NASA's Mars Odyssey spacecraft watches comet flyby

Artist's concept of NASA's Mars Odyssey spacecraft. 

Credit: NASA/JPL-Caltech

The longest-lived robot ever sent to Mars came through its latest challenge in good health, reporting home on schedule after sheltering behind Mars from possible comet dust.

NASA's Mars Odyssey was out of communications with Earth, as planned, while conducting observations of comet C/2013 A1 Siding Spring on Sunday, Oct. 19, as the comet flew near Mars.

The comet sped within about 88,000 miles (139,500 kilometers) of Mars, equivalent to about one-third of the distance between Earth and Earth's moon.

Mars Odyssey had performed a maneuver on Aug. 5 to adjust the timing of its orbit so that it would be shielded by Mars itself during the minutes, around 1 p.m. PDT (4 p.m. EDT) today, when computer modeling projected a slight risk from high-velocity dust particles in the comet's tail.

"The telemetry received from Mars Odyssey this afternoon confirms not only that the spacecraft is in fine health but also that it conducted the planned observations of comet C/2013 A1 Siding Spring within hours of the comet's closest approach to Mars," said Odyssey Mission Manager Chris Potts of NASA's Jet Propulsion Laboratory, Pasadena, Calif., speaking from mission operations center at Lockheed Martin Space Systems, Denver.

THEMIS

Comet C/2013 A1 Siding Spring observations were made by the orbiter's Thermal Emission Imaging System (THEMIS).

Resulting images are expected in coming days after the data is downlinked to Earth and processed.

THEMIS is also scheduled to record a combined image of the comet and a portion of Mars later this week.

In addition, the Odyssey mission is using the spacecraft's Neutron Spectrometer (NS) and the Russian-made, High Energy Neutron detector (HEND) to assess possible effects on Mars' atmosphere of dust and gas from the comet.

Three NASA Mars orbiters, two Mars rovers and other assets on Earth and in space are studying comet Siding Spring.

This comet is making its first visit this close to the sun from the outer solar system's Oort Cloud, so the concerted campaign of observations may yield fresh clues to our solar system's earliest days more than 4 billion years ago.

Following the comet flyby, operations teams have also confirmed the good health of NASA's Mars Reconnaissance Orbiter and of NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) orbiter.

Mars Odyssey has worked at the Red Planet longer than any other Mars mission in history.

NASA launched the spacecraft on April 7, 2001, and Mars Odyssey arrived at Mars Oct. 24, 2001.

Besides conducting its own scientific observations, the mission provides a communication relay for robots on the Martian surface.

Developing a better motor for the Mars Rover

Elias Brassitos, a doctoral candidate in Distinguished Professor Dinos Mavroidis' Biomedical Mechatronics Laboratory, is developing a rotary robotic actuator that produces more power in a lighter package for a manipulator arm on NASA's Mars Rover. 

Credit: Brooks Canaday

In the world of robotics, identifying actuators that are strong and compact is probably one of the most important open technological problems yet to be resolved.

More often than not, the mechanical elements that translate data into doing are big, rough, and generally unfriendly for use in everyday robotics, said Dinos Mavroidis, Distinguished Professor of Mechanical and Industrial Engineering at Northeastern University.

In the mid-2000s, Mavroidis' lab set out to develop a new kind of actuator—small enough to sit inside the joints of prosthetic limbs, but powerful enough for everyday tasks such as lifting and walking.

Backed by two new grants—one from the National Science Foundation, the other from the National Aeronautics and Space Administration—Mavroidis' team will work to tailor the technology for use in advanced space applications as well as everyday household robots.

The gear bearing drive, or GBD, as the team's unique actuator is called, consists of a motor embedded directly inside the gear transmission, allowing for cheaper, lighter, and stronger functioning. The GBD is a compact mechanism with two key abilities.

It operates as an actuator providing torque and as a joint providing support. Back in 2006, Mavroidis and then graduate student Brian Weinberg developed the idea in collaboration with John Vranish, a NASA Goddard Space Flight Center engineer.

Elias Brassitos, a doctoral candidate in Mavroidis' lab, will use funding from a Space Technology Research Fellowship to develop the GBD for use on the Mars Rover.

"For space applications, everything needs to be lighter and stronger," said Brassitos, who noted that the device would replace the entire joint assembly for the rover's manipulator, the arm that extends outside the vehicle to collect rock samples and other things

"Mobile Robotics, particularly the use of rovers as part of a wider NASA exploration strategy, puts pressures on actuation technology," said Brett Kennedy, supervisor of the Robotic Vehicles and Manipulators Group at the Jet Propulsion Laboratory in Pasadena, Calif.

