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Robotic Arm, Landing Site Characterization, and Simulation for Entry, Descent, and Landing

Phoenix Mars Lander
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Launched in 2007, the Phoenix Lander explores the northern region of Mars and measures volatiles, especially water and complex organic molecules in the Martian arctic plains. The Mobility and Robotic Systems Section is primarily responsible for robotic arm control, software development, operations, and system oversight during spacecraft implementation. In addition, we support orbital image analysis for landing site selection, and simulation for spacecraft targeting for entry, descent, and landing (EDL).

Robotic Arm (RA)

JPL Robotics has led the development of the robotic arm mechanism, and provides all algorithms, software, and operations tools for it. Its development incorporates system engineering, electronics, software, control algorithms, operations user interfaces, mechanical design, and a bio-barrier to keep the RA sterile prior to landing.

The robotic arm is critical to the measurement needs of the Phoenix mission. With a reach of two meters, and design similar to a backhoe, the arm can access large portions of the terrain around the lander. It will dig trenches, abrade frozen regolith, scoop soil and ice particles, and deliver these samples to the onboard science instruments for detailed chemical and geological analysis.

Landing Site Characterization

The Mobility and Robotic Systems Section has also developed a rock detection and mapping tool used to assist in selecting the Phoenix landing site. This software analyzes rock shadows in MRO HiRISE orbital images to determine size and distribution of these landing hazards. Resultant maps are then translated into safe landing probability estimates over the entire region. Based on this automated image analysis, the Phoenix landing site was modified from the original selection earlier in the mission.

Mosaic of CFA rock abundance maps from HiRISE coverage or 3-ro landing ellipse (HiRISE geometry: M. Mellon, Univ. of Colorado; Mosaic: R.Arvidson, Washington Univ.)

EDL Targeting and Simulation

As the Phoenix spacecraft approaches Mars, a process called "targeting" is used to determine the final aim point for the spacecraft's entry into the Martian atmosphere. This aim point is chosen by running a physics-based EDL simulator called DSENDS.

Phoenix Landing Points and Ellipse From DSENDS
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DSENDS uses an initial guess at an aim point provided by an inter-planetary trajectory solution, and then propagates the spacecraft trajectory from entry through landing. Based upon the miss-distance to the desired landing site, DSENDS adjusts the aim point. The new aim point is then fed back to the inter-planetary trajectory tools and is used to determine the final trajectory correction maneuver (i.e., thruster firings) needed to achieve precision landing. Using the hazard map of the surface described above, a Monte-Carlo simulation of the EDL sequence is used to determine the dispersions of the landing point, and the associated risk of landing.

For more details on all aspects of the Phoenix Lander mission, visit the Phoenix Project website.

People on This Project
J. (Bob) Balaram
Joseph Carsten
Christopher Lim
Matthew Robinson
Ashitey Trebi-Ollennu
Ashitey Trebi-Ollennu
Richard Volpe
Jeng Yen

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