wisconsin-Madison Astronomy Department. Many important systematic effects are noticed, and many months are
spent debugging the instrument. First light is roughly in December, 1998.
Also in 1999, Nate Stebor writes his undergraduate thesis on CMB polarization, and Brian Keating earns his doctorate for work on POLAR and CMB polarization theory.
- March 2000
After considerable debugging, POLAR is deemed ready for concerted observations,
although still only possessing a single frequency band of 26-36 GHz.
After a mere three months of observations through the unstable spring of 2000, POLAR is shut down for the summer. The decision is made to mate the radiometer
to the newly constructed COMPASS telescope, possessing a 2.6 meter primary dish
that allows exploration of CMB polarization at smaller angular scales where the
signal is thought to be higher. The spring of 2000 was thus POLAR's only season of large angular-scale observations. COMPASS takes its first data in the following year.
- June 2000-July 2001
Intensive analysis efforts are performed by Brian Keating and Chris O'Dell,
although Dr. Keating is performing this work as a post-doc at Caltech in his spare time. The analysis is slow going, and a nasty offset is discovered in the data.
Two analysis "ringers" are brought in from the outside, Max Tegmark and Angelica de Oliveira-Costa. The work accelerates. After discovering how to effectively treat the offset, a new upper limit on large angular scale polarization is set, roughly at the level of 10 µK.