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NASA NTRS1987

32 GHz deep space communications

The present analysis of the use of a 32-GHz (Ka-band) downlink for deep space communications notes significant benefits over current standard 8.4-GHz downlinks; the consequences of the 8-dB telemetry performance gain thus obtained is presently evaluated for the case of the Cassini and Mars Sample Return missions. This potential can only be realized, however, with upgradings of both the ground stations in the Deep Space Network and the spacecraft communications subsystem. Proposals are made for the use of a Ka-band beacon on the Mars observer spacecraft, as well as the demonstration of such a system aboard the CRAF.

Hansen, D. M.↗

NASA NTRS1988

Optical communications for future deep-space missions

The development of key technologies for an optical communications system for deep-space probes is discussed. Aspects of the technology include the pulse-position modulation technique for data transmission, a solid-state laser with a Nd:YAG crystal end, nondiffraction-limited receivers, and the application of avalanche photodiodes to improve photon detection. Mission benefits and flight opportunities and applications are discussed. Experiments to test optical communication systems are being planned for the Space Shuttle and the Mars Rover Sample Return misson. Future missions which will probably use the system include Cassini and the Mariner Mark II.

Rayman, Marc D.↗

NASA NTRS1988

Spacecraft technology requirements for future NASA missions

By working with advanced planners in the NASA Office of Space Science and Applications (OSSA), a spacecraft technology model has been generated that represents the predominant themes of their respective programs for the next twenty years. This set of missions serves as a base from which a few representative and challenging landmark missions have been extracted to serve as a focal point for identifying the most critical technology issues. Each mission requires significant advances in several technology disciplines in order to be feasible. The mission set selected to serve as a technology focus reflects the increased emphasis within NASA on a potential civil space leadership initiative, and include the Geostationary Earth Observing PLatform from the Planet Earth initiative and the precursor Mars Rover and Sample Return mission from the Mars Exploration Initiative. These missions are briefly described and the key technology requirements are discussed.

Hudson, Wayne R.↗

NASA NTRS1987

New techniques for the detection and capture of micrometeoroids

In order to understand the origin and distribution of the biogenic elements and their compounds in the solar system, it will be necessary to study materials from many classes of objects. Chemical, elemental, and isotopic measurements of returned samples of comets, asteroids, and possibly extra-solar system dust clouds would provide information on a particularly important class: primitive objects. Extraterrestrial micron-sized particles in the vicinity of Earth are one source of such materials that might otherwise be inaccessible. The Space Station appears to be an eminently suitable platform from which to collect and detect these various particles. The primary challenge, however, is to collect intact, uncontaminated particles which will be encountered at tens of kilometers per seconds. A concept for a micrometeoroid detector that could be deployed from the Space Station was developed which uses a large area detector plate implanted with acoustic transducers. When an impact event occurs, the resulting signal is subjected to spectral analysis providing positive detection, momentum information, and angle of incidence. The primary advantage of this detector is the large area which increases the probability of measuring events. A concept of a nondestuctive micrometeoroid collector for use from a Space Station was also developed. The collector utilizes input port charging of the incoming particle followed by staged high voltage deceleration for nondestructive capture. Low velocity particles (local contamination) would be rejected due to insufficient energy and only uncontaminated micrometeoroids would be collected.

Wolfe, J. H.↗

NASA NTRS1988

The Mars Observer database

Mars Observer will study the surface, atmosphere, and climate of Mars in a systematic way over an entire Martian year. The observations of the surface will provide a database that will be invaluable to the planning of a future Mars sample return mission. Mars Observer is planned for a September 1992 launch from the Space Shuttle, using an upper-stage. After the one year transit the spacecraft is injected into orbit about Mars and the orbit adjusted to a near-circular, sun-synchronous low-altitude, polar orbit. During the Martian year in this mapping orbit the instruments gather both geoscience data and climatological data by repetitive global mapping. The scientific objectives of the mission are to: (1) determine the global elemental and mineralogical character of the surface material; (2) define globally the topography and gravitational field; (3) establish the nature of the magnetic field; (4) determine the time and space distribution, abundance, sources, and sinks of volatile material and dust over a seasonal cycle; and (5) explore the structure and aspects of the circulation of the atmosphere. The science investigations and instruments for Mars Observer have been chosen with these objectives in mind. These instruments, the principal investigator or team leader and the objectives are discussed.

Albee, Arden L.↗

NASA NTRS1988

The soils of Mars

A mineralogical model for the Mars fine soil that includes as major components smectite clays absorbed and coated with amorphous iron oxyhydroxides and perhaps mixed with small amounts of better-crystalized iron oxides as separate phases is proposed. Also present as accessory minerals are sulfate minerals such as kieserite (MgSO4.H2O) and/or anhydrite (CaSO4), rutile (TiO2), and maghemite (Fe2O3) or magnetite (Fe3O4), the last two as magnetic components. Carbonates may be present at low concentrations only (less than 1 to 2 pct). However, a prime question to be addressed by a Mars Sample Return Mission shall be related to the mineralogical composition of the soil, and its spatial variability.

