|Requirement||Primary reflector||Secondary reflector|
|Contour shape||off-axis ellipsoid||off-axis ellipsoid|
|Size (mm)||1555.98 1886.79||1050.96 1104.39|
|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|
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.
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