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Chapter 1. Overview - The Analysis of Autonomous Planners and their Scalability onto Spacecraft Platforms With Limited...

Chapter 1. Overview

1.1. Drive For Development of Autonomous Systems


The drive to develop autonomous planners capable of efficient system maintenance and path generation is part of a larger effort to design and deploy autonomous systems that aim to expand the reach of space probes and land rovers. In comparison to spacecraft and rover vehicles that are controlled by operation personnel on Earth, the use of autonomous agents can help increase the amount of data that is collected on a mission, may help decrease the overall operating costs of a mission, and may offer improved navigation capabilities in areas where direct communication with Earth is no feasible or not realistic.

Because energy resources are limited and the duration of a space mission is finite, a system capable of automatic path generation, object identification and data collection can help increase the overall amount of data that is gathered during the life of a mission. As opposed to a spaceship or rover that spends valuable time waiting to receive command sequences in response to sensor data that is transmitted for analysis to earth, a system capable of autonomous task generation and science-discovery analysis can spend the vast majority of time acquiring data and further exploring the environment.

A space mission that requires attendance by a large number of ground-based personnel is also very expensive when compared to a system with a varying array of autonomous capabilities. Because of the uncertainties involved in any space venture mission, not only must communication and direct control personnel be available at all times, but back up, contingency event specialists must also be available [7]. For the Mars Pathfinder Mission in 1996, the mission operations and data analysis budget for the time 30 days after launch to the end of the mission was allocated at $14 million. For the in-flight control and science operations segments of the Mars Global Surveyor missions of 2003 and 2005, cost caps have been set at $20 million per year [1]. Although the cost of maintenance upkeep and constant communication with a spacecraft or land rover, including downlink and uplink capabilities, realistically cannot be reduced to zero, the use of autonomous capabilities can reduce the number of overall personnel that must continue to monitor a space mission.

Spacecraft and discovery rover agents that employ autonomous capabilities also have a reduced reliance on communications links with earth. As a consequence, autonomous agents are better able to study and take advantage of fortuitous, short-lived events and have the ability to investigate regions where direct communication with Earth or with other support satellites is not feasible [11]. In highly volatile environments a new travel plan and sequence of commands may need to be quickly developed; damage to a spacecraft or rover might be unavoidable if the intelligent agent must wait for earth-bound scientists to generate a sequence of commands in response to a dangerous event. There are many scenarios where autonomous path planning and navigation capabilities are vital to the successful completion of a mission, including a close encounter with a comet, successful travel through an asteroid belt, traversal through a canyon and/or other highly potentially dangerous terrain or an encounter with a solar flare, a volcano on the surface of Io, or a radiation shower.

In addition, as mission goals include the movement of space vehicles and landing of rovers on planets, satellites, and asteroids that are at increasing distances from earth, direct communication between earth and a satellite or rover becomes impractical. For example, at the time of ideal alignment, a transmission from Pluto takes 3.9 hours to reach earth. In conjunction with this large time delay, complications with long-distance message passing arise, including the attenuation of signals and the availability of signal monitoring sites on earth, which, related to the brief discussion on budgetary constraints, require additional efforts and personnel so that efficient coordination can be attained.

The development of efficient autonomous agents is thus driven by monetary as well as various technical constraints. The use of autonomous agents reduces the need for constant human interaction, allows for the deployment of agents into environments that are beyond the range of communication technologies, and permits for the investigation of environments and objects where real-time changes to a plan timeline may be required.
2010-07-19 18:44 Читать похожую статью
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