Gary Noreen

Integrated network architecture for sustained human and robotic exploration

The National Aeronautics and Space Administration (NASA) Exploration Systems Mission Directorate is planning a series of human and robotic missions to the Earths Moon and to Mars. These missions will require telecommunication and navigation services. This paper sets forth presumed requirements for such services and presents strawman lunar and Mars telecommunications network architectures to satisfy the presumed requirements. The paper suggests that a modest ground network would suffice for missions to the near-side of the Moon. A constellation of three Lunar Telecommunications Orbiters connected to a modest ground network could provide continuous redundant links to a polar lunar base and its vicinity. For human and robotic missions to Mars, a pair of areostationary satellites could provide continuous redundant links between a mid-latitude Mars base and Deep Space Network antennas augmented by large arrays of 12-m antennas

Telecommunications systems evolution for Mars Exploration

This paper describes the evolution of telecommunication systems at Mars. It reviews the telecommunications capabilities, technology and limiting factors of current and planned Mars orbiters from Mars Global Surveyor to the planned Mars Telecommunications Orbiter (MTO).

Orbit design based on global maps of telecom metrics

This paper describes a tool to aid orbit design called the Telecom Orbit Analysis and Simulation Tool (TOAST). By specifying the six orbital elements of an orbit, a time frame of interest, a horizon mask angle, and some telecom parameters such as transmitter power, frequency, antenna gains, antenna losses, required link margin, and received threshold powers for the rates, TOAST enables the user to view orbit performance as animations of two- or three-dimensional telecom metrics at any point on the planet (i.e., on global planetary maps). Supported metrics include: (i) number of contacts; (ii) total contact duration; (iii) maximum communication gap; (iv) maximum supportable rate; and (v) return data volume at a best single rate or with an adaptive rate, along with; (vi) the orbiters footprint and (vii) local solar times. Unlike other existing tools, which generally provide geometry, view periods and link analysis for an orbiter with respect to a single location on the planet, TOAST generates telecom performance metrics over the entire planet. The added capabilities provide the user an extra degree of freedom in analyzing orbits and enable the user to focus on meeting specific mission requirements, such as what data rates can be supported, what data volume can be expected, and what the time gap will be between communication periods. Although TOAST can be used to study and select orbits about any planet, we describe here its use for missions to Mars. TOAST is being used to analyze candidate orbits for the 2009 Mars Telecommunications Orbiter mission. Telecom predicts generated by TOAST for MTO orbit candidates are laying a foundation for selecting the MTO service orbit. This paper presents numerical simulations and telecom predicts for four candidate MTO orbits.

Selecting Codes, Modulations, Multiple Access Schemes and Link Protocols for Future NASA Missions

NASAs Space Communication and Navigation (SCaN) office has been designing an agency-wide space communication and navigation architecture to support NASA space exploration and science missions out to 2030. SCaN chartered a study in 2007 to select codes, modulations, multiple access techniques and link protocols for this architecture. The study was conducted by Goddard Space Flight Center, the Jet Propulsion Laboratory and consultants to NASA. This paper provides an overview of the study, describes the process used to carry out the study, and summarizes study results. Companion papers at this conference provide detailed technical information and analyses.

Low cost deep space hybrid optical/RF communications architecture

This paper reports on a study of hybrid optical/Radio Frequency (RF) architectures for deep space missions. Previous proposed optical deep space communication architectures were generally designed to achieve 90% or better availability 24/7. This study, instead, considered alternative metrics and architectures. It focuses on a strategy to use RF links and existing RF infrastructure for navigation and for communications requiring high availability, and optical communication links only for high volume downlink data. The optical link can then be designed to maximize data volume rather than availability. Utilizing Automatic Repeat Request (ARQ) with this strategy, a high level of completeness is possible even with low link availability - though with an increase in latency and spacecraft memory requirements. This strategy is suitable for deep space missions whose high volume links are dominated by science data that can tolerate long delays. The study found that with this optical downlink strategy, a single ground telescope can provide the principal expected benefit of optical communications (high data volume) at much lower cost than optical infrastructures designed to provide 90% availability 24/7. The study found also that data volume can, in some cases, be maximized by arraying all ground telescopes at a single site so that they have identical weather statistics. This low cost architecture, here named Single Optical Site (SOS), can eventually be augmented with multiple sites to provide high optical availability.

End-to-end information system concept for the Mars Telecommunications Orbiter

The Mars Telecommunications Orbiter (MTO) was intended to provide high-performance deep space relay links to landers, orbiters, sample-return missions, and approaching spacecraft in the vicinity of Mars, to demonstrate interplanetary laser communications, to demonstrate autonomous navigation, and to carry out its own science investigations. These goals led to a need for an array of end-to-end information system (EEIS) capabilities unprecedented for a deep space mission. We describe here the EEIS concept for provision of six major types of services by the MTO: relay, open-loop recording, Marscraft tracking, timing, payload data transport, and Earthlink data transport. We also discuss the key design drivers and strategies employed in the EEIS design, and possible extensions of the MTO EEIS concept to accommodate scenarios beyond the original MTO mission requirements

Evaluation of Multiple Access Techniques for Simultaneous Space Communications and Tracking

The National Aeronautics and Space Administration has conducted a comprehensive study to identify the most appropriate and efficient modulation, coding, multiple access and link protocol options for future space communication links supported by NASAs Ground Network, space network, deep space network, and earth-based ground terminals and in-situ relay satellites envisioned for Constellation Program mission support at the Moon and Mars. This paper briefly describes the study process and summarizes the multiple access recommendations for future NASA space communications.

CCSDS application profiles for the Mars environment

A common set of communications protocols needs to be agreed upon amongst all participants in a communications network to enable intercommunication. The mechanism to achieve this objective is an application profile, which specifies which protocols within the five layers (physical, data link, network, transport, and application) of the CCSDS protocol stack are applicable to the elements of the network. The first step in establishing an application profile for an enterprise is to evaluate and choose which communication protocols and space data application standards are to be used by the asset classes (e.g., orbiters, landers, probes) defined within the enterprise. Once this list of standards has been chosen, the individual options within these standards need to be evaluated in order that a specific subset of these options can be chosen. The application profile defines a program’s communications policy for that specific enterprise. Application profiles define the baseline communications capabilities for all the missions participating in a given enterprise, enabling each individual mission to select an appropriate set of options when implementing the CCSDS recommendations for space data system standards.