A multiple-rendezvous,sample-return mission to two near-Earth asteroids

We propose a dual-rendezvous mission, targeting near-Earth asteroids, including sample-return. The mission, Asteroid Sampling Mission (ASM), consists of two parts: (i) flyby and remote sensing of a Q-type asteroid, and (ii) sampling of a V-type asteroid. The targeted undifferentiated Q-type are found mainly in the near-Earth space, and to this date have not been the target of a space mission. We have chosen, for our sampling target, an asteroid from the basaltic class (V-type), as asteroids in this class exhibit spectral signatures that resemble those of the well-studied Howardite–Eucrite–Diogenite (HED) meteorite suite. With this mission, we expect to answer specific questions about the links between differentiated meteorites and asteroids, as well as gain further insight into the broader issues of early Solar System (SS) evolution and the formation of terrestrial planets. To achieve the mission, we designed a spacecraft with a dry mass of less than 3 tonnes that uses electric propulsion with a solar-electric power supply of 15 kW at 1 Astronomical Unit (AU). The mission includes a series of remote sensing instruments, envisages landing of the whole spacecraft on the sampling target, and employs an innovative sampling mechanism. Launch is foreseen to occur in 2018, as the designed timetable, and the mission would last about 10 years, bringing back a 150 g subsurface sample within a small re-entry capsule. This paper is a work presented at the 2008 Summer School Alpbach,“Sample return from the Moon, asteroids and comets” organized by the Aeronautics and Space Agency of the Austrian Research Promotion Agency. It is co-sponsored by ESA and the national space authorities of its Member and Co-operating States, with the support of the International Space Science Institute and Austrospace.     

A sample collector for robotic sample return missions I: Temperature effect on collected mass

Sample return is playing an increasingly important role in solar system exploration. Among the possible mission on the horizon, are sample return from asteroids, comets, the Moon and Mars. A collector initially intended for near-Earth asteroids is the touch-and-go-impregnable-pad (TGIP). Here we explore the effect of temperature on its collection capabilities. Temperatures expected on near-Earth asteroid mission targets range from −43 to 36 °C. Experiments were conducted at −75, −50, −25, 23, 65, and 105 °C. It was found that the mass of sample collected by the TGIP increased almost linearly to 23 °C and then leveled off at higher temperatures. We also found that the collector did not lose its ability to collect samples after being subjected to −75 °C temperatures (essentially frozen) and then thawed. These experiments have shown that the TGIP can operate effectively at temperatures expected on near-Earth asteroids, especially if collection is performed on the sunward side of the asteroid.     

A sample collector for robotic sample return missions II: Radiation tests

Sample return from small solar system objects is playing an increasingly important part in solar system exploration. Critical to such missions is a robust, simple, and economic sample collector. We have developed a collector such as this for near-Earth asteroid sample return missions that we have termed the Touch-and-Go Impregnable Pad (TGIP). The collector utilizes a silicone substrate that is pushed into the dust and gravel surface layer of the asteroid. As part of a systematic evaluation of the TGIP, we have investigated the resilience of this substrate to ionizing radiations. Several miniature versions of the collector, containing typically ∼3 g of the collection substrate, were exposed to 0.564 MeV beta particles from a ⁹⁰Sr source and a 6 MeV electron beam in a linear accelerator to simulate the wide range of energies of solar and galactic ionizing radiation. Various radiation levels up to eight times greater than expected on a six-year asteroid mission (in the case of beta radiation) and 50 times greater than expected (in the case of the 6 MeV electron radiation) were administered to the substrate. After irradiation, the efficiency of the substrate in collecting samples of mock regolith was compared with that of collectors that had not been irradiated. No difference beyond experimental uncertainty was observed and we suggest that the operational TGIP will not be affected adversely by radiation doses expected during a typical six-year inner solar system mission.     

