Robo-AO Overview: System, capabilities, performance

Robo-AO Overview:System, capabilities, performance

Christoph Baranec (PI)

Why Robo-AO?

Robotic – high efficiency observing

Laser Guide Star – high sky coverage

Adaptive Optics – spatial resolution set by D

Small Telescopes – lots of available time

Robo-AO at the P60

Robotic

Reed Riddle (software lead) to fill in details

following this presentation…

Laser guide star

• Rayleigh LGS (e.g. Starfire, Mt. Wilson, MMT, WHT, SOAR, LBT?)

– Range gated – 650 m at 10 km – mV~9

– On/off operation

– More robust operation in presence of clouds/haze

• Waived by FAA – no human spotters required

• Interface with USSTRATCOM– Send them target list 3-4 days prior to lasing

– Will receive list of ‘open windows’ for each target

AO system

• High order wavefront will be measured by laser and corrected by deformable mirror

• Stellar image motion captured by one of the science cameras and used to drive tip/tilt corrector

• Single atmospheric dispersion corrector for both science instruments (not UV)

Visible science instrument

• Andor iXonEM+ DU-888

• Electron Multiplying CCD

• 1024 x 1024 pixels

• 44” x 44” square FoV• 0.043” pixels (Nyquist at λ = 620 nm)

• Full frame rate: 9 Hz

• Sub frame rate: ~200 Hz

Baseline NIR camera: InGaAs

• InGaAs – (Xenics: Xeva)– Delivery in 8 weeks from order– 0.9-1.7 μm sensitivity– 180 e- read noise– 7000 e-/s dark current– ~200k e- full well– 320 x 256 pixels (0.062”/pixel Nyquist λ = 900 nm)– ~20 x 16 arc sec field

Xeva-1.7-320

Ideal (future?) NIR camera

• HgCdTe – (Teledyne: H2RG)+ 2’ FoV, 0.062” pixels (Nyquist at λ = 900 nm)

+ Excellent noise

+ Flexible readout – integrating while T/T guiding

- Cost – no $$ yet…- Development time

Likely initial observing modes

• Infrared Science:– Tip/tilt sensing with visible, integrate on IR

camera

• Visible Science:– Fast readout of visible camera - Lucky

imaging/post facto shift and add

• H2RG will give additional capability

AO capabilities – quick answer

• ~Diffraction-limited resolution visible

• 0.5+ Strehl in the NIR

• General imaging

Range of: filters, exposure times, camera setup

Error budget

Assuming mV=17 T/T star

Performance – H-Strehl

• mV < 15 dominated seeing, HO errors. mV > 19 dominated T/T errors• Greater than 40% Strehl with mV = 19 T/T in median conditions

• FWHM at H < 0.26” in even 75% worst seeing conditions

*At Zenith