"We are always looking for ways to pack more torque, more power, and more functions into smaller packages," added Kennedy, who has high hopes that the GBD will help them do just that.

First, Brassitos must design various GBD architectures, each of which might be good for different applications. He'll design and build a prototype at Northeastern, and then assemble and test the device at the JPL.

While Brassitos works to develop the GBD for space, another graduate student will work to "commercialize it for earth."

In collaboration with the startup company Foodinie, which aims to make robots for the modern household kitchen, doctoral candidate Andy Kong and Mavroidis are developing an off-the-shelf version of the gear bearing drive that inventors can use for a variety of applications.

In some cases, the team will develop it for specialized needs as in the case of the Mars rover.

"There is a possibility for the GBD to be a source for innovation in the area of compact actuators for robotic systems," Mavroidis said.

NASA Mars Rover: Terramechanics research keeps rovers rolling

The Curiosity rover, which lifted off Nov. 26, 2011, will arrive at the Red Planet in August 2012. 

The rover, shown here during testing inside the Spacecraft Assembly Facility at the Jet Propulsion Laboratory in California, is about the size of a Mini Cooper and weighs roughly five times as much as the Spirit and Opportunity rovers.

In May 2009, the Mars rover Spirit cracked through a crusty layer of Martian topsoil, sinking into softer underlying sand. 

The unexpected sand trap permanently mired the vehicle, despite months of remote maneuvering by NASA engineers to attempt to free the rover.

The mission mishap may have been prevented, says MIT's Karl Iagnemma, by a better understanding of terramechanics—the interaction between vehicles and deformable terrain.

Iagnemma says scientists have a pretty good understanding of how soils interact with vehicles that weigh more than 2,000 pounds. But for smaller, lighter vehicles like the Mars rovers, the situation is murkier.

"There's a lot of knowledge in civil engineering about how soils will react when subjected to heavy loads," says Iagnemma, who is a principal research scientist in the Department of Mechanical Engineering.

"When you take lightweight vehicles and granular soils of varying composition, it's a very complex modeling process."

Karl Iagnemma

Now Iagnemma and researchers from Washington University in St. Louis and the Jet Propulsion Laboratory (JPL) in Pasadena, Calif., have developed a model called Artemis that accurately simulates rover mobility over various types of soil and terrain.

The model works much like a video game: A user plugs in commands to, for example, move the simulated rover forward a certain distance—instructions similar to those that NASA engineers give to rovers on Mars.

The simulation then predicts how the rover will move, based on the underlying soil properties, vehicle characteristics and a terrain's incline.

The team tested the model against observations in the field, including actual drive paths from previous Mars rovers, and found that the simulations behaved much like actual rovers in various terrains.



The researchers also performed experiments in the lab, rolling a replica of a Mars rover's wheel over Martian-like sand. The tests established relationships between wheel dynamics and soil properties—information that the team used to further refine the model.

Carmine Senatore

"Once you have a model you trust that is really representative of how the rover behaves, it can help mission planners make path plans in a safer way," says team member Carmine Senatore, who is a research scientist at MIT.

"It could say that this path looks shorter and faster, but if the soil is not what we expected, it may be much more dangerous, so it's better to go another way."

Senatore, Iagnemma, Raymond Arvidson of Washington University, and collaborators will outline the details of the model in a paper to appear in the Journal of Field Robotics.

Beach Sand and Cake Flour
For the most part, the terrain over which Mars rovers travel—including the most recent Curiosity mission—is relatively benign, consisting mostly of flat, firm surfaces.

But occasionally, rovers encounter more challenging environments, such as steep dunes covered in fine, loose soil.

"Think about the difference between beach sand, which you can walk on and even play volleyball on, and cake flour," Iagnemma says. "The reason [for that difference] goes down to the microscale of the material."

To know how much work is required for a rover to get over a dune, Iagnemma says one needs to understand the properties of an environment's soil.

To develop its model, the team estimated soil properties on Mars based on a variety of data sources, including measurements of the planet by orbiting sensors and images from the rovers themselves, as well as data on the amount of torque required to drive a wheel through a particular type of terrain.

The team coupled Martian soil data with properties of the rover, such as its size and weight, and developed a model to predict the likelihood and extent to which a rover may sink into a given terrain.

