Planetary Probes Research Articles

Structural Concept Study for Planetary Probes and Sample Return Vehicles

A parametric structural investigation of a new atmospheric entry vehicle concept for future planetary probes and sample return vehicles was conducted. During launch and reentry, the vehicle may experience large structural loads. To enable rapid assessment of candidate vehicle configurations for different missions, a parametric structural dynamics analysis methodology was developed. The methodology generates finite-element models and enables rapid modification to all aspects of the models, including geometry, material properties, load and boundary conditions, mesh parameters, and analysis controls. Analyses including quasi-static inertial loading, vibration frequency response, acoustic loading, and reentry loading were conducted for the structural concept study. Several geometry, mass, and material parameters were varied from to of their baseline value and analyzed. A total of 136 analyses were conducted on 34 unique vehicle configurations. Of the parameters investigated, cone angle and vehicle diameter were found to be the most influential on the vehicle’s mass and structural response. The highest stress observed was for an inertial launch analysis conducted on a cone angle model, which had 2.7x the baseline stress and only 1.4x the baseline mass. This analysis methodology is shown to facilitate and expedite future planetary exploration mission analyses.

A novel sparse boosting method for crater detection in the high resolution planetary image

Impact craters distributed on planetary surface become one of the main barriers during the soft landing of planetary probes. In order to accelerate the crater detection, in this paper, we present a new sparse boosting (SparseBoost) method for automatic detection of sub-kilometer craters. The SparseBoost method integrates an improved sparse kernel density estimator (RSDE-WL1) into the Boost algorithm and the RSDE-WL1 estimator is achieved by introducing weighted l1 penalty term into the reduced set density estimator. An iterative algorithm is proposed to implement the RSDE-WL1. The SparseBoost algorithm has the advantage of fewer selected features and simpler representation of the weak classifiers compared with the Boost algorithm. Our SparseBoost based crater detection method is evaluated on a large and high resolution image of Martian surface. Experimental results demonstrate that the proposed method can achieve less computational complexity in comparison with other crater detection methods in terms of selected features.

Making the Venus Concept Watch 1.0

Over the past year we have celebrated the 50th anniversary of planetary exploration, which started with the Venus flyby of Mariner-2; and the 35th anniversary of the Pioneer-Venus multi-probe mission where one large and three small probes descended to the surface of Venus, encountering extreme environmental conditions. At the surface of Venus the temperature is about 460°C, and the pressure is 92bar, with a highly corrosive super-critical CO2 atmosphere. At a Venusian altitude of 50km the pressure and temperature conditions are near Earth-like, but the clouds carry sulfuric acid droplets. Deep probe missions to Jupiter and Saturn, targeting the 100bar pressure depth encounter similar pressure and temperature conditions as the Pioneer-Venus probes did. Mitigating these environments is highly challenging and requires special considerations for designs and materials. While assessing such space mission concepts, we have found that there is an overlap between the extreme environments in planetary atmospheres and the environments experienced by deep-sea explorers back on Earth. Consequently, the mitigation approaches could be also similar between planetary probes and diver watches. For example, both need to tolerate about 100bar of pressure—although high temperatures are not factors on Earth. Mitigating these environments, the potential materials are: titanium for the probe and the watch housing; sapphire for the window and glass; resin impregnated woven carbon fiber for the aeroshell׳s thermal protection system and for the face of the watch; and nylon ribbon for the parachute and for the watch band. Planetary probes also utilize precision watches; thus there is yet another crosscutting functionality with diver watches. Our team, from the Innovation Design Engineering Program of the Royal College of Art, has designed and built a concept watch to commemorate these historical events, while highlighting advances in manufacturing processes over the past three to five decades, relevant to both future planetary mission designs and can be used to produce deep diver watches. In this paper we describe our design considerations; give a brief overview of the extreme environments these components would experience on both Venus and Earth; the manufacturing techniques and materials we used to build the Venus Watch; and its outreach potential to bring a distant concept of planetary exploration closer to Earth. We will also address lessons learned from this project and new ideas forward, for the next generation of this concept design.