Small satellite survey mission to the second Earth moon

This paper presents an innovative space mission devoted to the survey of the small Earth companion asteroid by means of nano platforms. Also known as the second Earth moon, Cruithne, is the target identified for the mission. Both the trajectory to reach the target and a preliminary spacecraft budget are here detailed. The idea is to exploit high efficient ion thrusters to reduce the propellant mass fraction in such a high total impulse mission (of the order of 1e6 Ns). This approach allows for a 100 kg class spacecraft with a very small Earth escape energy (5 km²/s²) to reach the destination in about 320 days. The 31% propellant mass fraction allows for a payload mass fraction of the order of 8% and this is sufficient to embark on such a small spacecraft a couple of nano-satellites deployed once at the target to carry out a complete survey of the asteroid. Two 2U Cubesats are here considered as representative payload, but also other scientific payloads or different platforms might be considered according with the specific mission needs. The small spacecraft used to transfer these to the target guarantees the manoeuvre capabilities during the interplanetary journey, the protection against radiations along the path and the telecommunication relay functions for the data transmission with Earth stations. The approach outlined in the paper offers reliable solutions to the main issues associated with a deep space nano-satellite mission thus allowing the exploitation of distant targets by means of these tiny spacecraft. The study presents an innovative general strategy for the NEO observation and Cruithne is chosen as test bench. This target, however, mainly for its relevant inclination, requires a relatively large propellant mass fraction that can be reduced if low inclination asteroids are of interest. This might increase the payload mass fraction (e.g. additional Cubesats and/or additional scientific payloads on the main bus) for the same 100 kg class mission.     

载人小行星探测的总体方案设想

载人探测近地小行星的工程规模和技术难度介于载人探月和载人火星探测之间,是人类开展载人火星探测和飞向更遥远深空的跳板,对于航天技术的发展和科学问题的探索有着极其重要的意义。在调研国外载人小行星探测方案设想的基础上,结合我国航天技术现状和发展趋势,提出了一种载人小行星探测的总体方案设想,并梳理了载人小行星探测的关键技术。研究成果可以作为我国载人小行星探测任务论证和设计的有益参考。     

Mission analysis and performance comparison for an Advanced Solar Photon Thruster

The so-called “compound solar sail”, also known as “Solar Photon Thruster” (SPT), is a design concept, for which the two basic functions of the solar sail, namely light collection and thrust direction, are uncoupled. In this paper, we introduce a novel SPT concept, termed the Advanced Solar Photon Thruster (ASPT), which does not suffer from the simplified assumptions that have been made for the analysis of compound solar sails in previous studies. After having presented the equations that describe the force on the ASPT and after having performed a detailed design analysis, the performance of the ASPT with respect to the conventional flat solar sail (FSS) is investigated for three interplanetary mission scenarios: an Earth–Venus rendezvous, where the solar sail has to spiral towards the Sun, an Earth–Mars rendezvous, where the solar sail has to spiral away from the Sun, and an Earth-NEA rendezvous (to near-Earth asteroid 1996FG3), where a large change in orbital eccentricity is required. The investigated solar sails have realistic near-term characteristic accelerations between 0.1 and 0.2 mm/s². Our results show that an SPT is not superior to the flat solar sail unless very idealistic assumptions are made.     

Synergistic approach of asteroid exploitation and planetary protection

The asteroid and cometary impact hazard has long been recognised as an important issue requiring risk assessment and contingency planning. At the same time asteroids have also been acknowledged as possible sources of raw materials for future large-scale space engineering ventures. This paper explores possible synergies between these two apparently opposed views; planetary protection and space resource exploitation. In particular, the paper assumes a 5 tonne low-thrust spacecraft as a baseline for asteroid deflection and capture (or resource transport) missions. The system is assumed to land on the asteroid and provide a continuous thrust able to modify the orbit of the asteroid according to the mission objective. The paper analyses the capability of such a near-term system to provide both planetary protection and asteroid resources to Earth. Results show that a 5 tonne spacecraft could provide a high level of protection for modest impact hazards: airburst and local damage events (caused by 15–170 m diameter objects). At the same time, the same spacecraft could also be used to transport to bound Earth orbits significant quantities of material through judicious use of orbital dynamics and passively safe aero-capture manoeuvres or low energy ballistic capture. As will be shown, a 5 tonne low-thrust spacecraft could potentially transport between 12 and 350 times its own mass of asteroid resources by means of ballistic capture or aero-capture trajectories that pose very low dynamical pressures on the object.     

