Remote Sensing

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23 pages, 5606 KiB

Open AccessArticle

Toward a European Facility for Ground-Based Radar Observations of Near-Earth Objects

by Giuseppe Pupillo, Simona Righini, Roberto Orosei, Claudio Bortolotti, Giuseppe Maccaferri, Mauro Roma, Marco Mastrogiuseppe, Tonino Pisanu, Luca Schirru, Stefano Cicalò, Antonio Tripodo, Jorma Harju, Antti Penttilä, Anne K. Virkki, Uwe Bach, Alexander Kraus, Alessio Margheri, Riccardo Ghiani, Maria N. Iacolina, Giuseppe Valente, Detlef Koschny, Richard Moissl and Gunther Sessler Show full author list Hide full author list

Remote Sens. 2024, 16(1), 38; https://doi.org/10.3390/rs16010038 - 21 Dec 2023

Cited by 2 | Viewed by 1682

Abstract

In this work, we present the preliminary results of radar observations of Near-Earth Objects (NEOs) carried out by European radio telescopes in the framework of the European Space Agency (ESA) project “NEO observation concepts for radar systems”, aimed at deriving the functional requirements [...] Read more.

In this work, we present the preliminary results of radar observations of Near-Earth Objects (NEOs) carried out by European radio telescopes in the framework of the European Space Agency (ESA) project “NEO observation concepts for radar systems”, aimed at deriving the functional requirements of a planetary radar system, evaluating the available European assets to perform NEO radar observations, and carrying out test radar campaigns. In the first part of the project, we executed the performance analysis of a possible European planetary radar system. Instrumental features, as much as issues like the impact of weather conditions on signal propagation at different radio frequencies, were considered. This paper focused on the test campaigns, performed in the years 2021–2022 in collaboration with the Jet Propulsion Laboratory (JPL), which led to the observation of several asteroids including 2021 AF8, (4660) Nereus, and 2005 LW3, which allowed us to derive astrometric measurements, as well as to measure physical properties, such as rotation periods, and observe how one of the targets is actually a binary asteroid. The obtained results demonstrated that European radio astronomical dishes, although employed only as receivers (in bistatic or multistatic configurations) and for a limited amount of time, are able to provide a significant contribution to the constitution of a European network to increase the opportunities for NEO monitoring and studies, if a transmitting antenna—equipped with a suitable high-power transmitter—were made available. Full article

(This article belongs to the Special Issue Radar for Planetary Exploration)

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15 pages, 17805 KiB

Open AccessArticle

Evidence of Widespread Volcanic Activity near Hebrus Valles on Mars Revealed by SHARAD

by Stefano Nerozzi, Michael S. Christoffersen, John W. Holt and Christopher W. Hamilton

Remote Sens. 2023, 15(20), 4967; https://doi.org/10.3390/rs15204967 - 14 Oct 2023

Cited by 1 | Viewed by 1864

Abstract

Hebrus Valles is an outflow channel system in the plain-forming terrains of southeastern Utopia Planitia, Mars. These terrains may have formed through a combination of liquid water and volcanic processes, yet their nature, subsurface structure, and composition remain unclear. We investigate these terrains [...] Read more.

Hebrus Valles is an outflow channel system in the plain-forming terrains of southeastern Utopia Planitia, Mars. These terrains may have formed through a combination of liquid water and volcanic processes, yet their nature, subsurface structure, and composition remain unclear. We investigate these terrains by mapping subsurface reflectors across 540 Shallow Radar (SHARAD) profiles and applying two complementary loss tangent inversion techniques. We find moderate loss tangent values across some subregions of Granicus Valles and Hyblaeus Fossae (tan δ = 0.0162 ± 0.0004 and tan δ = 0.019 ± 0.002, respectively), suggesting the presence of basaltic lava flows. We interpret non-detections in the other flows in Granicus Valles to be due to the presence of radar-lossy materials formed through aqueous processes, which supports the hypothesized occurrence of lahars in this region. A small area near Hebrus Valles exhibits subsurface reflectors with low to moderate loss tangents (tan δ = 0.010 ± 0.003), suggesting the presence of pristine lava flows or sedimentary materials capped by lava flows. We also find a widespread occurrence of very low-loss tangent materials near Hyblaeus Dorsa (tan δ = 0.0045 ± 0.0002), which may represent a lobe of the Medusae Fossae Formation or similar high-porosity materials buried underneath a lava flow. Together, these findings suggest that volcanic activity played a central role in the formation of terrains across the broader Hebrus Valles region. Full article

