Discovering the sky at the Longest Wavelengths (DSL)
Albert Jan Boonstra (TU Delft - Signal Processing Systems, Netherlands Institute for Radio Astronomy (ASTRON))
Michael Garrett (Netherlands Institute for Radio Astronomy (ASTRON))
Gert Kruithof (Netherlands Institute for Radio Astronomy (ASTRON))
Michael Wise (Netherlands Institute for Radio Astronomy (ASTRON))
Arnold Van Ardenne (Netherlands Institute for Radio Astronomy (ASTRON))
Jingye Yan (Chinese Academy of Sciences)
Ji Wu (Chinese Academy of Sciences)
Jianhua Zheng (Chinese Academy of Sciences)
Eberhard K A Gill (TU Delft - Space Engineering)
Jian Guo (TU Delft - Space Systems Egineering)
Mark Bentum (University of Twente)
Julien N. Girard (CEA-Saclay)
Xiaoyu Hong (Chinese Academy of Sciences)
Tao An (Chinese Academy of Sciences)
Heino Falcke (Radboud Universiteit Nijmegen)
Marc Klein-Wolt (Radboud Universiteit Nijmegen)
Shufan Wu (Chinese Academy of Sciences)
Wen Chen (Chinese Academy of Sciences)
Leon Koopmans (University Medical Center Groningen)
Hanna Rothkaehl (Polish Academy of Sciences)
Xuelei Chen (Chinese Academy of Sciences)
Maohai Huang (Chinese Academy of Sciences)
Linjie Chen (Chinese Academy of Sciences)
Leonid Gurvits (TU Delft - Astrodynamics & Space Missions, Joint Institute for VLBI ERIC)
Philippe Zarka (ENS-PSL Research University & CNRS)
Baptiste Cecconi (ENS-PSL Research University & CNRS)
Hans De Haan (Stip BV)
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Abstract
The radio sky at frequencies below ∼30 MHz is virtually unobservable from Earth due to ionospheric disturbances and the opaqueness of the ionosphere below ∼10MHz, and also due to strong terrestrial radio interference. Deploying a radio observatory in space would open up this largely unexplored frequency band for science in astronomy, cosmology, geophysics, and space science. A Chinese-European team is proposing an ultra long wavelength (ULW) radio interferometer mission DSL (Discovering the Sky at the Longest Wavelengths). The proposed radio interferometer will be deployed in low-altitude lunar orbit, exploiting the radio quietness of the lunar far side. DSL will consist of a mother-spacecraft for data transport and control, plus eight small micro-satellites each equipped with three orthogonal dipoles. These satellites form a virtual distributed observatory with adjustable baselines, allowing different scientific observation strategies. The satellites are configured in a flexible quasi-linear array in nearly identical orbits, guaranteeing low relative drift rates. Short orbital periods and orbit precession ensure quick filling of the interferometric spatial frequency (u, v, w) space, enabling high quality imaging. The science themes considered for the DSL mission include pioneering studies of the unknown and exploratory science such as the search for signatures of the cosmological Dark Ages, complementing current (e.g. LOFAR) and future SKA telescope searches; full-sky continuum survey of discrete sources, including ultra-steep spectrum extragalactic sources, pulsars, and transients (galactic and extragalactic); full-sky map of continuum diffuse emission; solar-terrestrial physics, planetary sciences, and cosmic ray physics. The main frequency band covered is 1-30 MHz extending down to 0.1 MHz, and up to about 50 MHz for cross-referencing with ground-based instruments. DSL will support a variety of observational modes, including broad-band spectral analysis for Dark Ages, radio interferometric cross-correlations for imaging, and flexible raw data downlink capability. Data processing will be performed at radio astronomy science data centres in Europe and China.