Characterizing the Radio Quiet Region Behind the Lunar Farside for Low Radio Frequency Experiments
Neil Bassett, David Rapetti, Jack O. Burns, Keith Tauscher, Robert MacDowall
备注：
14 pages, 8 figures, accepted to Advances in Space Research. Additional physical insight such as the skin depth of the lunar material added since previous version. Inset of figure 5 revised to be more legible. Results unchanged
Low radio frequency experiments performed on Earth are contaminated by both ionospheric effects and radio frequency interference (RFI) from Earth-based sources. The lunar farside provides a unique environment above the ionosphere where RFI is heavily attenuated by the presence of the Moon. We present electrodynamics simulations of the propagation of radio waves around and through the Moon in order to characterize the level of attenuation on the farside. The simulations are performed for a range of frequencies up to 100 kHz, assuming a spherical lunar shape with an average, constant density. Additionally, we investigate the role of the topography and density profile of the Moon in the propagation of radio waves and find only small effects on the intensity of RFI. Due to the computational demands of performing simulations at higher frequencies, we propose a model for extrapolating the width of the quiet region above 100 kHz that also takes into account height above the lunar surface as well as the intensity threshold chosen to define the quiet region. This model, which we make publicly available through a Python package, allows the size of the radio quiet region to be easily calculated both in orbit or on the surface, making it directly applicable for lunar satellites as well as surface missions.
First Lunar Farside SETI Observations for Periodic Signals with the Low-frequency Radio Spectrometer of Chang'E-4 Mission
Institute for Frontiers in Astronomy and Astrophysics, Beijing Normal University（北京师范大学天文与前沿科学研究院）；School of Physics and Astronomy, Beijing Normal University（北京师范大学物理与天文学院）；Institute for Astronomical Science, Dezhou University（德州大学天理研究所）；College of Computer and Information, Dezhou University（德州大学计算机与信息学院）；Institute for Astrophysics, Zhengzhou University（郑州大学天体物理研究所）
The Lunar Farside Transients and Technology Telescope (LFT3) Mission
University of Oxford（牛津大学）；University of California（加州大学）；Trinity College Dublin（都柏林三一学院）；Stanford University（斯坦福大学）；Heliospace；The University of Edinburgh（爱丁堡大学）；Brookhaven National Laboratory（布鲁克海文国家实验室）；SETI Institute（SETI研究所）；University of New Mexico（新墨西哥大学）
The farside of the Moon is a pristine, quiet platform to conduct low radio frequency observations of the early Universe's Dark Ages, as well as space weather and magnetospheres associated with habitable exoplanets. In this paper, the astrophysics associated with NASA-funded concept studies will be described including a lunar-orbiting spacecraft, DAPPER, that will measure the 21 cm global spectrum at redshifts 40-80, and an array of low frequency dipoles on the lunar farside surface, FARSIDE, that would detect exoplanet magnetic fields. DAPPER observations (17-38 MHz), using a single cross-dipo…
FARSIDE (Farside Array for Radio Science Investigations of the Dark ages and Exoplanets) is a Probe-class concept to place a low radio frequency interferometric array on the farside of the Moon. A NASA-funded design study, focused on the instrument, a deployment rover, the lander and base station, delivered an architecture broadly consistent with the requirements for a Probe mission. This notional architecture consists of 128 dual polarization antennas deployed across a 10 km area by a rover, and tethered to a base station for central processing, power and data transmission to the Lunar Gatewa…
Modelling Radio Frequency Interference on the Lunar Farside
Trinity College Dublin（都柏林三一学院）；The University of Edinburgh（爱丁堡大学）；University of Oxford（牛津大学）；Heliospace（赫利奥空间）；Radio Astronomy Laboratory, University of California, Berkeley（加州大学伯克利分校射电天文实验室）
