Abstract

In segmented-mirror telescopes, wave-front discontinuities caused by segment misalignment are a major problem because they severely degrade optical performance. While angular misalignments are usually measured with deflectometric wave-front sensors (e.g., Shack-Hartmann sensors), a number of techniques have been proposed for the measurement of vertical discontinuities (pistons). In earlier papers we presented an instrument called UPC-ZEBRA that uses a novel interferometric technique to measure piston error during the daytime with an uncertainty of 5 nm within a 30-μm range. Here we present the most representative results obtained during the testing stage and a detailed analysis of error sources. The main modifications to be introduced for the instrument’s use as a phasing calibration system are also outlined.

© 2004 Optical Society of America

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References

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  1. J. Nelson, T. Mast, S. Faber, “The design of the KECK observatory and telescope,” Keck Observatory Report 90 (W. M. Keck Observatory, Kamuela, Hawaii, 1985).
  2. G. Chanan, M. Troy, F. Dekens, S. Michaels, J. Nelson, T. Mast, D. Kirkman, “Phasing the mirror segments of the Keck telescopes: the broadband phasing algorithm,” Appl. Opt. 37, 140–155 (1998).
    [CrossRef]
  3. G. Chanan, M. Troy, E. Sirko, “Phasing the Keck telescope with out-of-focus images in the infrared,” Appl. Opt. 38, 704–713 (1999).
    [CrossRef]
  4. G. Chanan, M. Troy, C. Ohara, “Phasing the mirror segments of the Keck telescopes: a comparison of different techniques,” in Optical Design, Materials, Fabrication, and Maintenance, P. Dierickx, ed., Proc. SPIE4003, 188–202 (2000).
    [CrossRef]
  5. G. Chanan, C. Ohara, M. Troy, “Phasing the mirror segments of the Keck telescope II: the narrow-band phasing algorithm,” Appl. Opt. 39, 4706–4714 (2000).
    [CrossRef]
  6. Grantecan Project Office, GTC Conceptual Design (Grantecan S.A., La Laguna, Spain, 1997).
  7. C. Pizarro, J. Arasa, F. Laguarta, N. Tomàs, A. Pintó, “Design of an interferometric system for the measurement of phasing errors in segmented mirrors,” Appl. Opt. 41, 4562–4570 (2002).
    [CrossRef] [PubMed]
  8. A. Pintó, F. Laguarta, R. Artigas, C. Cadevall, “New interferometric technique for piston measurement in segmented mirrors,” J. Opt. A 4, S369–S375 (2002).
    [CrossRef]
  9. A. Pintó, “New interferometric technique for piston measurement and phasing of segmented mirrors,” Ph.D. dissertation (Universitat Politècnica de Catalunya, Barcelona, Spain, 2002).

2002

C. Pizarro, J. Arasa, F. Laguarta, N. Tomàs, A. Pintó, “Design of an interferometric system for the measurement of phasing errors in segmented mirrors,” Appl. Opt. 41, 4562–4570 (2002).
[CrossRef] [PubMed]

A. Pintó, F. Laguarta, R. Artigas, C. Cadevall, “New interferometric technique for piston measurement in segmented mirrors,” J. Opt. A 4, S369–S375 (2002).
[CrossRef]

2000

1999

1998

Arasa, J.

Artigas, R.

A. Pintó, F. Laguarta, R. Artigas, C. Cadevall, “New interferometric technique for piston measurement in segmented mirrors,” J. Opt. A 4, S369–S375 (2002).
[CrossRef]

Cadevall, C.

A. Pintó, F. Laguarta, R. Artigas, C. Cadevall, “New interferometric technique for piston measurement in segmented mirrors,” J. Opt. A 4, S369–S375 (2002).
[CrossRef]

Chanan, G.

Dekens, F.

Faber, S.

J. Nelson, T. Mast, S. Faber, “The design of the KECK observatory and telescope,” Keck Observatory Report 90 (W. M. Keck Observatory, Kamuela, Hawaii, 1985).

Kirkman, D.

Laguarta, F.

C. Pizarro, J. Arasa, F. Laguarta, N. Tomàs, A. Pintó, “Design of an interferometric system for the measurement of phasing errors in segmented mirrors,” Appl. Opt. 41, 4562–4570 (2002).
[CrossRef] [PubMed]

A. Pintó, F. Laguarta, R. Artigas, C. Cadevall, “New interferometric technique for piston measurement in segmented mirrors,” J. Opt. A 4, S369–S375 (2002).
[CrossRef]

Mast, T.

