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This paper presents a novel method for verifying interfaces and generating interface control documents (ICDs) from a system model in SysMLTM. In systems and software engineering, ICDs are key artifacts that specify the interface(s) to a system or subsystem, and are used to control the documentation of these interfaces. ICDs enable independent teams to develop connecting systems that use the specified interfaces. In the context of the Thirty Meter Telescope (TMT), interface control documents also act as contracts for delivered subsystems. The Alignment and Phasing system (APS) is one such subsystem. APS is required to implement a particular interface, and formulates requirements for the interfaces to be provided by other components of TMT that interface with APS. As the design of APS matures, these interfaces are frequently refined, making it necessary for related ICDs to be updated. In current systems engineering practice, ICDs are maintained manually. This manual maintenance can lead to a loss in integrity and accuracy of the documents over time, resulting in the documents no longer reflecting the actual state of the interfaces of a system. We show how a system model in SysMLTM can be used to generate ICDs automatically. The method is demonstrated through application to interface control documents pertaining to APS. Specifically, we apply the method to the interface of APS to the primary mirror control system (M1CS) and of APS to the Telescope Control System (TCS). We evaluate the newly introduced method through application to two case studies.

SCDU (Spectral Calibration Development Unit) is a vacuum test bed that was built and operated for the SIM-Planetquest Mission and has successfully demonstrated the calibration of spectral instrument error to an accuracy of better than 20 picometers. This performance is consistent with the 1 micro-arc second goal of SIM. The calibration procedure demonstrated in the test bed is traceable to the SIM flight instrument. This article is a review of all aspects of the design and operation of the hardware as well as the methodology for spectral calibration. Spectral calibration to better than 20 picometers and implications for flight are discussed.

We describe the current performance of an adaptive optics testbed for optical communication. This adaptive optics system allows for simulation of night and day-time observing on a 1 meter telescope with a 97 actuator deformable mirror.

Work is underway at the University of Chicago and Caltech Optical Observatories to implement a sodium laser guide star adaptive optics system for the 200 inch Hale telescope at Palomar Observatory. The Chicago sum frequency laser (CSFL) consists of two pulsed, diode-pumped, mode-locked Nd:YAG lasers working at 1.064 micron and 1.32 micron wavelengths. Light from the two laser beams is mixed in a non-linear crystal to produce radiation centered at 589 nm with a spectral width of 1.0 GHz (FWHM) to match that of the Sodium-D2 line. Currently the 1.064 micron and 1.32 micron lasers produce 14 watts and 8 watts of TEM-00 power respectively. The laser runs at 500 Hz rep. rate with 10% duty cycle. This pulse format is similar to that of the MIT-Lincoln labs and allows range gating of unwanted Rayleigh scatter down an angle of 60 degrees to zenith angle. The laser system will be kept in the Coude lab and will be projected up to a laser launch telescope (LLT) bore-sited to the Hale telescope. The beam-transfer optics, which conveys the laser beam from the Coude lab to the LLT, consists of motorized mirrors that are controlled in real time using quad-cell positioning systems. This needs to be done to prevent laser beam wander due to deflections of the telescope while tracking. There is a central computer that monitors the laser beam propagation up to the LLT, the interlocks and safety system status, laser status and actively controls the motorized mirrors. We plan to install a wide-field visible camera (for high flying aircraft) and a narrow field of view (FoV) IR camera (for low-flying aircraft) as part of our aircraft avoidance system.

Adaptive optics systems with Shack-Hartmann wavefront sensors require reconstruction of the atmospheric phase error from subaperture slope measurements, with every sensor in the array being used in the computation of each actuator command. This fully populated reconstruction matrix can result in a significant computational burden for adaptive optics systems with large numbers of actuators. A method for generating sparse wavefront reconstruction matrices for adaptive optics is proposed. The method exploits the relevance of nearby subaperture slope measurements for control of an individual actuator, and relies upon the limited extent of the influence function for a zonal deformable mirror. Relying only on nearby sensor information can significantly reduce the calculation time for wavefront reconstruction. In addition, a hierarchic controller is proposed to recover some of the global wavefront information. The performance of these sparse wavefront reconstruction matrices was evaluated in simulation, and tested on the Palomar Adaptive Optics System. This paper presents some initial results from the simulations and experiments.

Adaptive optics (AO) systems currently under investigation will require at least two orders of magitude increase in thenumber of actuators, which in turn translates to effectively a 10 4 increase in compute latency. Since the performance ofan AO system invariably improves as the compute latency decreases, it is important to study how today’s computersystems will scale to address this expected increase in actuator utilization. This paper answers this question bycharacterizing the performance of a single deformable mirror (DM) Shack-Hartmann natural guide star AO systemimplemented on the present-generation digital signal processor (DSP) TMS320C6701 from Texas Instruments. Wederive the compute latency of such a system in terms of a few basic parameters, such as the number of DM actuators, thenumber of data channels used to read out the camera pixels, the number of DSPs, the available memory bandwidth, aswell as the inter-processor communication (IPC) bandwidth and the pixel transfer rate. We show how the results wouldscale for future systems that utilizes multiple DMs and guide stars. We demonstrate that the principal performancebottleneck of such a system is the available memory bandwidth of the processors and to lesser extent the IPC bandwidth.This paper concludes with suggestions for mitigating this bottleneck.Keywords: Adaptive optics, wavefront processors, TMS320C6701

