Table 1:

Design requirements of the Planck telescope reflectors.

Requirement	Primary reflector	Secondary reflector
Contour shape	off-axis ellipsoid	off-axis ellipsoid
Size (mm)	1555.98 1886.79	1050.96 1104.39
Radius of
Curvature (mm)	1440 0.25	-643.972 0.2
Conic constant	-0.86940 0.0003	-0.215424 0.0003
Stability of best fit ellipsoid
along each axis	0.1 mm
around each axis	0.1 mrad
Mechanical surface errors rms spec (goal)a
ring 1	7.5 m (5 m)
ring 2	12 m (8 m)
ring 3	20 m (13 m)
ring 4	33 m (22 m)
ring 5	50 m (33 m)
Surface roughness	m on scales <0.8 mm
Surface dimplingb	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
Temperatures
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.