DIRECTIONS FOR SPACE-BASED LOW-FREQUENCY RADIO ASTRONOMY .1. SYSTEM CONSIDERATIONS

Although observations at the low end of the radio astronomy spectrum w ere the precursor of all work in radio astronomy, this portion of the spectrum has languished for decades while research at the upper radio frequencies has fluorished. Previous work at low frequencies (below 30 MHz) has clearly shown that sensitive high-resolution ground-based ob servations are extremely difficult to make, if not impossible. Observa tion quality at low frequencies can leap forward using space-based int erferometers. Radio telescopes such as these can be built principally from ''off-the-shelf'' components. A relatively low cost space program can make great strides in deploying arrays of antennas and receivers that would produce data contributing significantly to our understandin g of galaxies and galactic nebulae. This paper discusses the various a spects of low-frequency telescopes such as past history and significan t issues like sensitivity, interfer-ence, baseline calibration, wave s cattering, and mapping. All aspects of the first stages of space-based , low-frequency radio telescopes can be accomplished with no dependenc ies on new types of hardware. The time has come to open the final elec tromagnetic frontier in astronomy.