Improved data reduction algorithm for the needle probe method applied to in-situ thermal conductivity measurements of lunar and planetary regoliths

The needle probe method (also known as the ‘hot wire’ or ‘line heat source’ method) is widely used for in-situ thermal conductivity measurements on terrestrial soils and marine sediments. Variants of this method have also been used (or planned) for measuring regolith on the surfaces of extra-terrestrial bodies (e.g., the Moon, Mars, and comets). In the near-vacuum condition on the lunar and planetary surfaces, the measurement method used on the earth cannot be simply duplicated, because thermal conductivity of the regolith can be ~2 orders of magnitude lower. In addition, the planetary probes have much greater diameters, due to engineering requirements associated with the robotic deployment on extra-terrestrial bodies. All of these factors contribute to the planetary probes requiring a much longer time of measurement, several tens of (if not over a hundred) hours, while a conventional terrestrial needle probe needs only 1 to 2min. The long measurement time complicates the surface operation logistics of the lander. It also negatively affects accuracy of the thermal conductivity measurement, because the cumulative heat loss along the probe is no longer negligible. The present study improves the data reduction algorithm of the needle probe method by shortening the measurement time on planetary surfaces by an order of magnitude. The main difference between the new scheme and the conventional one is that the former uses the exact mathematical solution to the thermal model on which the needle probe measurement theory is based, while the latter uses an approximate solution that is valid only for large times. The present study demonstrates the benefit of the new data reduction technique by applying it to data from a series of needle probe experiments carried out in a vacuum chamber on a lunar regolith simulant, JSC-1A. The use of the exact solution has some disadvantage, however, in requiring three additional parameters, but two of them (the diameter and the volumetric heat capacity of the probe) can be measured and the other (the volumetric heat capacity of the regolith/stimulant) may be estimated from the surface geologic observation and temperature measurements. Therefore, overall, the new data reduction scheme would make in-situ thermal conductivity measurement more practical on planetary missions.

Reacting to nuclear power systems in space: American public protests over outer planetary probes since the 1980s

The United States has pioneered the use of nuclear power systems for outer planetary space probes since the 1970s. These systems have enabled the Viking landings to reach the surface of Mars and both Pioneers 10 and 11 and Voyagers 1 and 2 to travel to the limits of the solar system. Although the American public has long been concerned about safety of these systems, in the 1980s a reaction to nuclear accidents – especially the Soviet Cosmos 954 spacecraft destruction and the Three Mile Island nuclear power plant accidents – heightened awareness about the hazards of nuclear power and every spacecraft launch since that time has been contested by opponents of nuclear energy. This has led to a debate over the appropriateness of the use of nuclear power systems for spacecraft. It has also refocused attention on the need for strict systems of control and rigorous checks and balances to assure safety. This essay describes the history of space radioisotope power systems, the struggles to ensure safe operations, and the political confrontation over whether or not to allow the launch the Galileo and Cassini space probes to the outer planets. Effectively, these efforts have led to the successful flights of 12 deep space planetary probes, two-thirds of them operated since the accidents of Cosmos 954, Three Mile Island, and Chernobyl.

High Energy Astrophysics and Fundamental Physics Missions in Japan

ISAS is the main branch institute of JAXA responsible for space science, conducting academic research by making the maximum use of its own scientific satellites, planetary probes, sounding rockets, and scientific balloons, and of collaborations with, and support from, other divisions/institutions of JAXA. By conducting observations not possible from the ground with the utilization of the space environment, we study the structure of the universe including the large-scale cosmological structure, nearby planetary systems, and the origin of universe. Currently we are concentrating on X-ray and Gamma-ray astronomy, infrared astronomy and radio astronomy. ASTRO-H is the largest international X-ray observatory which is currently under development, with launch scheduled for 2015. SPICA is being prepared as the next generation large and cooled infrared telescope. A number of working groups have been established to prepare missions with a vision towards the future.

