Adaptive optics (AO) is useful in correcting the blurring effects of the atmosphere responsible for most energy in the halo of the point spread function. A coronagraph can further enhance faint companion searches by reducing the diffraction rings surrounding a well corrected image peak. Here, we use a coronagraph on the Advanced Electro-Optical System (AEOS) at the Maui Space Surveillance Complex (MSSC) to test these benefits. The spatial characteristics of the scattered energy produced at AEOS are explored from the viewpoint of searching for faint stellar companions. The benefit of using AO is found to be 3 to 4.5 stellar magnitudes for a ten second integration time at 1 to 2 microns, with the most benefit at radial distances less than one arcsecond. More advanced AO/coronagraphic systems should be able to produce even better results. Using AO and a coronagraph should be strongly considered when attempting to image faint companions.

Adaptive optics (AO) is useful in correcting the blurring effects of the atmosphere responsible for most energy in the halo of the point spread function. A coronagraph can further enhance faint companion searches by reducing the diffraction rings surrounding a well corrected image peak. Here, we use a coronagraph on the Advanced Electro-Optical System (AEOS) at the Maui Space Surveillance Complex (MSSC) to test these benefits. The spatial characteristics of the scattered energy produced at AEOS are explored from the viewpoint of searching for faint stellar companions. The benefit of using AO is found to be 3 to 4.5 stellar magnitudes for a ten second integration time at I to 2 microns, with the most benefit at radial distances less than one arcsecond. More advanced AO/coronagraphic systems should be able to produce even better results. Using AO and a coronagraph should be strongly considered when attempting to image faint companions.

The multiple-star system ι Cas was observed as a calibration for our adaptive optics observations in 2001 July with the Advanced Electro-Optical System (AEOS) 3.63 m telescope in Maui, Hawaii, and the first ever image of the faint astrometric component Aa (along with A and B) was obtained at the H-band wavelength. Another image was obtained in 2002 February with the same telescope, but that time in the I band. This wider image includes the C component and is the first to show four components. By combining our images with seven recent speckle interferometry measurements, a 47 yr period relative orbit is derived for the A-Aa components. Comparing the motion of B with respect to the A-Aa system, previous A-B orbits are rejected in favor of simple rectilinear motion of B across the field. Nevertheless, the history of the relative vector separation between B and A reveals the suborbital motion of A around its center of gravity with Aa, leading to a true orbit for A. The masses of A and Aa are thus determined to be 1.99 ± 0.28 and 0.69 ± 0.12 M☉, respectively. Combining our differential photometry in the I and H bands with B and V information from the Tycho-2 catalog, we derive spectral types for all four from their colors: component A is spectral type A3 with peculiar red colors, Aa is G6, B is F5, and C is K3.

Adaptive optics images of Iota Cassiopeia taken in the I and H bands with the 3.63m AEOS telescope on Haleakala show a strong waffle-like pattern. The Parametric Blind Deconvolution (PBD) point spread function is modified to include such an optical aberration pattern, and position angles, separations, and magnitude differences are obtained for the components of the quadruple star system. The H band image of the astrometric companion is the first ever, the I band image is the first to show all four components, and by combining our data with previous visual and speckle measurements, the orbits and masses of components A and Aa are derived for the first time. The faint sub-solar mass component is 2.3, 2.9, 3.7, and 4.2 magnitudes fainter than its nearby (0.4") companion at H, I, V, and B bands, respectively.

The Starfire Optical Range has measured stellar scintillation to 0.9 to 1.7 microns over a wide range of elevation angles. The telescope pupil was imaged on to a mask with four circular aperture of scaled diameters 0.1, 0.2, 0.75 and 1.5 m. These smaller pupils were then re- imaged onto InGaAs photodiodes operating at 10 kHz. The entire 3.5m pupil was also imaged onto a fifth photodiode. Since all five signals were recorded simultaneously, the influence of aperture diameter on scintillation statistics can be readily seen. The detectors were located at pupil planes; no fluctuations due to atmospheric tilt were measured. Comparisons of power spectral densities, signal variances and other fluctuation statistics have been made as functions of the aperture diameter and elevation angle. Experimental results and theoretical expectations reveal widespread agreement. Within experimental error, log-normal statistics are followed. High spatial frequency content increased with elevation angle. Aperture averaging of scintillation variance followed a 7/6th dependence. Increasing the aperture dimensions had an even larger effect on the number of fluctuations below a given threshold. Scintillation in the near-IR has been shown to produce consistent result with previous studies performed at visible wavelengths.

