Asteroid 2005 YU55 was listed on NASA's "Sentry Risk Page" as having as small (about one in 10 million) chance of hitting the Earth in the next century. We observed this asteroid with the Arecibo Planetary Radar system on April 19-23 2010. ... We obtained radar images of asteroid 2005 YU55 at 11 PM local time on 2011 Nov 9 using the Arecibo Observatory Planetary Radar System in Puerto Rico and the Robert W. Byrd Green Bank Telescope in West Virginia. ... Last modified 2011 November 14 . ...

... 2.3 Data acquisition Spectra generated by the Multibeam correlator contain the usual structure seen in spectra from other H i instruments: a bandpass spectrum which is the sum of the sky , ground and receiver temperatures multiplied by the product of the filters in the receiver chain; superimposed on this is a noise ... Note also that sources extended much beyond ,40 arcmin can be imaged poorly in HIPASS images because of the bandpass sidelobe effect described in Section 3.3. ...