The flying eyeball

August 13, 2005 NASA engineers are developing an unmanned "flying eyeball" that will be used as an assistant to astronauts for the space shuttle and International Space Station. Named "Mini AERCam", which stands for Miniature Autonomous Extravehicular Robotic Camera, the free-flying robotic inspection vehicle uses pressurized cold-gas (xenon) for propulsion and carries battery-powered cameras that will help astronauts perform inspections of the exterior of the space station or shuttle. The Mini AERCam technology demonstration unit has been integrated into the approximate form and function of a flight system, and represents a significant technology breakthrough in the field of free-flying robotic space vehicles. The nanosatellite-class spherical Mini AERCam free flyer is 7.5 inches in diameter and weighs approximately 10 pounds, yet it incorporates significant additional capabilities compared to the 35 pound, 14 inch AERCam Sprint free flyer that flew as a remotely piloted Shuttle flight experiment in 1997.

Mini AERCam hosts a full suite of miniaturized avionics, instrumentation, communications, navigation, video, power, and propulsion subsystems, including two video imagers and one higher resolution still-frame imager. Technology innovations include a rechargeable xenon gas propulsion, rechargeable lithium ion battery, custom avionics based on the PowerPC 740 microprocessor, "camera-on-a-chip" CMOS imagers with wavelet video compression, micro electromechanical system (MEMS) gyros, GPS relative navigation, digital radio frequency communications, micropatch antennas, digital instrumentation network, and compact mechanical packaging.

The Mini AERCam vehicle is designed for either remotely piloted operations or supervised autonomous operations including automatic stationkeeping, point-to-point maneuvering, and automated docking approaches. Free-flyer testing has been conducted on an air-bearing table and in a six degree-of-freedom closed-loop orbital simulation. In the airbearing table environment, the free-flyer hardware is placed in the cradle of a tetherless airbearing sled, which produces a nearly frictionless environment. The free-flyer fires its thrusters to maneuver along the airbearing surface while it transmits video and telemetry to the pilot control and display station. The orbital simulation models the three-dimensional dynamics of the free-flyer in proximity to the ISS, and produces corresponding God's eye views and simulated free-flyer camera views. A high-fidelity simulation is achieved by directly interfacing to free-flyer thruster driver signals, emulating the MEMS gyro responses in hardware, and using the "truth" state to drive a GPS signal generator connected to the free-flyer GPS receiver.

Mini AERCam aims to provide beneficial on-orbit views of maintenance and servicing tasks that cannot be obtained from fixed cameras, cameras on robotic manipulators, or cameras carried by EVA crewmembers. On ISS, for example, Mini AERCam could be used for supporting robotic arm operations by supplying orthogonal views to the robot operator, for supporting crew spacewalk operations by supplying views to the ground crews monitoring the spacewalk, and for carrying out independent visual inspections of areas of interest around the ISS. The potential applications of Mini AERCam also extend to future long-duration human exploration missions, for which intelligent mobile inspection agents are likely to become essential crew helpers.

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