Regional in situ validation of satellite altimeters: Calibration and cross-calibration results at the Corsican sites

The in situ validation of the satellite altimeter sea surface heights is generally performed either at a few local points directly flown over by the satellites or using the global tide gauge network. A regional in situ calibration method was developed by NOVELTIS in order to monitor the altimeter data quality in a perimeter of several hundred kilometres around a given in situ calibration site. The primary advantage of this technique is its applicability not only for missions flying over dedicated sites but also for missions on interleaved or non repetitive orbits. This article presents the altimeter bias estimates obtained with this method at the Corsican calibration site, for the Jason-1 mission on its nominal and interleaved orbits as well as for the Jason-2 and Envisat missions. The various regional bias estimates (8.2 cm and 7.4 cm for Jason-1 respectively on the nominal and interleaved orbits in Senetosa, 16.4 cm for Jason-2 in Senetosa and 47.0 cm for Envisat in Ajaccio, with an accuracy between 2.5 cm and 4 cm depending on the mission) are compared with the results obtained by the other in situ calibration teams. This comparison demonstrates the coherency at the centimetre level, the stability and the generic character of the method, which would also be of benefit to the new and future altimeter missions such as Cryosat-2, SARAL/AltiKa, Sentinel-3, Jason-3, Jason-CS.     

An in situ laser induced breakdown spectroscope (LIBS) for Chandrayaan-2 rover: Ablation kinetics and emissivity estimations

A miniaturized in situ laser induced breakdown spectroscope-LIBS is one of the two lunar rover payloads to be flown in India’s next lunar mission Chandrayaan-2, with an objective to carry-out a precise qualitative and quantitative elemental analyses of lunar regolith at the proximity of the landing region. As per the imposed mission constraints and the executed design optimization studies, a compact and light-weight LIBS prototype model is developed at our premises. This paper mainly concerns with the estimation of theoretical aspects; especially on evaluation of elemental ablation parameters and signal-to-noise ratio (SNR) calculations for the designed instrument. Theoretical estimations and simulations yielded an incident laser power density of the order of 5 × 10¹⁰ W/cm² on the target surface at a defined lens-to-surface distance (LTSD) of 200 mm and revealed an SNR > 100 for most of the elements under consideration. This paper also addresses the impact of LTSD variation on detection capability. The estimation of plasma-temperatures was carried out utilizing the emission spectra obtained under high vacuum environments employing the LIBS laboratory model. Experimental investigations and the performed theoretical estimations asserted the successful operation of the configured LIBS instrument for in situ elemental analyses on lunar surface.     

ASTEX: An in situ exploration mission to two near-Earth asteroids

ASTEX (ASTeroid EXplorer) is a concept study of an in situ exploration mission to two Near-Earth-Asteroids (NEAs), which consists of an orbiting element and two individual lander units. The target candidates have different mineralogical compositions, i.e. one asteroid is chosen to be of “primitive’’ nature, the other to be a fragment of a differentiated asteroid. The main scientific goals of the ASTEX mission are the exploration of the physical, geological, and mineralogical nature of the NEAs. The higher level goal is the provision of information and constraints on the formation and evolution of our planetary system. The study identified realistic mission scenarios, defined the strawman payload as well as the requirements and options for the spacecraft bus including the propulsion system, the landers, the launcher, and assessed and defined the requirements for the mission’s operational ground segment.     

Ion dynamics associated with Alfven wave in the near-Earth magnetotail: Two-dimensional global hybrid simulation

Ion dynamics in the near-Earth magnetotail region is examined during periods of fast Earthward flow with a two-dimensional (2-D) global-scale hybrid simulation. The simulation shows that shear Alfven waves are generated at x ∼ −10R_E, where the strong earthward flow is arrested by the dipole field, and propagate along field lines from the equator to both southern and northern polar ionosphere. Non-gyrotropic ion velocity distributions occur where the large-amplitude Alfven waves are dominant. The simulation indicates that the Alfven waves are generated by interaction of the fast earthward flow with the stationary near-Earth plasma. Beam ions are found to be pitch-angle scattered and trapped in the wave field, leading to the non-gyrotropic ion distributions in the high-latitude plasma sheet boundary. In addition, significant particle heating and acceleration are found to occur behind the dipolarization front due to the effect of wave turbulence.     

