ALFA: a constellation mission for low frequency radioastronomy

The ALFA mission is proposed to be the first astronomical observatory to make high-resolution radio images in the vast region of the electromagnetic spectrum below Earth´s ionospheric cutoff between 30 kHz and 30 MHz. The ALFA imaging interferometer consists of 16 identical small satellites with dipole antennas and low frequency radio receivers, distributed in a spherical array 100 km in diameter, yielding images with thousands of times the resolution previously available in this frequency range. The array will be placed in a nearly circular distant retrograde orbit about the Earth, with a typical range of 10⁶ km. Each satellite communicates directly with a small (11 m.), low-cost antenna at each DSN site, providing parallel data paths and continuous coverage. As a result, the array is resilient to individual satellite failures; observing by the rest of the array will be unaffected