The CubeSat Low Frequency Explorer (CLE) in Lunar Orbit
Abstract
In radio astronomy, as in astronomy in general, a wide range of frequencies is observed, as each spectral band offers a unique window to study astrophysical phenomena. At the low-frequency part of the radio spectrum, telescopes such as LOFAR, GMRT and the MWA provide windows to study for example cosmology, pulsars, and (extra)galactic phenomena. Observing at even lower frequencies is very interesting as well, but, due to the influence of the Earth's ionosphere this is not possible from Earth. Thus, the only option to observe the lowest frequencies is a telescope in space. In 2009 the OLFAR radio telescope based on a swarm of (50+) nano-satellites in lunar orbit was proposed. In order to assess the status of current-day technologies for OLFAR, the CubeSat Low Frequency Explorer (CLE) mission concept and technology study was conducted. This was done in the context of the SysNova "LUnar Cubesats for Exploration (LUCE)" challenge of ESA's General Studies Programme (GSP). The CLE mission concept is aiming at conducting radio astronomy below 30 MHz. This CLE radio mission and technology analysis is helping to pave the way towards deploying a larger scale distributed low frequency radio telescope in space, in the coming decades. The Sysnova mission scope includes a circular lunar orbit requirement of >500 km altitude, a total mass of <60 kg, and data communication to a Lunar Obiter in elliptical polar orbit. The CLE study looked into astronomical science to be conducted, and also looked into technical feasibility with associated Technology Readiness Levels (TRLs). It turned out that for CLE with current-day technologies an instantaneous bandwidth of 10 MHz and 4 satellites with maximum baselines of 10 km can be supported with roughly 15% observational duty cycle. Given radio instrument space heritage and recent developments such as the Chang'e 4 NCLE receiver, it should be technologically possible to develop CLE in the coming decade. For a larger scale system such as OLFAR with more than 50 satellites, it turns out that the inter-satellite and downlink communication bandwidth (and associated mass) are currently the main limiting factors. However, novel optical communication links and novel RF communication schemes are currently being developed, and this give a promising outlook.
- Publication:
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42nd COSPAR Scientific Assembly
- Pub Date:
- July 2018
- Bibcode:
- 2018cosp...42E.281B