Goldstone Solar System Radar Research Articles

Surface scattering model for dual-polarization planetary radars

This work presents a surface scattering model to interpret radar polarimetry derived from dual-polarization planetary radar systems, such as Arecibo Observatory and the Goldstone Solar System Radar. This model divides surface scattering contributions within a radar echo into quasi-specular and diffuse components, and further divides the quasi-specular component into single- and double-bounce scattering. In particular, the increase in the degree of linear polarization resulting from dihedral double-bounce scattering is emphasized, in addition to the increase in the circular polarization ratio. This mechanism is illustrated in radar observations of young craters on the Moon by the Mini-RF radar on board the Lunar Reconnaissance Orbiter. Arecibo radar observations of 8 near-Earth asteroids are compared to this model and the implications for the physical properties of these objects are discussed. This work provides new insight in interpreting radar polarimetry from dual-polarization planetary radar systems and is broadly applicable to all solar system targets.

Radar Observations of Old Centaur Rocket from 1966

Abstract We report the results of radar observations of a near-Earth object discovered on 17 September 2020, with the Pan-STARRS 1 telescope at the Haleakala Observatory in Hawaii. Initially, this object was considered an asteroid and even received the standard provisional designation 2020 SO by the Minor Planet Center. However, its Earth-like orbit and low relative velocity suggested that the object may be of artificial origin, being the Centaur rocket booster from the Surveyor 2 mission that was launched to the Moon on 20 September 1966. In the period from November 2020 to March 2021, this object approached the Earth twice within one lunar distance of the Earth. Radar observations were conducted on 30 November in bistatic mode with the 70-m Goldstone Solar System Radar DSS-14 and 32-m radio telescope RT-32 at the Svetloe Observatory, while the object was in the visibility window of two antennas at about 200 thousand km from the Earth. The main goal of the study was to determine the physical properties of this object using radar astronomy to clarify its origin.

Feed-Forward Neural Network Denoising Applied to Goldstone Solar System Radar Images

The study of Near-Earth Asteroids (NEA) is crucial for human safety. Small hazardous asteroids with small radar cross sections are not easy to detect, track, and characterize due to the small signal-to-noise ratio (SNR) of the radar echo. This manuscript describes the results obtained for the application of a feed-forward neural network (FFNN) denoising methodology to NEA data obtained from the Goldstone Solar System Radar (GSSR). We demonstrate an increase in the signal level of up to ×4 the original value—in terms of sigma above the mean noise—when applying the FFNN denoising technique to radar Z-score normalized Binary Phase Code (BPC) images. This improvement benefits better radar detection of NEAs in general. Reducing the noise background level for antennas that have lower aperture, e.g., 34 m dishes, enables the use of FFNN denoising to improve visual detections on those noisier conditions. In addition, reducing noise level benefits shorter integration times of the data to obtain adequate signal levels. When talking about detection of small bodies crossing the antenna beam, since the asteroids or debris can move across the beam quite fast, it is relevant to reduce the integration time to allow for an increased number of independent pieces of information crossing the target through the antenna beam. The increased distance between the signal level and the noise level enables a better detection of the small-bodies at shorter integration times and therefore would be very useful for the detection of objects in the cis-lunar space.

The Improved Capabilities of the Goldstone Solar System Radar Observatory

The Goldstone Solar System Radar (GSSR) facility is the largest fully steerable ground-based radar in the world for nonclassified high-resolution ranging and imaging of planetary and small-body targets. Over the years, the use of the GSSR to detect and characterize near-Earth objects (NEOs) has become critical to keep track of potential Earth-impacting hazardous NEO. This article relates the specific modifications made to the GSSR hardware and procedures in the last few years, as well as the new capabilities derived from those upgrades: reduced complexity in remote operations, increased experimental design versatility, and increased performance on bistatic radar experiments from GSSR to other complexes. In addition, we dedicate a section to provide an update on the current GSSR power capabilities as the new klystrons are installed. The work detailed in this article is intended to reach the broader science community in order to communicate how those modifications and the derived new capabilities can make science experiments more successful.

A Data-Taking System for Planetary Radar Applications

Most planetary radar applications require recording of complex voltages at sampling rates of up to 20[Formula: see text]MHz. I describe the design and implementation of a sampling system that has been installed at the Arecibo Observatory, Goldstone Solar System Radar, and Green Bank Telescope. After many years of operation, these data-taking systems have enabled the acquisition of hundreds of datasets, many of which still await publication.

Application Progress on Goldstone Solar System Radar and Its Inspiration for Deep Space Exploration in China

Application Progress on Goldstone Solar System Radar and Its Inspiration for Deep Space Exploration in China

Goldstone Solar System Radar Observatory: Earth-Based Planetary Mission Support and Unique Science Results

The Goldstone Solar System Radar (GSSR) facility is the only fully steerable radar in the world for high-resolution ranging and imaging of planetary and small-body targets. These observations provide information on surface characteristics, orbits, rotations, and polar ices for a wide variety of solar system objects. The resulting data are used not just for scientific studies of these objects, but also for frequent support of the National Aeronautics and Space Administration (NASA) flight projects, including many solar system exploration missions over the last three decades. For example, the GSSR has contributed to the Mars Exploration Rovers (MERs), Cassini, Hayabusa (MUSES-C), MESSENGER, NEAR, SOHO recovery, Mars Pathfinder, Lunar Prospector, Clementine, Magellan, and Viking. Other recent examples include measurement of lunar topography at high resolution near the lunar south pole, which is of particular interest concerning the impact site of the Lunar Crater Observation and Sensing Satellite (LCROSS) mission, and the characterization and orbit refinement of near-Earth asteroids, both for asteroid impact hazard mitigation and for identification of potential targets for future spacecraft missions. We also present important radar scientific results including near-Earth object (NEO) radar imaging of especially interesting objects, and the results from high accuracy determination of Mercury rotation via radar speckle displacement (RSD).

