ITC/USA 2014 Conference Proceedings / The Fiftieth Annual International Telemetering Conference and Technical Exhibition / October 20-23, 2014 / Town and Country Resort & Convention Center, San Diego, CA / In this paper we consider the possibility of using a communications system that is operating between probes on the surface of an asteroid and an orbiting satellite to more accurately determine spatial positions. This is done by measuring the round trip communication delay between the orbiter and various surface probes to estimate distance. From these distance measurements, the position can be determined using trilateration - the same basic technique behind the earth-based GPS system. Within the framework of this scenario, the location of the probes or the orbiter can be determined depending on the scenario.

As the number of spacecraft in simultaneous operation continues to grow, there is an increased dependency on ground-based navigation support. The current baseline system for deep space navigation utilizes Earth-based radiometric tracking, which requires long duration, often global, observations to perform orbit determination and generate a state update. The age, complexity, and high utilization of the assets that make up the Deep Space Network (DSN) pose a risk to spacecraft navigation performance. With increasingly complex mission operations, such as automated asteroid rendezvous or pinpoint planetary landing, the need for high accuracy and autonomous navigation capability is further reinforced. The Network-Based Navigation (NNAV) method developed in this research takes advantage of the growing inter-spacecraft communication network infrastructure to allow for autonomous state measurement. By embedding navigation headers into the data packets transmitted between nodes in the communication network, it is possible to provide an additional source of navigation capability. Simulation results indicate that as NNAV is implemented across the deep space network, the state estimation capability continues to improve, providing an embedded navigation network. To analyze the capabilities of NNAV, an analysis and simulation framework is designed that integrates navigation and communication analysis. Model-Based Systems Engineering (MBSE) and Agent-Based Modeling (ABM) techniques are utilized to foster a modular, expandable, and robust framework. This research has developed the Space Navigation Analysis and Performance Evaluation (SNAPE) framework. This framework allows for design, analysis, and optimization of deep space navigation and communication architectures. SNAPE captures high-level performance requirements and bridges them to specific functional requirements of the analytical implementation. The SNAPE framework is implemented in a representative prototype environment using the Python language and verified using industry standard packages. The capability of SNAPE is validated through a series of example test cases. These analyses focus on the performance of specific state measurements to state estimation performance, and demonstrate the core analytic functionality of the framework. Specific cases analyze the effects of initial error and measurement uncertainty on state estimation performance. The timing and frequency of state measurements are also investigated to show the need for frequent state measurements to minimize navigation errors. The dependence of navigation accuracy on timing stability and accuracy is also demonstrated. These test cases capture the functionality of the tool as well as validate its performance. The SNAPE framework is utilized to capture and analyze NNAV, both conceptually and analytically. Multiple evaluation cases are presented that focus on the Mars Science Laboratory's (MSL) Martian transfer mission phase. These evaluation cases validate NNAV and provide concrete evidence of its operational capability for this particular application. Improvement to onboard state estimation performance and reduced reliance on Earth-based assets is demonstrated through simulation of the MSL spacecraft utilizing NNAV processes and embedded packets within a limited network containing DSN and MRO. From the demonstrated state estimation performance, NNAV is shown to be a capable and viable method of deep space navigation. Through its implementation as a state augmentation method, the concept integrates with traditional measurements and reduces the dependence on Earth-based updates. Future development of this concept focuses on a growing network of assets and spacecraft, which allows for improved operational flexibility and accuracy in spacecraft state estimation capability and a growing solar system-wide navigation network.

ITC/USA 2013 Conference Proceedings / The Forty-Ninth Annual International Telemetering Conference and Technical Exhibition / October 21-24, 2013 / Bally's Hotel & Convention Center, Las Vegas, NV / In this paper we analyze fundamental local-area communication issues related to proximity operations around near-earth asteroids. We are motivated by NASA's plan to send robotic spacecraft to numerous such asteroids in the coming years in preparation for an eventual manned mission. We consider here the case where multiple probes are deposited on the surface of an asteroid and must communicate the data they collect to each other and to earth by using the orbiting `mothership' as a relay. With respect to this scenario, we statistically analyze the ability of surface probes in various locations to communicate with the mothership as well as their abilities to network with one another. For the purposes of this analysis, we assume the simplest possible communications scenario: a surface probe can communicate with the mothership only when it has an unobstructed line of sight. At the frequencies of interest here, line of sight is a necessary condition but it is obviously not sufficient - the end-to-end link margins of our communications system must be high enough to support the desired/required data rates. The work presented in this paper extends our previous research in which we only analyzed the visibility of the locations on the surface of the asteroid. Here, we consider how visibility affects the required communications bandwidth and buffer sizes for both surface-to-spacecraft and surface-to-surface scenarios.

ITC/USA 2012 Conference Proceedings / The Forty-Eighth Annual International Telemetering Conference and Technical Exhibition / October 22-25, 2012 / Town and Country Resort & Convention Center, San Diego, California / In this paper we analyze fundamental local-area communication issues related to proximity operations around near-earth asteroids. We are motivated by NASA's plan to send robotic spacecraft to numerous such asteroids in the coming years in preparation for an eventual manned mission. We consider here the case where multiple probes are deposited on the surface of an asteroid and must communicate the data they collect to each other and to earth by using the orbiting `mothership' as a relay. With respect to this scenario, we statistically analyze the ability of surface probes in various locations to communicate with the mothership as well as their abilities to network with one another. For the purposes of this analysis, we assume the simplest possible communications scenario: a surface probe can communicate with the mothership only when it has an unobstructed line of sight. At the frequencies of interest here, line of sight is a necessary condition but it is obviously not sufficient - the end-to-end link margins of our communications system must be high enough to support the desired/required data rates. Nonetheless, this simplistic analysis represents the first step in characterizing the communication system requirement for the asteroid-local portion of the system.