1

IRMS Preliminary results - overview

Optimize Field lenses in collimator and camera to for 1.39m field curvature on NFIRAOS

Get good imaging performance

Get marginal spectroscopy performance.

Recommend collimator re-design to gain full performance.

2

Pupil

Simple modification of field lens in collimator to match pupil to cold stop

Looks ok, some colour but with just changing field stop this is what you get.

IRMS MOSFIRE

3

Imaging

Modify field flattener in camera and field lens in collimator

Slightly worse, but within the original MOSFIE req. of over 0.97-2.45 microns with no re-focus.

IRMS MOSFIRE

IRMS- Imaging Mode

Field RMS spot diameter

Radius arc-sec pixels

0 0.079 1.27

0.71' 0.095 1.52

1' 0.114 1.82

4

Spectroscopy

In addition to collimator field lens and camera field flattener modification, allow for small refocus between spectral bands to improve image quality but image quality still worse than MOSFIRE.

about 82% enslit energy for design residual, so loss of spectral resolution occurs.

IRMS MOSFIRE

*Slit defocus not considered in calculation, calculation for an ideal ‘spherical’ slit mask

5

Spectroscopy

MOSFIRE criteria was ensquared energy 80% within 2 pixels (pixels 18 microns ), and MOSFIRE achieve roughly 90% on average for design residual, leaving margin for manufacturing tolerances.Need collimator redesign for new field curvature to regain full performance. Likely able to do this with lenses constrained to original lens groups ( a quick optimization was done which suggested this should be possible)

*Slit defocus not considered in calculation, calculation for an ideal ‘spherical’ slit mask

IRMS - Spectroscopic Mode

Enslit Energy in 2x2 pixels

Y-band

J-band

H-band K-band

avg 84% 83% 81% 82%

max 100% 95% 97% 100%

min 71% 70% 50% 40%

Half-Width (in microns) for 80% enslit energy

Y-band

J-band

H-band K-band

avg 16 17 18 17

max 24 24 33 28

min 9 11 12 12

Width ( in pixels ) for 80% enslit energy

Y-band

J-band

H-band K-band

avg 1.8 1.8 2.0 1.9

max 2.6 2.6 3.6 3.1

min 1.0 1.2 1.3 1.3

6

CSU – Configurable Slit Unit

Sag along slit height at slit mask in Keck is 4.17mm, and a 3 tiered arrangement of knife edges was used, for TMT, sag is ~50% more ( 6.4mm) so 5 tiered would probably be used

Sag along dispersion with keck was ~1mm, (@1.5’ )no correction for curvature on Keck, for TMT, will have ~1.6mm (@0.5’), so will have slit ‘blur’ for IRMS ( geometric blur of 24mas or 127nm RMS WFE for +/-0.8mm defocus). Slit losses at field edges will be marginal .