Beams LFI

Wish List

list of information to be inserted in the explanatory supplements

- Description of LFI FOV.

- Description of various telescope models as reported in the beam paper.

- Format of beam data

- Definition of various coordinate frames for beams

Overview

LFI is observing the sky with 11 pairs of beams associated with the 22 pseudo-correlation radiometers. Each beam of the radiometer pair (Radiometer Chain Assembly - RCA) is named as LFIXXM or LFIXXS. XX is the RCA number ranging from 18 to 28; M and S are the two polarization namely main-arm and side-arm of the Orthomode transduccers #darcangelo2009b.

Figure 1. A sketch of the Planck LFI field of view in the (u,v) plane is shown. The polarization direction on the sky are highlighted by the colored arrows. The M-polarization is shown in green and the S-polarization in red. Beam shapes are shown for completness and they are not representative of flight beams.

For the beam we consider these three regions:

main beam

is the portion of the pattern that extends up to 1.9, 1.3, and 0.9 degrees from the beam center at 30, 44, and 70 GHz, respectively.

near sidelobes

is the pattern contained between the main beam angular limit and 5 degrees from the beam center (this is often called intermediate beam).

far sidelobes

is the pattern at angular regions more than 5 degrees from the beam center.

Main Beams and Focal Plane calibration

Describe the RIMO content (beam section)

The beam solid angle, Ω[math]_A [/math], of an antenna is given by

[math] Ω_A \; = \; \int_{4π} \; P_n(θ,φ) \; dΩ \; = \; \int^{2π}_0 \int^π_0 \; P_n(θ,φ) \; sinθ \; dθ \; dφ [/math]

\Omega where [math]P_n (θ, φ) \; [/math] is the normalized power pattern and the field computed by GRASP is normalised to a total power of 4π watt, i.e.,

[math] \int^{2π}_0 \int^π_0 \; P_n(θ,φ) \; sinθ \; dθ \; dφ \; = \; 4π [/math]

Effective beams

TBW

Window Functions

TBW

Sidelobes

TBW

References

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1. References

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