Future missions to Venus will require electrical power, but providing power systems that work in the high temperature environment of the surface of Venus is difficult. Power system choices include ...solar power from photovoltaic arrays, batteries, radioisotope power systems, and wind. The current state of power technology for operation on the Venus surface sources is surveyed and assessed.
•The Venus environment makes electrical power systems for surface missions difficult.•Analysis suggests radioisotope power systems could be adapted to operate on Venus.•High temperature and low sunlight reduce power from solar arrays, possibly useable on small probes.•Other power systems such as wind have been proposed and may be developed in the future.
Spirit began operations in Gusev Crater in January 2004 and has returned data on three seasons of dust devil (DD) activity. Total DDs observed were 533 in season one, 101 in season two, and 127 in ...season three. Their general characteristics are the same within factors of 2 among the seasons, with median diameters of 19 m in season one, 24 m in season two, and 39 m in season three, and dust flux values for individual vortices ranging from 4.0 × 10−9 to 4.6 × 10−4 kg m−2 s−1 in season one, 5.2 × 10−7 to 6.2 × 10−5 kg m−2 s−1 in season two, and 1.5 × 10−7 to 1.6 × 10−4 kg m−2 s−1 in season three. All three seasons were initiated with the onset of southern Martian spring within 14 sols of the same Ls (181°) and their frequency increased to the period corresponding to late southern spring. The occurrences decreased monotonically in seasons one and three but apparently ended abruptly in season two when a large dust storm occurred; although the dusty atmosphere might have precluded the detection of active DDs, the abrupt cessation could result from conditions such as thermal stability of the atmosphere due to the presence of dust which could halt DD formation. Dust devils can contribute significant quantities of dust to the atmosphere, although it is unclear as to whether this dust stays locally or is injected into higher‐altitude winds and is distributed elsewhere. In the three DD seasons observed through Spirit, DDs in Gusev Crater injected a minimum average of ∼18 × 106 kg of material into the atmosphere each season.
The Spirit and Opportunity Mars Exploration Rovers (MER) landed on the surface of Mars in January 2004. Thermal infrared spectra taken by the Miniature Thermal Emission Spectrometer (Mini‐TES) ...instrument on board each rover, collected in both the upward‐looking and downward‐looking geometries, has allowed for the retrieval of atmospheric temperatures between 1 and 2000 m above the surface, the column optical depth of dust, and the column abundance of water vapor for more than one full Martian year. During this period, Mini‐TES has observed the annual cycle of temperature variations, the diurnal growth and decay of a near‐surface highly superadiabatic layer, and random temperature fluctuations on a timescale of less than a minute. Mini‐TES observations also record the timing, duration, and intensity of several local‐scale and regional‐scale dust storms and the annual variation of water vapor abundance at the two rover locations.
A full dust devil “season” was observed from Spirit from 10 March 2005 (sol 421, first active dust devil observed) to 12 December 2005 (sol 691, last dust devil seen); this corresponds to the period ...Ls 173.2° to 339.5°, or the southern spring and summer on Mars. Thermal Emission Spectrometer data suggest a correlation between high surface temperatures and a positive thermal gradient with active dust devils in Gusev and that Spirit landed in the waning stages of a dust devil season as temperatures decreased. 533 active dust devils were observed, enabling new characterizations; they ranged in diameter from 2 to 276 m, with most in the range of 10–20 m in diameter, and occurred from about 0930 to 1630 hours local true solar time (with the maximum forming around 1300 hours) and a peak occurrence in southern late spring (Ls ∼ 250°). Horizontal speeds of the dust devils ranged from <1 to 21 m/s, while vertical wind speeds within the dust devils ranged from 0.2 to 8.8 m/s. These data, when combined with estimates of the dust content within the dust devils, yield dust fluxes of 3.95 × 10−9 to 4.59−4 kg/m2/s. Analysis of the dust devil frequency distribution over the inferred dust devil zone within Gusev crater yields ∼50 active dust devils/km2/sol, suggesting a dust loading into the atmosphere of ∼19 kg/km2/sol. This value is less than one tenth the estimates by Cantor et al. (2001) for regional dust storms on Mars.
Venus, the “greenhouse planet,” is a scientifically fascinating place. The US National Academies of Sciences listed a Venus surface in situ explorer as one of the highest priority planetary science ...missions. A mission concept for a robotic mission to study the surface and atmosphere of Venus has been designed. The mission includes both surface robots, designed with an operational lifetime of 50 days on the surface of Venus, and also solar-powered airplanes to probe the middle atmosphere. At
450
∘
C
, and with 90 atmospheres of pressure of carbon-dioxide atmosphere, the surface of Venus is a hostile place for operation of a probe. The mission design trade-off looked at three options for surface operation: developing technology to operate at Venus surface temperatures, using an active refrigeration system to lower the temperature inside a “cool electronics enclosure,” or developing a hybrid system, where the computer system and the most temperature-sensitive electronics are on an aerial platform at lower temperature, and less sophisticated surface electronics operate at the ambient surface temperature. This paper presents the mission objectives, discusses the technology options for materials, power systems, electronics, and instruments, and presents a short summary of the mission.
