Kul Bhasin and Jeff Hayden

Glenn Research Center, Cleveland, Ohio

Jonathan R. Agre, Loren P. Clare, and Tsun-Yee Yan

Jet Propulsion Laboratory, Pasadena, Calfornia

Advanced Communication and Networking

Technologies for Mars Exploration

NASA/TM—2001-210975

September 2001

AIAA–2001–289
The NASA STI Program Office . . . in Profile

Since its founding, NASA has been dedicated to

the advancement of aeronautics and space

science. The NASA Scientific and Technical

Information (STI) Program Office plays a key part

in helping NASA maintain this important role.

The NASA STI Program Office is operated by

Langley Research Center, the Lead Center for

NASA’s scientific and technical information. The

NASA STI Program Office provides access to the

NASA STI Database, the largest collection of

aeronautical and space science STI in the world.

The Program Office is also NASA’s institutional

mechanism for disseminating the results of its

research and development activities. These results

are published by NASA in the NASA STI Report

Series, which includes the following report types:

• TECHNICAL PUBLICATION. Reports of

completed research or a major significant

phase of research that present the results of

NASA programs and include extensive data

or theoretical analysis. Includes compilations

of significant scientific and technical data and

information deemed to be of continuing

reference value. NASA’s counterpart of peerreviewed formal professional papers but

has less stringent limitations on manuscript

length and extent of graphic presentations.

• TECHNICAL MEMORANDUM. Scientific

and technical findings that are preliminary or

of specialized interest, e.g., quick release

reports, working papers, and bibliographies

that contain minimal annotation. Does not

contain extensive analysis.

• CONTRACTOR REPORT. Scientific and

technical findings by NASA-sponsored

contractors and grantees.

• CONFERENCE PUBLICATION. Collected

papers from scientific and technical

conferences, symposia, seminars, or other

meetings sponsored or cosponsored by

NASA.

• SPECIAL PUBLICATION. Scientific,

technical, or historical information from

NASA programs, projects, and missions,

often concerned with subjects having

substantial public interest.

• TECHNICAL TRANSLATION. Englishlanguage translations of foreign scientific

and technical material pertinent to NASA’s

mission.

Specialized services that complement the STI

Program Office’s diverse offerings include

creating custom thesauri, building customized

data bases, organizing and publishing research

results . . . even providing videos.

For more information about the NASA STI

Program Office, see the following:

• Access the NASA STI Program Home Page

at http://www.sti.nasa.gov

• E-mail your question via the Internet to

help@sti.nasa.gov

• Fax your question to the NASA Access

Help Desk at 301–621–0134

• Telephone the NASA Access Help Desk at

301–621–0390

• Write to:

 NASA Access Help Desk

 NASA Center for AeroSpace Information

 7121 Standard Drive

 Hanover, MD 21076
NASA/TM—2001-210975

September 2001

National Aeronautics and

Space Administration

Glenn Research Center

Prepared for the

19th International Communications Satellite Systems Conference and Exhibit

sponsored by the American Institute of Aeronautics and Astronautics

Toulouse, France, April 17–20, 2001

Kul Bhasin and Jeff Hayden

Glenn Research Center, Cleveland, Ohio

Jonathan R. Agre, Loren P. Clare, and Tsun-Yee Yan

Jet Propulsion Laboratory, Pasadena, Calfornia

Advanced Communication and Networking

Technologies for Mars Exploration

AIAA–2001–289
Available from

NASA Center for Aerospace Information

7121 Standard Drive

Hanover, MD 21076

National Technical Information Service

5285 Port Royal Road

Springfield, VA 22100

This report contains preliminary

findings, subject to revision as

analysis proceeds.

