High resolution magnetoresistive position sensor for the JWST

High resolution magnetoresistive position sensor for the JWST Tobias Junginger

Contents n The JWST ¨ Scientific goals ¨ Instruments n Nirspec (near infrared spectrograph) ¨ Microshutters ¨ The Grating wheel position sensor

The James Webb Space Telescope Infrared space telescope n scheduled for launch in 2013 n large mirror 6. 5 meters in diameter and a sunshield the size of a tennis court n Both will fold up in space n Orbit second sun-earth Langrangian point (1, 5 million kilometers from earth) n

Scientific goals Identify the first bright objects that formed in the early Universe n Assembly of Galaxies n The birth of stars and protoplanatary systems n study the physical and chemical properties of solar systems n

Instruments Type Wavelength Nircam imager with a large field of view and high angular resolution 0, 6 -5 μm Miri imager/spectrograph 5 -27 μm Nirspec Spectrograph 1 -5 μm

The Micro-shutters

The GWA (Grating Wheel Assembly)

The GWA Position Sensor

The GWA Position Sensor Requirements n n n n Can measure two dimensions Ready for using at a wide temperature range down to 4 K High sensitivity in movement direction (0, 3 arcsec) Low impact on the sensitivity by small deflections in Z axis Minimal power dissipation No forces in movement direction Compact size and very lightweight design (fieldplates + magnets < 10 g)

The GWA Position Sensor Breadboard Mount for the fieldplates Michelson Interferometer Light output to photo diode Mount for the magnets Piezoelectric positioning unit Light Input from Laser