Phobos Surveyor

The crater Stickney, a preferred target for Phobos Surveyor.

Pavone and his group have already constructed and tested two generations of rovers, and hopes to begin low-gravity testing of his rovers by the summer of 2013.[1] These tests will simulate the low-gravity environment of Phobos first by means of a crane and by 2015, Pavone hopes, using an aircraft designed to reduce the force of gravity for its occupants.[3] The testing arena will be designed to mimic the surface of Phobos as closely as possible, containing rocks and using flour to take the place of asteroid dust.[1]

In the mission concept,[7] the rovers would be released near Phobos's large crater Stickney, where the orbiter would hover in a stable orbit around Phobos, and where the rovers themselves would gain access to the innermost rock layers of Phobos for analysis in situ[1] and create a target for a future sample-return mission.[8] This would be important scientifically, as it would allow a determination of whether Phobos is an asteroid captured by Mars's gravity, or a fragment of Mars that was lifted into orbit by an asteroid or comet impact[3] and would increase knowledge on the nature of Mars itself.[8] A mission to Phobos would also give the scientific community greater insights into the formation and evolution of the Solar System into its present state.[8]

The low gravity of Phobos, as well as the existence of caves created by the impact that also created Stickney, make Phobos a prime target for the construction of a space colony, due to the ease of launching rockets from its surface (resulting from its low gravity) and the radiation protection provided by the caves.[9] Further assessment of the moon as a location for colonization and where on the moon human colonies should be constructed would be possible with the relatively inexpensive rovers before taking on the expense of manned missions.[6]

Measuring roughly 2 feet (0.6 m) across,[3] the rovers for Phobos Surveyor are shaped like sea urchins[2] in order to adapt to the low-gravity environments in which they are designed to function,[4] for which they have been often called "hedgehogs".[1][2][3][4][6] Propulsion of the hedgehogs, rather than with wheels as in traditional Mars rovers, involves three spinning disks[1] in an orthogonal configuration, which are accelerated or decelerated to change the hedgehogs' speed and whose inertia allows the hedgehogs to move around Phobos.[1] Consequently, the hedgehogs will move not by rotating themselves on the surface, but rather in a series of controlled hops or short flights across the surface of the body they are exploring,[2] powered by solar panels on each rover's surface.[6]

In addition to their ability to work well in conditions of low gravity, the hedgehog design, as well as other designs which move by hopping around a body's surface, have several advantages over traditional rovers. Rather than being stopped by geological features such as canyons and crevasses, these designs, collectively known as hoppers, can simply hop over such impediments.[6] In addition, hoppers cannot have stuck wheels, a problem which ended the mission of NASA's Spirit Mars rover.[6]

Although there will be some degree of control of the hedgehogs by humans on Earth, they are largely robotic and will take most decisions without human intervention,[1] determining their location and future movements by means of communication with each other.[6] Pavone states that the new system represents "the next level of autonomy in space."[1]

• Fobos Grunt
• Phobos And Deimos & Mars Environment
• Phobos program – 1988 Soviet missions to Mars
• List of missions to Mars – Wikipedia list article