Planetary Bistatic Radar

Planetary radar observations offer the potential for probing the properties of characteristics of solid bodies throughout the inner solar system and at least as far as the orbit of Saturn. In addition to the direct scientific value, precise orbital determinations can be obtained from planetary radar observations, which are in turn valuable for mission planning or spacecraft navigation and planetary defense. The next-generation Very Large Array would not have to be equipped with a transmitter to be an important asset in the world's planetary radar infrastructure. Bistatic radar, in which one antenna transmits (e.g., Arecibo or Goldstone) and another receives, are used commonly today, with the Green Bank Telescope (GBT) serving as a receiver. The improved sensitivity of the ngVLA relative to the GBT would improve the signal-to-noise ratios on many targets and increase the accessible volume specifically for asteroids. Goldstone-ngVLA bistatic observations would have the potential of rivaling the sensitivity of Arecibo, but with much wider sky access.Comment: 11 pages, 2 figures, To be published in the ASP Monograph Series, "Science with a Next-Generation VLA", ed. E. J. Murphy (ASP, San Francisco, CA

Definition phase of Grand Tour missions/radio science investigations study for outer planets missions

Scientific instrumentation for satellite communication and radio tracking systems in the outer planet exploration mission is discussed. Mission planning considers observations of planetary and satellite-masses, -atmospheres, -magnetic fields, -surfaces, -gravitational fields, solar wind composition, planetary radio emissions, and tests of general relativity in time delay and ray bending experiments

The Goldstone solar system radar: A science instrument for planetary research

The Goldstone Solar System Radar (GSSR) station at NASA's Deep Space Communications Complex in California's Mojave Desert is described. A short chronological account of the GSSR's technical development and scientific discoveries is given. This is followed by a basic discussion of how information is derived from the radar echo and how the raw information can be used to increase understanding of the solar system. A moderately detailed description of the radar system is given, and the engineering performance of the radar is discussed. The operating characteristics of the Arcibo Observatory in Puerto Rico are briefly described and compared with those of the GSSR. Planned and in-process improvements to the existing radar, as well as the performance of a hypothetical 128-m diameter antenna radar station, are described. A comprehensive bibliography of referred scientific and engineering articles presenting results that depended on data gathered by the instrument is provided

DISCUS - The Deep Interior Scanning CubeSat mission to a rubble pile near-Earth asteroid

We have performed an initial stage conceptual design study for the Deep Interior Scanning CubeSat (DISCUS), a tandem 6U CubeSat carrying a bistatic radar as main payload. DISCUS will be operated either as an independent mission or accompanying a larger one. It is designed to determine the internal macroporosity of a 260-600 m diameter Near Earth Asteroid (NEA) from a few kilometers distance. The main goal will be to achieve a global penetration with a low-frequency signal as well as to analyze the scattering strength for various different penetration depths and measurement positions. Moreover, the measurements will be inverted through a computed radar tomography (CRT) approach. The scientific data provided by DISCUS would bring more knowledge of the internal configuration of rubble pile asteroids and their collisional evolution in the Solar System. It would also advance the design of future asteroid deflection concepts. We aim at a single-unit (1U) radar design equipped with a half-wavelength dipole antenna. The radar will utilize a stepped-frequency modulation technique the baseline of which was developed for ESA's technology projects GINGER and PIRA. The radar measurements will be used for CRT and shape reconstruction. The CubeSat will also be equipped with an optical camera system and laser altimeter to sup- port navigation and shape reconstruction. We provide the details of the measurement methods to be applied along with the requirements derived of the known characteristics of rubble pile asteroids.Comment: Submitted to Advances in Space Researc

Stanford telemetry monitoring experiment on Lunar Explorer 35 Final report

Explorer 35 data analysis including occultation study and antenna pattern interpretation along with electromagnetic property experiment

Cassini Bistatic Radar Experiments: Preliminary Results on Titan’s Polar Regions

In bistatic radar observations, refected echoes from the surface of a target planet can be analyzed to infer its surface statistics and near-surface constituents. In this work, a preliminary inspection of two X-band bistatic radar observations gathered by the Cassini spacecraft about Titan’s polar regions is presented. Profles of relative dielectric constant and root-mean-square (rms) surface slope are provided as outputs of the analysis, discussed, and compared with the present knowledge of Titan geomorphology. For the assessment of the rms slope, proportional to the spectral broadening of refected echoes, a basic ftting procedure was applied to the received spectra using a Gaussian template, to later evaluate the full-width half-maximum of the ftting curve. The dielectric constant was computed from the power ratio between orthogonally circularly polarized components of signal refections from Titan. Dielectric constant estimates are, on average, consistent with the expected materials covering the dry surfaces of the planet, while slightly low values were found over the seas. The rms slopes are generally low compared to past bistatic observations of other targets. Titan’s north polar seas are revealed to feature an unprecedented smoothness, with 0.01◦ of slope as an upper bound. Similar values were inferred for isolated spots in the southern pole, hinting at the possible presence of basins flled with liquid hydrocarbons. The main issues with the analysis are emphasized throughout the document, and some ideas for future work are presented in the conclusions

Continued support in the study of lunar and planetary surfaces

Radar observations of various planetary surfaces are discussed. A radar investigation of Mars was conducted in conjunction with the Viking landing site selection process. Quasi-specular scattering from the lunar surface was interpreted in terms of horizonal scale dependence upon observing wavelengths. Furthermore, the effect of the extremely high temperatures encountered on the surface of Venus upon the dielectric constant of geophysical materials, and hence on the interpretation of radar results, was considered. The use of radio and radar techniques for the study of Saturns rings was also investigated

Ka-band (32 GHz) benefits to planned missions

The benefits of using 32 GHz downlinks for a set of deep space missions, as well as the implications to radio science and the Deep Space Network (DSN) are documented. The basic comparison is between the use of the current X-band (8.4 GHz) and a 32 GHZ (Ka-band) downlink. There was shown to be approximately an 8 dB (about 600%) link advantage for 32 GHz. This 8 dB advantage would be able to either reduce mission cost or improve mission science return. Included here are studies on how the 8 dB advantage would be used for the Cassini and Mars Sample Return missions. While the work is preliminary, it shows that the 8 dB advantage can be exploited to provide large benefits to future deep space missions. There can be significant mass and/or power savings to the spacecraft, which can translate into cost savings. Alternatively, the increased downlink telecommunications performance can provide a greater science return