This project is solving the Seven Minutes of Science challenge.
Mars environmental monitoring using Wireless Sensor Networks (WSNs)
Project Goal: To exploit the ejectable Ballast Mass Devices of the Mars Science Laboratory (MSL) for Mars geologic and climate conditions monitoring purposes, using existing technologies that have already been succesfully applied to earth.
ENTRY, DESCENT AND SENSOR DROP
Prior to the MSL’s entry into the Mars atmosphere, the first 150 kg will be jettisoned to prepare the MSL for atmospheric entry by altering its angle of descent. BMD consisted of two 75-kilo loads will enclose hundreds of sensor nodes and a sink node, each. The loads will be of a cluster shell type with sphere-cone shape. The shell will be ceramic, while the sensor nodes will be impact-protected using rubber exterior.
BMDs will enter the planet’s atmosphere and deploy a parachute. Next, at a safe-impact height, they will drop the nodes by ejecting their lower hatches. The sink nodes attached under the top shells will land on Mars.
During the MSL’s descent in the planet’s atmosphere, the second 150 kg will be jettisoned. BMD will consist of six 25-kilo loads of a cluster-shell bomb type with cylinder parabola shape. Four of them will enclose hundreds of sensor nodes and two of them will enclose both a sink node and a smaller quantity of sensor nodes. The two sink nodes will be protected from impact by rubber exterior.
Descent BMDs will also deploy a parachute, release the nodes from a safe-impact height by rejecting the nose. The remaining shell will be rejected and the sink nodes will land using the same parachute.
In order to properly predict the ground placement of the nodes, certain mathematical models on node aerial delivery were applied. These models include environmental parameters, such as, prediction for the wind gusts, air resistance and the gravitational field, which interact with the nodes during their atmospheric diffusion. These calculations are useful since they allow us to ensure maximum efficiency of the sensors' clusters, by extracting dispersion patterns based on the drop height.
The above displayed results were extracted using the atmospheric and gravitational parameters of Mars, accounting for a globose sensor node geometry (in order to determine the air resistance and wind gust constants), and for a 99% accuracy of spreading. The initial conditions, which are included and thoroughly described in the source code, were adjusted in order to satisfy a certain scenario, which includes a specific drop height, specific initial velocities and specific intervals for the wind gust speed and angle distribution.
Avoiding re-contact with the main vehicle
Regarding the 1st phase of jettisoning, it is feasible to predict the area of deployment of the 2 WSNs, by taking into consideration the initial conditions of the jettisoning procedure. The 2 masses, after being jettisoned at an altitude of 1660 km (and since they are not affected by aerodynamic forces due to the lack of atmosphere), they will go into planetary orbit with predictable conditions, which will slowly fade towards the Martian surface. Since the initial conditions of jettisoning (angle of jettisoning, initial velocity) are preset (as to accommodate for a certain angle of atmospheric entrance for the MSL), we can predict the orbit of the 2 masses and hence ensure the deployment of the 2 WSNs at a specific geographic area, which doesn't interfere with the Mars Rover Landing site and is, most importantly, unreachable by the Rover. Regarding the 2nd phase of jettisoning, we must ensure the deployment of the 6 WSNs in an area around the Mars Rover landing site, allowing a sufficient landing radius for the Rover to be fully deployed, hence minimizing the chances of collision. This can be achieved by taking into consideration the 2-D ground spreading profiles of the sensor node networks (which we have calculated) so that we can modify the foci and range of the dispersions. Since the initial conditions of the jettisoning are preset (as to accommodate for a certain angle of ground approach for the MSL), blades were added on the 2nd phase jettisoned masses, as to enhance their stability and range capabilities. This will ensure that safe area of landing for the Mars Rover, in the center of the spreading areas of the WSNs.
WSN DEVELOPMENT AND DATA TRANSFER
Wireless Sensors Networks developed will use self-organizing protocols and nodes will trace each-other within range using an initial ‘’hello’’ message. Data aggregation will initiate and sensing information will be transferred hop-by-hop to the sink nodes and the cluster head nodes that will be created from existing algorithms. Sink nodes will sustain an adequate storage memory for keeping the data gathered by the network.
Life expectancy of the nodes and sinks can be prolonged by using existing renewable energy techniques (solar cells, compact and reliable, are the most effective for our case) to such duration that even future missions will be able to collect the data generated by the WSNs.
The cluster head nodes and sinks, emerged by the descent phase BMDs, can transfer their data to the Mars Rover during its nearby passage. Alternatively, sinks can transfer their data directly to the orbital satellites.
More beyond, at the faraway networks created by the entry phase BMDs, sinks will transfer their data to the orbital satellites, which will perform their passage above the inaccessible by the Mars Rover areas.
Finally, all the data produced by the Wireless Sensor Networks will be transmitted by the orbital satellites to Earth for further analysis.
Mobile - friendly presentation
Project InformationLicense: GNU General Public License
Source Code/Project URL: https://github.com/aristodemos/marsSense.git
ResourcesPresentation - https://docs.google.com/presentation/d/1Gkh17k5zd78tMP6-wkrRe5Ld6bLGjCDdQzMrqFjSyBE/pub?start=false&loop=false&delayms=5000
Mobile friendly site - Brief Description of the Idea - http://www.rvl.io/pafi/s7minofscience
Node Scattering Manipulation Based on Trajectory Model in Wireless Sensor Networks - http://www.academia.edu/2820069/Node_scattering_manipulation_based_on_trajectory_model_in_wireless_sensor_network
Performance Study of Node Placement in Sensor Networks - http://dl.acm.org/citation.cfm?id=977910
Performance Study of Node Placement for Congestion Control in Wireless Sensor Networks - http://dl.acm.org/citation.cfm?id=1790377
Official Page - http://pafi.koding.com/marssense/