(This article belongs to the Special Issue Radar for Planetary Exploration)

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15 pages, 5618 KiB

Open AccessArticle

Unveiling the Subsurface of Late Amazonian Lava Flows at Echus Chasma, on Mars

by Federico Mansilla, María-Paz Zorzano, Iraklis Giannakis and Javier Ruiz

Remote Sens. 2023, 15(5), 1357; https://doi.org/10.3390/rs15051357 - 28 Feb 2023

Cited by 1 | Viewed by 2755

Abstract

The Echus-Kasei region on Mars has been exposed to different episodic volcanic, fluvial, and glacial events in Amazonian time. The goal of the present work is to demonstrate the usefulness of radar instruments to find preserved late Amazonian subsurface structures that may have [...] Read more.

The Echus-Kasei region on Mars has been exposed to different episodic volcanic, fluvial, and glacial events in Amazonian time. The goal of the present work is to demonstrate the usefulness of radar instruments to find preserved late Amazonian subsurface structures that may have been encapsulated underneath recent lava flows on Mars. We have analysed 27 radar observations of the SHAllow RADar (SHARAD) instrument on board the Mars Reconnaissance Orbiter (MRO), over the region of Echus Chasma. We discovered the presence of subsurface reflectors in five consecutive SHARAD radargrams at a depth from 35 to 79 m beneath the structure of a lava fan that formed about 59 ± 4 Ma ago. Some vents are preserved above the surface of this lava flow, which stands at a height of 80 m above the surrounding surface. A few kilometres to the north, we find other subsurface reflectors at a depth of about 30 m and a long pit chain formed by the collapse of a lava tube. These kinds of subsurface late Amazonian structures are of interest for astrobiology because they date from the last period when the planet still experienced intense volcanic activity over regions that were previously extensively covered by water. Full article

(This article belongs to the Special Issue Radar for Planetary Exploration)

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16 pages, 21054 KiB

Open AccessArticle

Resolving Ambiguities in SHARAD Data Analysis Using High-Resolution Digital Terrain Models

by Léopold Desage, Alain Herique, Sylvain Douté, Sonia Zine and Wlodek Kofman

Remote Sens. 2023, 15(3), 764; https://doi.org/10.3390/rs15030764 - 28 Jan 2023

Cited by 1 | Viewed by 2004

Abstract

The SHAllow RADar (SHARAD) onboard Mars Reconnaissance Orbiter (MRO) is a 20 MHz Synthetic Aperture Radar (SAR) that probes the first hundreds of meters of the Martian subsurface. In order to interpret the detection of subsurface interfaces with ground penetrating radars, simulations using [...] Read more.

The SHAllow RADar (SHARAD) onboard Mars Reconnaissance Orbiter (MRO) is a 20 MHz Synthetic Aperture Radar (SAR) that probes the first hundreds of meters of the Martian subsurface. In order to interpret the detection of subsurface interfaces with ground penetrating radars, simulations using Digital Terrain Models (DTM) are necessary. This methodology paper focuses on the analysis of the first tens of meters of the Martian subsurface with SHARAD, comparing the use of different high-resolution DTMs for radar simulation, namely, from the High-Resolution Stereo Camera (HRSC) onboard the Mars Express and from the Context Camera (CTX) onboard MRO. The region of Terra Cimmeria was chosen as a demonstration area. It is a highly cratered southern midlatitude region, where, as will be discussed, the higher resolution of the aforementioned terrain models is mandatory to describe the surface at an acceptable level of detail for shallow subsurface radar interpretation. With a DTM corrected by photoclinometry using CTX imagery, we show that a reflector that was visible on SHARAD data but not on the simulation made with an HRSC DTM is, in fact, a surface echo that was not reproduced by the HRSC surface model. We also show that, unlike laser altimetry DTMs, optical DTMs are prone to artifacts that can make radar analysis more complicated for some scenarios. Reciprocally, we show that the comparison between radar and its corresponding simulated data is a way of assessing a DTM’s quality, which is especially useful in missions where ground control points are lacking, unlike Martian observations. Full article

