Martian Satellite Phobos Research Articles

Trajectory Design of Perseus: A CubeSat Mission Concept to Phobos

The Martian satellites Phobos and Deimos hold many unanswered questions that may provide clues to the origin of Mars. These moons are low Δv stopover sites to Mars. Some human missions to Mars typically identify Phobos and Deimos as staging bases for Mars surface exploration. Astronauts could base initial operations there in lieu of repeated voyages to and from the planet surface, to refuel transiting spacecraft, to teleoperate robotics and other critical machinery, and to develop habitable infrastructure ahead of human landings. Despite their strategic and scientific significance, there has been no successful dedicated mission to either moon. For this reason, we propose Perseus, a geological imaging CubeSat mission to Phobos. Perseus, a 27U, 54kg CubeSat will return thermal and visible images at resolutions better than currently available over most of Phobos’ surface. This includes visible images at 5m/pixel and thermal images at 25m/pixel of Phobos’ surface. The Perseus mission is nominally intended to be a co-orbital mission, where the spacecraft will encounter Phobos on its Martian orbit. However, a hyperbolic rendezvous mission concept, to image Phobos on a hyperbolic flyby, is also considered to reduce the risks associated with orbit capture and to reduce mission costs. This paper presents the preliminary feasibility, science objectives, and technological development challenges of achieving these science goals. We then formulate two rendezvous concepts as a series of three nonlinear optimization problems that span the design tree of mission concepts. The tree’s root node is the heliocentric cruise problem, which identifies the near-optimal launch and arrival windows for the Perseus spacecraft. The leaf nodes of the design tree are the two rendezvous concepts that identify near-optimal co-orbital and hyperbolic trajectories for Phobos’ reconnaissance. The design problems are solved using evolutionary algorithms, and the performance of the selected mission concepts is then examined. The results indicate that a co-orbital encounter allows about one encounter per day with about 6 min per encounter. The hyperbolic encounter, on the other hand, allows a single encounter where the spacecraft will spend about 2 min in the imaging region with respect to Phobos. The spacecraft will obtain higher resolution images of Phobos on this feasible region than have ever been seen for most of the surface. These detailed images will help identify candidate landing sites and provide critical data to derisk future surface missions to Phobos.

Simulating re-impacts from craters at the deepest location of Phobos to generate its blue spectral units

The spatial distribution pattern of ejecta from an impact crater on the surface of a body in space holds clues to understanding the ejecta launch conditions, the crater excavation process, and the dynamical environment. In particular, focusing on re-impact sites from larger or deeper craters on the surface is important, as they tend to preserve much of the original information. The surface of the Martian satellite Phobos is spectrally divided into red and blue units. The former are globally distributed, while the blue units have been observed inside and outside the Stickney crater—the largest and deepest crater on Phobos. Outside the crater, the blue units are concentrated in the region from the south to the west (south-west blue units) and in the region east of the crater (east blue units). Several models can explain the concentration of east blue units. However, the mode of formation of south-west blue units is still unknown, despite its vast area. We proposed that the combination of ejecta from Stickney and Limtoc (a crater located on the floor of Stickney) contributed to the formation of the blue units. We tested the model using ballistic simulations incorporating, an updated shape model with randomly generated ejecta velocities, different values of orbital radii to Mars, and various launching velocities, to track the emplacement of the ejecta particles. The results showed that the distribution of the two blue units is recreated when the combined re-impact sites of ejecta from Stickney and Limtoc have orbital radius (XPh) values of XPh > 3.34 Mars radii (RM) and XPh < 3.04 RM, respectively. The observations and the results suggest that Phobos comprises an inner blue layer covered by red materials globally and locally excavated blue materials. Using the squared term of the orbital evolution, we calculate the approximate age of Stickney to > 23 Myr, which may be sufficiently old to be estimated from the crater densities. We restrict the age of Limtoc to < 109 Myr, which indicates that this crater is one of the youngest features on Phobos.

Dusty plasmas at Martian satellites

Dusty plasmas are shown to be formed in a surface layer over the illuminated part of Martian satellites Phobos and Deimos owing to photoelectric and electrostatic processes. The distribution functions of photoelectrons near surfaces of the satellites, altitude dependences of the density of dust particles, and their charges and sizes, as well as electric fields, have been determined within a physical-mathematical model for the self-consistent description of densities of photoelectrons and dust particles over the surface of the illuminated parts of Phobos and Deimos. In view of a weak gravitational field, dust particles rising over the surfaces of Phobos and Deimos are larger than those over the surface of the Moon. In this case, the role of adhesion, which is a significant process preventing the separation of dust particles from the lunar surface, is much smaller on Phobos and Deimos.

