1 / 17

Palomar Tomograph

Palomar Tomograph. V. Velur 1 , B. Platt 2 , M. Britton 1, R. Dekany 1 1 Caltech Optical Observatories, California Institute of Technology 2 Interferometry and Large Optics, Jet Propulsion Laboratory. Introduction:.

fordon
Télécharger la présentation

Palomar Tomograph

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Palomar Tomograph V. Velur1, B. Platt2, M. Britton1, R. Dekany1 1 Caltech Optical Observatories, California Institute of Technology 2 Interferometry and Large Optics, Jet Propulsion Laboratory

  2. Introduction: • Palomar Tomograph (PT) is a compact multiple guide star wavefront sensor system that can be used to confirm tomographic wavefront sensing algorithms • 4 Hartmann Shack low noise CCD based wavefront sensors (three 16x16 sub-apertures, one 3x3 sub-aperture) excluding the PALAO active high order wavefront sensor. • PALAO also has a dedicated 16x16 SHWFS that feeds data to a real time computer

  3. Principle of operation of the MGSU

  4. The “bird-of-prey” (BoP) Focusing lens Field lens Lenslet array collimator Penta prism

  5. A single Hartmann Shack WFS channel Scimeasure’s Little Joe Camera with CCD39 chip XY stage and sleeve

  6. The MGSU/ tomograph assembly:

  7. Spots on the focal plane array:(4x4 pixels/sub-ap., 16x16 spots aligned FPA with >0.1 pixel RMS offset) http://eraserhead.caltech.edu/palomar/MGSU/lab_data/lab.html

  8. Salient features of the PT • The system can be used with the PALAO tip-tilt and high order AO loop closed or with both or either being open using low noise CCD based SHWFS. We can record data 50-2000 Hz. • 3.2 Terabytes of total data storage space with two SCSI Ultra 160/RAID on two striped RAID disks that can record data at 2000 Hz from 4 cameras acquiring 14 bit data from 64x64 pixels. Data is compressed using custom lossless compression format and can be extracted to fits image with time tags. • BoPs can acquire guide stars over a continuous 90 arc-sec. diameter field. The optical train is designed to be telecentric over this range so that pupil shear is >1.2% (2 microns) at the lenslet pupil (size=1.728 mm) over the FoV. • Linux based camera control interface and motion control. All control schemes are written in C/C++. All control code is checked into CVS repository with version control. Documentation and user manuals that are available via. www. ssh-agent, ssh-add help us to talk to all cameras from one shell. • A 5 ft high commercial 19” rack is populated with a KVM, a 1U rack mounted monitor, 10 Mbps network link, a network power switch etc for ease of operation. Newport’s latest LTA series high speed actuators used to pick off guide stars with one motor controller controlling all 8 axes. • A custom timing module can be used to trigger as many as 6 cameras to run at integral frame rates in a synchronous fashion. This can be used when guide stars are of different brightness or to study variations in time of the wavefront sensed from each pick off arm.

  9. Performance • We have successfully locked on a Tempel 1 (18 magnitude comet (extended object)) at 2.0 air-masses with the 3x3 SHWFS built in the same fashion. • PALAO HOWFS performance Bright guide star Strehls as high as 80% at 2.2 mm Maximum frame rate 2000Hz (<7e- read noise) Limiting magnitude ~13.5mV, 10-15% Strehl at 2.2 mm Read noise 3.5e- at < 500 fps Mean Wavefront 165 nm • Typical read noise for e2V’s CCD 39 chips is 3e-s at 500 Hz and 7e-s at 2000 Hz • In parallel - Matthew’s work on modeling anisoplatism

  10. Combined measurement error and fitting error vs. sub-ap. Diameter, for ro(0.5 micron) =0.15 m, 3e-s of read noise and system transmission=0.36. (Each curve is truncated by fitting error term, indicating that there is no star brightness that results in that level of wavefront measurement error.) Measurement error vs. sub-ap diameter, for ro(0.5 micron) =0.15 m, 3e-s of read noise and system transmission=0.36 After R. Dekany et al., 2001 Beyond conventional adaptive optics, Venice, Italy

  11. Laboratory set-up: collimator iris CCD camera w/ BoP Point source Focusing lens Alignment telescope Axis defining iris holder F#15.4 focus

  12. Custom BoP alignment jig: Lockable XY and focus stage Gimbal mount 5 axis stage 5 axis stage

  13. Camera simulator with reticle: Grid to simulate CCD pixels

  14. Camera controllers and data recording: CCD camera controllers Network power switch KVM video switch 8 axis motor controller 1U rack-mountable monitor 3 x dell 1U PCs with SCSI HDD and Ultra SCSI 160 port 3.2 Terabyte RAID array

  15. Current status: • 3 BoPs aligned individually • The data acquisition system is ready with synchronous recording capability To do: • Mount the 4 BoPs in the MGSU cage • Mount penta prisms and align • Solve frame rate issues with cameras. • 7 work days of installation schedule (JPL – Chris Shelton and Jennifer Roberts)

  16. Web-site/ documentation: http://eraserhead.caltech.edu/palomar/MGSU/MGSU.html

More Related