Mars Phobos and Deimos Survey (M-PADS) – A martian Moons orbiter and Phobos lander

We describe a Mars ‘Micro Mission’ for detailed study of the martian satellites Phobos and Deimos. The mission involves two ∼330 kg spacecraft equipped with solar electric propulsion to reach Mars orbit. The two spacecraft are stacked for launch: an orbiter for remote investigation of the moons and in situ studies of their environment in Mars orbit, and another carrying a lander for in situ measurements on the surface of Phobos (or alternatively Deimos). Phobos and Deimos remain only partially studied, and Deimos less well than Phobos. Mars has almost always been the primary mission objective, while the more dedicated Phobos project (1988–89) failed to realise its full potential. Many questions remain concerning the moons’ origins, evolution, physical nature and composition. Current missions, such as Mars Express, are extending our knowledge of Phobos in some areas but largely neglect Deimos. The objectives of M-PADS focus on: origins and evolution, interactions with Mars, volatiles and interiors, surface features, and differences. The consequent measurement requirements imply both landed and remote sensing payloads. M-PADS is expected to accommodate a 60 kg orbital payload and a 16 kg lander payload. M-PADS resulted from a BNSC-funded study carried out in 2003 to define candidate Mars Micro Mission concepts for ESA’s Aurora programme.     

X-ray redshifts with the International X-ray Observatory (IXO)

We explore the capabilities of the future space science mission IXO (International X-ray Observatory) for obtaining cosmological redshifts of distant Active Galactic Nuclei (AGNs) using the X-ray data only. We first find in which regions of the X-ray luminosity (L_X) versus redshift (z) plane the weak but ubiquitous Fe Kα narrow emission line can deliver an accurate redshift (δz < 5%) as a function of exposure time, using a CCD-based Wide Field Imager (IXO/WFI) as the one baselined for IXO. Down to a 2–10 keV X-ray flux of 10⁻¹⁴ erg cm⁻² s⁻¹ IXO/WFI exposures of 100 ks, 300 ks and 1 Ms will deliver 20%, 40% and 60% of the redshifts. This means that in a typical 18′ × 18′ IXO/WFI field of view, 4, 10 and 25 redshifts will be obtained for free from the X-ray data alone, spanning a wide range up to z ∼ 2–3 and fairly sampling the real distribution. Measuring redshifts of fainter sources will indeed need spectroscopy at other wavebands.     

Modeling PSBL high speed ion beams observed by Cluster and Double Star

On October 8, 2004, the Cluster and Double Star spacecraft crossed the near-Earth (12–19 R_E) magnetotail neutral sheet during the recovery phase of a small, isolated substorm. Although they were separated in distance by ∼7 R_E and in time by ∼30 min, both Cluster and Double Star observed steady, but highly structured Earthward moving >1000 km/s high speed H⁺ beams in the PSBL. This paper utilizes a global magnetohydrodynamic (MHD) simulation driven by Wind spacecraft solar wind input to model the large-scale structure of the PSBL and large-scale kinetic (LSK) particle tracing calculations to investigate the similarities and differences in the properties of the observed beams. This study finds that the large-scale shape of the PSBL is determined by the MHD configuration. On smaller scales, the LSK calculations, in good qualitative agreement with both Cluster and Double Star observations, demonstrated that the PSBL is highly structured in both time and space, on time intervals of less than 2 min, and spatial distances of the order of 0.2–0.5 R_E. This picture of the PSBL is different from the ordered and structured region previously reported in observations.     

Charge exchange interactions on near-Earth proton radiation for orbit perturbation of high area-to-mass ratio objects

This novel concept expels neutral gas in the presence of geomagnetically-trapped protons in near-Earth orbit. The expelled neutral gas acts to induce charge exchange collisions with the geomagnetically-trapped protons and induce drag on objects which pass through it. The charge exchange collisions between the neutral gas and the geomagnetically-trapped protons create neutrals with similar kinetic energy that are not confined by the geomagnetic field. The charge exchange neutrals are able to collide with orbital objects and perturb their orbits. The delta-v applied by the charge exchange neutral flux is greatest on high area-to-mass objects. Numerical simulation shows charge exchange neutral impacts produce a delta-v on objects on the order of 3.8 x 10⁻¹¹ m/s at a distance of 1 km from the center of the expelled gas in a 1,000 km orbit. The impulse imparted by charge exchange neutral impacts is at least six orders of magnitude smaller than that provided by the induced drag caused by gas expulsion. The localized drag increase can force a majority of small objects into the orbit of the expelled gas cloud, even if that orbit is retrograde to the initial orbit of the objects. This new technique can be applied to the remediation of space debris.     

