Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published February 2010 | Published
Journal Article Open

Measuring Planck beams with planets


Aims. Accurate measurement of the cosmic microwave background (CMB) anisotropy requires precise knowledge of the instrument beam. We explore how well the Planck beams will be determined from observations of planets, developing techniques that are also appropriate for other experiments. Methods. We simulate planet observations with a Planck-like scanning strategy, telescope beams, noise, and detector properties. Then we employ both parametric and non-parametric techniques, reconstructing beams directly from the time-ordered data. With a faithful parameterization of the beam shape, we can constrain certain detector properties, such as the time constants of the detectors, to high precision. Alternatively, we decompose the beam using an orthogonal basis. For both techniques, we characterize the errors in the beam reconstruction with Monte Carlo realizations. For a simplified scanning strategy, we study the impact on estimation of the CMB power spectrum. Finally, we explore the consequences for measuring cosmological parameters, focusing on the spectral index of primordial scalar perturbations, n_s. Results. The quality of the power spectrum measurement will be significantly influenced by the optical modeling of the telescope. In our most conservative case, using no information about the optics except the measurement of planets, we find that a single transit of Jupiter across the focal plane will measure the beam window functions to better than 0.3% for the channels at 100–217 GHz that are the most sensitive to the CMB. Constraining the beam with optical modeling can lead to much higher quality reconstruction. Conclusions. Depending on the optical modeling, the beam errors may be a significant contribution to the measurement systematics for n_s.

Additional Information

© 2010 ESO. Received: 13 August 2009; accepted: 1 October 2009. We thank Andrea Catalano, Fabio Noviello, Maura Sandri, and Vladimir Yurchenko for providing realistic models of the Planck beams. We also thank Ludovic Montier for providing HFI non-linear response curves. Jean-Loup Puget, Jean-Michel Lamarre, Francois Bouchet, and many members of the Planck HFI and LFI Core teams gave helpful comments on this work. Chris Hirata and Hans Kristian Eriksen provided useful discussions on the process of beam reconstruction. Jan Tauber, Marco Bersanelli, and Warren Holmes gave very useful comments on drafts of this paper. Some results in this paper made use of the HEALPix software package (Górski et al. 2005). This research used resources of the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the US Department of Energy under Contract No. DE-AC02-05CH11231. This work was partially performed at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with NASA. K.M.H. receives support from JPL subcontract 1363745.

Attached Files

Published - Huffenberger2010p7479Astron_Astrophys.pdf


Files (502.6 kB)
Name Size Download all
502.6 kB Preview Download

Additional details

August 21, 2023
October 20, 2023