1 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

2 Introduction: Palomar Tomograph (PT) is a compact multiple guide star wavefront sensor system that can be used to confirm tomographic wavefront sensing algorithms 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. 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 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) Penta prism collimator Lenslet array Field lens Focusing lens

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

6 The MGSU/ tomograph assembly:

7

8 Spots on the focal plane array: (4x4 pixels/sub-ap., 16x16 spots aligned FPA with >0.1 pixel RMS offset)

9 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 Hz. 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 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. 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. 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. 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 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. 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.

10 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. 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 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 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 In parallel - Matthew’s work on modeling anisoplatism

11 Measurement error vs. sub-ap diameter, for r o (0.5 micron) =0.15 m, 3e - s of read noise and system transmission=0.36 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.) After R. Dekany et al., 2001 Beyond conventional adaptive optics, Venice, Italy

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

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

14 Camera simulator with reticle: Grid to simulate CCD pixels

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

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

17 Web-site/ documentation: