SALT Technology Development Lisa Crause India-South Africa Astronomy Workshop – SAAO 6 August 2012

SALT Image Quality Large focus gradient, bifurcated stars seen in out of focus images, all seemed to be randomly variable as well Traced to problematic interface ring transmitting forces into the corrector & disrupting the 4 SAC mirrors

The SAC Fix Brought SAC down Replaced interface with a pair of collars Developed Clean Room Washed M5 & M3

SAC Alignment & Testing Optically aligned & tested the mirrors Checked system performance at angle & over temp range Re-installed SAC

On-Sky Testing Used a bare CCD on an XY stage to tile the focal plane & check the post-fix performance (also for direct comparison with images taken before the fix) SALTICAM was re-installed after its upgrade & it too produced beautiful, uniform images over the full 10 arcmin field

Inductive Edge Sensors Capacitive edge sensors were unsuitable due to their sensitivity to humidity & dust Capacitive edge sensors were unsuitable due to their sensitivity to humidity & dust Contract signed with Fogale Nanotech in June 2012 for their inductive edge sensors Contract signed with Fogale Nanotech in June 2012 for their inductive edge sensors Excellent results obtained: insensitive to humidity & consistent behaviour with temperature changes Excellent results obtained: insensitive to humidity & consistent behaviour with temperature changes Maximum deviation of 30 nm over 5 days Maximum deviation of 30 nm over 5 days To be installed in situ & phased in, starting with the central 7 segments To be installed in situ & phased in, starting with the central 7 segments

Inductive Edge Sensors 12 sensors/segment, each mounted to a Clearceram L-bracket for a 3.5 mm gap 12 sensors/segment, each mounted to a Clearceram L-bracket for a 3.5 mm gap Primary mirror alignment should hold for at least 5 days, longer if ΔT <20 C Primary mirror alignment should hold for at least 5 days, longer if ΔT <20 C Expect a substantial increase in observing efficiency due to the alignment time saved & better overall IQ Expect a substantial increase in observing efficiency due to the alignment time saved & better overall IQ Full installation to take ~2 years Full installation to take ~2 years Pathfinder for ELTs Pathfinder for ELTs

RSS: Our Insane Spectrograph

Robert Stobie Spectrograph (RSS) Various problems with optics, mostly due to troublesome lens fluid Various problems with optics, mostly due to troublesome lens fluid Major overhaul of all mechanisms by SALT while the optics were being repaired Major overhaul of all mechanisms by SALT while the optics were being repaired Latest throughput issue traced to the collimator optics Latest throughput issue traced to the collimator optics Keen to tackle the repair/replacement ourselves this time Keen to tackle the repair/replacement ourselves this time

RSS Near Infrared Arm Being built by the University of Wisconsin Being built by the University of Wisconsin NIR to have most of RSS-Vis functionality, but will operate from 0.8 to 1.7 microns NIR to have most of RSS-Vis functionality, but will operate from 0.8 to 1.7 microns Semi-warm design is an economical way to extend optical instruments into the near infrared Semi-warm design is an economical way to extend optical instruments into the near infrared Pre-dewar part -40 C & & 120 K Pre-dewar part -40 C & & 120 K

RSS Near Infrared Arm RSS spectroscopy from the atmospheric cut-off (320 nm) to the H-band, in 1 shot! RSS spectroscopy from the atmospheric cut-off (320 nm) to the H-band, in 1 shot! Tracker weight budget is already being exceeded so will need to upgrade its load capacity to make provision for NIR Tracker weight budget is already being exceeded so will need to upgrade its load capacity to make provision for NIR Tracker upgrade project is funded & will be carried out by SALT & SAAO staff Tracker upgrade project is funded & will be carried out by SALT & SAAO staff Timescale: late 2014? Timescale: late 2014?

High Resolution Spectrograph SALT HRS: fibre-fed echelle spectrograph under construction at Durham’s Centre for Advanced Instrumentation SALT HRS: fibre-fed echelle spectrograph under construction at Durham’s Centre for Advanced Instrumentation Commissioning due to start towards the end of this year Commissioning due to start towards the end of this year Blue & red beams to cover nm & nm Blue & red beams to cover nm & nm λ/Δλ from to via 4 different modes λ/Δλ from to via 4 different modes

High Resolution Spectrograph Pair of object & sky fibres for each mode Pair of object & sky fibres for each mode Optics to be housed in a vacuum tank & the whole instrument will be sealed in a thermally stabilised enclosure in the spectrometer room below the telescope Optics to be housed in a vacuum tank & the whole instrument will be sealed in a thermally stabilised enclosure in the spectrometer room below the telescope Payload Fibre Instrument Feed for HRS designed & built at the SAAO Payload Fibre Instrument Feed for HRS designed & built at the SAAO

Conclusion We have grown the most from the biggest challenges SALT’s presented so far & we have much more to learn!