Title:	12 GHz radio-holographic surface measurement of the RRI 10.4m telescope
Authors:	Balasubramanyam, R. Venkatesh, S. Raju, Sharath B.
Issue Date:	Sep-2009
Publisher:	Astronomical Society of the Pacific
Citation:	ASP Conference Series, 2009, Vol.407, p434
Abstract:	A modern Q-band low noise amplifier (LNA) front-end is being fitted to the 10.4~m millimeter-wave telescope at the Raman Research Institute (RRI) to support observations in the 40-50~GHz frequency range. To assess the suitability of the surface for this purpose, we measured the deviations of the primary surface from an ideal paraboloid using radio holography. We used the 11.6996 GHz beacon signal from the GSAT3 satellite, a 1.2~m reference antenna, commercial Ku-band Low Noise Block Convereters (LNBC) as the receiver front-ends and a Stanford Research Systems (SRS) lock-in amplifier as the backend. The LNBCs had independent free-running first local oscillators (LO). Yet, we recovered the correlation by using a radiatively injected common tone that served as the second local oscillator. With this setup, we mapped the surface deviations on a 64 × 64 grid and measured an rms surface deviation of ˜ 350~μm with a measurement accuracy of ˜ 50~μm.
Description:	Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)
URI:	http://hdl.handle.net/2289/4140
Alternative Location:	http://adsabs.harvard.edu/abs/2009ASPC..407..434B http://arxiv.org/abs/0910.2946
Copyright:	2009 Astronomical Society of the Pacific.
Additional information:	Proceedings of the conference held 8-12 December 2008, at National Centre for Radio Astrophysics (NCRA), TIFR, Pune, India. Edited by D. J. Saikia, D. A. Green, Y. Gupta, and T. Venturi. San Francisco: Astronomical Society of the Pacific.
Appears in Collections:	Research Papers (A&A)

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