Mars Sample Return: Do Australians trust NASA?

Mars Sample Return (MSR) represents an important scientific goal in space exploration. Any sample return mission will be extremely challenging from a scientific, economic and technical standpoint. But equally testing, will be communicating with a public that may have a very different perception of the mission. A MSR mission will generate international publicity and it is vital that NASA acknowledge the nature and extent of public concern about the mission risks and, perhaps equally importantly, the public’s confidence in NASA’s ability to prepare for and manage these risks. This study investigated the level of trust in NASA in an Australian population sample, and whether this trust was dependent on demographic variables. Participants completed an online survey that explored their attitudes towards NASA and a MSR mission. The results suggested that people believe NASA will complete the mission successfully but have doubts as to whether NASA will be honest when communicating with the public. The most significant finding to emerge from this study was that confidence in NASA was significantly (p < 0.05) related to the respondent’s level of knowledge regarding the risks and benefits of MSR. These results have important implications for risk management and communication.     

In orbit performance of butane propulsion system

The present work focuses on the determination of the in orbit performance of the Alsat-1 microsatellite propulsion system. The satellite mass is 90 kg, of which 6.2 kg is the propulsion system dry mass. The system is a butane propulsion system using low power resistojet thruster with 2.3 kg of propellant. The liquefied butane gas was selected due to its higher storage density and safety compared to the other propellants used for microsatellites. The purpose of this paper is the analysis of the firings performed after the launch of the satellite and to evaluate the system specific impulse and thrust level during the system lifetime. A total of 273 firings were performed on the Alsat-1 propulsion system in the period between the end of 2002 and mid 2009, the cumulated firing time is more than 12 h 49 min. The analysis of all the propulsion telemetry data shows that the system provides a total mission delta V of 25.3 m/s which is more than the 10 m/s specified for this mission. Furthermore, the mission average specific impulse and thrust are respectively 99.9 s and 48.8 mN.     

Excavation of artificial caverns inside asteroids by leveraging rotational self-energy

Future space ventures will likely require exploitation of near-Earth asteroid resources. Moreover, it can be envisaged that asteroids may host habitats in their interiors. In fact, a cavern inside an asteroid would be a natural radiation shield against cosmic radiation and may also serve as a confined environment for storage of mined material such as water ice or other processed volatiles such as propellants. To this end, this paper proposes to leverage the asteroid rotational self-energy to remove material from the asteroid interiors and create a spherical cavern, by means of the orbital siphon concept. The siphon is a chain of tether-connected payload masses (the asteroid material), which exploits the rotation of the asteroid for the delivery of mass from the asteroid to escape. Under certain conditions the siphon can be initiated to ensure self-sustained flow of mass from the asteroid to escape. A net orbital siphon effect is generated by connecting new payloads at the bottom of the chain while releasing the upper payloads. Key parameters are discussed, such as the required siphon dimension and the maximum size of the internal cavity that can be excavated, as a function of the asteroid rotational period. Moreover, assuming elastic material behaviour, a closed-form expression for the stress tensor is found and a failure criterion is used to identify regions in the asteroid interiors subjected to the larger stresses. It is shown that the conditions for failure are relaxed as the radius of the internal void increases.     

深空撞击载荷总体技术分析与效能仿真

以近地小行星2016HO3为深空撞击目标开展科学探测,从爆炸成型弹丸技术、安全可靠爆炸技术、撞击载荷分离技术、撞击效能仿真技术等7个方面系统详细地进行了基于聚能爆炸成型弹丸的撞击载荷技术体系解析与技术内涵阐述,给出了深空撞击载荷初步总体设计方案;通过弹丸撞击靶板的数值模拟仿真,得到了撞击速度在0.2～0.4 cm/μs...