DSL: Interferometric Imaging with Linear microsatellite Array in Lunar Orbit

Low frequency sky map and global spectrum are basically unexplored domain. It is of significant importance to understand early universe, such as the universe Dark Ages and cosmic dawn. Many ground experiments are implemented in order to reveal the mystery of low frequency universe, but ground observations are hardly convincible because of the ionospheric blockage and man-made low frequency interferences.

A space mission is proposed by NSSC to map low frequency sky and measure global spectrum since 2014, soon later proposed to the CAS-ESA space science joint mission as Discovering the Sky at Longest wavelength (DSL). The concept is composed of a mother satellite and 8 daughter satellites forming a linear array around the lunar low orbit. Taking the advantages of Moon shielding, the space array receives only cosmic radiation from the sky without radio interferences from the Earth. Longest baseline of 100km is selected to produce low frequency sky at an angular resolution of 0.1 degree, which almost the recognized size of a point radiation sources, taking into account the scattering by the inter-galaxies medium. A pathfinder microsatellite Longjiang-2 is already in the lunar orbit piggybacking on Chinese ChangE-4 program in 21st May, 2018. Continuously spectrum from 1-30MHz is retrieved in 3 orthogonal polarizations. Further study on phase A/B is already supported by the Strategic Priority Program on Space Science, Chinese Academy of Science.