In this report we compare the cost of an array of small antennas to that of a single large antenna assuming both the array and single large antenna have equal performance and availability. The single large antenna is taken to be one of the 70-m antennas of the Deep Space Network. The cost of the array is estimated as a function of the array element diameter for three different values of system noise temperature corresponding to three different packaging schemes for the first amplifier. Array elements are taken to be fully steerable paraboloids and their cost estimates were obtained from commercial vendors. Array loss mechanisms and calibration problems are discussed. For array elements in the range 3 - 35 m there is no minimum in the cost versus diameter curve for the three system temperatures that were studied. Resch, George M. and Cwik, T. W. and Jamnejad, V. and Logan, R. T. and Miller, R. B. and Rogstad, Dave H. Jet Propulsion Laboratory ANTENNA ARRAYS; APERTURES; COST ESTIMATES; SYSTEMS ANALYSIS; TELECOMMUNICATION; CALIBRATING; COHERENCE; DEEP SPACE NETWORK; ENERGY DISSIPATION; NOISE TEMPERATURE...