Active Occulter

Roy Coulter

Institute for Astronomy/ UH

Design Parameters

• Near limb observations with minimal scattered light

• Moving edge centered on optical axis for good occulting

• Radial motion and rotating assembly• Must fit within 13mm field stop volume• Radial slit sensing with offset bias for limb

position adjustment• Motion requirement – a ‘few’ arc seconds,

+100 hz• Thermal control via heat pipe technology• Manual switching between observing modes

Active Occulter Concept

PI piezo electric bender, 60 V200+ Hz @ ±5 arc-sec

Thermal control:3mm heat pipes + copperstrap for occulting edge

Permanent drive system,insert bolted in place andstored on heat stop

Single photo sensor Rotation and limb position set visually by observer

Active Occulter Concept (cont.)

5mm x 5mm stopFOV = 128” x 128”

Irradiance = 2.5 W/mm2 .375 W/mm2 @ 85% refl.Thermal loads:Limb image - 24 W0.1 mm gap - 1 WOcculter - 0.7 W ave.Tracker slit - ~100 mW

max