Available electronically at http://gltrs.grc.nasa.gov/GLTRS
NASA/TM—2001-210975 1

Advanced Communication and Networking Technologies for 

Mars Exploration 

Kul Bhasinand Jeff Hayden 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

Jonathan R. Agre, Loren P. Clare, and Tsun-Yee Yan 

Jet Propulsion Laboratory 

Pasadena, California 91109 

Abstract–Next-generation Mars communications networks will provide communications and 

navigation services to a wide variety of Mars science vehicles including: spacecraft that are arriving 

at Mars, spacecraft that are entering and descending in the Mars atmosphere, scientific orbiter 

spacecraft, spacecraft that return Mars samples to Earth, landers, rovers, aerobots, airplanes, and 

sensing pods. In the current architecture plans, the communication services will be provided using 

capabilities deployed on the science vehicles as well as dedicated communication satellites that will 

together make up the Mars network. This network will evolve as additional vehicles arrive, depart or 

end their useful missions. Cost savings and increased reliability will result from the ability to share 

communication services between missions. 

This paper discusses the basic architecture that is needed to support the Mars Communications 

Network part of NASA's Space Science Enterprise (SSE) communications architecture. The network 

may use various networking technologies such as those employed in the terrestrial Internet, as well 

as special purpose deep-space protocols to move data and commands autonomously between vehicles 

at disparate Mars vicinity sites (on the surface or in near-Mars space) and between Mars vehicles 

and earthbound users. The architecture of the spacecraft on-board local communications is being 

reconsidered in light of these new networking requirements. The trend towards increasingly 

autonomous operation of the spacecraft is aimed at reducing the dependence on resource scheduling 

provided by Earth-based operators and increasing system fault tolerance. However, these benefits 

will result in increased communication and software development requirements. As a result, the 

envisioned Mars communications infrastructure requires both hardware and protocol technology 

advancements. This paper will describe a number of the critical technology needs and some of the 

ongoing research activities. 

1. Introduction 

Future Mars exploration will be supported by a multiplicity of in situ intercommunicating entities 

that require the ability to share information among themselves and with the Earth users. There will 

be multiple active missions, producing ever-increasing amounts of scientific data and many of these 

missions will also need a significant amount of local communication (e.g., teams of rovers). The 

aggregate data produced by these missions will be multiplexed through a backbone network to the 

Earth that will eventually support data rates in the Gigabit per second range. This is a substantial 

increase over the current capabilities. , The current Mars Global Surveyor mission is representative of 

the state-of-the-practice in Mars-to-Earth telecommunications and utilizes direct links to Earth based 

on X-band microwave communication link technologies at data rates up to approximately 85 kilobits 

per second. Clearly, new technologies will need to be brought to bear to achieve this increased 

capacity and to support the new in situ networking. The Mars communication architecture will be 

designed to evolve in such a way as to meet anticipated near term (2001-2010), mid-term (2010-

2020), and far-term (beyond 2020) requirements. The architecture itself will be defined in terms of 

several types of communication subnetworks, called architectural elements1

, and specific technology 

 

1

In [1], a different architectural decomposition was defined. However, in the interest of having a 

common set of terms with the Mars communication activities, we use the nomenclature of the Mars 

program for this paper. 
NASA/TM—2001-210975 2

developments are described in the context of these elements. These architectural elements for the 

Mars network are defined below: 

A. Mars-Earth backbone network – This architectural element provides the long haul data links 

directly between Mars vehicles and the Earth as well as the Earth-based infrastructure elements. 

The remote assets include elements with long-haul capabilities (certain Mars surface vehicles, 

spacecraft in Mars orbit) and the in-space data relay network. The Earth-ground segments include 

the deep space network (DSN), NASA and other space agency Intranets and virtual private 

networks (VPN’s), and the Internet. The critical technologies involve increasing the capacity 

and the autonomous operation of the remote long haul space link assets. 

B. Mars vehicle proximity networks – These involve the wireless links with distances that are 

relatively near to the planet. There are three types of proximity links. 

1. Orbiter to/from Surface (called access network in [1]): This architectural element provides 

the data links between Mars surface/airborne vehicles and spacecraft in Mars orbit. The 

orbiters will typically contain the long haul links to Earth and will host a gateway to the 

backbone network to relay between the backbone elements and the mission spacecraft and/or 

vehicles, or will forward to another proximity vehicle. 