The Starfire Optical Range has measured atmospheric scintillation on 1.06 micron laser beams propagated from the ground to retroreflectors on satellites and back to the ground. The primary purpose of this experiment was to examine upward scintillation on laser beams, especially the results of varying the number of beams and their diameters. Separating the energy into beams that sample different portions of the atmosphere reduces the scintillation if the atmospheric turbulence each traverses is independent. How much the beam diameter affects scintillation is determined by diffraction and the size of the Fried parameter.

To image extrasolar planets at their large contrast, high-resolution adaptive optics (AO) is needed to correct atmospheric seeing. The 1.5-m AO system at the Starfire Optical Range was used to confirm theoretical models. Halo levels were reduced by a factor of 4, on average, from 0.5 to 3.0 arc sec radius, which when combined with the increased Strehl ratio improved the gain by a factor of 80. Speckle lifetimes ranged from 5 to 30 ms at 0.3 arc sec, which is much longer than the 0.6-ms AO update time. These results show good agreement with predictions for current technology and reveal no limitations, in principle, to the detection of planets by use of AO systems with higher speeds and resolutions.

In order to image faint stellar companions from the ground, high resolution adaptive optics (AO) is needed to correct atmospheric seeing. The 3.5m AO system at the Starfire Optical Range (SOR) was used to confirm theoretical models of scattered light. Halo levels were reduced by a 50 percent at 0.5 inch, which, when combined with the increased Strehl ratio, improved the gain by a factor of 23. Speckle lifetimes ranged form 20 ms at 0.1 inch to 4 ms at 0.4 inch, much longer than the 0.7 ms correction time. These results show good agreement with predictions for current technology and reveal no limitations in principle to detection of exo- solar planets using AO systems with higher speed and resolution.

This paper looks at the detection limits using the new adaptive optics system on the 3.5 m SOR telescope, reported by P. Ryan et al.(1) at this conference. We discuss recent advances in our understanding of the nature of high frequency wavefront structure. We analyze the various sources of high-frequency wavefront error, arising from residual adaptive optics errors, and other sources of scattered light. We characterize the AO system efficiency in the K band in terms of profile, noise level and noise time correlation. A sharp edge coronograph was used and it improved the performance as much as needed to detect brown dwarfs. Finally we give the exposure time required to detect such companions using the actual AO associated with the coronographic device, and we also point out what needs to be improved on the AO system as well as on the coronographic device in order to reach the level required for detecting exoplanets.

On 15 September 1996, a high altitude research balloon was launched SW of the Starfire Optical Range (SOR) on Kirtland AFB, NM. The primary purpose of the balloon launch was to test a low power satellite communications package developed under the direction of Dr. Charles Swenson of Utah State University. An equally important objective of this experiment was to collect laser scintillation data from the balloon at the 1.5-meter telescope located at the SOR. Scintillation data was also obtained from a star near the location (azimuth and elevation) of the balloon for comparison. The balloon payload was illuminated from the ground with a small aperture 810 nm laser diode transmitter and retro-reflected into the 1.5-meter telescope from a 1 inch optical corner cube. The returned light was detected by a photomultiplier tube. This paper examines the statistics of intensity fluctuations from these two sources and compares experimental results with theory.

The Starfire Optical Range (SOR) has measured scintillation at 1.5 microns over a wide range of elevation angles. Comparison of measured results with theoretical expectations revealed widespread agreement. Increasing zenith angle produced increased spatial correlation distances and loss of high spatial frequency content. The magnitude of the increase in correlation distance agreed with accepted theory which predicts dependence on the distance to the turbulence, which is at the tropopause in this case. The bandwidth of the collected signal had no discernible effect on correlation distance nor on the amount of scintillation For the experimental bandwidths used, none were expected. Aperture averaging followed Yura and McKinley's prediction of a diameter to the 7/6th dependence. Using spatially separated apertures was also shown to be effective at decreasing the amount of scintillation beyond total area effects. Increasing the aperture dimensions had an even larger effect on the number of fades below a given threshold. For optical communication applications, this should be considered closely.

A new adaptive optics system has been constructed for moderately high resolution in the near infrared at the Multiple Mirror Telescope (MMT). The system, called FASTTRAC II, has been designed to combine the highest throughput with the lowest possible background emission by making the adaptive optical element be an existing and necessary part of the telescope, and by eliminating all warm surfaces between the telescope and the science camera's dewar. At present, only natural guide stars are supported, but by the end of 1995, we will add the capability to use a single sodium resonance beacon derived from a laser beam projected nearly coaxially with the telescope. In this paper, we present a description of FASTTRAC II, and show results from its first test run at the telescope in April 1995.