We discuss conceptual design issues for a 1600 actuator tweeter mirror/multiconjugate AO upgrade to the 349 actuator Palomar Adaptive Optics System (PALAO). Based upon a 42 X 42 actuator Photonex deformable mirror technology, developed by Xinetics, Inc., this upgrade would enable unique science at visible wavelengths and deliver unprecedented near-infrared Strehl ratios for modestly bright (mV equals 9) guide stars. When used in conjunction with the existing 349 actuator Xinetics, Inc. deformable mirror, a series of pressing issues regarding the practical utility of multiconjugate adaptive correction for extremely large telescopes could be addressed. By utilizing a low noise (EEV39) wavefront sensor camera developed by SciMeasure Analytical Systems, Inc., this system would provide on-axis K-band Strehl ratio of > 95%, improving scientific throughput and enabling the detection and spectroscopy of unresolved companions in an unprecedented contrast space around nearby stars.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

SciMeasure, in collaboration with Emory University and the Jet Propulsion Laboratory (JPL), has developed an extremely versatile CCD controller for use in adaptive optics, optical interferometry, and other applications requiring high-speed readout rates and/or low read noise. The overall architecture of this controller system will be discussed and its performance using both EEV CCD39 and MIT/LL CCID-19 detectors will be presented. Initially developed for adaptive optics applications, this controller is used in the Palomar Adaptive Optics program (PALAO), the AO system developed by JPL for the 200' Hale telescope at Palomar Mountain. An overview of the PALAO system is discussed and diffraction-limited science results will be shown. Recently modified under NASA SBIR Phase II funding for use in the Space Interferometry Mission testbeds, this controller is currently in use on the Micro- Arcsecond Metrology testbed at JPL. Details of a new vacuum- compatible remote CCD enclosure and specialized readout sequence programming will also be presented.

We describe the current performance of the Palomar 200 inch (5 m) adaptive optics system, which in December of 1998 achieved its first high order (241 actuators) lock on a natural guide star. In the K band (2.2 micrometer), the system has achieved Strehl ratios as high as 50% in the presence of 1.0 arcsecond seeing (0.5 micrometer). Predictions of the system's performance based on the analysis of real-time wavefront sensor telemetry data and an analysis based on a fitted Kolmogorov atmospheric model are shown to both agree with the observed science image performance. Performance predictions for various seeing conditions are presented and an analysis of the error budget is used to show which subsystems limit the performance of the AO system under various atmospheric conditions.

During its first year of shared-risk observations, the PALAO/PHARO adaptive optics system has been employed to obtain near-infrared R approximately 1000 spectra of solar system targets at spectroscopic slit widths of 0.5 and 0.1 arcsec, and corresponding spatial resolution along the slit as fine as 0.08 arcsec. Phenomena undergoing initial investigation include condensate formation in the atmospheres of Neptune, and the Saturnian moon, Titan. We present the results of this AO spectroscopy campaign and discuss AO specific considerations in the reduction and interpretation of this data.

SciMeasure, in collaboration with Emory University and the Jet Propulsion Laboratory, has developed a very versatile CCD controller for use in adaptive optics, optical interferometry, and other applications requiring high-speed readout rates and/or low read noise. The overall architecture of this controller system will be discussed and its performance using both EEV CCD39 and MIT/LL CCID-19 detectors will be presented. This controller is used in the adaptive optics system, developed by JPL, for the 200” Hale telescope at Palomar Mountain. Early diffraction-limited science results, recently achieved by the AO system, are presented. We gratefully acknowledge the financial support of NASA through SBIR contracts NAS8-97195 and NAS8-98081.

Control laws for an adaptive optics system for the Palomar Mountain Hale Telescope are described. These are derived using a linear matrix model of the optics, which gives the Hartman-sensor centroids and the science camera wavefront as functions of deformable mirror (DM) commands and atmospheric phase. The matrices defining this system can be directly measured from the optics, some at finer spatial resolution than the wavefront sensor can resolve. A minimum-wavefront compensator feeds back both the wavefront sensor centroids and previous DM commands, using the atmospheric covariance to smooth the response at the finer spatial scale. The DM command feedback provides direct observability of waffle, piston and other modes unobservable in the wavefront sensor. Compensator gains can be updated using Kalman filtering techniques to track the evolution of the atmospheric covariance matrix.

During the nights of 18-22 March 1998, the Palomar 200 adaptive optics (AO) breathed its first breathe of life, closing lock on a natural guide star for the first time. We present telescope result obtained during the initial closed- loop tip/tilt test of the AO system at the 5m Hale Telescope on Palomar Mountain. (PHARO). Early tip/tilt correction result demonstrate a factor of approximately 1.3 improvement in peak IR irradiance for several second exposures. The facility AO and PHARO systems are scheduled for a series of engineering runs throughout 1998. Initial closure of the 241 actuator high order natural guide star adaptive loop is expected this summer.

We present laboratory subsystem test results obtained during integration of the Palomar 200” Adaptive Optics System at Jet Propulsion Laboratory. These results pertain to the 241 actively controlled actuator, Shack-Hartmann sensed, initial delivery of a system optimized for near infrared observation with the 5 meter diameter telescope at Palomar Mountain. This system initially exploits natural guide stars. Our intention is to provide a wide-ranging summary of subsystem performance measurements and several lessons learned. Noteworthy among these results is our measurement of 6.3 ± 0.2 electron read noise performance of our initial WFS camera, based upon a 64 x 64 pixel MIT/LL CCD detector, running at 600 kilopixel per sec per output amplifier. This camera was constructed by SciMeasure Analytical Systems, Inc. of Decatur, GA.