Table 1:

Design requirements of the Planck telescope reflectors.

Primary reflector Secondary reflector
Contour shape off-axis ellipsoid off-axis ellipsoid
Size (mm) 1555.98 $\times $ 1886.79 1050.96 $\times $ 1104.39
Radius of    
Curvature (mm) 1440 $\pm $ 0.25 -643.972 $\pm $ 0.2
Conic constant -0.86940 $\pm $ 0.0003 -0.215424 $\pm $ 0.0003
Stability of best fit ellipsoid
along each axis $\pm $0.1 mm
around each axis $\pm $0.1 mrad

Mechanical surface errors rms spec (goal)a
ring 1 7.5 $\mu $m (5 $\mu $m)
ring 2 12 $\mu $m (8 $\mu $m)
ring 3 20 $\mu $m (13 $\mu $m)
ring 4 33 $\mu $m (22 $\mu $m)
ring 5 50 $\mu $m (33 $\mu $m)
Surface roughness $R_{\rm q}<0.2~\mu$m on scales <0.8 mm

Surface dimplingb
${\pm}2~\mu$m PTV
Reflector thickness 80 mm 65 mm
Reflectivity (25-1000 GHz)
Beginning of life >99.5 per cent
End of life >98.5 (goal 99.0)c
Mass 30.6 kg 14.5 kg
First eigenfrequency >120 Hz
Operational 45 K
Qualification 30-325 K

Notes. (a) Each ring is a concentric ellipse with the same ellipticity as the rim of the reflector, dividing the major axis in 5 equal pieces. Ring 1 is the innermost ring and ring 6 the outermost one.
(b) Defined in Sect. 3.1.
(c) At telescope level, the total emissivity is specified to be <6% (<3% goal), including also the effect of dust deposited on the reflectors.

Source LaTeX | All tables | In the text

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