2. Mars inter-spacecraft networks - This architectural element provides the data link between 

spacecraft flying in formation, clusters, or constellations in the Mars vicinity. It also includes 

the communication interfaces between approaching/departing spacecraft. In particular, 

spacecraft in a communication constellation that intercommunicate to relay the data to Earth 

are included. 

3. Mars surface networks (called proximity network in [1]): This architectural element provides 

the data links between surface vehicles (rovers, airplanes, aerobots, landers, and sensors) 

spread out in an ad hoc network. 

C. Local area networks (LAN’s) on-board the Mars vehicles (included in the access network [1]): 

This architectural element interconnects the various modules of the vehicle through an internal 

LAN consisting of one or more types of serial or parallel interconnected busses. 

The choice of protocol suites for use in the Mars Network is critical as this is the first true deep 

space-based “network” [2]. Standardization of the protocol interfaces facilitates the use of familiar 

terrestrial software constructs that provide transparency and hide the details of the communication 

architecture. There is a powerful incentive to provide transparency as this reduces software 

development costs and increases software reliability. Where possible, Internet protocol (IP)-

compliant services can be used to enable the use of powerful Internet-like applications (ftp, e-mail), 

application program interfaces (sockets), and languages (Java, Java Script, HTML, XML, etc.) that 

simplify the task of coding operations that move data and command and coordinate activities between 

Mars vehicles. However, due to differences between terrestrial environments and those at planetary 

distances, several important services that are unique to the deep space-based environment are desired. 

Examples of these services include accommodation of long propagation delay times, handling 

periodic link outages efficiently, providing intermediate-node data custody, best-effort delivery of 

data with portions missing and noted, and non-blocking function operation. Applications built on top 

of these services may need to be explicitly modified from their terrestrial counterparts. The benefits 

derivable from maintaining an open communications architecture (such as the Internet) will help to 

achieve the long lifetime of the Mars networks and the need to accommodate missions planned 

over the next 10 to 30 years. In the long term, these issues are being examined in the context of the 

Interplanetary Internet (IPN) where the Mars network represents a subnetwork within the larger space 

network [3]. 

Protocol layering can be used to support this transparency while providing the ability to include 

customized services within a well-defined reference model. There are two basic design questions that 

must be considered. These are 1) what services and interfaces are presented to the application layer 

software developers, and 2) what protocols are used to implement the services at each layer. As an 
example of the former, an application programmer interface (API) that is identical to sockets may be 

provided, but the underlying protocols may be specially tailored to the space links. As an example of 

the latter, with proper layering, one could easily replace a standard IP routing protocol (e.g., BellmanFord) with a non-internet routing protocol (such as an ad hoc routing scheme), with no application 

layer changes. The choice to use a non-standard protocol at a given layer may be warranted by 

specific aspects of the environment such as power efficiency, or to provide a service that is not 

available in any existing protocol. In recognition of the fact that there is not a unique protocol suite 

that provides the best solution for each architectural element, there is a need to define the interfaces 

between the selected protocols and to develop gateways that will perform translations while 

maintaining transparency. 

A heterogeneous collection of spacecraft is anticipated to be deployed and their internal architectures 

can range from fully distributed to fully integrated to accommodate the specific requirements of the 

vehicle’s mission. Many Mars vehicles will implement on-board, Local Area Networks (LAN's) to 

route data and commands between subsystems and science instruments. Standards are emerging that 

define common interfaces for the on-board communication needs. Integration with the general Mars 

communication architecture through common protocols that provide standard naming and addressing 

schemes will permit simplified access to resources (e.g., instruments) by users and other vehicles. 

The Mars network will eventually provide both scheduled and on-demand service to users and 

vehicles. The eventual operational concept for the Mars network is that it will enable the user to 

control his/her vehicle (or instrument) or the vehicle to move its data to Earth without explicit 

scheduling by ground personnel, thereby reducing overall mission operations costs. The Earth-side 

support of the Mars network is basically the maintenance of the Earth-Mars backbone link and its 

connection to the Earth-side space agency intranets and ultimately the Internet. Eventually the data 

that traverses the backbone will be self-routing, wherein the destination addresses in the data packets 

find the end-point user or space vehicle applications. The mission operations group need not concern 

itself with packet routing. 