G. Chanan, M. Troy, F. Dekens, S. Michaels, J. Nelson, T. Mast, D. Kirkman, “Phasing the mirror segments of the Keck telescopes: the broadband phasing algorithm,” Appl. Opt. 37, 140–155 (1998).
[CrossRef]

J. Nelson, T. Mast, S. Faber, “The design of the KECK observatory and telescope,” Keck Observatory Report 90 (W. M. Keck Observatory, Kamuela, Hawaii, 1985).

Michaels, S.

Nelson, J.

G. Chanan, M. Troy, F. Dekens, S. Michaels, J. Nelson, T. Mast, D. Kirkman, “Phasing the mirror segments of the Keck telescopes: the broadband phasing algorithm,” Appl. Opt. 37, 140–155 (1998).
[CrossRef]

J. Nelson, T. Mast, S. Faber, “The design of the KECK observatory and telescope,” Keck Observatory Report 90 (W. M. Keck Observatory, Kamuela, Hawaii, 1985).

Ohara, C.

G. Chanan, C. Ohara, M. Troy, “Phasing the mirror segments of the Keck telescope II: the narrow-band phasing algorithm,” Appl. Opt. 39, 4706–4714 (2000).
[CrossRef]

G. Chanan, M. Troy, C. Ohara, “Phasing the mirror segments of the Keck telescopes: a comparison of different techniques,” in Optical Design, Materials, Fabrication, and Maintenance, P. Dierickx, ed., Proc. SPIE4003, 188–202 (2000).
[CrossRef]

Pintó, A.

C. Pizarro, J. Arasa, F. Laguarta, N. Tomàs, A. Pintó, “Design of an interferometric system for the measurement of phasing errors in segmented mirrors,” Appl. Opt. 41, 4562–4570 (2002).
[CrossRef] [PubMed]

A. Pintó, F. Laguarta, R. Artigas, C. Cadevall, “New interferometric technique for piston measurement in segmented mirrors,” J. Opt. A 4, S369–S375 (2002).
[CrossRef]

A. Pintó, “New interferometric technique for piston measurement and phasing of segmented mirrors,” Ph.D. dissertation (Universitat Politècnica de Catalunya, Barcelona, Spain, 2002).

Pizarro, C.

Sirko, E.

Tomàs, N.

Troy, M.

Appl. Opt.

J. Opt. A

A. Pintó, F. Laguarta, R. Artigas, C. Cadevall, “New interferometric technique for piston measurement in segmented mirrors,” J. Opt. A 4, S369–S375 (2002).
[CrossRef]

Other

A. Pintó, “New interferometric technique for piston measurement and phasing of segmented mirrors,” Ph.D. dissertation (Universitat Politècnica de Catalunya, Barcelona, Spain, 2002).

J. Nelson, T. Mast, S. Faber, “The design of the KECK observatory and telescope,” Keck Observatory Report 90 (W. M. Keck Observatory, Kamuela, Hawaii, 1985).

Grantecan Project Office, GTC Conceptual Design (Grantecan S.A., La Laguna, Spain, 1997).

G. Chanan, M. Troy, C. Ohara, “Phasing the mirror segments of the Keck telescopes: a comparison of different techniques,” in Optical Design, Materials, Fabrication, and Maintenance, P. Dierickx, ed., Proc. SPIE4003, 188–202 (2000).
[CrossRef]

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Figures (8)

Fig. 1
Fig. 1

UPC-ZEBRA interferometer positioned over an intersegment.

Fig. 2
Fig. 2

Experimentally measured composite spectrum (dots) and mathematical fit (continuous curve).

Fig. 3
Fig. 3

Intersegment simulator: segment 1 is on the left, mounted on a manual vertical stage and a PZT; segment 2 is on the right. The bottom part of the UPC-ZEBRA interferometer is seen at the top of the figure.

Fig. 4
Fig. 4

UPC-ZEBRA interferometer installed on the GTC test bench.

Fig. 5
Fig. 5

Experimental interferograms acquired (a) under phased segment conditions, (b) with 8-μm piston, (c) with piston and angular misalignments. The measurement range was set to 12 μm.

Fig. 6
Fig. 6

Accuracy test performed with the phased intersegment simulator.

Fig. 7
Fig. 7

Repeatability tests. The piston measurement range was set to (a) 4 and (b) 12 μm.

Fig. 8
Fig. 8

Linearity test for a 12-μm measurement range. (a) plot of UPC-ZEBRA piston versus HP10719A piston and (b) plot of residuals between UPC-ZEBRA and HP10719A pistons versus HP10719A piston.

Tables (1)

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Table 1 UPC-ZEBRA Specifications

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