A novel concept is presented in this paper for a human mission to the lunar L2 (Lagrange) point that would be a proving ground for future exploration missions to deep space while also overseeing scientifically important investigations. In an L2 halo orbit above the lunar farside, the astronauts aboard the Orion Crew Vehicle would travel 15% farther from Earth than did the Apollo astronauts and spend almost three times longer in deep space. Such a mission would serve as a first step beyond low Earth orbit and prove out operational spaceflight capabilities such as life support, communication, hi…
This is the final report submitted to NASA for a Probe-class concept study of the "Farside Array for Radio Science Investigations of the Dark ages and Exoplanets" (FARSIDE), a low radio frequency interferometric array on the farside of the Moon. The design study focused on the instrument, a deployment rover, the lander and base station, and delivered an architecture broadly consistent with the requirements for a Probe mission. This notional architecture consists of 128 dipole antennas deployed across a 10 km area by a rover, and tethered to a base station for central processing, power and data…
The Lunar Lander Neutron and Dosimetry (LND) Experiment aboard the Chang$'$E-4 Lander on the lunar-far side measures energetic charged and neutral particles and monitors the corresponding radiation levels. During solar quiet times, galactic cosmic rays (GCRs) are the dominating component of charged particles on the lunar surface. Moreover, the interaction of GCRs with the lunar regolith also results in upward directed albedo protons which are measured by the LND. In this work, we used calibrated LND data to study the GCR primary and albedo protons. We calculate the averaged GCR proton spectrum…
An array of low-frequency dipole antennas on the lunar farside surface will probe a unique, unexplored epoch in the early Universe called the Dark Ages. It begins at Recombination when neutral hydrogen atoms formed, first revealed by the cosmic microwave background. This epoch is free of stars and astrophysics, so it is ideal to investigate high energy particle processes including dark matter, early Dark Energy, neutrinos, and cosmic strings. A NASA-funded study investigated the design of the instrument and the deployment strategy from a lander of 128 pairs of antenna dipoles across a 10 kmx10…
A new era of exploration of the low radio frequency Universe from the Moon will soon be underway with landed payload missions facilitated by NASA's Commercial Lunar Payload Services (CLPS) program. CLPS landers are scheduled to deliver two radio science experiments, ROLSES to the nearside and LuSEE to the farside, beginning in 2021. These instruments would be pathfinders for a 10-km diameter interferometric array, FARSIDE, composed of 128 pairs of dipole antennas proposed to be delivered to the lunar surface later in the decade. ROLSES and LuSEE, operating at frequencies from 100 kHz to a few …
Earth-based observations are complicated by the opacity of Earth's ionosphere at very low frequencies and strong man-made radio frequency interference. This explains long standing interest in building a low frequency radio telescope on the farside of the Moon. Experience from ground-based observations near the ionospheric cutoff in dealing with the interference, ionosphere, and wide-field imaging/dynamic range problems provides crucial information for future radioastronomic experiments on the Moon. In this purpose we observed non-intensive solar bursts on the example of solar drift pairs (DP) …
The trajectory design for the Dark Ages Radio Explorer (DARE) mission con-cept involves launching the DARE spacecraft into a geosynchronous transfer orbit (GTO) as a secondary payload. From GTO, the spacecraft then transfers to a lunar orbit that is stable (i.e., no station-keeping maneuvers are required with minimum perilune altitude always above 40 km) and allows for more than 1,000 cumulative hours for science measurements in the radio-quiet region located on the lunar farside.