As the interest in Mars exploration grows and new vehicles are deployed with more and better 

communications assets, the architecture will acquire greater capabilities. In sections 2-4, we describe 

the potential near-term (out to 2010), mid-term (out to 2020) and far-term (beyond 2020) scenarios for 

the Mars network. Then in section 5 we discuss new technologies that address the requirements that 

we foresee in terms of the architectural elements. 

2. Mars Near-Term Communication Architecture 

The near-term architecture for the Mars communication infrastructure is illustrated in Figure 1. This 

architecture provides moderately high-speed communication between Earth and Mars vehicles via the 

radio frequency (X-, Ka-band) equipment incorporated on each scientific orbiter sent to Mars as well 

as on-board the large rovers. Each of these orbiting vehicles incorporates a moderately high data rate 

RF backbone link to the Earth-based DSN as well as a moderate data rate proximity link to other 

Mars surface vehicles. Many of the orbiters will also provide navigation information to the surface 

elements. In addition, the 

infrastructure will be 

augmented by a dedicated 

communications satellite 

(ASI Telesat) to be put in 

place to perform data 

relay functions for surface 

vehicles, such as the 

Scout-class that do not 

have the ability to 

communicate directly 

to Earth. As shown 

in the figure, low rate 

Backbone Network

Proximity Networks

Science Orbiters with

Comm. Capability

Robotic Lander/

Sensor Network

Mars

Direct to Earth

Telesat

Figure 1. Mars Near-Term Communication Architecture 

NASA/TM—2001-210975 3
proximity networks will be employed between Mars vehicles, such as between landers and rovers as 

necessary. Missions using intercommunicating sensor pods are possible, but not yet planned. 

3. Mars Mid-Term Communication Architecture 

The mid-term architecture for the Mars communication infrastructure is illustrated in Figure 2 and 

includes the Robotic Outpost, representing the first permanent presence on Mars. Sensor networks 

will be used to monitor the local environment around the outpost. This architecture provides highspeed communication between Earth and Mars vehicles via a micro-satellite constellation designed 

specifically for Mars communications and navigation purposes [4]. Each of these spacecraft 

incorporates a high data 

rate Ka-band package for 

the backbone connection 

to the Earth-based DSN 

as well as high data rate 

access links to Mars 

vehicles. One or more 

Mars communications 

satellites (MarSat) 

will be placed in 

Areosynchronous Mars 

Orbit (AMO) and used 

to provide continuous 

coverage for the 

Microsats and ground 

vehicles in view. It will support the high-rate communications to/from Earth. This MarSat would 

become an always available, high-speed link for the Robotic Outpost below it. In addition, there is 

likely to be one or more Earth orbiting relay stations that operates using high-speed RF or optical 

means to provide additional DSN capacity and availability. 

4. Mars Far-Term Communication Architecture 

The far-term architecture for the Mars communication infrastructure will be used in support of Human 

Exploration and Development of Space (HEDS) missions and is illustrated in Figure 3. This 

architecture provides high availability, high-speed communication between Earth and the Mars Base 

and other Mars vehicles. The traffic patterns will drastically shift from the predominantly data-toearth requirement to a high volume of two-way traffic, consisting of a wide variety of types (e.g., 

voice, video, data) to/from Earth to support the human presence. There will also be an increased need 

for local communications 

to handle the human 

generated local traffic. 