Diurnal Temperature Regime in the Regolith Surface Layer of the Lagado Planitia Region on Phobos: Model Predictions for Different Seasons

The paper contains the data on the thermal and physical characteristic of the surface regolith of the Martian satellite Phobos obtained from the spaceborne remote sensing (with the Mariner 9, Viking, and Mars Global Surveyor orbiters and the Phobos-2 spacecraft) and the results of the numerical modeling of the thermal regime in the surface regolith (on diurnal and seasonal scales) performed for the prospective landing site in the Lagado Planitia region located in the anti-Martian hemisphere of Phobos.

Ultraviolet spectral reflectance of carbonaceous materials

A number of planetary spacecraft missions have carried instruments with sensors covering the ultraviolet (UV) wavelength range. However, there exists a general lack of relevant UV reflectance laboratory data to compare against these planetary surface remote sensing observations in order to make confident material identifications. To address this need, we have systematically analyzed reflectance spectra of carbonaceous materials in the 200–500 nm spectral range, and found spectral-compositional-structural relationships that suggest this wavelength region could distinguish between otherwise difficult-to-identify carbon phases. In particular (and by analogy with the infrared spectral region), large changes over short wavelength intervals in the refractive indices associated with the trigonal sp2π–π* transition of carbon can lead to Fresnel peaks and Christiansen-like features in reflectance. Previous studies extending to shorter wavelengths also show that anomalous dispersion caused by the σ–σ* transition associated with both the trigonal sp2 and tetrahedral sp3 sites causes these features below λ = 200 nm. The peak wavelength positions and shapes of π–π* and σ–σ* features contain information on sp3/sp2, structure, crystallinity, and powder grain size. A brief comparison with existing observational data indicates that the carbon fraction of the surface of Mercury is likely amorphous and submicroscopic, as is that on the surface of the martian satellites Phobos and Deimos, and possibly comet 67P/Churyumov–Gerasimenko, while further coordinated observations and laboratory experiments should refine these feature assignments and compositional hypotheses. The new laboratory diffuse reflectance data reported here provide an important new resource for interpreting UV reflectance measurements from planetary surfaces throughout the solar system, and confirm that the UV can be rich in important spectral information.

Sesquinary catenae on the Martian satellite Phobos from reaccretion of escaping ejecta.

The Martian satellite Phobos is criss-crossed by linear grooves and crater chains whose origin is unexplained. Anomalous grooves are relatively young, and crosscut tidally predicted stress fields as Phobos spirals towards Mars. Here we report strong correspondence between these anomalous features and reaccretion patterns of sesquinary ejecta from impacts on Phobos. Escaping ejecta persistently imprint Phobos with linear, low-velocity crater chains (catenae) that match the geometry and morphology of prominent features that do not fit the tidal model. We prove that these cannot be older than Phobos' current orbit inside Mars' Roche limit. Distinctive reimpact patterns allow sesquinary craters to be traced back to their source, for the first time across any planetary body, creating a novel way to probe planetary surface characteristics. For example, we show that catena-producing craters likely formed in the gravity regime, providing constraints on the ejecta velocity field and knowledge of source crater material properties.

Adaptive Reachability Analysis to Achieve Mission Objectives in Strongly Non-Keplerian Systems

Adaptive numerical reachability analysis is studied as a tool for coping with sensitive, strongly non-Keplerian dynamics when planning impulsive spacecraft maneuvers in pursuit of mission objectives at small-body systems. The concept of an objective reachability map is developed beginning from analytical results for the Kepler problem and is shown to become intricately structured for the environments of asteroid Itokawa and Martian satellite Phobos. An existing method for efficient map computation via heuristic refinement, originally applied to chart safety outcomes on a planar maneuver domain, is extended for application to spherical domains and two types of non-Boolean science objectives defined for target locations on the body surface: cumulative observation time and surface payload deployment accuracy. In addition to its potential as a tool for preliminary mission design and the general study of small-body dynamics, this reachability analysis method is also examined and discussed as a resource for receding-horizon planning onboard an autonomous spacecraft.

