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Use of a Surface Polarizer to Reduce the Spectral Baseline Ripple of the Parkes Telescope

Published online by Cambridge University Press:  25 April 2016

D. R. Williams  and
B. MacA. Thomas
D. R. Williams
Affiliation:
Division of Radiophysics, CSIRO, Sydney
B. MacA. Thomas
Affiliation:
Division of Radiophysics, CSIRO, Sydney
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Extract

Baseline ripple measurements are of two general kinds, those associated with on-source mechanisms and those with off-source mechanisms (Poulton 1974; Morris 1974). We are here principally concerned with on-source baseline ripples, which occur when a strong continuum radio source is present in the beam. The ripples are particularly conspicuous (Padman 1977, 1978) with a large instrument, such as the Parkes 64-m telescope, where the ripple period is rapid. Here baseline uncertainty becomes especially severe for the detection and study of wide lines, such as the H/He complex and the formamide multiplet near 1.54 GHz. Off-source baseline ripples also occur because of other effects, but in principle they can be removed by subtracting a reference-region spectrum taken while tracking the telescope over the same hour-angle range at the same declination under stable conditions. Improvement of the off-source baseline ripple which arises from stray radiation would also be expected to result from the technique described here.

Type
Contributions
Information
Publications of the Astronomical Society of Australia , Volume 4 , Issue 1 , 1980 , pp. 33 - 37
Copyright
Copyright © Astronomical Society of Australia 1980

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References

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