Active Control of Large Telescopes: Active Optics

  • André Preumont
Part of the Solid Mechanics and Its Applications book series (SMIA, volume 246)


This chapter deals with the control of the primary mirror of large telescopes in order to compensate the deformation due to manufacturing errors, the thermal gradients, and the changing gravity loads. The case of a monolithic mirror is considered first, followed by that of segmented mirrors (all telescopes with a primary mirror larger than 8 m will be segmented). The control strategy is based on a quasi-static model between the actuator inputs and the sensor outputs (Jacobian); the feedback loop uses a singular value decomposition (SVD) controller shaped in the frequency domain. Next, the dynamic response of the telescope is considered and its possible interaction with the SVD controller is analyzed. A stability robustness test is used to evaluate the stability margin and derive guidelines on the control bandwidth, natural frequency, and structural damping of the telescope structure to avoid spillover instability. The final section discusses some important scaling rules for telescopes of increasing size. The chapter concludes with a reference list.


Active optics E-ELT Segmented mirror Edge sensor Co-phasing SVD controller Loop shaping Spillover Control-structure interaction 


  1. 1.
    Agarwal BD, Broutman LJ (1990) Analysis and performance of fiber composites, 2nd edn. Wiley, New YorkGoogle Scholar
  2. 2.
    Angeli GZ, Cho MK, Whorton MS (2002) Active optics and architecture for a giant segmented mirror telescope. In: Angeli, Gilmozzi (eds) Future giant telescopes. SPIE 4840, Paper No. 4840–22, pp 129–139Google Scholar
  3. 3.
    Aubrun JN, Lorell KR, Mast TS, Nelson JE (1987) Dynamic analysis of the actively controlled segmented mirror of the W.M. Keck ten-meter telescope. IEEE Control Syst Mag 7(6):3–10CrossRefGoogle Scholar
  4. 4.
    Aubrun JN, Lorell KR, Havas TW, Henninger WC (1988) Performance analysis of the segment alignment control system for the ten-meter telescope. Automatica 24(4):437–453CrossRefzbMATHGoogle Scholar
  5. 5.
    Bastaits R (2010) Extremely large segmented mirrors: dynamics, control and scale effects. Ph.D. thesis, Université Libre de Bruxelles, Active Structures LaboratoryGoogle Scholar
  6. 6.
    Bastaits R, Rodrigues G, Mokrani B, Preumont A (2009) Active optics of large segmented mirrors: dynamics and control. AIAA J Guid Control Dyn 32(6):1795–1803CrossRefGoogle Scholar
  7. 7.
    Bely PY (2003) The design and construction of large optical telescopes. Springer, BerlinGoogle Scholar
  8. 8.
    Blevins RD (1979) Formulas for natural frequencies and mode shapes, Van Nostrand ReinholdGoogle Scholar
  9. 9.
    Dimmler M, Erm T, Bauvir B, Sedghi B, Bonnet H, Müller M, Wallander A (2008) E-ELT primary mirror control system. SPIE, Ground-based and airborne telescopes II, p 7012Google Scholar
  10. 10.
    Gilmozzi R, Spyromilio J (2008) The 42 m European ELT: status. In: Stepp LM (ed) Ground-based and airborne telescopes II, SPIE 7012Google Scholar
  11. 11.
    Lake MS, Peterson LD, Levine MB (2002) Rationale for defining structural requirements for large space telescopes. AIAA J Spacecr Rocket 39(5):674–681CrossRefGoogle Scholar
  12. 12.
    Lake MS, Peterson LD, Mikulas MM (2006) Space structures on the back of an envelope: John Hedgepeth’s design approach. AIAA J Spacecr Rocket 43(6):1174–1183CrossRefGoogle Scholar
  13. 13.
    Nelson J, Sanders G (2008) The status of the thirty meter telescope project. In: Stepp LM (ed) Ground-based and airborne telescopes II SPIE 7012Google Scholar
  14. 14.
    Noethe L (2002) Active optics in modern, large optical telescopes. Prog Opt 43:1–70CrossRefGoogle Scholar
  15. 15.
    Preumont A, Bastaits R, Rodrigues G (2009) Scale effects in active optics of large segmented mirrors. Mechatronics 19(8):1286–1293CrossRefGoogle Scholar
  16. 16.
    Wilson RN, Franza F, Noethe L (1987) Active optics 1. A system for optimizing the optical quality and reducing the costs of large telescopes. J Modern Opt 34(4):485–509Google Scholar

Copyright information

© Springer International Publishing AG 2018

Authors and Affiliations

  1. 1.Active Structures LaboratoryUniversité Libre de BruxellesBrusselsBelgium

Personalised recommendations