In May 2007 the first US fully autonomous rendezvous and capture was successfully performed by DARPA's Orbital Express (OE) mission. Since then, the Boeing ASTRO spacecraft and the Ball Aerospace NEXTSat have performed multiple rendezvousand docking maneuvers to demonstrate the technologies needed for satellite servicing. MSFC's Advanced Video Guidance Sensor (AVGS) is a primary near-field proximity operations sensor integrated into ASTRO's Autonomous Rendezvous and Capture Sensor System (ARCSS), which provides relative state knowledge to the ASTRO GN&C system. This paper provides an overview of the AVGS sensor flying on Orbital Express, and a summary of the ground testing and on-orbit performance of the AVGS for OE.The AVGS is a laser-based system that is capable of providing range and bearing at midrange distances and full six degree-of-freedom (6DOF) knowledge at near fields. The sensor fires lasers at two different frequencies to illuminate the Long Range Targets (LRTs) and the Short Range Targets (SRTs) on NEXTSat.Subtraction of one image from the other image removes extraneous light sources and reflections from anything other than the comer cubes on the LRTs and SRTs.This feature has played a significant role for Orbital Express in poor lighting conditions. The very bright spots that remain in the subtracted image are processed by the target recognition algorithms and the inverse-perspective algorithms, to provide 3DOF or 6DOF relative state information." Although Orbital Express has configured the ASTRO ARCSS system to only use AVGS at ranges of 120 m or less, some OE scenarios have provided opportunities for AVGS to acquire and track NEXTSat at greater distances.Orbital Express scenarios to date that have utilized AVGS include a berthing operation performed by the ASTRO robotic arm, sensor checkout maneuvers performed by the ASTRO robotic arm, 10-m unmated operations, 30-m unmated operations, and Scenario 3-1 anomaly recovery.The AVGS performed very wellduring the pre-unmated operations, effectively tracking beyond its 10-degree Pitch and Yaw limit-specifications, and did not require I-LOAD adjustments before unmated operations.AVGS provided excellent performance in the 10-m unmated operations, effectively tracking and maintaining lock for the duration of this scenario, and showing good agreement between the short and long range targets. During the 30-m unmated operations, the AVGS continuously tracked the SRT to 31.6 m, exceeding expectations, and continuously tracked the LRT from 8.8 m out to 31.6 m, with good agreement between these two target solutions.After this scenario was aborted at a 10-m separation during remate operations, the AVGS tracked the LRT out 54.3 m, until the relative attitude between the vehicles was too large. The vehicles remained apart for eight days, at ranges from 1 km to 6 km. During the approach to remate in this recovery operation, the AVGS began tracking the LRT at 150 m, well beyond the OE planned limits for AVGS ranges, and functioned as the primary sensor for the autonom...
The Modular Reconfigurable High Energy (MRHE) program aimed to develop technologies for the automated assembly and deployment of large-scale space structures and aggregate spacecraft. Part of the project involved creation of a terrestrial robotic testbed for validation and demonstration of these technologies and for the support of future development activities. This testbed was completed in 2005, and was thereafter used to demonstrate automated rendezvous, docking, and self-assembly tasks between a group of three modular robotic spacecraft emulators. This paper discusses the rationale for the MRHE project, describes the testbed capabilities, and presents the MRHE assembly demonstration sequence.I. E l Introduction urrent spacecraft design methodologies generally revolve about the concept of a solitary, monolithic spacecraft C bus. Such spacecraft are very capable, but also face significant limitations in view of future plans and visions for expanded human presence on-orbit, on the moon, and on Mars. Perhaps foremost is the spacecraft size limitation presented by current and next-generation launch vehicles, especially when considering the requirement to boost spacecraft beyond Earth orbit. Manned spacecraft clearly must carry additional resources and possess significant capabilities beyond those required for their unmanned counterparts, especially for extended-duration missions. This will likely require the assembly or construction of larger vehicles and/or structures in orbit, in order to concentrate these resources in locations where they are readily accessible and can be used effectively. This may take the form of large aggregate spacecraft that would then move out of low Earth orbit, or perhaps orbiting resource depots that would store consumables such as fuel, food, and water and provide large-scale power generation capabilities for future use. Besides merely allowing for the possibility of larger spacecraft, in-space assembly also offers potential benefits by allowing more-flexible use of launch vehicle types and launch dates.Although we have experience with on-orbit construction in the form of Mir and the International Space Station, such tasks are still difficult, time consuming, and expensive. Frequently requiring astronaut extravehicular assistance, they can be dangerous as well. Automation using robotic vehicles has the potential to reduce cost, time, and risk for such tasks, although it will also require additional development of numerous supporting technologies. These technologies include improved local sensing and relative navigation; more-efficient microthrusters and manipulators; robust fault-detection and correction software for automated rendezvous, docking, and assembly tasks; adaptive planning and scheduling; human-robotic interaction for complicated tasks that cannot be completely automated; and mechanical mechanisms such as deployable booms, tethers, docking interfaces, and other construction tools.Development of modular or standardized hardware and software components and interfaces will al...
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