Mars Radar Observations with the Goldstone Solar System Radar

The Goldstone Solar System Radar (GSSR) has successfully collected radar echo data from Mars over the past 30 years. As such, the GSSR has played a role as a specific mission element within Mars exploration. The older data provided local elevation information for Mars, along with radar scattering information with global resolution. Since the upgrade to the 70-m Deep Space Network (DSN) antenna at Goldstone completed in 1986, Mars data has been collected during all but the 1997 Mars opposition. Radar data, and non-imaging delay-Doppler data in particular, requires significant data processing to extract elevation, reflectivity and roughness of the reflecting surface. The spatial resolution of these experiments is typically some 20 km in longitude by some 150 km in latitude. The interpretation of these parameters while limited by the complexities of electromagnetic scattering, do provide information directly relevant to geophysical and geomorphic analyses of Mars. The usefulness of radar data for Mars exploration has been demonstrated in the past. Radar data were critical in assessing the Viking Lander 1 site as well as, more recently, the Pathfinder landing site. In general, radar data have not been available to the Mars exploration community at large. A project funded initially by the Mars Exploration Directorate Science Office at the Jet Propulsion Laboratory (JPL), and later funded by NASA's Mars Data Analysis Program has reprocessed to a common format a decade's worth of raw GSSR Mars delay-Doppler data in aid of landing site characterization for the Mars Program. These data will soon be submitted to the Planetary Data System (PDS). The radar data used were obtained between 1988 and 1995 by the GSSR, and comprise some 63 delay-Doppler radar tracks. Of these, 15 have yet to be recovered from old 9-track tapes, and some of the data may be permanently lost.

Digital elevation models of the Moon from Earth-based radar interferometry

Three-dimensional (3D) maps of the nearside and polar regions of the Moon can be obtained with an Earth-based radar interferometer. This paper describes the theoretical background, experimental setup, and processing techniques for a sequence of observations performed with the Goldstone Solar System Radar in 1997. These data provide radar imagery and digital elevation models of the polar areas and other small regions at /spl sim/100 m spatial and /spl sim/50 m height resolutions. A geocoding procedure relying on the elevation measurements yields cartographically accurate products that are free of geometric distortions such as foreshortening.

Topography of the lunar poles from radar interferometry: a survey of cold trap locations.

Detailed topographic maps of the lunar poles have been obtained by Earth-based radar interferometry with the 3.5-centimeter wavelength Goldstone Solar System Radar. The interferometer provided maps 300 kilometers by 1000 kilometers of both polar regions at 150-meter spatial resolution and 50-meter height resolution. Using ray tracing, these digital elevation models were used to locate regions that are in permanent shadow from solar illumination and may harbor ice deposits. Estimates of the total extent of shadowed areas poleward of 87.5 degrees latitude are 1030 and 2550 square kilometers for the north and south poles, respectively.

High‐resolution stratospheric dynamics measurements with the NASA/JPL Goldstone Solar System Radar

We have used, for the first time that we are aware of, the NASA/JPL Goldstone planetary radar to study the Earth's atmosphere. With its high bandwidth and power, we were able to achieve a height resolution of 20 m, which is significantly better than the usual 150‐m resolution for stratospheric radars. Here we discuss the observation of a very thin scattering layer that persisted over several hours at the same height just above the tropopause. We question the assumption of turbulent radar scatter based on the available evidence, and also investigate the two‐minute oscillation observed in the vertical velocity.

Design concepts of a 1 MW CW X-band transmit/receive system for planetary radar

The conceptual design of the 1 MW X-band transmit system for the Goldstone Solar System Radar represents the next step in the quest to expand planetary radar exploration. The radar transmitter requirements are summarized. The characteristics and expected performance of the major elements are discussed, including the klystrons, power amplifiers, microwave transmission lines, feed systems, beam power supply, heat exchanger, phase stable exciter, and the monitor/control system. An assessment of the technology development needed to meet the system requirements is given, and possible areas of difficulty are outlined.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Radar characteristics of the equatorial plains of Venus from Goldstone Observations: Implications for interpretation of Magellan data

Based on analyses of recent high resolution observations of the approximately 1000 km diameter Heng‐0 ring structure by the Goldstone Solar System Radar, we predict that the structure is a large corona. Calibrated values of radar backscatter coefficient (σ°) indicate lateral variations of a factor of 4 in Fresnel reflectivity in the vicinity of Heng‐0, as well as in other areas of the plains, at scales of tens of km. We predict that areas with very low reflectivity values, which occur in a variety of geological settings, are soil‐dominated, with bulk densities as low as 1.5 g/cm3.