help

Can Radio Frequency Interference be Confused with Astronomical Signals?

-- | May 24, 2014

Question: I was reading this article on your website: https://public.nrao.edu/telescopes/radio-frequency-interference
I was looking at the image on the far right which shows what happens when a nearby satellite crosses the path of a star detected by a ground based radio telescope. my question to what I am seeing is, can this truly be considered noise interference emanating from the satellite exclusively or can we be seeing a form of lensing occurring due to the magnetic wave characteristics of the satellite’s transmitted radio signals? can we also be seeing background details that where not detectable with just a single radio telescope? Could we be detecting dark matter this way? what are we really seeing? Is it just solely transmissions from the satellite, mixture of Gaussian noise? or something more? — David

Answer: In order for the satellite to produce lensed emission from the objects beyond it the satellite would need to be quite massive (thus behaving like a gravitational lens). We also know that communication satellites emit very strong (by astronomical standards) emission at specific wavelengths that we can measure. It is that strong emission that we detect with our radio telescopes, and which produces the interference pattern shown in the lower-right-hand figure at the web site you refer to. In fact, that specific interference pattern has the hallmark of a strong “source” (the satellite’s transmission signal) that is not quite in the direction that the radio telescope interferometer is looking, but not so far away that it cannot be detected. This slightly offset positioning of the interfering signal results in the “ripple” pattern measured by the radio interferometer.

Jeff Mangum

The National Radio Astronomy Observatory is a facility of the U.S. National Science Foundation operated under cooperative agreement by Associated Universities, Inc.
	Founded in 1956, the NRAO provides state-of-the-art radio telescope facilities for use by the international scientific community. NRAO telescopes are open to all astronomers regardless of institutional or national affiliation. Observing time on NRAO telescopes is available on a competitive basis to qualified scientists after evaluation of research proposals on the basis of scientific merit, the capability of the instruments to do the work, and the availability of the telescope during the requested time. NRAO also provides both formal and informal programs in education and public outreach for teachers, students, the general public, and the media.
	The U.S. National Science Foundation (NSF) is an independent federal agency created by Congress in 1950 "to promote the progress of science; to advance the national health, prosperity, and welfare; to secure the national defense..."
	AUI collaborates with the scientific community and research sponsors to plan, build, and operate cutting-edge facilities. We cultivate excellence, deliver value, enhance education, and engage the public.