Abstract
The Hartebeesthoek Radio Astronomy Observatory of South Africa is currently developing a lunar laser ranger (LLR) system based on a one metre aperture telescope in collaboration with National Aeronautics and Space Administration and the Observatoire de la Côte d’Azur. This LLR will be an addition to a limited list of operating LLR stations globally and it is expected to achieve sub-centimetre range precision to the Moon. Key to this expectation including the overall telescope operational performance is thermal analysis of the telescope structure, based on the thermal properties of component materials and their interaction with the environment through conventional heat transfer mechanisms. This paper presents transient thermal simulation results of the telescope’s optical tube and one metre primary mirror in terms of thermal variations and consequent structural deformations. The results indicate that on a non-windy, cloud-free and winter day, the temperature gradients on the structure could be within 1 °C with respect to the temporal ambient air temperatures at the site when these are between 9 and 23 °C. Furthermore, these gradients were coupled with thermally-induced total deformations that vary between 2.9 and 40.7 μm of the assembled telescope components. In overall, these findings suggest that both the tube and especially the mirror may respond very slowly to ambient temperatures; however, correcting for structural thermal variations is imperative in maximizing the pointing accuracy of the telescope thereby increasing the chance being on-target with the retroreflectors located on the Moon surface.
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References
Bely P (2003) The design and construction of large optical telescopes. Springer, New York
Bremer M, Penalver J (2002) FE model-based interpretation of telescope temperature variations. In: Workshop on integrated modelling of telescopes. International Society for Optics and Photonics, pp 186–195
Cengel YA, Ghajar AJ (2011) Heat and mass transfer: fundamentals & applications. McGraw-Hill, New York
Cho M, Corredor A, Vogiatzis K, Angeli G (2009) Thermal performance prediction of the TMT telescope structure. In: SPIE Optical Engineering+ Applications. International Society for Optics and Photonics, pp 74270E-74215E
Cho M, Corredor A, Vogiatzis K, Angeli G (2010) Thermal analysis of the TMT telescope structure. In: SPIE Astronomical Telescopes+ Instrumentation. International Society for Optics and Photonics, pp 77380C–77312C
Combrinck L (2011) Development of a satellite and lunar laser ranger and its future applications in South Africa. In: Proceedings of the 62nd international astronautical congress. Oct 2011, Cape Town, available at: http://iafastro.directory/iac/archive/browse/IAC-11/A2/1/
Combrinck L, Botha R (2014) Challenges and progress with the development of a Lunar Laser Ranger for South Africa. In: Proceedings of the 18th international workshop on laser ranging: pursuing ultimate accuracy and creating new synergies, 11–15 Nov 2013, Fujiyoshida, available at: http://cddis.gsfc.nasa.gov/lw18/docs/papers/Session13/13-05-04-Combrinck.pdf
Combrinck WL, Merry CL (1997) VLBI Antenna axis offset and intersection determination using GPS. J Geophys Res 102(B11): 24741–24743
Dalcher A, Yang T, Chu C (1977) High temperature thermal-elastic analysis of dissimilar metal transition joints. J Eng Mater Technol 99(1):65–69
Green DW (2008) Perry’s chemical engineers’ handbook. McGraw-hill, New York
Greve A, Bremer M (2010) Thermal design and thermal behaviour of radio telescopes and their enclosures. Springer, Berlin
Greve A, Bremer M, Penalver J, Raffin P, Morris D (2005) Improvement of the IRAM 30-m telescope from temperature measurements and finite-element calculations. IEEE Trans Antennas Propag 53(2):851–860
Hartebeesthoek Radio Astronomy Observatory (HartRAO) (2005) Proposed re-location and conversion of CNES SLR system to South Africa in collaboration with OCA and the greater ILRS community. Available at http://www.hartrao.ac.za/iisgeo/docs/LLR_proposal.doc
Hirt C, Seeber G (2008) Accuracy analysis of vertical deflection data observed with the Hannover Digital Zenith Camera System TZK2-D. J Geodesy 82(6):347–356
Jedamzik R, Johansson T, Westerhoff T (2010) Modeling of the thermal expansion behaviour of ZERODUR at arbitrary temperature profiles. In: SPIE Astronomical Telescopes+ Instrumentation. International Society for Optics and Photonics, pp 77390I–77312
Lawrence KL (2012) ANSYS workbench tutorial release 14. SDC Publications, Mission
Mészáros L, Jaskó A, Pál A, Csépány G (2014) Accurate Telescope Mount Positioning with MEMS Accelerometers. arXiv preprint arXiv:1407.0035
Mittag M, Hempelmann A, Gonzalez-Perez J, Schmitt J (2008) The temperature dependence of the pointing model of the hamburg robotic telescope. Publ Astron Soc Pac 120(866):425–429
Murphy Jr T, Adelberger EG, Battat J, Carey L, Hoyle CD, LeBlanc P, Michelsen E, Nordtvedt K, Orin A, Strasburg JD (2008) The apache point observatory lunar laser-ranging operation: instrument description and first detections. Publ Astron Soc Pac 120(863):20–37
Perry J (1943) Thermal effects upon the performance of lens systems. Proc Phys Soc 55(4):257
Pisanu T, Buffa F, Morsiani M, Pernechele C, Poppi S (2010) Thermal behavior of the Medicina 32-meter radio telescope. In: SPIE Astronomical Telescopes+ Instrumentation. International Society for Optics and Photonics, pp 773935–773939
Planchard DC, Planchard MP (2013) SolidWorks 2013 Tutorial. SDC Publications, Mission
Schott A (2011) ZERODUR®–Zero Expansion Glass Ceramic. Data sheet, Mainz
Shinnaga H, Chamberlin R, Phillips T, Dowel D, Yoshida H, Peng R (2004) A consideration of thermal effect on pointing measured on a Nasmyth focus of the CSO 10.4 m Leighton telescope at λ350 μm. Technical memorandum
Vogiatzis K, Sadjadpour A, Roberts S (2014) TMT telescope structure thermal model. In: SPIE Astronomical Telescopes+ Instrumentation. International Society for Optics and Photonics, pp 915011–915012
Wresnik J, Haas R, Boehm J, Schuh H (2007) Modeling thermal deformation of VLBI antennas with a new temperature model. J Geodesy 81(6-8):423-431
Acknowledgments
P. L. Tsela hereby acknowledges research support in part by the National Research Foundation of South Africa for the grant, Unique Grant No. 93952. Any opinion, finding and conclusion or recommendation expressed in this material is that of the author(s) and the NRF does not accept any liability in this regard. Further, we express our gratitude to the Inkaba yeAfrica project, the Department of Science and Technology of South Africa and HartRAO for support. We also acknowledge support from the Mechanical Engineering Department at the University of Pretoria for providing access to ANSYS software.
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Tsela, P., Combrinck, L., Botha, R. et al. Thermal analysis of the LLR optical telescope tube assembly based in Hartebeesthoek Radio Astronomy Observatory. Acta Geod Geophys 51, 393–403 (2016). https://doi.org/10.1007/s40328-015-0132-6
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DOI: https://doi.org/10.1007/s40328-015-0132-6