(This article belongs to the Special Issue Radar for Planetary Exploration)

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17 pages, 7459 KiB

Open AccessArticle

An Innovative Synthetic Aperture Radar Design Method for Lunar Water Ice Exploration

by Yanyan Zhang, Fei Zhao, Sheng Chang, Mingliang Liu and Robert Wang

Remote Sens. 2022, 14(9), 2148; https://doi.org/10.3390/rs14092148 - 30 Apr 2022

Cited by 1 | Viewed by 2248

Abstract

Owing to the Moon’s rough surface, there is a growing controversy over the conclusion that water ice exists in the lunar permanently shadowed regions (PSRs) with a high circular polarization ratio (CPR). To further detect water ice on the Moon, an innovative design [...] Read more.

Owing to the Moon’s rough surface, there is a growing controversy over the conclusion that water ice exists in the lunar permanently shadowed regions (PSRs) with a high circular polarization ratio (CPR). To further detect water ice on the Moon, an innovative design method for spaceborne synthetic aperture radar (SAR) system is proposed, to obtain radar data that can be used to distinguish water ice from lunar regolith with a small difference in the dielectric constants. According to Campbell’s dielectric constant model and the requirement that SAR radiometric resolution is smaller than the contrast of targets in images, a newly defined SAR system function involved in the method is presented to evaluate the influence of some system parameters on the water ice detection capability of SAR. In addition, several simulation experiments are performed, and the results demonstrate that the presented SAR design method may be helpful for lunar water ice exploration. Full article

(This article belongs to the Special Issue Radar for Planetary Exploration)

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Review

Jump to: Research, Other

36 pages, 66724 KiB

Open AccessReview

Planetary Radar—State-of-the-Art Review

by Anne K. Virkki, Catherine D. Neish, Edgard G. Rivera-Valentín, Sriram S. Bhiravarasu, Dylan C. Hickson, Michael C. Nolan and Roberto Orosei

Remote Sens. 2023, 15(23), 5605; https://doi.org/10.3390/rs15235605 - 2 Dec 2023

Cited by 4 | Viewed by 8429

Abstract

Planetary radar observations have provided invaluable information on the solar system through both ground-based and space-based observations. In this overview article, we summarize how radar observations have contributed in planetary science, how the radar technology as a remote-sensing method for planetary exploration and [...] Read more.

Planetary radar observations have provided invaluable information on the solar system through both ground-based and space-based observations. In this overview article, we summarize how radar observations have contributed in planetary science, how the radar technology as a remote-sensing method for planetary exploration and the methods to interpret the radar data have advanced in the eight decades of increasing use, where the field stands in the early 2020s, and what are the future prospects of the ground-based facilities conducting planetary radar observations and the planned spacecraft missions equipped with radar instruments. The focus of the paper is on radar as a remote-sensing technique using radar instruments in spacecraft orbiting planetary objects and in Earth-based radio telescopes, whereas ground-penetrating radar systems on landers are mentioned only briefly. The key scientific developments are focused on the search for water ice in the subsurface of the Moon, which could be an invaluable in situ resource for crewed missions, dynamical and physical characterization of near-Earth asteroids, which is also crucial for effective planetary defense, and a better understanding of planetary geology. Full article

(This article belongs to the Special Issue Radar for Planetary Exploration)