At this point in time, 

the Mars network will 

become the most 

important hub of the 

Interplanetary Internet 

and handle data from 

other deep space 

missions. In order to 

support communications 

at all times, relay stations 

placed at gravitationally 

stable Lagrangian points 

associated with the sun 

and the Earth may be 

Backbone Network

Proximity Networks

Local Area Networks Communication

MicroSats at 4,000 km

Formation Flyers

Mars

Robotic Outpost

MarSat

Relay at Earth

Orbit

Figure 2. Mars Mid-Term Communication Architecture

Backbone Network

Proximity Networks

MicroSats

Formation

Flyers

Mars

MarSat

Relay at Lagrangian Point

Optical Relay at

Earth Orbit

HEDS Outpost

Figure 3. Mars Far-Term Communication Architecture 

NASA/TM—2001-210975 4
employed to avoid blackouts during the periods that the sun is between Earth and Mars. These relay 

stations will also be backbone elements of the intra-solar system IPN communications network. Each 

of these relay stations may incorporate high data rate microwave and optical packages for the intrabackbone communications links. Multiple Mars communications satellites (MarSat) in 

Areosynchronous Mars Orbit (AMO) will be used to handle the high data rate communications link 

from other communication assets and ground vehicles to Earth either directly or via the relay network. 

They will be the primary high availability, high-speed relay links for the manned Mars stations and 

expeditions below. 

5. Description of technologies by architectural element 

Below we describe key communication and networking technologies for the backbone, proximity, and 

spacecraft bus architectural elements. 

Technologies for backbone networks 

Technologies for the Mars backbone networks need to focus on delivering higher data rates at very 

long distances and also address the transport layer protocols issues for such distances. The use of Ka 

band technologies will allow increase in data rates currently achievable at X-band frequencies. In the 

long term various methods of employing optical communications will be the next step to increase the 

data rates. 

At the physical layer, the backbone technologies that are under development address increasing the 

data communications rate on several fronts. For use in the near term, the technologies will increase 

the radiated power output of Ka-band transmitters, improve the sensitivity of receivers, and handle 

higher rate digital bit-streams. These technologies include: 1) high efficiency Ka-band 30W and 

100W traveling wave tube amplifiers (TWTA's), 2) ultra low noise cooled receivers, 3) highefficiency Ka-Band MHEMT MMIC solid state amplifiers, 4) high rate modem circuits, 5) efficient 

optical power sources, and 6) micro-radian acquisition and tracking technologies. 

The current state-of-the-art for 32 GHz TWTA’s is the 20 W amplifier on the Cassini spacecraft. Its 

efficiency of ~ 40% represented a doubling of what had been achieved up to that time. Developing 

space-qualified amplifiers producing greater than 200 W of RF power will require the use of a 

different type of circuit than used in the lower power amplifiers. Previously the development of a 

dramatically different amplifier would require several iterations before producing an amplifier that 

met the desired performance. However, recently the number of required iterations has been drastically 

reduced due to greatly improved computer modeling capability. New development in high quality 

heterostructural materials will allow production of hi-efficiency Ka-Band MHEMT MMICs 

amplifiers with 0.1 micron device structure to operate at more than 50% efficiency. 

Critical optical technologies, such as the laser telescope in Figure 4, 

are also being developed that promise large gains in signal to noise 

ratios. 

Simulation and optimization of the 

TWT designs, Figure 5, are being 

pursued to increase power, 

efficiency, reliability, and data 

transmission rate for TWT amplifiers 

while reducing design time and cost. 

The physical layer backbone technologies that are intended for deployment in the far term will 

increase the data rates even further. These technologies are: 1) optical links targeted for multi-Mbps 

rates, 2) 200W TWTA's, and 3) large, lightweight antenna structures. 

Figure 5. TWT schematic Figure 4. Laser 

Communication Telescope 

NASA/TM—2001-210975 5
The backbone data links will continue to require special techniques to operate at Earth-Mars distances 

with low SNR. Work is continuing, for near term implementation, on coding (Turbo codes) to 

increase the total amount of data passed during a transmission. These codes are used to recover data 

that would otherwise be lost due to noise and dropouts. 

The link and network layer activities will focus on providing efficient error control through variants 

of Automatic Repeat Request (ARQ) tailored for the deep space links. In-space network store-andforward technologies that enable data routing by address (not by command) must provide the 

translation between the protocols used on the long haul backbone link and the final proximity link. 

