NATIONAL ASTRONOMY AND IONOSPHERE CENTER . ... Arecibo Ionospheric Observatory Commissioned for service, 1 November, 1963. ... One of its first accomplishments: Establishing the rotating rate of Mercury, which turned out to be 59 days rather than the previously estimated 88 days. €а . ... The National Astronomy and Ionosphere Center (NAIC) begins. €а . ... First radar ranging to an Earth-crossing asteroid (1862 Apollo) . ... 2007 . ... Asteroid 2007 TU24 passed only 1.4 times the distance to the moon. ...

... 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. ...