PALM-3000 Observers Information - 2021B

* A note on the P3K WFS upgrade:
P3K underwent a significant upgrade to the WFS camera and RTC system during the 2019B semester, culminating in a successful re-commissioning of the 64x mode in November 2019. This mode has been in regular use since, and has demonstrated significant improvement in faint-end performance. The 16x mode was subsequently commissioned in November 2020 and is now available for general use. 16x mode is being used routinely for NGS fainter than R~11, and down to R>15, but detailed analysis of the 16x performance and limiting NGS magnitude is ongoing. This observer information page has been fully updated with the current results of re-commissioning and details of the upgraded system. Further details on the measured/expected performance of these modes is available below. Other important details relevant to observation planning since the WFS upgrade can be found in the Expected Overhead section.

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 (NGS) in proximity to the science target.

2021B Call for Proposals

PALM-3000 will be available for PHARO science and private instrument observations in 2021B.

Instruments Status

  • PALM-3000 is fully operational and supported by Palomar staff. Wavefront correction in 64x has demonstrated performance in the range of 120-140 nm RMS wavefront error (equivalent to K-Strehl = 88%), which is nearing the ultimate expected performance level of 105 nm RMS (the 105 nm requirement is for a V = 5 guide star in median seeing conditions). The peak performance of PALM-3000 in excellent seeing (0.3" Ks) is 91% K-Strehl, corresponding to 105 nm RMS (July 2014).

    The current performance of 160nm RMS has been demonstrated in 64x with V = 8 guide stars, which does approximately meet the design specification.

    In November 2019 P3K 's wavefront sensor (WFS) was upgraded to an OCAM2k EM-CCD camera with sub-electron read-noise. Peak performance on bright (V<8) guide stars has not yet exceeded that seen with the pre-upgrade system. However, for fainter NGS, 64x mode has shown comparable correction to what the pre-upgrade system achieved on guide stars two magnitudes brighter.

  • Instrument Status:
    • PHARO (public)
      • Is currently operational at the summit.
    • P1640 (decommissioned, PI: B. Oppenheimer, AMNH)
      • Coronagraph + CAL is performing routine science in a large exoplanet imaging and spectroscopic survey.
    • SDC (private; PI: G. Serabyn, JPL)
      • Stellar Double Coronagraph, working with PALM-3000 since first light in May 2014.
    • Fiber Nuller (private; PI: G. Serabyn, JPL)
      • Initial FN tests with PALM-3000 successful in June 2012.
    • TMAS (private; co-I's: R. Dekany, COO)
      • First full-aperture visible-light AO successful 27 Sept 2012. Strategies for concurrent visible + NIR observations (using PHARO) are under continuing investigation.
    • DARKNESS (private; PI: B. Mazin, UCSB)
      • Development of energy-resolving MKID imager funded by NSF in Summer 2013. Successful first light demonstrated in August 2016.
    • PARVI (semi-private; PI: G. Vasisht, JPL)
      • PARVI is the Palomar Radial Velocity Instrument, a fiber-fed high-resolution spectrograph for precision radial velocity measurements of exoplanetary systems. PARVI is available for community use as of 2021B. Contact Gautam Vasisht (JPL) or Chas Beichman (IPAC) if considering a PARVI proposal.

Measured Performance vs. NGS Brightness

  • s64 pupil sampling mode: Small (8.3cm) subapertures
    • We show below the P3K+PHARO K-band Strehl ratio obtained from September 2019 to November 2019 taken in median or better seeing conditions (1.2 or better Ks seeing) over 5 re-commissioning nights. The mean bright star (brighter than 8th mv) Ks strehl ratio obtained in median or better seeing conditions NEAR ZENITH and after low order non common path errors are removed is ~75%. When moving off of zenith, if the non common path errors are not removed, strehl ratios will degrade by 10-40% depending on local conditions. Contact the Palomar staff for more information. A stable lock has been achieved on targets as faint as mV=16.2 in this mode during median conditions. Data are shown against the pre-upgrade engineering data with the old WFS (CCD50 data), demonstrating that the upgraded 64x mode delivers comparable performance to pre-upgrade performance in all subaperture modes (e.g. 64x, 32x, 8x).
  • s16 pupil sampling mode: Larger (32.5 cm) subapertures
    • The 16x mode was commissioned in November 2020, with general use beginning immediately after.
    • Theoretical performance curves for 64x vs. 16x are provided below.
    • Note that 16x mode is expected to extend faint end performance beyond 64x mode by 2 magnitudes once it is optimized, out-performing 64x for NGS fainter than ~mV=11.
    • However, 64x surpassed its expected performance for targets fainter than mV=12, with an absolute limit near mV=16 rather than the expected mV=13. Whether this extended magnitude limit translates linearly to 16x mode (implying a limiting magnitude of ~mV=18) remains to be seen.
    • November 2020 commissioning data below shows 16x only matching 64x performance. Improvements to 16x mode have been delivered in 2021A, boosting performance compared to the commissioning data shown below, but are not yet quantified.
Measured Performance of P3K OCAM upgrade vs. CCD50 (pre-upgrade)
Ks_strehl_OCAMvCCD50.png

