Investigations of long pulse sodium laser guide stars

Rampy, Rachel; Gavel, Donald T.; Rochester, Simon; Holzlöhner, Ronald

doi:10.1117/12.926621

Cited by 11 publications

(13 citation statements)

References 9 publications

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“…9 This laser has a pulse and spectral format that will take maximum advantage of sodium optical pumping. 10,11 In the mean time, the ancient dye-laser, originally commissioned in 1996, 12 will continue to be used as the ShaneAO LGS beacon source throughout the remainder of this year. The optical table layout is shown in Figure 2.…”

Section: Instrument Descriptionmentioning

confidence: 99%

ShaneAO: wide science spectrum adaptive optics system for the Lick Observatory

Gavel¹,

Kupke²,

Dillon³

et al. 2014

SPIE Proceedings

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A new high-order adaptive optics system is now being commissioned at the Lick Observatory Shane 3-meter telescope in California. This system uses a high return efficiency sodium beacon and a combination of low and high-order deformable mirrors to achieve diffraction-limited imaging over a wide spectrum of infrared science wavelengths covering 0.8 to 2.2 microns. We present the design performance goals and the first on-sky test results. We discuss several innovations that make this system a pathfinder for next generation AO systems. These include a unique woofer-tweeter control that provides full dynamic range correction from tip/tilt to 16 cycles, variable pupil sampling wavefront sensor, new enhanced silver coatings developed at UC Observatories that improve science and LGS throughput, and tight mechanical rigidity that enables a multi-hour diffractionlimited exposure in LGS mode for faint object spectroscopy science.

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Section: Instrument Descriptionmentioning

confidence: 99%

ShaneAO: wide science spectrum adaptive optics system for the Lick Observatory

Gavel¹,

Kupke²,

Dillon³

et al. 2014

SPIE Proceedings

Self Cite

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“…Consequently, high-power lasers are required to form the guide stars. Although there is much ongoing work to optimize return from the sodium layer, there are limits to the amount of return flux related to the density of the layer [35]. A guide-star brightness equivalent to V 5.1 mag has been demonstrated on sky [36], but this is much brighter than is typically achieved [24].…”

Section: Laser Guide Starsmentioning

confidence: 99%

“…Wave-front sensing is most sensitive at the diffraction limit, and so the larger size of LGS spots results in a worse-than-optimal correction. Larger spots are brighter (more scattering area), however, and so there is a tradeoff between photon flux and spot size [35].…”

Section: Laser Guide Starsmentioning

confidence: 99%

Laser-Guide-Star Satellite for Ground-Based Adaptive Optics Imaging of Geosynchronous Satellites

Marlow

Carlton

Yoon

et al. 2017

Journal of Spacecraft and Rockets

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In this study, the feasibility and utility of using a maneuverable nanosatellite laser guide star from a geostationary equatorial orbit have been assessed to enable ground-based, adaptive optics imaging of geosynchronous satellites with next-generation extremely large telescopes. The concept for a satellite guide star was first discussed in the literature by Greenaway and Clark in the early 1990s ("PHAROS: An Agile Satellite-Borne Laser Guidestar," Proceedings of SPIE, Vol. 2120, 1994, and expanded upon by Albert in 2012 ("Satellite-Mounted Light Sources as Photometric Calibration Standards for Ground-Based Telescopes," Astronomical Journal, Vol. 143, No. 1, 2012, p. 8). With a satellite-based laser as an adaptive optics guide star, the source laser does not need to scatter, and is well above atmospheric turbulence. When viewed from the ground through a turbulent atmosphere, the angular size of the satellite guide star is much smaller than a backscattered source. Advances in small-satellite technology and capability allowed the revisiting of the concept on a 6U CubeSat, measuring 10 × 20 × 30 cm. It is shown that a system that uses a satellite-based laser transmitter can be relatively low power (∼1 W transmit power) and operated intermittently. Although the preliminary analysis indicates that a single satellite guide star cannot be used for observing multiple astronomical targets, it will only require a little propellant to relocate within the geosynchronous belt. Results of a design study on the feasibility of a small-satellite guide star have been presented, and the potential benefits to astronomical imaging and to the larger space situational awareness community have been highlighted.

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“…For example, both GMT and TMT will initially include six lasers to meet the demand of MCAO systems in the purpose of diffraction-limited capacity [7,8] . Compared with cw lasers, long pulsed sodium lasers are preferable because they allow for Rayleigh blanking and fratricide avoidance in multiple LGS systems [9] . However, pulsed lasers also lead to higher effective light intensity irradiated at the sodium layer, which may result in decline of normalized photon returns efficiency as well as brightness because of transition saturation.…”

Section: Introductionmentioning

confidence: 99%

Experimental demonstration of brighter sodium resonant scattering with 1.7 GHz sideband repumping for long pulse laser

Zhang

Wang

et al. 2014

SPIE Proceedings

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Adaptive Optics (AO) based on artificial beacons is the key to achieve high resolution images from large ground-based telescopes. Long pulsed lasers are preferable to create sodium laser guide stars (LGS) as they allow for Rayleigh blanking. However, these lasers may increase the effective light intensity irradiated at the sodium layer, which may lead to transition saturation, and then decline the normalized return flux efficiency. The return flux might be boosted by optical repumping, which could make full use of the advantages of optical pumping without trapping the atoms to the F=1 ground state. In this paper, we study the optical repumping effect by using a small scale long pulsed sodium laser developed in Technical Institute of Physics and Chemistry (TIPC), Chinese Academy of Sciences, whose pulse format may be pretty suitable for large telescopes. An electro-optic phase modulator is used to produce 1.713 GHz sidebands from the D 2a center wavelength with the fraction of 20%. As for a vacuum sodium cell at the temperature of 40 ℃, when the effective laser intensity increases from 4.53 × 10 2 W/m 2 to 6.99 × 10 5 W/ m 2 , resonant fluorescence with and without repumping is measured. The result illustrates that the resonant scattering brightness with repumping can be as over 3 times as without it when the light intensity changes between 4.53×10 2 W/m 2 to 5 ×10 4 W/ m 2 . The saturated phenomenon is also observed. This gives direct evidence that repumping could improve the performance of sodium laser guide stars based on TIPC long pulsed lasers. To our knowledge, this is the first experimental demonstration of the repumping effect with the TIPC type long pulsed laser in laboratory.

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Investigations of long pulse sodium laser guide stars

Cited by 11 publications

References 9 publications

ShaneAO: wide science spectrum adaptive optics system for the Lick Observatory

ShaneAO: wide science spectrum adaptive optics system for the Lick Observatory

Laser-Guide-Star Satellite for Ground-Based Adaptive Optics Imaging of Geosynchronous Satellites

Experimental demonstration of brighter sodium resonant scattering with 1.7 GHz sideband repumping for long pulse laser

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