Spectrophotometric investigation of Phobos with the Rosetta OSIRIS-NAC camera and implications for its collisional capture

The Martian satellite Phobos has been observed on 2007 February 24 and 25, during the pre- and post-Mars closest approach (CA) of the ESA Rosetta spacecraft Mars swing-by. The goal of the observations was the determination of the surface composition of different areas of Phobos, in order to obtain new clues regarding its nature and origin. Near-ultraviolet, visible and near-infrared (263.5–992.0 nm) images of Phobos's surface were acquired using the Narrow Angle Camera of the OSIRIS instrument onboard Rosetta. The six multi-wavelength sets of observations allowed a spectrophotometric characterization of different areas of the satellite, belonging respectively to the leading and trailing hemisphere of the anti-Mars hemisphere, and also of a section of its sub-Mars hemisphere. The pre-CA spectrophotometric data obtained with a phase angle of 19° have a spectral trend consistent within the error bars with those of unresolved/disc-integrated measurements present in the literature. In addition, we detect an absorption band centred at 950 nm, which is consistent with the presence of pyroxene. The post-CA observations cover from NUV to NIR a portion of the surface (0° to 43°E of longitude) never studied before. The reflectance measured on our data does not fit with the previous spectrophotometry above 650 nm. This difference can be due to two reasons. First, the OSIRIS observed area in this observation phase is completely different with respect to the other local specific spectra and hence the spectrum may be different. Secondly, due to the totally different observation geometry (the phase angle ranges from 137° to 140°), the differences of spectral slope can be due to phase reddening. The comparison of our reflectance spectra, both pre- and post-CA, with those of D-type asteroids shows that the spectra of Phobos are all redder than the mean D-type spectrum, but within the spectral dispersion of other D-types. To complement this result, we performed an investigation of the conditions needed to collisionally capture Phobos in a way similar to that proposed for the irregular satellites of the giant planets. Once put in the context of the current understanding of the evolution of the early Solar system, the coupled observational and dynamical results we obtained strongly argue for an early capture of Phobos, likely immediately after the formation of Mars.

The design philosophy of the Phobos-Grunt space vehicle

This paper covers the main features of Russia’s Phobos-Grunt space mission, whose primary goal is to return soil samples from the Martian satellite Phobos. The mission scenario, major design solutions, and evolution of the project throughout its development are described.

Laser transmission module with a switchable directional pattern for the rangefinder of the Phobos–Ground spacecraft

This paper describes the operating principle and lists the main characteristics of a laser transmission module for the rangefinder intended for use in the far-space expedition to the Martian satellite Phobos, intended to start in 2011. A distinguishing feature of the laser included in the transmission module is rapid, nonmechanical switching of the direction of the directional pattern for measuring oblique ranges and computing the normal to the surface.

The thermophob experiment: Direct investigations of the thermophysical properties of the regolith of phobos

The methodology and the main features of the Thermophob experiment developed for the direct analysis of the thermophysical properties of the surface of the Martian satellite Phobos from the Phobos-Grunt lander are considered. The methodical and engineering aspects of the measurements are discussed, and the design of the instrument and the potential of the interpretation of the measurement results with accounting for the theoretical estimates and the data of the laboratory tests are discussed.

Near infrared diode laser spectroscopy of C2H2, H2O, CO2 and their isotopologues and the application to TDLAS, a tunable diode laser spectrometer for the martian PHOBOS-GRUNT space mission

A near-infrared tunable diode laser spectrometer called TDLAS has been developed that combines telecommunication-type as well as new-generation antimonide laser diodes to measure C2H2, H2O, CO2 and their isotopologues in the near infrared. This sensor is devoted to the in situ analysis of the soil of the Martian satellite PHOBOS, within the framework of the Russian space mission PHOBOS-GRUNT. In the first part of the paper, we report accurate spectroscopic measurements of C2H2 and 13C12CH2 near 1.533 μm, of H2O and CO2 at 2.682 μm and of the isotopologues 13C16O2 and 16O12C18O near 2.041 μm and H2 17O, H2 18O and HDO near 2.642 μm. The achieved line strengths are thoroughly compared to data from molecular databases or from former experimental determinations. In the second part of the paper, we describe the TDLAS spectrometer for the PHOBOS-GRUNT mission.

Project of the mission to Phobos

This article provides the main scientific objectives and characteristics of the Phobos-Soil project, intended to fly to the Martian satellite Phobos, deliver its soil samples to the Earth, as well as explore Phobos, Mars, and the Martian environment with onboard scientific instruments. We give the basic parameters of the ballistic scenario of the mission, spacecraft, and some scientific problems to be solved with the help of the scientific instruments installed on the spacecraft.

