The author of this article, Brian Palmer, discusses how NASA has set up the communications network and information system for the Curiosty Rover, so that information may be adequately sent to, and received from the Rover in a timely manner. As a high-profile NASA mission, the project?s engineers have designed the information network with fail-safes in mind, by creating multiple relay components to transmit information between the Rover and mission control back on Earth.
To explain the layout of this network, one can split the separate components of the network (or the nodes), into four different groups. The first is NASA mission control, or simply NASA. From this node, there are different lines of communication (directed edges), leading to the different parts of the Deep Space Network, which include three major hubs in the Mojave Desert, Spain, and another in Australia). There are probably directed edges between all three, but for convenience?s sake, let us consider directed edges going from both Spain and Australia to the Mojave node (after all, it would make sense that the central space telecommunications hub be out in the desert, where there is less likely to be interference). Next, all three of the Deep Space Network nodes would have directed edges leading to Curiosity itself. Finally, directed edges would lead from Curiosity to a pair of orbiters circling around Mars, named Odyssey and Reconnaissance (these in turn, would have directed edges pointing back to NASA?s node). By observing the path of these directed edges, one can see that these nodes and their respective pathways form a strongly connected network ? that is, any information at any one node in the network can move to any another node in the network via a series of pathways.
For a mission such as the Curiosity Rover, a strongly connected network is crucial for being able to relay information both TO and FROM the Rover. To relay information to the Rover, there are three separate hubs, so that if there is any problem at one or two of the nodes, there is always a third one. Also, having more than one hub allows information to be split up and dispersed along separate edges (if there are traffic limitations applied to specific edges, maximizing the dispersion along different routes, as we did with the traffic example earlier this semester, would be ideal).? This also applies to relaying information back to the main NASA node ? Curiosity can parse and send the data along both of the orbiter?s paths. Finally, one could imagine a situation where information is being sent in a constant steady, or equilibrium state, amongst these nodes, along all available edges. According to the previous explanation, and by using equilibrium dispersion by assigning value ?a? to NASA?s node, and setting the summation of all values equal to zero:
a+(a/3)+(a/3)+(2a/3)+a+(a/2)+(a/2)=1; (13a)/3=1; a=3/13
The equilibrium numerical values in this case indicate the amount of information at/passing through the hub during equilibrium. Relay hubs ?Spain,? and ?Australia,? have equal values of 1/13, while the central relay hub in the Mojave has a value of 2/13, and the orbiter nodes (Odyssey and Reconnaissance), have values of 3/26. Interestingly enough, both NASA ground command and Curiosity have the same equilibrium values ? this would seem to make sense, as all the information passed from the ground to ends up at the satellite, and in response to the received commands, the satellite sends a proportional amount of information back to the ground to be received.
Source: http://www.washingtonpost.com/national/health-science/mars-rover-gets-instructions-daily-from-nasa-via-a-network-of-antennae/2012/10/29/60e6e040-1c65-11e2-ad90-ba5920e56eb3_story.html
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Source: http://blogs.cornell.edu/info2040/2012/10/29/communications-networks-and-nasas-curiosity-mars-rover/
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