Presentation on theme: "“Riding the Hub”: The MMT Adaptive Secondary Douglas Miller University of Arizona The AO System Current Performance of the MMT AO System Ongoing Development."— Presentation transcript:
“Riding the Hub”: The MMT Adaptive Secondary Douglas Miller University of Arizona The AO System Current Performance of the MMT AO System Ongoing Development Science Instruments
Searching for Exrasolar Systems The MMT AO NGS Team Vidhya Vaitheeswaran Software Engineer Matt Kenworthy Instrument Scientist Doug Miller Manager Richard Sosa Technician Guido Brusa Mirror Scientist Manny Montoya Technician Phil Hinz PI Thomas Stalcup AO Scientist
IR observations are often limited by background light from the telescope optics. Typical AO systems have background emission of ~20% A deformable secondary system can have an emissivity of ~5-7%. This can translate into 3-4x speed improvement in observations. Advantages of a Deformable Secondary
Thermally Clean Pupil Images taken at 11 microns of the MMT adaptive secondary. Emissivity of the telescope was measured at 7%. Emission from sky Blackbody emission From central hole in primary Emission from sky and telescope Camera with cold pupil stop misaligned. Camera with cold pupil stop aligned.
The MMT AO System 1.Measure aberrations due to the atmosphere with WFS Camera 2.Calculate secondary shape needed to correct measured aberration 3.Apply shape to the deformable secondary Loop run at 550 Hz WFS Camera Reconstructor Computer Adaptive Secondary Mirror 12x12 Shack-Hartmann Sensor Correct 56 modes Send new position commands to the 336 actuators
Current Performance We typically achieve 20-30% Strehl in H band on bright stars, measured with an engineering camera installed in the AO top box. Limiting magnitude is V~14.5 Curves are loop speeds of 550, 275, 137 and 68 Hz
Performance -vs- Mode Above 60 modes we do not see improved Strehl Need an improved interaction matrix “Reconstructor on the sky” technique currently being developed (Brusa et al. Glasgow SPIE 2004) Expected Strehl
First light obtained November 2002 Science observations interspersed starting in Jan Runs were scheduled once per trimester through Two runs per trimester since January 2005.
Ongoing Development Transition of AO System to Facility Instrument Calibration Stand PC-based Reconstructor Computer Rayleigh Laser Guide Stars (Stalcup, Baranec and Lloyd- Hart talks later today)
Facility Instrument MMT staff will perform normal NGS AO operation Installation of DM and NGS topbox Operation of AO system for observers Routine system maintenance Software maintenance Transition complete by early 2007 (hopefully) AO Team will continue development and improvements
PC Reconstructor Computer Current Reconstructor is a VME system written in Assembler (1990s technology) Replacement is a dual processor PC-based system written in C under standard Linux. Latencies of ~200 usec are achievable with straightforward implementation. Much more flexible. Lab tests are complete. On-Sky test will take place Sunday night.
PC Reconstructor Computer Speed up AO loop (~1 kHz) Input accelerometer information into the AO loop to compensate for the 20 Hz vibration Chop with AO secondary Test new algorithms
Calibration Stand The DM is convex! Test stand uses a Hindle optical test to measure the surface shape of the DM All lenses in the test stand are spherical Allow us to calibrate the flat position The current gap (40 microns) A new gap (100 microns) needed for chopping with the DM Deformable Mirror Spherical Calibration Mirror Interferometer
MMTAO Science Cameras ARIES: m imager MIRAC-BLINC: 7-25 m imager and nuller Clio: 3-5 m imager Jupiter at 4.8 m Protoplanetary Nebula at 9.8 and 11.7 m IC 2149 at 2.1 m Don McCarthySuresh SivinandamBill Hoffmann Craig KulesaAri HeinzePhil Hinz Phil Hinz
New and Improved Instruments Purple: “Old” micron Imager Green: “New” micron echelle spectrometer Don McCarthy and Craig Kulusa New MIRAC IV 256x256 array (old 128x128) Lower dark current 8-13 micron grism spectrometer Phil Hinz and Bill Hoffman Phil
Hub Vibrations June 2005 elevation 43 degrees wind velocity 10 mph wind direction 241 degrees azimuth 124 degrees => Out of the wind June 2006 elevation 60 wind velocity 27 mph wind direction 45 degrees azimuth 315 degrees => Out of the wind
See John Codona’s talk: ?? PSF sidelobes are over 7 magnitudes fainter at 3 /D away. The pattern is stable and can be reliably subtracted off to reach the limit of the sky background. PSF suppression is easier at M band where Strehls are typically 90% John Codona and Matt Kenworthy Diffraction Suppression via Phase Manipulation PSF with no Phase Manipulation