Banin, A.↗

NASA NTRS1988

Lunar placement of Mars quarantine facility

Advanced mission scenarios are currently being contemplated that would call for the retrieval of surface samples from Mars, from a comet, and from other places in the solar system. An important consideration for all of these sample return missions is quarantine. Quarantine facilities on the Moon offer unique advantages over other locations. The Moon offers gravity, distance, and vacuum. It is sufficiently near the Earth to allow rapid resupply and easy communication. It is sufficiently distant to lessen the psychological impact of a quarantine facility on Earth's human inhabitants. Finally, the Moon is airless, and seems to be devoid of life. It is, therefore, more suited to contamination control efforts.

Davidson, James E.↗

NASA NTRS1988

A Mars orbital laser altimeter for rover trafficability: Instrument concept and science potential

Limited information on the types of geologic hazards (boulders, troughs, craters etc.) that will affect rover trafficability on Mars are available for the two Viking Lander sites, and there are no prospects for increasing this knowledge base in the near future. None of the instrument payloads on the upcoming Mars Observer or Soviet PHOBOS missions can directly measure surface obstacles on the scales of concern for rover safety (a few meters). Candidate instruments for the Soviet Mars 92 orbiter/balloon/rover mission such as balloon-borne stereo imaging, rover panoramic imaging, and orbital synthetic aperature imaging (SAR) are under discussion, but data from this mission may not be available for target areas of interest for the U.S. Mars Rover Sample Return (MRSR) mission. In an effort to determine how to directly measure the topography of surface obstacles that could affect rover trafficability on Mars, we are studying how to design a laser altimeter with extremely high spatial and vertical resolution that would be suitable for a future Mars Orbiter spacecraft (MRSR precursor or MRSR orbiter). This report discusses some of the design issues associated with such an instrument, gives examples of laser altimeter data collected for Mars analog terrains on Earth, and outlines the scientific potential of data that could be obtained with the system.

Garvin, J. B.↗

NASA NTRS1988

The structure of the Martian cryolithosphere upper levels

Structural inhomogeneities of the Martian cryolithosphere upper levels were studied by the proposed crater method. On the basis of analysis of 127 photomaps of 1:2 million scale morphological and morphometrical parameters of all the fresh craters larger than 1 km in diameter with fluidized ejecta and without it were investigated. Using the parameters of the craters, the roof depths of ice-bearing rocks were estimated and the data on the ice relative constant in the excavated permafrost layer were obtained. These data were used for the construction of maps of the boundary depth between ice-free nearsurface layer and ice-bearing rocks. A series of maps of the relative ice content for individual permafrost horizons was constructed. It was deduced from the obtained maps that the zone of the dryest nearsurface rocks on Mars is in the latitude belt + or - 30 degrees where maximum floor depths of the ice-bearing rocks vary from 400 to more than 400 m. It was found that the thickness of ice-free rocks in the Southern Hemisphere is larger than in the Northern one. The tendency of similarity of latitudinal zonality observed both on the maps of the minimal and mean roof depths may be considered as an indicator of structural stability of upper horizons of the Martian cryolithosphere down to the depths of 300 to 400 m. The areas of minimal ice content in the nearsurface layers coincide with the zone of maximum thickness of ice-free rocks. The ice relative content in Martian rocks becomes systematically higher from 30 deg latitude to the polars. The same tendency is observed in depth. The data obtained may be useful for the selecting of landing sites for Mars samples return and other missions.

Kuzmin, R. O.↗

NASA NTRS1988

Valles Marineris, Mars: An optimum science-sample site

The Valles Marineris troughs offer an opportunity to sample rocks that reflect various ages and compositions, giving insight into important processes on Mars. Most of the samples would be located within reasonable proximity and could be easily reached by rovers or balloons. Although landing a spacecraft on the floor of the Valles Marineris may be too dangerous for the first sample-return mission to Mars, the scientific rewards would be so great that such a landing should be considered for later flights.

Lucchitta, B. K.↗

NASA NTRS1988

Martian sediments and sedimentary rocks

Martian sediments and sedimentary rocks, clastic and nonclastic, should represent a high priority target in any future return-sample mission. The discovery of such materials and their subsequent analysis in terrestrial laboratories, would greatly increase the understanding of the Martian paleoclimate. The formation of Martian clastic sedimentary rocks, under either present, low-pressure, xeric conditions or a postulated, high-pressure, hydric environment, depends upon the existence of a supply of particles, various cementing agents and depositional basins. A very high resolution (mm-cm range) photographic reconnaissance of these areas would produce a quantum jump in the understanding of Martian geological history. Sampling would be confined to more horizontal (recent) surfaces. Exploration techniques are suggested for various hypothetical Martian sedimentary rocks.

Markun, C. D.↗

NASA NTRS1988

Computer modeling of the mineralogy of the Martian surface, as modified by aqueous alteration

Mineralogical constraints can be placed on the Martian surface by assuming chemical equilibria among the surface rocks, atmosphere and hypothesized percolating groundwater. A study was made of possible Martian surface mineralogy, as modified by the action of aqueous alteration, using the EQ3/6 computer codes. These codes calculate gas fugacities, aqueous speciation, ionic strength, pH, Eh and concentration and degree of mineral saturation for complex aqueous systems. Thus, these codes are also able to consider mineralogical solid solutions. These codes are able to predict the likely alteration phases which will occur as the result of weathering on the Martian surface. Knowledge of the stability conditions of these phases will then assist in the definition of the specifications for the sample canister of the proposed Martian sample return mission. The model and its results are discussed.