THE ORBITS AND MASSES OF THE MARTIAN SATELLITES AND THE LIBRATION OF PHOBOS

This paper reports on an update to the orbits and masses of the Martian satellites Phobos and Deimos. We obtained the orbits by fitting a numerical integration to all available Earth-based astrometry through the opposition of 2003, spacecraft imaging observations through 2007, and the Doppler tracking of the Viking and Phobos 2 spacecraft; the Doppler data provide information on the satellite masses. Our dynamical model included the figure acceleration due to a librating Phobos; we determined the amplitude of the forced libration. We also took into account the secular acceleration of Phobos due to the tide that it raises on Mars and estimated the Martian tidal quality factor Q. We provide an assessment of the accuracy of the orbits and a geometrical description of the orbits in the form of mean elements.

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.

Pressing Issues of the Day in Studying Deep Space

Two problems in studying deep space are discussed that are, in the author's opinion, the most important. The first is soil sampling from the smaller bodies of the Solar System, such as the Martian satellite Phobos and asteroids of groups C and S of the Main Asteroid Belt. This soil (so-called primordial substance) can help to elucidate some problems of the Solar System's formation; in particular, to construct a reliable model of the internal structure of the Earth. The second problem is to reveal all sufficiently large asteroids penetrating inside the Earth's orbit and to catalog those asteroids that are hazardous from the viewpoint of collision with the Earth. To this end, it is suggested to launch five or six Earth-orbiting spacecraft with telescopes capable of recording objects down to a brightness of 22– 25m. It is pointed out that both problems can be solved in the near future using comparatively cheap standardized space vehicles launched into near-Earth orbits by the Soyuz carrier rocket and boosted further by electro-jet engines of small thrust.

Solar eclipses of Phobos and Deimos observed from the surface of Mars

The small martian satellites Phobos and Deimos orbit in synchronous rotation with inclinations of only 0.01 degrees and 0.92 degrees , respectively, relative to the planet's equatorial plane. Thus, an observer at near-equatorial latitudes on Mars could occasionally observe solar eclipses by these satellites (see ref. 1, for example). Because the apparent angular diameter of the satellites is much smaller than that of the Sun, however, such events are more appropriately referred to as transits. Transit data can be used for correcting and refining the orbital ephemerides of the moons. For example, Phobos is known to exhibit a secular acceleration that is caused by tidal dissipation within Mars. Long-term, accurate measurements are needed to refine the magnitude and origin of this dissipation within the martian interior as well as to refine the predicted orbital evolution of both satellites. Here we present observations of six transits of Phobos and Deimos across the solar disk from cameras on Mars aboard the Mars Exploration Rovers Spirit and Opportunity. These are the first direct imaging observations of satellites transiting the Sun from the surface of another planet.

ISM observation of Phobos reinvestigated: Identification of a mixture of olivine and low‐calcium pyroxene

We reinvestigate the infrared spectral image cube of the Martian satellite Phobos obtained by the Infrared Spectrometer for Mars (ISM) instrument on board PHOBOS 2 using a band detection method based on the wavelet transform. Two absorption bands are identified at 1.04 μm and 1.9 μm. The position and profile of these bands are compatible with a mixture of low‐calcium pyroxene and olivine in specific regions on the surface of the satellite. This identification is confirmed by the strong spatial correlation of these two bands, which also corresponds to areas with a lower albedo. Finally, we discuss clues pointing toward possible local hydration of Phobos.

Power-law indices of asteroidal grooves and strength

The strength of an asteroid is a valuable parameter, but it is difficult to measure directly. Although impact experiments have made a large contribution, the problem of the relationship between an asteroid’s size and its strength has not been solved. This paper introduces a valuable parameter for natural bodies, the power-law index ϕ of the size distribution of fracture planes [ ]. This index can be regarded as parameterizing the strength, because strength is controlled by the size of the largest fracture. The power-law indices ϕ of the Martian satellite Phobos and the asteroid Gaspra were found to be 5.9 and 6.5, respectively. These values are close to 6, which is the theoretical value expected for the “fully cracked” condition of Housen and Holsapple (1999). The implications of this result for the size-strength relationship of asteroids are discussed.

Equal Area Map Projection for Irregularly Shaped Objects

Approximately half of the planetary bodies in our solar system imaged by spacecraft have irregular shapes. Since maps are used to record, interpret and display these irregularly shaped bodies, a special map projection, which can display them faithfully, is desirable. Unfortunately, no mathematical approach that permits true conformal or equal-area projections has been developed. In this paper, a novel approach to construct a special equal area map projection for irregularly shaped objects is suggested. Using this innovative approach, equal area map projections for two Martian satellites—Phobos and Deimos are—developed.