Using a constellation of small satellites to characterize the RF quiescence of the lunar farside

Radio images of red-shifted 21-cm signals from neutral hydrogen originating from the very early Universe, the so-called Dark Ages before the first stars formed, are impossible to obtain from Earth due to man-made radio frequency interference (RFI) and the opacity of the ionosphere below ∼30 MHz. To efficiently block the RFI, which would otherwise overwhelm the weak cosmological signal, requires a large low-frequency radio array on the far-side of the Moon. Such a lander mission is technically challenging and carries a budget that is currently unlikely to be included in any national or international mission plan. Our goal is to use a constellation of small satellites in lunar orbit to collect pathfinder data to demonstrate the feasibility of using the Moon as a radio-shield, and map out the spatial extent of this RF quiescent zone. The team led by the Hawaii Space Flight Laboratory (HSFL) at the University of Hawaii at Manoa is designing a mission to characterize the spatial extent of the RF quiescence zone on the lunar farside to support future missions to explore the cosmos using radio observatories on the surface. This paper examines the design of this mission starting with a baseline architecture that uses a modified SSTL X50 satellite bus as mothership that carries one or more nanosats to lunar orbit. The mothership will then deploy it/them to form the constellation, as well as act as the communications relay between them and Earth. The initial baseline mission utilizes the standard Super Strypi launch vehicle. Although it is desirable to have a mothership and several nanosats evenly distributed in an equatorial lunar orbit, performance limitations of the standard launch vehicle only permit the mothership with one nanosat in a highly elliptical orbit that would allow measurement of the relevant RF environment continuously for at least a year. The nanosat would crosslink the collected data to the mothership, which will relay the data to Earth as well as act as an RF collecting station itself.