Robust cut-cell algorithms for DSMC implementations employing multi-level Cartesian grids

Robust cut-cell algorithms are detailed for general multi-level Cartesian grid direct simulation Monte Carlo (DSMC) implementations. Different approaches for each component of the cut-cell algorithms are elaborated and compared, based on time efficiency, robustness, and ease of implementation. Special situations that arise in sorting the surface triangles, calculating the cut-cell volume, and identifying multiple cut-volumes contained in a single Cartesian cell, are handled by the algorithms, and their effects on the overall simulation results are analyzed using test cases. Three-dimensional DSMC simulations are conducted for a Mach number 20.2 N2 gas flowing over a Planetary Probe geometry showing good agreement with experimental heat flux measurements. Rarefied flow over a geometry resembling the MIR Space Station is also conducted, to demonstrate the ability of the proposed cut-cell algorithms to handle complex geometries. The time required to cut the surface meshes from the background Cartesian grids and to calculate the volume of the resulting cut-cells is found to be comparable to the time cost for one DSMC simulation time step for cases considered.

Planetary and exoplanetary low frequency radio observations from the Moon

We analyze the planetary and exoplanetary science that can be carried out with precursor as well as future low frequency radio instruments on the Moon, assessing the limiting noise sources, comparing them to the average and peak spectra of all planetary radio components as they will be seen from the Lunar surface or orbit. We identify which objectives will be accessible with each class of instrument, and discuss the interest of these observations compared to observations by planetary probes and to ground-based observations by large low-frequency radio arrays. The interest of goniopolarimetry is emphasized for pathfinder missions.

The Huygens surface science package (SSP): Flight performance review and lessons learned

The Surface Science Package (SSP) was one of six instruments flown onboard the Huygens probe to Titan, the largest moon of Saturn, in the framework of the NASA/ESA/ASI Cassini–Huygens mission (Matson et al., 2002). The SSP operated throughout the probe's descent and after landing on Titan on 14th January 2005. This paper reviews scientific results from the Surface Science Package, and also reports previously unpublished flight data which illustrate the performance of the measurement systems in the Titan environment.This review provides some lessons learned that may be useful for further detailed analysis of the Huygens mission data, and for payloads for future missions to Titan, in which there has been recent interest (e.g., the Titan Saturn System Mission (TSSM) (Joint TSSM Science Definition Team, 2009), TANDEM (Coustenis et al., 2009) or the Titan Mare Explorer (TiME) Discovery-class proposal (Stofan et al., 2010)), as well as for planetary probe missions more generally.

Adaptive Selective Learning for automatic identification of sub-kilometer craters

Counting craters is a fundamental task of planetary science, because it provides the only tool for measuring relative ages of planetary surfaces. However, advances in surveying craters present in data gathered by planetary probes have not kept up with advances in data collection. It becomes extremely challenging to automatically count a very large number of small, sub-kilometer size craters in a deluge of high resolution planetary images. In this paper, we combine active learning with semi-supervised learning to build an adaptive learning system to automatically detect craters from high resolution panchromatic planetary images. We propose an Adaptive Selective Algorithm to iteratively enrich an original small training set, using unlabeled test set without additional human labeling effort, to detect craters from a large volume of images. We propose three strategies to improve detection accuracy by integrating classification with exploration on unlabeled samples. The Majority Vote Strategy is used to automatically obtain class labels by exploiting unlabeled samples. The De-Mixed Strategy is used on instance filtering to obtain reliable samples. The Active Stability Strategy is used to obtain an appropriate class distribution in the constructed training set by detecting unstable classes. By using those three strategies, we actively select test instances from test images into an existing small initial training set while rebuilding the classifier in the mean time. Our proposed algorithms are empirically evaluated on a large high resolution Martian image, exhibiting a heavily cratered Martian terrain characterized by heterogeneous surface morphology. The experimental results demonstrate that the proposed approach achieves a higher accuracy than other existing approaches to a large extent.

