Design and analysis for interferometric measurements of the GMT primary mirror segments

Burge, James H.; Kot, L.; Martin, Hubert M.; Zehnder, Rene; Zhao, Chunyu

doi:10.1117/12.672484

Cited by 29 publications

(19 citation statements)

References 12 publications

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“…This architecture is similar to the interferometric test tower used in the manufacture of monolithic 8.4 m mirrors. 38,62 Three technologies using this centralized laser source provide a possible metrology architecture that satisfies the requirements for telescope assembly and operation. These include an absolute metrology technique using a modulated dual-frequency laser, dynamic Zernike wavefront sensing for coarse mirror phasing, and array heterodyne interferometry (AHI) for fine phasing.…”

Section: Metrology Architecturementioning

confidence: 99%

“…Interferometric techniques such as with a laser tracker 38 are typically used, with six point measurements per segment to solve for rigid body displacement (three translational and three rotational DOF) and an additional three per segment to account for thermal expansion. However, such a point measurement system, or a distributed metrology system, is infeasible for a telescope with hundreds or thousands of individual mirror segments.…”

Section: Advanced Metrologymentioning

confidence: 99%

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Architecture for in-space robotic assembly of a modular space telescope

Lee

Backes

Burdick

et al. 2016

J. Astron. Telesc. Instrum. Syst

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Abstract. An architecture and conceptual design for a robotically assembled, modular space telescope (RAMST) that enables extremely large space telescopes to be conceived is presented. The distinguishing features of the RAMST architecture compared with prior concepts include the use of a modular deployable structure, a general-purpose robot, and advanced metrology, with the option of formation flying. To demonstrate the feasibility of the robotic assembly concept, we present a reference design using the RAMST architecture for a formation flying 100-m telescope that is assembled in Earth orbit and operated at the Sun-Earth Lagrange Point 2.

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Section: Metrology Architecturementioning

confidence: 99%

Section: Advanced Metrologymentioning

confidence: 99%

Architecture for in-space robotic assembly of a modular space telescope

Lee

Backes

Burdick

et al. 2016

J. Astron. Telesc. Instrum. Syst

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“…These techniques have been used in aligning the testing system for the primary mirror of the New Solar Telescope and they will be used again in the alignment of testing system for the primary segments of the Giant Magellen Telescope. 10 …”

Section: Discussionmentioning

confidence: 97%

Use of computer generated holograms for alignment of complex null correctors

2006

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Large diameter, non-axisymmetric aspheric mirrors can be measured interferometrically using null correctors that employ computer generated holograms (CGHs). The testing of off axis segments for the new class of giant telescopes pose requirements that beyond the state of the art for CGHs alone. The long radius of curvature and the magnitude of the aspheric departure require other lenses and mirrors to be used along with the CGH. The alignment of these systems is very sensitive and the absolute accuracy of the alignment is critical to the system performance. We have developed techniques that use diffracted light from patterns on the CGH to accurately define the alignment of multi-element null correctors. We will present results from the null test of the 1.7-m New Solar Telescope primary mirror. The optical shape of this mirrors is an off-axis paraboloid from an f/0.7 parent.

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“…1 An optical test is being developed for the off-axis segments that uses a large 3.8-m tilted mirror to fold the light path and to compensate the 14.5 mm of aspheric departure. 2 We recognize the importance of corroborating the measurements from the principal optical test to insure that the correct surface is manufactured.…”

Section: Introductionmentioning

confidence: 98%

Alternate surface measurements for GMT primary mirror segments

et al. 2006

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The primary mirror for the 25-m Giant Magellan Telescope is made of seven circular segments, each of 8.4-m diameter. The lack of axisymmetry and the steep aspheric departure present significant technical challenges for the metrology. These segments will be measured interferometrically using a complex system of mirrors and holograms to give a null test with high spatial resolution. While analysis predicts this system will meet requirements, an additional set of measurements will be used to corroborate the principal interferometric measurement. The set of tests, including these alternate surface measurements, assures that all aspects of the mirror surface are measured completely and redundantly. The corroboration tests discussed in this paper are:Direct surface profile using metrology system based on a laser tracker, measuring low order shape errors Shear testing with full aperture interferometer, separating small scale errors in the null test from those in the mirror Slope testing with scanning pentaprism, measuring low order shape errors and sampling small scale errors

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Design and analysis for interferometric measurements of the GMT primary mirror segments

Cited by 29 publications

References 12 publications

Architecture for in-space robotic assembly of a modular space telescope

Architecture for in-space robotic assembly of a modular space telescope

Use of computer generated holograms for alignment of complex null correctors

Alternate surface measurements for GMT primary mirror segments

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