BLOGMARS PERSEVERANCE ROVER


Docking the Robotic Arm
Mars Perseverance Sol 87 - Left Navigation Camera: First time docking on Mars, on Sol 87 [May 18th, 2021]. This image was acquired by Perserverance’s left navigation camera shortly after the arm finished docking. The Bit Carousel is the conical object in the center of the image. Credits: NASA/JPL-Caltech. Download image ›

Every time we collect a rock sample on Mars, Perseverance performs an hours-long set of carefully choreographed operations with its robotic arm, the coring drill, and the Adaptive Caching Assembly. One of these operations is docking: the process by which the arm aligns itself with the Bit Carousel on the front of the rover, so that the corer can drop off and pick up new drill bits.

Docking happens twice during sample collection. First, the robotic arm docks to drop off the currently-chucked abrading bit and pick up a coring bit with an empty sample tube. Then, after collecting a rock sample, it docks again to drop off the coring bit with a now-filled sample tube, which will be processed, sealed, and stored by the caching assembly.

NASA's Mars Perseverance rover acquired this image using its SHERLOC WATSON camera, located on the turret at the end of the rover's robotic arm.
Mars Perseverance Sol 21 - WATSON Camera: An overview picture of the dock on the front of Perseverance, taken by the WATSON camera on the Robotic Arm. A door in front of the bit carousel was still closed when this image was acquired and has since been opened. Credits: NASA/JPL-Caltech. Download image ›
Docking works by guiding a set of small posts on the end of the robotic arm into a matching set of cones on the dock. Imagine plugging your charger into your phone or computer – even if you don’t think about it, you rely a lot on the tactile feedback from your hand and fingertips to feel if you need to slide the plug to the side, to line it up a little better, and to know when it’s reached the bottom. Docking works the same way. A force sensor on the end of the robotic arm tells Perseverance how hard it’s pushing and in which directions, and Perseverance uses this data to guide the arm into place and to determine when docking is complete. (The dock also includes microswitches at the bottom of each cone which are pressed when the arm is almost docked, which serve as an extra verification). Once the posts reach the bottom of the cones, the robotic arm pushes harder into the dock with almost 650N (146 lbs) of force to make sure it stays docked during bit exchange.

I’ve worked on docking for most of my 6-year career at JPL, and my goal has been to make it reliable and easy – just like plugging in your phone. Getting to this point required a lot of design and testing (including docking almost 2000 times in various testbeds here on Earth), and it’s been a privilege to see docking happen successfully many times on Mars already. I’ll always be a little nervous every time we collect a sample, but my fingers are crossed for many more successful and easy docking attempts.



About This Blog

These blog updates are provided by self-selected Mars 2020 mission team members who love to share what Perseverance is doing with the public.

Dates of planned rover activities described in these blogs are subject to change due to a variety of factors related to the Martian environment, communication relays and rover status.

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Contributors+

  • Mariah Baker
    Planetary Scientist, Smithsonian National Air & Space Museum
    Washington, DC
  • Iona Brockie
    Sampling Engineer, NASA/JPL
    Pasadena, CA
  • Sawyer Brooks
    Docking Systems Engineer, NASA/JPL
    Pasadena, CA
  • Adrian Brown
    Deputy Program Scientist, NASA HQ
    Washington, DC
  • Denise Buckner
    Student Collaborator, University of Florida
    Gainesville, FL
  • Fred Calef III
    Mapping Specialist, NASA/JPL
    Pasadena, CA
  • Alyssa Deardorff
    Systems Engineer, NASA/JPL
    Pasadena, CA
  • Kenneth Farley
    Project Scientist, Caltech
    Pasadena, CA
  • Brad Garczynski
    Student Collaborator, Purdue University
    West Lafayette, IN
  • Erin Gibbons
    Student Collaborator, McGill University
    Montreal, Canada
  • Louise Jandura
    Chief Engineer for Sampling & Caching, NASA/JPL
    Pasadena, CA
  • Lydia Kivrak
    Student Collaborator, University of Florida
    Gainesville, FL
  • Rachel Kronyak
    Systems Engineer, NASA/JPL
    Pasadena, CA
  • Matt Muszynski
    Vehicle Systems Engineer, NASA/JPL
    Pasadena, CA
  • Pegah Pashai
    Vehicle Systems Engineer Lead, NASA/JPL
    Pasadena, CA
  • David Pedersen
    Co-Investigator, PIXL Instrument, Technical University of Denmark (DTU)
    Copenhagen, Denmark
  • Vivian Sun
    Science Operations Systems Engineer, Staff Scientist, NASA/JPL
    Pasadena, CA
  • Jennifer Trosper
    Project Manager, NASA/JPL
    Pasadena, CA
  • Roger Wiens
    Principal Investigator, SuperCam / Co-Investigator, SHERLOC instrument, LANL
    Los Alamos, NM

Tools on the Perseverance Rover+

The Perseverance rover has tools to study the history of its landing site, seek signs of ancient life, collect rock and soil samples, and help prepare for human exploration of Mars. The rover carries:


CAMERAS & SPECTROMETERS
GROUND-PENETRATING RADAR
ENVIRONMENTAL SENSORS
TECHNOLOGY DEMO
SAMPLE COLLECTION

Where is the Rover?

Image of a rover pin-point at Perseverance's location on Mars, Jezero Crater

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