Connected Element Interferometry High angular resolution is achieved by combining the signals from two or more antennas. Very Long Baseline Interferometry Antennas at widely seprated geographical locations can be combined into a synthetic radio telescope by locally recording the signals on high capacity magnetic tapes and combining the signals afterwards. Spectroscopy Emission which is intrinsically narrow band, such as that associated with quantum transitions in atoms and molecules, is recorded with spectrometers which separate the signal into many adjacent narrow frequency bands. Polarization Measurements Polarization characteristics of radio emission requires the ability to measure orthogonal polarization modes. Simple measurements can sometimes be made by changing the polarization orientation of a feedhorn.
Sophicated measurements require the simultaneous recording of both senses of polarization.
To realize the full potential of the NASA space communication facilities for radio astronomy, the equipment and operational procedures available to astronomers using the DSN should equal the capabilities available at radio observatories. Because radio astronomy research adapts rapidly to scientific discoveries and new opportunities in technology and innovative procedures, the DSN is challenged to being able to operate in a flexible research and development mode. The ability of VLBI observations to determine complex radio source structure is enhanced by increasing the number and geographical diversity of antennas. Consequently, the use of non-DSN space communications antennas may be requested for VLBI research.