Washington — Engineers at the US Naval Research Laboratory’s Naval Center for Space Technology (NCST) recently completed level testing of the Defense Advanced Research Projects Agency’s (DARPA) robotic payload components for the Geosynchronous Satellite Automated Service (RSGS) program.
Once in orbit, the RSGS robotic service vehicle will scan and service satellites in geosynchronous orbit (GEO), where hundreds of satellites provide communications, weather monitoring, support for national security missions and other vital functions.
The RSGS program is a public-private partnership between DARPA and Northrop Grumman’s SpaceLogistics, with NRL developing the robotic service payload.
“This partnership will enable revolutionary service capabilities for commercial and government users for visual diagnostics, upgrades, orbit modification and satellite repairs,” said Bernie Kelm, Superintendent of Spacecraft Engineering, NCST. “As a payload robotic developer, we have designed this innovative suite of spaceflight hardware and software that will enhance national capabilities in satellite service.”
The RSGS payload includes flight hardware components, automated control algorithms, multiple highly customized electronic designs, and flight software running on five single-board computers. NRL also identified and purchased ingenious seven-degrees of freedom robotic arms, outfitting them with control electronics, cameras, lights and a machine tool changer.
In addition, NRL has developed the robotic tool for handling satellites for customers via their standard launch vehicle interface and purchased another tool to capture resupply items compliant with DARPA’s Payload Orbital Delivery (POD) design standard.
“Our diverse team of NCST engineers have focused their efforts on the RSGS program’s robotic payload for the past seven years,” said William Vincent, RSGS Program Director at NRL. “Robot payload is one of the most complex payload developments in NRL ever.”
NRL engineers have developed several avionics and control systems running on a distributed SpaceWire network to support the long-term mission of controlling all sensors and actuators in a robust and redundant manner. NRL has purchased color and multicolor cameras, along with designing LED lighting units to provide situational awareness during robotic activities.
“Our algorithm team has developed machine vision, position control, collision avoidance, and compliance control algorithms that support robotic control and enable autonomous wrestling capabilities,” Vincent said. “Algorithms are implemented in flight software that also provides all the command and control functions of the payload and provides control interfaces to the spacecraft’s vector control.”
Robotic movements require special planning to ensure safe spacecraft operations. NRL developed the Integrated Robotic Workstation (IRW) to achieve this. IRW supports mission planning to develop new mission activities. Once the mission is planned, IRW supports triage activities to check all automated motion commands in the payload simulator to check order loads before they are dispatched.
Finally, using NRL’s NRL ground control Neptune® software, IRW commands all robotic payload activities and displays and directs telematic payload metering during operations. To implement this effort, Maher’s systems engineering team spent years conducting system analyzes, documenting requirements and interfaces, and creating a robust verification and verification plan.
“The engineers worked closely with the integration and test teams to make sure the system met all the requirements as it came together to test the component, subsystem and payload level,” Vincent said. “Once complete, the robotic payload will enable a wide range of envisioned missions and future missions yet to be envisioned.”
The RSGS team recently completed environmental testing of the first two flying robotic arm systems. This included simulating the launch environment in the NRL Vibration Laboratory, simulating both the vacuum ranges and maximum space temperatures in the NRL Thermal Vacuum Chamber (TVAC), and ensuring the electromagnetic interference (EMI) function in the EMI chamber test.
During TVAC testing, the robotic arm system demonstrated performance beyond temperatures representing actual conditions in orbit. Under extreme vacuum and temperature conditions, the robot arm performed a variety of operations including triggering pre-planned robotic calibration movements, instrument operation, camera and light functions.
The second robotic arm system is integrated with a separate test containing the entire avionics suite. It is currently undergoing motion performance testing. This fall, the second arm system will complete environmental testing. Robotic performance testing to demonstrate and validate the functionality of robotic algorithms in a Robotics Test (RTB) is being conducted at the NRL Space Robotics Laboratory. The RTB consists of a non-spaceflight version of the robotic flight arm system and the avionics hardware that powers the flight software. This high-accuracy robotics test allows ground verification of several system-wide robotic performance characteristics of an RSGS payload.
The characterization of the compliance control algorithm and the performance characterization of the Marman Ring Detector algorithm have been completed. Contact dynamics is being tested at RTB, which uses a sled floating on a thin layer of air to simulate an arm contact with client spacecraft weighing from 75 to 3,000 kg (165 – 6,613 lb). Dog testing, expression, and editing are scheduled for later this summer.
The Flight Programs team is preparing to start the qualification exam. Testing is done in a software test with a real-time dynamic simulation that generates robot arm simulation inputs for robotic control algorithms and dynamic images of input into machine vision algorithms. This test allows the NRL team to test flight algorithms using realistic control loops to fully validate the system completely prior to launch.
“The systems engineering and verification efforts required by RSGS are intense,” said Amy Hurley, NRL Principal Systems Engineer. “It’s amazing to see years of systems engineering and a robust verification and validation plan successfully combine together.”
About the US Naval Research Laboratory
NRL is a scientific and engineering discipline dedicated to research that drives innovative developments for the United States Navy and Marine Corps from the seabed into space and into the information realm. NRL is located in Washington, D.C. with major field locations at Stennis Space Center, Mississippi; Key West, Florida; Monterey, California, and employs approximately 3,000 civilian scientists, engineers, and support personnel.
About the Naval Center for Space Technology
To maintain and enhance a strong base of space technology and provide expert assistance in the development and acquisition of space systems for naval missions, the NCST’s activities span from basic and applied research to advanced development in all areas of interest in the Naval Space Program. These activities include the development of spacecraft, systems that use these spacecraft, and ground command and control stations.
For more information, contact NRL Corporate Communications at (202) 480-3746 or email@example.com.
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