Zolensky, M. E.↗

NASA NTRS1989

Viking and Mars Rover exobiology

Other than Earth, Mars is the planet generating the greatest interest among those researching and contemplating the origin and distribution of life throughout the universe. The similarity of the early environments of Earth and Mars, and the biological evolution on early Earth provides the motivation to seriously consider the possibility of a primordial Martian biosphere. In 1975 the Viking project launched two unmanned spacecraft to Mars with the intent of finding evidence of the existence of present or past life on this planet. Three Viking Biology experiments were employed: the Labeled Release experiment, the Gas Exchange Experiment, and the Pyrolytic Release experiment. Each of these three experiments tested for microbial existence and utilization of a substrate by examining the gases evolved from specific chemical reactions. Although the results of these experiments were inconclusive, they inferred that there are no traces of extant life on Mars. However, the experiments did not specifically look for indication of extinct life. Therefore, most of the exobiologic strategies and experiments suggested for the Mars Rover Sample Return Mission involve searching for signature of extinct life. The most significant biological signatures and chemical traces to detect include: isotopic and chemical signatures of metabolic activity, anomalous concentrations of certain metals, trace and microfossils, organically preserved materials, carbonates, nitrates, and evaporites.

Schwartz, D. E.↗

NASA NTRS1989

High-precision radiometric tracking for planetary approach and encounter in the inner solar system

The benefits of improved radiometric tracking data have been studied for planetary approach within the inner Solar System using the Mars Rover Sample Return trajectory as a model. It was found that the benefit of improved data to approach and encounter navigation was highly dependent on the a priori uncertainties assumed for several non-estimated parameters, including those for frame-tie, Earth orientation, troposphere delay, and station locations. With these errors at their current levels, navigational performance was found to be insensitive to enhancements in data accuracy. However, when expected improvements in these errors are modeled, performance with current-accuracy data significantly improves, with substantial further improvements possible with enhancements in data accuracy.

Christensen, C. S.↗

NASA NTRS1988

Integrated strategies for the exploration of Mars

Two mission programs for the manned exploration of Mars are discussed. The first is a four-man, split/spring mission proposed for 2001-2003. It includes the manned exploration of Phobos and teleoperated exploration of the Martian surface using unmanned vehicles with sample return capabilities. The second program is a series of three split/sprint missions planned for between 2005 and 2012. These missions include the exploration of three different areas of the Martian surface by three different four-man crews. Each crew would spend 20 days on Mars with manned sorties to Phobos and Deimos.

Craig, Mark K.↗

NASA NTRS1989

A predictive guidance algorithm for Mars entry

This report presents the derivation, logic, and performance of a Mars entry guidance algorithm for the Mars Rover Sample Return Mission. This algorithm guides the Mars entry vehicle along an equilibrium glide trajectory designed to satisfy a set of equality and inequality constraints at chute deploy. An equilibrium glide assumption permits analytic prediction of terminal state conditions and eliminates the need for determining numeric state sensitivities. Trajectory deviations due to dispersions or uncertainties in Martian atmosphere, vehicle aerodynamics, or entry interface conditions are accommodated simply by predicting the compensating equilibrium glide profile and achieving this profile with the available lift control. This Mars Predictive Equilibrium Glide guidance scheme was tested on a range of vehicle configurations with a variety of aerodynamic, atmosphere, and trajectory dispersions with a high degree of success.

Tigges, M. A.↗

NASA NTRS1989

Geologic setting of an unusual Martian channel - Hypotheses on origin

Several areas within the Memnonia region of Mars have been proposed as candidate sites for a Mars sample return mission. Geologic studies of these areas made from computer-enhanced high-resolution Viking images show that an assemblage of rocks having different ages and compositions are accessible to a roving vehicle. In addition, evidence of recent fluvial episodes is indicated by small channels that incises materials emplaced during the Amazonian Period. The channel discussed in this paper is located near the highland-lowland boundary in the Memnonia MC-16SW quadrangle of Mars. It is of particular interest because of distinctive morphologic characteristics compared to other Martian channels. Although several hypotheses are advanced to explain the origin of the channel, none of the arguments are completely satisfactory. However, it is believed that water mobilized from ice in the subjacent regolith (hypothesis 1) or that condensate water from highly volatile ash flows (hypothesis 2) are the most likely origins for the channel.

Scott, D. H.↗

NASA NTRS1989

Rocket propellants from Martian resources

In order for extensive round trip travel to become feasible in terms of mass required in low Earth orbit, propellant manufacturing at Mars becomes essential. Martian resources lend themselves to relatively easy generation of several promising propellant combinations. Not only manned missions but also smaller unmanned missions such as sample return may benefit from this technology.

French, J. R.↗