High resolution magnetoresistive position sensor for the JWST

Tobias Junginger

Contents

The JWSTScientific goals Instruments

Nirspec (near infrared spectrograph)Microshutters The Grating wheel position sensor

The James Webb Space Telescope

Infrared space telescope scheduled for launch in 2013 large mirror 6.5 meters in diameter and a

sunshield the size of a tennis court Both will fold up in space Orbit second sun-earth Langrangian point

(1,5 million kilometers from earth)

Scientific goals

Identify the first bright objects that formed in the early Universe

Assembly of Galaxies The birth of stars and protoplanatary

systems study the physical and chemical properties

of solar systems

InstrumentsType 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)

41

1

23

3

RR

R

RR

RUU eB

The GWA Position Sensor

Can measure two dimensions Ready for using at a wide temperature range down to 4K 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 < 10g)

The GWA Position Sensor Requirements

The GWA Position Sensor Breadboard

Michelson Interferometer

Light Input from Laser

Light output to photo diode

Mount for the fieldplates

Mount for the magnets

Piezoelectric positioning unit