Iagnemma and Senatore refined the model with experiments in the lab. The researchers set up a bed of both coarse and fine soil, similar to sediment that has been observed on Mars. They built a straight track overhead, and attached a spare wheel from the Mars rover Opportunity.

Powering the wheel with a motor, the team observed the wheel's performance, noting how much the wheel sank into the soil, and the amount of torque needed to overcome sinking.

"Sometimes in a car you end up doing things like rocking it back and forth," Iagnemma says. "There's limited strategies for a Mars rover because it's not a very dynamic vehicle, and moves very slowly. So we have to be more creative and develop strategies to get out."

More information: Paper: onlinelibrary.wiley.com/journal/10.1002/(ISSN)1556-4967

NASA tests Zoe, the new Mars rover prototype, in Chile

NASA scientists said Friday they were testing a prototype of a robot the US space agency hopes to send to Mars in 2020 in Chile's Atacama desert.

NASA hopes to use this kind of rover to explore life-friendly sites found by Curiosity, the rover already searching for signs of life on Mars.

It has been there since last August.

The researchers say the desert, the driest spot on Earth, mimics the conditions of the Red Planet, and the agency has used it in the past to test space-bound equipment.

The robot, controlled remotely from the US, will continue testing through Sunday.

The solar-powered 771-kilogram (1,700-pound) machine is equipped with cameras and a drill able to dig up to a meter (three feet) deep.

It is testing its sensors, its cameras, its ability to store energy, as it searches for evidence of microbial life in the desert.

The Zoe robot will use a one-meter drill, shown here protruding above the robot's solar cell deck, to search for subsurface life in Chile's Atacama Desert. 

Carnegie Mellon University's Robotics Institute and the SETI Institute are leading the NASA-sponsored field experiment. 

Credit: Carnegie Mellon University

ESA Mars Express marks the spot for Curiosity landing

Gale Crater is 154 km wide and is located at latitude 5.4 degrees south and longitude 137.9 degrees east.

This image, taken by the High Resolution Stereo Camera (HRSC) of Mars Express, has a resolution of 100 metres per pixel. It is colour-coded based on a digital terrain model derived from stereo image data.

Credits: ESA/DLR/FU Berlin (G. Neukum).

Oblique view of Mount Sharp inside Gale Crater, with the original and revised landing ellipses marked.

Credits: NASA/JPL-Caltech/ESA/DLR/FU Berlin/MSSS

This artist's concept depicts the moment that NASA's Curiosity rover touches down onto the Martian surface.

The entry, descent, and landing (EDL) phase of the Mars Science Laboratory mission begins when the spacecraft reaches the Martian atmosphere, about 81 miles (131 kilometers) above the surface of the Gale crater landing area, and ends with the rover safe and sound on the surface of Mars.

Entry, descent, and landing for the Mars Science Laboratory mission will include a combination of technologies inherited from past NASA Mars missions, as well as exciting new technologies. Instead of the familiar airbag landing systems of the past Mars missions, Mars Science Laboratory will use a guided entry and a sky crane touchdown system to land the hyper-capable, massive rover.

The sheer size of the Mars Science Laboratory rover (over one ton, or 900 kilograms) would preclude it from taking advantage of an airbag-assisted landing.

Instead, the Mars Science Laboratory will use the sky crane touchdown system, which will be capable of delivering a much larger rover onto the surface. It will place the rover on its wheels, ready to begin its mission after thorough post-landing checkouts.

The new entry, descent and landing architecture, with its use of guided entry, will allow for more precision. Where the Mars Exploration Rovers could have landed anywhere within their respective 93-mile by 12-mile (150 by 20 kilometer) landing ellipses, Mars Science Laboratory will land within a 12-mile (20-kilometer) ellipse!

This high-precision delivery will open up more areas of Mars for exploration and potentially allow scientists to roam "virtually" where they have not been able to before.

In the depicted scene, Curiosity is touching down onto the surface, suspended on a bridle beneath the spacecraft's descent stage as that stage controls the rate of descent with four of its eight throttle-controllable rocket engines.

The rover is connected to the descent stage by three nylon tethers and by an umbilical providing a power and communication connection.

When touchdown is detected, the bridle will be cut at the rover end, and the descent stage flies off to stay clear of the landing site.

NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology, Pasadena, Calif., manages the Mars Science Laboratory Project for the NASA Science Mission Directorate, Washington.
More information about Curiosity is at http://mars.jpl.nasa.gov/msl/.

Credits: NASA/JPL-Caltech