Definition of a standard network layer interface will facilitate integration of the long haul, local and 

on-board LAN would represent a significant achievement. In addition, a network management 

protocol tailored for deep space, but similar to the Internet’s Simple Network Management Protocol 

(SNMP) will be required to configure and operate the backbone. 

The backbone network will most likely support a variety of protocols for the higher layers. The 

transport and application layers may utilize variants of Internet-based protocols (e.g., TCP, UDP, 

FTP), near-Earth space protocols (e.g., SCPS-TP) or deep-space protocols such as the CCSDS File 

Delivery Protocol (CFDP) [5]. The trend is to use the protocols to enable data to be passed as a 

semantically meaningful package (such as a record in a file versus just a bit stream) to and between 

intermediate spacecraft en route to a science vehicle at the Mars end (in forward direction) or to Earth 

(in the return direction). In CFDP, the intermediate points provide a “custody” service, and assume 

responsibility for package delivery, removing the need for end-to-end acknowledgments over the 

links with long propagation delay. A second important feature of CFDP is to allow the delivery of 

partially complete packages, with the rationale that some precious data is better then none, as long as 

one is informed of the missing parts. 

The application level services that may be implemented on top of the backbone in the far term will 

be directed toward creating an environment that can leverage from the state-of-the practice software 

engineering for terrestrial applications. Bringing Internet capabilities to the space backbone such as 

network servers to provide temporary storage, network switching, firewall protection, multicast 

services, email services, software control (XML, Java, Java Script, etc.) will be necessary for the 

implementation of autonomy in the operation of the network. Network access on-demand by user or 

vehicle will be important feature that will reduce the cost of network control and mission operations. 

Technologies for proximity networks 

Orbiter to/from Surface Interfaces– Mars surface vehicles may employ multiple RF subsystems. 

In the near term a proximity system that listens and radiates omni-directionally would be used for 

communication with relatively fast moving objects, such as a low altitude orbiter, for return of science 

data, video, or high-resolution images or for receiving lengthy software changes from Earth. This 

subsystem, perhaps UHF, may also be used for surface-to-surface proximity communications wherein 

a vehicle could coordinate its science data gathering with other nearby vehicle(s); and it could locate 

the other vehicle(s) using direction and ranging capabilities built into that system. A lower rate, 

directional antenna system would be employed as a backup link to Earth for transmitting and 

receiving short command strings and for sending back status telemetry and minimal science data. 

It would also be used in emergencies wherein the vehicle may send SOS messages to the Mars 

network or the Earth may attempt to regain command control of a malfunctioning vehicle. In later 

time frames, electronically steerable antennas may become feasible for both local and longer distance 

links. 

The physical layer technologies needed for the proximity network elements that are used for communications between an orbiter and a surface vehicle are the small volume, mass, and power RF 

receivers and transmitters that utilize the UHF, X-band, and Ka-band frequency regimes. Antenna 

development includes agile phased arrays, small steerable dishes, and omni-directional antennas. 

Also at the physical layer, the RF to digital interface developments include novel modem designs. 

NASA/TM—2001-210975 6
The use of focused antennas, Ka-band (20GHz-30GHz) receivers and transmitters is encouraged for 

vehicles that have moderate to large data files to transfer (100kB to multi-MB).

SiGe Radio Frequency Solid State Power Amplifiers 

(see Figure 6) are being developed at 8.4 GHz for 

orbiter to surface links. These amplifiers can be 

easily integrated with digital devices and circuit on Si 

substrate to reduce size of communication subsystem. 

The Micro 

Communications and Avionics System (MCAS – Figure 7) 

for Mars orbit link has been developed. This is a 

multimission transceiver for low power and low mass 

missions. The transceiver has the following characteristics: 

Mass < 150g, Volume < 100 cm3

, Coherent BPSK 

(Manchester/NRZ, Supp/Resid), Convolutional coding (K=7, R=1/2), 0.5W Output power, and NF < 

3dB, stability 10-6. The next generation highly miniaturized system is under development. 