64x and 16x Commissioning data vs. Theoretical Performance curves:

16x_commiss.png

Expected System Capabilities

For 2020B, PALM-3000 will support natural guide star wavefront sensing in the following correction modes:

Number of subapertures per pupil diameter WFS limiting mag WFS best performance mag Notes
64 V < 16 V < 11  
16 V<18 (?)   Available beginning in 2021A
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.

Guide Star Selection

PALM-3000 has a patrol range for NGS selection of ~90 arcsecond in diameter (allowing a guide star up to 90" away from the science target to be utilized, with the understanding that anisoplanatism error (not accounted for in any data elsewhere on this page) degrades performance significantly beyond ~30 arc sec radius in H/K bands (and beyond ~15 arc sec in Y/J bands.)

The WFS acquisition camera FOV is ~ 95 arc sec x 80 arc sec (TBC).

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: s64
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 science observing in 2021B, we expect observations performed in a single AO mode in a localized part of the sky to approach 2 minutes. Large changes in telescope pointing or AO pupil mode will add 5 minutes to the acquisition overhead.

Since the delivery of the WFS upgrade in November 2019, an increase in WFS flexure has been observed and is under investigation. The previous statement on overhead generally still applies. However, a sudden degradation in WFS performance is experienced when crossing the meridian. Observations that consistently stay to one side of meridian do not experience this issue, and can expect the <2 minutes acquisition time per target as usual. Procedural and hardware mitigations for this issue are under active development, but, for now, observers should expect that the longer system alignment script (additional 5 minutes) will be required whenever crossing meridian.

Closed-loop AO image dithering on PHARO is expected to be functional at a level equal to or better than the prior PALAO 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 PALAO. 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") and Neptune (shown below; V~8 and diameter ~ 2.3"). Contact the PALM-3000 PI for further information.

Neptune_JHK.png

Contact information Technical inquiries for specific observing proposals not addressed here can be referred to Principal Investigator Richard Dekany at Caltech Optical Observatories or Seth Meeker at JPL (seth.r.meeker@jpl.nasa.gov 818.354.9900).

Last updated - 27 Feb 2020 - S. Meeker

Topic attachments
I Attachment History Action Size Date Who Comment
JPEGjpg 1108_P3k_S64_StrehlPerf.jpg r1 manage 66.4 K 2012-03-08 - 18:48 RichardDekany  
PNGpng 16x_commiss.png r1 manage 64.7 K 2021-03-05 - 22:20 SethMeeker 16x_commissioning_summary
PNGpng Ks_strehl_OCAMvCCD50.png r1 manage 189.6 K 2021-03-05 - 22:21 SethMeeker ocam_v_ccd50
PNGpng Neptune_JHK.png r1 manage 376.0 K 2020-02-27 - 21:40 SethMeeker  
PNGpng Performance_Curves.png r1 manage 206.0 K 2018-03-10 - 02:30 SethMeeker  
PNGpng STREHLvsMV_20191107.png r1 manage 146.3 K 2020-02-27 - 21:26 SethMeeker ocam_commiss_strehl
PNGpng p3k_strehl.png r2 r1 manage 286.5 K 2015-08-22 - 23:07 RickBurruss  
PNGpng p3k_strehls.png r1 manage 137.5 K 2013-09-03 - 19:23 RickBurruss  
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Topic revision: r41 - 2021-03-05 - SethMeeker
 
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