The Panoramic Camera (Pancam) on the Mars Exploration Rover mission has acquired in excess of 20,000 images of the Pancam calibration targets on the rovers. Analysis of this data set allows estimates ...of the rate of deposition and removal of aeolian dust on both rovers. During the first 150–170 sols there was gradual dust accumulation on the rovers but no evidence for dust removal. After that time there is ample evidence for both dust removal and dust deposition on both rover decks. We analyze data from early in both rover missions using a diffusive reflectance mixing model. Assuming a dust settling rate proportional to the atmospheric optical depth, we derive spectra of optically thick layers of airfall dust that are consistent with spectra from dusty regions on the Martian surface. Airfall dust reflectance at the Opportunity site appears greater than at the Spirit site, consistent with other observations. We estimate the optical depth of dust deposited on the Spirit calibration target by sol 150 to be 0.44 ± 0.13. For Opportunity the value was 0.39 ± 0.12. Assuming 80% pore space, we estimate that the dust layer grew at a rate of one grain diameter per ∼100 sols on the Spirit calibration target. On Opportunity the rate was one grain diameter per ∼125 sols. These numbers are consistent with dust deposition rates observed by Mars Pathfinder taking into account the lower atmospheric dust optical depth during the Mars Pathfinder mission.
Oxygen, metals, silicon, and glass are raw materials that will be required for long-term habitation and production of structural materials and solar arrays on the Moon. A process sequence is proposed ...for refining these materials from lunar regolith, consisting of separating the required materials from lunar rock with fluorine. The fluorine is brought to the Moon in the form of potassium fluoride, and is liberated from the salt by electrolysis in a eutectic salt melt. Tetrafluorosilane produced by this process is reduced to silicon by a plasma reduction stage; the fluorine salts are reduced to metals by reaction with metallic potassium. Fluorine is recovered from residual MgF and CaF
2 by reaction with K
2O.
The atmospheric composition and geologic structure of Venus have been identified by the US National Research Council׳s Decadal Survey for Planetary Science as priority targets for scientific ...exploration; however, the high temperature and pressure at the surface, along with the highly corrosive chemistry of the Venus atmosphere, present significant obstacles to spacecraft design that have severely limited past and proposed landed missions. Following the methodology of the NASA Innovative Advanced Concepts (NIAC) proposal regime and the Collaborative Modeling and Parametric Assessment of Space Systems (COMPASS) design protocol, this paper presents a conceptual study and initial feasibility analysis for a Discovery-class Venus lander capable of an extended-duration mission at ambient temperature and pressure, incorporating emerging technologies within the field of high temperature electronics in combination with novel configurations of proven, high Technology Readiness Level (TRL) systems. Radioisotope Thermal Power (RTG) systems and silicon carbide (SiC) communications and data handling are examined in detail, and various high-temperature instruments are proposed, including a seismometer and an advanced photodiode imager. The study combines this technological analysis with proposals for a descent instrument package and a relay orbiter to demonstrate the viability of an integrated atmospheric and in-situ geologic exploratory mission that differs from previous proposals by greatly reducing the mass, power requirements, and cost, while achieving important scientific goals.
•Advanced mission concept to explore Venus surface and atmosphere.•We develop concept of operations and communications infrastructure.•We propose high-temperature instrument packages for descent and landing.•We analyze a Radioisotope Thermal Power Generation system.
In the long term, settlement of Mars will require local refining of industrial and construction materials. One of the most significant industrial materials is steel. It is proposed that steel can be ...harvested on Mars in the form of reduced iron available on the surface from meteoric nickel–iron. This may be one of the most easily available resources on Mars.
This paper presents an exploration strategy for human missions beyond Low Earth Orbit (LEO) and the Moon that combines the best features of human and robotic spaceflight. This “Human Exploration ...using Real-time Robotic Operations” (HERRO) strategy refrains from placing humans on the surfaces of the Moon and Mars in the near-term. Rather, it focuses on sending piloted spacecraft and crews into orbit around Mars and other exploration targets of interest, and conducting astronaut exploration of the surfaces using telerobots and remotely-controlled systems. By eliminating the significant communications delay or “latency” with Earth due to the speed of light limit, teleoperation provides scientists real-time control of rovers and other sophisticated instruments. This in effect gives them a “virtual presence” on planetary surfaces, and thus expands the scientific return at these destinations. HERRO mitigates several of the major issues that have hindered the progress of human spaceflight beyond Low Earth Orbit (LEO) by: (1) broadening the range of destinations for near-term human missions; (2) reducing cost and risk through less complexity and fewer man-rated elements; (3) offering benefits of human-equivalent in-situ cognition, decision-making and field-work on planetary bodies; (4) providing a simpler approach to returning samples from Mars and planetary surfaces; and (5) facilitating opportunities for international collaboration through contribution of diverse robotic systems. HERRO provides a firm justification for human spaceflight—one that expands the near-term capabilities of scientific exploration while providing the space transportation infrastructure needed for eventual human landings in the future.
► Paper presents exploration strategy that combines best features of human and robotic spaceflight. ► Astronauts explore surfaces of planetary bodies in deep gravity wells with telerobotics. ► Astronauts operate in locations that are energetically much easier to access than going to surface. ► Operations occur within cognitive horizon/distance to enable real-time operation of telerobots. ► Strategy justifies human spaceflight while expanding near-term capabilities in scientific exploration.
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