Giant segmented mirror telescope: a point design based on science drivers

We have made simultaneous and nearly simultaneous measurements of ᏸ 0 , the outer scale of turbulence, at the Palomar Observatory by using three techniques: angle-of-arrival covariance measurements with the Generalized Seeing Monitor ͑GSM͒, differential-image-motion measurements with the adaptiveoptics system on the Hale 5-m telescope, and fringe speed measurements with the Palomar Testbed Interferometer ͑PTI͒. The three techniques give consistent results, an outer scale of approximately 10 -20 m, despite the fact that the spatial scales of the three instruments vary from 1 m for the GSM to 100 m for the PTI.

Section: Introductionmentioning

confidence: 99%

Comparison of measurements of the outer scale of turbulence by three different techniques

Ziad

Schöck²,

Chanan³

et al. 2004

“…[1][2][3][4][5][6][7] The majority of these telescopes involve a highly segmented primary mirror, with several hundred up to even a few thousand segments. The optimal number of segments used to fill a particular aperture size is the result of a key design trade-off: Larger segments are in general more difficult to fabricate whereas smaller segments are more difficult to align and control, principally as a result of their larger numbers.…”

Section: Introductionmentioning

confidence: 99%

Control and alignment of segmented-mirror telescopes: matrices, modes, and error propagation

Chanan¹,

MacMartin²,

Nelson³

et al. 2004

Starting from the successful Keck telescope design, we construct and analyze the control matrix for the active control system of the primary mirror of a generalized segmented-mirror telescope, with up to 1000 segments and including an alternative sensor geometry to the one used at Keck. In particular we examine the noise propagation of the matrix and its consequences for both seeing-limited and diffractionlimited observations. The associated problem of optical alignment of such a primary mirror is also analyzed in terms of the distinct but related matrices that govern this latter problem.

“…[1][2][3][4] Most of these design concepts involve a highly segmented primary mirror, with as many as a few thousand segments. The outof-plane degrees of freedom of each segment must be actively controlled, which requires precise information about the displacement of each segment.…”

Section: Introductionmentioning

confidence: 99%

Measurement accuracy in control of segmented-mirror telescopes

MacMartin¹,

Chanan²

2004

Design concepts for future large optical telescopes have highly segmented primary mirrors, with the out-of-plane degrees of freedom actively controlled. We estimate the contribution to errors in controlling the primary mirror that results from sensor noise and, in particular, compare mechanical measurements of relative segment motion with optical wave-front information. Data from the Keck telescopes are used to obtain realistic estimates of the achievable noise due to mechanical sensors. On the basis of these estimates, mechanical sensors will be more accurate than wave-front information for any of the telescope design concepts currently under consideration, and therefore supplemental wave-front sensors are not required for real-time figure control. Furthermore, control system errors due to sensor noise will not significantly degrade either seeing-limited or diffraction-limited observations.