PALM-3000 Observers Information - 2012A

Overview

PALM-3000 and its back-end instruments are optimized for high-angular resolution science at visible and near-infrared wavelengths. As the world's highest order adaptive optics system, PALM-3000 corrects for atmospheric turbulence to an unprecedented degree using a new 3,388 actuator Xinetics deformable mirror in conjunction with the former 349 actuator Xinetics DM and separate fast tip-tilt mirror. Wavefront sensing requires a bright natural guide star in proximity to the science target.

2012A Call for Proposals

PALM-3000 will be available for shared-risk science observations, per the Call for Proposals in 2012A.

Current Instruments Status

PALM-3000 has achieved first on-sky correction with both the low- and high-order DM's. Engineering tests indicate initial performance in the range of 150-160 nm RMS wavefront error (peak K-Strehl = 82% to date), not yet at the expected performance level of 105 nm RMS (the 105nm requirement is for a V = 5 guide star (in median seeing conditions), current performance of 160nm RMS has been seen down to V = 8).
Engineering and initial shared-risk science will continue through 2011A with each of three instruments:
- PHARO (public)
  - Is currently operational at the summit. A new Y-band filter installed in Aug 2011 appears optically flawed and is being investigated.
- P1640 (private)
  - Coronagraph + CAL is undergoing integration and testing at JPL in Pasadena.
  - IFS have been upgraded to a science-grade H2RG detector at AMNH in New York City, expected arrival at Palomar is September 27, 2011.
- SWIFT (private)
  - Is currently undergoing refurbishment at Oxford University, UK and is expected to return to Palomar in October 2011.

Expected System Capabilities

For 2012A, PALM-3000 will support natural guide star wavefront sensing (only) in the following correction modes:

Number of subapertures per pupil diameter	WFS limiting mag	WFS best performance mag	Notes
64	V < 10	V < 7
32	V < 12	V < 10
8	V < 17	---	Not offered in 2012A
16	V < 14	---	Not offered in 2012A - unlikely to be implemented due to funding constraints

PALM-3000 correction will be best in the direction of the guide star, and fall off due to atmospheric anisoplanatism. The corrected field of view diameter will vary with conditions, but is generally expected to be between 1-2 arcmin diameter in K-band, decreasing to 10-20 arcsec in I-band.

Ultimate Expected Performance on Bright Guide Stars

The bright star wavefront error budget for PALM-3000 is as follows:

* Assumptions

Mean turbulence weighted wind speed = 9.5 m/s
Zenith pointing
Guide star brightness V ~ 5
AO mode: N = 64 AO

Seeing	r_0(0.5um)	RMS residual wavefront error	Strehl Ratio							Notes
			r'	i'	Z	Y	J	H	K
			0.62um	0.75um	.88um	1.03um	1.25um	1.64um	2.2um
0.7"	0.14 m	83 nm	48%	61%	70%	78%	84%	90%	95%	Variations in non-common-path errors may limit PHARO K Strehl to ~90% even in excellent seeing
1.1" (median)	0.092 m	105 nm	32%	46%	57%	66%	76%	85%	91%	See above
1.6"	0.07 m	165 nm	26%	38%	47%	54%	61%	68%	73%	-

Expected Observing Overheads

Instrument requirement #0480 states that PALM-3000 shall be ready to begin a science exposure < 2 minutes after the end of a telescope slew (< 1 minute goal). During shared-risk science observing in 2012A, we expect observations performed in a single AO mode in a localized part of the sky to approach the final requirement. For now, changes in telescope pointing or AO mode may result in greater acquisition overheads.

Closed-loop AO image dithering on PHARO is expected to be functional at a level equal to or better than the prior PALMAO system (smallest step size ~ 5 mas), with improved non-common-path flexure during long exposures. Early engineering tests confirm PALM-3000 has improved flexure stability compared to PALMAO. These results are being quantified.

Wide-field astrometry

We do not recommend precision wide-field PHARO astrometric programs, due to the uncharacterized nature of our dual-DM-conjugate correction architecture. Contact the PALM-3000 PI for further details.

Extended objects

PALM-3000 is designed to support NGS observations of Uranus and Neptune, but optimization on these targets will require additional calibration effort. To date, in S64 mode, good correction has been obtained locking on Saturn's moon Titan (V~8 and diameter ~ 1"). Contact the PALM-3000 PI for further information.

Contact information

Technical inquiries for specific observing proposals not addressed here can be referred to Principal Investigator Dr. Richard Dekany at Caltech Optical Observatories.

Last updated - 01 Sept 2011

Topic revision: r4 - 2011-09-01 - RichardDekany

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