A radio telescope placed in lunar orbit, or on the surface of the Moon's farside, could be of great value to the Search for Extraterrestrial Intelligence (SETI). The advantage of such a telescope is that it would be shielded by the body of the Moon from terrestrial sources of radio frequency interference (RFI). While RFI can be identified and ignored by other fields of radio astronomy, the possible spectral similarity between human and alien-generated radio emission makes the abundance of artificial radio emission on and around the Earth a significant complicating factor for SETI. A Moon-based…
The Moon is a unique platform for fundamental astrophysical measurements of gravitation, the Sun, and the Universe. Lacking a permanent ionosphere and, on the farside, shielded from terrestrial radio emissions, a radio telescope on the Moon will be an unparalleled heliospheric and astrophysical observatory. Crucial stages in particle acceleration near the Sun can be imaged and tracked. The evolution of the Universe before and during the formation of the first stars will be traced, yielding high precision cosmological constraints. Lunar Laser Ranging of the Earth-Moon distance provides extremel…
The Dark Ages Radio Experiment (DARE) seeks to study the cosmic Dark Ages approximately 80 to 420 million years after the Big Bang. Observations require truly quiet radio conditions, shielded from Sun and Earth electromagnetic (EM) emissions, on the far side of the Moon. DARE's science orbit is a frozen orbit with respect to lunar gravitational perturbations. The altitude and orientation of the orbit remain nearly fixed indefinitely, maximizing science time without the need for maintenance. DARE's observation targets avoid the galactic center and enable investigation of the universe's first st…
Jet Propulsion Laboratory, California Institute of Technology（加州理工学院喷气推进实验室）；Blue Origin Enterprises（蓝色起源公司）；California Institute of Technology（加州理工学院）；University of Michigan（密歇根大学）；University of Colorado Boulder（科罗拉多大学博尔德分校）
The Far-side Array for Radio Science Investigations of the Dark ages and Exoplanets (FARSIDE) is a proposed mission concept to the lunar far side that seeks to deploy and operate an array of 128 dual-polarization, dipole antennas over a region of 100 square kilometers. The resulting interferometric radio telescope would provide unprecedented radio images of distant star systems, allowing for the investigation of faint radio signatures of coronal mass ejections and energetic particle events and could also lead to the detection of magnetospheres around exoplanets within their parent star's habit…
Site selection for the Laser Interferometer Lunar Antenna (LILA)
Vanderbilt University（范德堡大学）；Lunar Resources, Inc.（月球资源有限公司）；University of Texas Rio Grande Valley（得克萨斯大学里奥格兰德河谷分校）；Université Paris Cité, Institut de physique du globe de Paris, CNRS（巴黎西岱大学，巴黎地球物理研究所，法国国家科学研究中心）；California Institute of Technology（加州理工学院）；Johns Hopkins Applied Physics Laboratory（约翰斯·霍普金斯大学应用物理实验室）
Electrical coupling of a horizontal dipole antenna to a dielectric half-space: applications to radio astronomy from the lunar surface
Lawrence Berkeley National Laboratory（劳伦斯伯克利国家实验室）；University of California, Berkeley（加州大学伯克利分校）；The Blackett Laboratory, Imperial College London（帝国理工学院布莱克特实验室）；Brookhaven National Laboratory（布鲁克海文国家实验室）
Neutral hydrogen pervades the infant Universe, and its redshifted 21-cm signal allows one to chart the Universe. This signal allows one to probe astrophysical processes such as the formation of the first stars, galaxies, (super)massive black holes and enrichment of the pristine gas from z~6 to z~30, as well as fundamental physics related to gravity, dark matter, dark energy and particle physics at redshifts beyond that. As one enters the Dark Ages (z>30), the Universe becomes pristine. Ground-based low-frequency radio telescopes aim to detect the spatial fluctuations of the 21-cm signal. Compl…
The redshifted 21-cm monopole is expected to be a powerful probe of the epoch of the first stars and galaxies ($10<z<35$). The global 21-cm signal is sensitive to the thermal and ionization state of hydrogen gas and thus provides a tracer of sources of energetic photons -- primarily hot stars and accreting black holes -- which ionize and heat the high redshift intergalactic medium (IGM). This paper presents a strategy for observations of the global spectrum with a realizable instrument placed in a low altitude lunar orbit, performing night-time 40-120 MHz spectral observations, while on the fa…