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Other

Jump to: Research, Review

15 pages, 1825 KiB

Open AccessTechnical Note

Data Pre-Processing and Signal Analysis of Tianwen-1 Rover Penetrating Radar

by Shuning Liu, Yan Su, Bin Zhou, Shun Dai, Wei Yan, Yuxi Li, Zongyu Zhang, Wei Du and Chunlai Li

Remote Sens. 2023, 15(4), 966; https://doi.org/10.3390/rs15040966 - 9 Feb 2023

Cited by 6 | Viewed by 2266

Abstract

The Rover-mounted Subsurface Penetrating Radar (RoSPR) is one of the scientific payloads onboard China’s first independent Mars exploration mission, Tianwen-1. The radar aims to characterize the thickness of the upper Martian soil and investigate the subsurface stratigraphy by collecting and processing the data. [...] Read more.

The Rover-mounted Subsurface Penetrating Radar (RoSPR) is one of the scientific payloads onboard China’s first independent Mars exploration mission, Tianwen-1. The radar aims to characterize the thickness of the upper Martian soil and investigate the subsurface stratigraphy by collecting and processing the data. This article is mainly divided into two parts, the introduction of data pre-processing and analysis of pre-processed radar signals, aiming at helping scientists make more effective use of radar data. The first part describes the operating principle of the RoSPR and the procedure of radar data pre-processing at all levels. Data pre-processing is mainly designed to transfer the raw data format to a common PDS (Planetary Data System) and eliminate the influence of the instrument. In the signal analysis part, the performances of both self-check signals and echo signals of low- and high-frequency channels are analyzed, which indicate a stable radar system and are useful for background removal. Phase and time calibration is of great importance for improving data quality and making the radar data more accurate. Moreover, further processing is required to obtain clear radar images, such as filtering, background removal and gain setting. Full article

(This article belongs to the Special Issue Radar for Planetary Exploration)

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18 pages, 13639 KiB

Open AccessTechnical Note

Electromagnetic Signal Attenuation Characteristics in the Lunar Regolith Observed by the Lunar Regolith Penetrating Radar (LRPR) Onboard the Chang’E-5 Lander

by Chunyu Ding, Yan Su, Zhonghan Lei, Zongyu Zhang, Mi Song, Yuanzhou Liu, Ruigang Wang, Qingquan Li, Chunlai Li and Shaopeng Huang

Remote Sens. 2022, 14(20), 5189; https://doi.org/10.3390/rs14205189 - 17 Oct 2022

Cited by 9 | Viewed by 2928

Abstract

The Chinese Chang’E-5 probe landed in the Mons Rümker of Oceanus Procellarum on the near side of the Moon. The lunar regolith penetrating radar (LRPR) carried by the Chang’E-5 probe allows for the determination of in situ lunar regolith dielectric properties, which are [...] Read more.

The Chinese Chang’E-5 probe landed in the Mons Rümker of Oceanus Procellarum on the near side of the Moon. The lunar regolith penetrating radar (LRPR) carried by the Chang’E-5 probe allows for the determination of in situ lunar regolith dielectric properties, which are probably related to the age and chemical composition of the regolith. In this paper, we analyze the Chang’E-5 LRPR data with the frequency shift method to estimate the loss tangent of the lunar regolith within a depth of ∼2.8 m. The loss tangent of the Chang’E-5 landing site is constrained to be 0.0148 ± 0.0016, which is substantially higher than that of the typical lunar regolith. The high loss tangent is found to be characteristic of the young basalt age (∼2.0 Ga) and high TiO

_{2}

+FeO content (28.21 ± 1.57%) of the Chang’E-5 landing site. Integrated analysis of results from Chang’E-3, Chang’E-4, and Chang’E-5 show that the younger is the geologic age of the mare unit, the greater is the loss tangent of the lunar regolith, and the weaker is the radar electromagnetic signal penetrating ability. Full article

(This article belongs to the Special Issue Radar for Planetary Exploration)

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