The CCSDS Proximity-1 link layer protocol is presently being designed specifically for deep space 

surface-orbiter links [6] that are characterized by relatively short propagation times and relatively 

high SNR. Proximity-1 will be used in the near- and mid-term as the Mars protocol for the short-link 

portion of the surface-orbiter-Earth links. Proximity-1 allows the orbiter to access multiple, 

heterogeneous surface assets through a common hailing procedure. Once a session has been 

established between the orbiter and the surface element, the link can be moved to a set of working 

channels. Various types of communication services are accommodated such as the use of fixed block 

size or variable length messaging. The protocol provides a reliable message delivery service and a 

“best-effort” service. Some procedures are in place for handling contention from multiple orbiters; 

however, coordination methods are still being defined. 

At the network layer, the data is either handed over to the backbone network where a simple relay 

function is required to accomplish the hop to Earth, or if the data is destined for another surface 

vehicle, it is handled by the proximity network layer. The technologies needed at the transport and 

application layers are similar to those discussed for the backbone network above, with shorter delays 

and greater need for energy and storage efficiency. 

Mars Inter-spacecraft Networks – Most of the inter-spacecraft proximity networks will be 

implemented in multiple spacecraft systems that operate in a cooperative fashion, such as in 

constellations, formations, or clusters. These multiple spacecraft systems can be considered a single 

mission entity that might accomplish its scientific or infrastructure task by passing data between each 

other. Reasons for this inter-spacecraft communication may include coordination of relative alignment 

and positioning, distribution of computing tasks, master-slave or peer-to-peer cooperation, event 

timing and measurement triggering, and data passing in support of implementing a general 

communications network. 

The physical layer technologies needed for the inter-spacecraft network elements are small volume, 

mass, and power RF receivers and transmitters that utilize the UHF, S-band, X-band, and Ka-band 

frequency regimes. Antenna development includes agile phased arrays and omni directional antennas. 

Optical communications devices will eventually take part in inter-spacecraft networks. Also at 

the physical layer, further RF/optical to digital interfaces and modem advances are needed. 

Another function of these communication physical layers will be the ability to measuring relative 

distances and attitudes between the spacecraft. The precision of these measurements will be 

Figure 6.SiGe Solid State Power 

Amplifier 

Figure 7. MCAS Testbed 

NASA/TM—2001-210975 7
dependent on the mission of the cooperative spacecraft. Coarse measurement will be satisfied by 

various RF system capabilities in range measurement. Fine measurement will be accomplished with 

the optical systems. 

At the inter-spacecraft network's data link and network layers a peer-to-peer communication scheme 

is most appropriate. Modifications of Proximity-1 or emerging wireless LAN technologies (e.g., 

IEEE 802.11 [7] or Bluetooth [8]) are under consideration. These wireless LAN's will need 

asynchronous and real-time capabilities and will need to handle ad hoc joining and leaving for starcentered formations or more general multi-hop topologies. Also, motion dominated by predictable 

orbital mechanics may be incorporated in the link topology driven network adaptations. 

The transport and application layers for the inter-spacecraft networks will use technologies similar to 

those used in the terrestrial Internet and for real-time applications on Earth. Additional development 

will be needed to implement network services to provide time synchronization and distributed 

computing coordination. In general, the autonomous coordination of the multi-spacecraft set will be 

accomplished at and above the inter-spacecraft network application layer, as in an agent-based 

architecture. 

Mars surface networks– The Mars surface proximity networks are those wireless networks that are 

used to intercommunicate between the various entities in the Mars atmosphere or on the Mars surface. 

These proximity links are of somewhat lower data rate (multi-kilobits per second) than interspacecraft links (multi-megabits per second) and use different technologies. These networks are used 

to coordinate actions between Mars landers, rovers, aerobots, airplanes, etc. The surface proximity 

networks are also used to relay data from weak emitters to nearby, more capable data gatherers (such 

as intelligent landers or rovers) that can pass the data up the communications chain to Earth via their 

access network system. 