Investigation on design and reliability analysis of a new deployable and lockable mechanism

The traditional structure of the deployable and lockable mechanism on soft-landing gear system is complicated and unreliable. To overcome the defects, a new deployable and lockable mechanism for planetary probes is developed. The compression assembly shares a set of new mechanism with the deployment assembly and locking assembly. The new mechanism shows some advantages: more steady deployment, simpler mechanism and higher reliability. This paper presents an introduction of the deployment and locking theory of the new mechanism, and constitutes the fault tree, which would contribute to qualitative and quantitative analyses. In addition, probability importance and criticality importance of the new mechanism are derived and calculated. The reliability modeling and analysis of the mechanism are accomplished from static torque margin, torque and the work by torque. In investigation results, reliability rate that the new mechanism could deploy successfully is 0.999334. The crucial problems concentrate on the insufficiency of storage force torque of high strength spring, the lubrication failure between the inner cylinder and the outer cylinder of the strut and the stuck soft-landing gear system. And then, the paper presents some improvement approaches and suggestions according to the problems discussed above.

Acoustic attenuation, phase and group velocities in liquid-filled pipes II: Simulation for spallation neutron sources and planetary exploration

This paper uses a finite element method (FEM) to compare predictions of the attenuation and sound speeds of acoustic modes in a fluid-filled pipe with those of the analytical model presented in the first paper in this series. It explains why, when the predictions of the earlier paper were compared with experimental data from a water-filled PMMA pipe, the uncertainties and agreement for attenuation data were worse than those for sound speed data. Having validated the FEM approach in this way, the versatility of FEM is thereafter demonstrated by modeling two practical applications which are beyond the analysis of the earlier paper. These applications model propagation in the mercury-filled steel pipework of the Spallation Neutron Source at the Oak Ridge National Laboratory (Tennessee), and in a long-standing design for acoustic sensors for use on planetary probes. The results show that strong coupling between the fluid and the solid walls means that erroneous interpretations are made of the data if they assume that the sound speed and attenuation in the fluid in the pipe are the same as those that would be measured in an infinite volume of identical fluid, assumptions which are common when such data have previously been interpreted.

Particle Simulations of Planetary Probe Flows Employing Automated Mesh Refinement

Particle Simulations of Planetary Probe Flows Employing Automated Mesh Refinement

Implementation of the Earth-based planetary radio occultation inversion technique

The planetary radio occultation technique is one of the earliest suggested and achieved methods to detect the planetary atmosphere, and has been conducted by almost every deep space planetary probe. The principles, modules, inversion results and primary analysis of the SHAO Planetary Occultation observation Processing system (SPOPs) are presented in this paper. Utilizing open-loop and closed-loop Doppler residual data of the Mars Express radio occultation experiment provided by ESA PSA and NASA PDS, the temperature, pressure, molecular number density profiles of Martian atmosphere and electron density profiles of the ionosphere are successfully retrieved, and the results are validated by the released radio science level 04 products of the ESA MaRS group. This system can also process the atmosphere radio occultation observations of other planets and theirs natural satellites. The implementation of the planetary radio occultation technique is of significance to China’s YH-1 Mars exploration project, as well as for future planetary exploration missions from China.

Atmospheric Planetary Probes and Balloons in the Solar System

A primary motivation for in situ probe and balloon missions in the solar system is to progressively constrain models of its origin and evolution. Specifically, understanding the origin and evolution of multiple planetary atmospheres within our solar system would provide a basis for comparative studies that lead to a better understanding of the origin and evolution of our own solar system as well as extra-solar planetary systems. Hereafter, the authors discuss in situ exploration science drivers, mission architectures, and technologies associated with probes at Venus, the giant planets and Titan.

Optical spectroscopy investigation of N2–CH4 plasma jets simulating Titan atmospheric entry conditions

Planetary probes penetrating at supersonic speed into high atmosphere require the development of composite materials for thermal protection of the surface exposed to a high enthalpy flux. Rarefied arc plasmas can be used to simulate the atmospheric re-entry plasmas. The aim of this paper is to describe the latest results of optical emission measurements of the CH (A–X) system, the CN violet (B–X) bands and the NH (A–X) electronic transitions in a N2–CH4 plasma source (Titan's atmosphere) and in a gas mixture of Ar–CH4. In order to deduce the plasma parameters, such as rotational and vibrational temperatures, of these molecular species in the plasma environment, numerical simulation codes have been implemented. In this context, rotational temperatures near 7000 K for CN and 3500 K to 2800 K for the hydrides NH and CH, respectively, are observed. The vibrational temperature of the CH molecule is around 3800 K while those of the CN and NH molecules are 9500 K and 7900 K, respectively.

Raman spectroscopic approach to analytical astrobiology: the detection of key geological and biomolecular markers in the search for life

The compilation of this Theme Issue of Philosophical Transactions of the Royal Society on the theme of Raman spectroscopic analysis of materials from extreme environments is timely for several reasons, perhaps the most significant of these being the realization in the last decade that this technique

Attitude and angular rates of planetary probes during atmospheric descent: Implications for imaging

Attitude dynamics data from planetary missions are reviewed to obtain a zeroth-order expectation on the tilts and angular rates to be expected on atmospheric probes during descent: these rates are a strong driver on descent imager design. While recent Mars missions have been equipped with capable inertial measurements, attitude measurements for missions to other planetary bodies are rather limited but some angular motion estimates can be derived from accelerometer, Doppler or other data. It is found that robust camera designs should tolerate motions of the order of 20–40°/s, encountered by Mars Pathfinder, Pioneer Venus, Venera and the high speed part of the Huygens descent on Titan. Under good conditions, parachute-stabilized probes can experience rates of 1–5°/s, seen by the Mars Exploration Rovers and Viking, Galileo at Jupiter, and the slow speed parts of the Huygens descent. In the lowest 20 km of the descent on Titan, the Huygens probe was within 2° of vertical over 95% of the time. Some factors influencing these motions are discussed.

Bill Gates’ Great-Great-Granddaughter’s Honeymoon: An Astronomy Activity for Several Different Age Groups

When students finish a unit or course on the planets these days, they are often overwhelmed with facts, comparisons, and images. A good culminating activity, to help them organize their thinking and review ,i s to have them divide into small groups travel agencies and come up with their top ten solar system “tourist sights” for future space vacationers, complete with images. The history of the activity and its variants, and resources to help instructors and students, are reviewed. 1. BACKGROUND In a recent paper Fraknoi 2008, we offered an annotated listing of the best image repositories available for astronomy education these days. However, the number of images in these repositories is so large, students and novice instructors can be forgiven for sometimes feeling completely overwhelmed. Indeed, this author has been teaching astronomy for over 30 years, and he feels overwhelmed! This is particularly true in the area of solar system images, where new planetary probes are sometimes adding thousands of images to our repositories in a year. The activity below is an enjoyable way to help students organize some of the images and information they come across in an introductory unit or course on the planets.

Fluid loading effects for acoustical sensors in the atmospheres of Mars, Venus, Titan, and Jupiter

This paper shows that corrections for fluid loading must be undertaken to Earth-based calibrations for planetary probe sensors, which rely on accurate and precise predictions of mechanical vibrations. These sensors include acoustical instrumentation, and sensors for the mass change resulting from species accumulation upon oscillating plates. Some published designs are particularly susceptible (an example leading to around an octave error in the frequency calibration for Venus is shown). Because such corrections have not previously been raised, and would be almost impossible to incorporate into drop tests of probes, this paper demonstrates the surprising results of applying well-established formulations.