Some example applications include: 

1. Sensor webs for in-situ science – Small, low-cost, low-power nodes that provide sensors, 

multihop communications and on-board data processing using limited power supplies. These may 

be formed into arrays of randomly placed sensors that will self-organize to perform their sensing 

and communication functions. On-board processing is used to reduce the raw data by triggering 

on observed phenomena, performing local analysis and by combining results with neighboring 

sensors. These types of systems offer the unique ability to perform simultaneous multipoint 

measurement of a common phenomenon in order to a) derive a combined signal with higher SNR, 

b) correlate the various signals in order to localize an event or perform fusion, or c) “image” 

(“spatially pixelate”) a region, such as seismic swarm characterization. Experiments designed 

to utilize these “network science” techniques are just beginning to emerge. 

2. Rover collective. – Multiple rovers act as a coordinated unit to survey a region. Scout class 

(i.e., no DTE capability) elements maintain connectivity to base station via “bucket brigade” 

communication relay. This latter capability might also be achieved using stationary relay nodes 

that a rover drops off as it moves about (possibly picking them back up later). 

3. Robotic outpost – Support interaction among a variety of robots and rovers to enable teamoriented operations such as support for interacting components of an in situ propellant production 

process. 

4. HEDS outpost – Extension of the robotic outpost to more complex and demanding requirements. 

Also, an ad hoc network may be deployed as a supporting infrastructure that provides wireless 

connectivity (e.g., voice) and position tracking as humans (etc.) move about. 

Surface ad hoc networks are currently under investigation for commercial, military and space 

applications. A combination of factors make the space environment unique with respect to the 

commercial and military applications and require additional research to realize these surface ad hoc 

networks for planetary exploration. The systems will need to be self-organizing and autonomous so 

that they can be automatically deployed and robust to faults imposed by the harsh environment. 

Overall cost is extremely dependent on the mass and size, greatly limiting the amount of energy or 

power generation capability that can be included. This drives the need for high-energy efficiency in 

the operational algorithms. Multihop networks that store and forward the information are useful from 

NASA/TM—2001-210975 8
an energy efficiency point of view as well as help overcome line-of-site and long distance constraints. 

These networks need to adapt in order to squeeze out as much information as conditions permit; to 

send data even if holes occur in the file/stream, or perhaps even deliver data with errors as there might 

not be another chance to retransmit or collect the data. Most scenarios will benefit from a feedforward of assets as much as possible, i.e., to build on previous mission assets as new in situ assets are 

overlaid. These will extend over very long time periods in comparison to commercial/military mission 

needs. 

At the physical layer, the RF regime used is UHF, S-band, and X-band. Antennas are near omnidirectional and are very small and lightweight. Very low power infrared may be included in the 

physical layer for very short distances. Very small, low mass and power integrated receivers, 

transmitters, and modems will be developed for at the physical layer of the surface proximity 

networks. 

The surface proximity network's data link layers may use a variation of Proximity-1 that is peer-topeer and modified for low energy use or they may be modeled after wireless LAN's such as Bluetooth 

or IEEE 802.11, but with modifications. The protocols will accommodate network dynamics such as 

faults, ad hoc-style handoff for mobile nodes, and cluster-based network routing and management. 

Many other protocol issues specific to sensor networks are currently under investigation in the 

research community. Energy efficiency in the link and network layers is important as well as 

geographic routing and data aggregation [9]. Most intelligent vehicle systems will likely provide 

proxy network services for the simpler more basic systems. Example services include temporary 

storage, data routing, multicast capability, time and operations synchronization, and network 

provisioning. 

Technologies for On-board LAN 

The various subsystems on-board the spacecraft are also following the general trend towards 

operating as a distributed system of autonomous but cooperating subsystems. The features/functions 

of the subsystems are increasingly implemented through software that is running on powerful 

processors embedded in the subsystems. The instrument and subsystem network interfaces to the 

on-board LAN physical layer are becoming increasingly complex and varied. Depending on the 

spacecraft complexity, there may be several types of local busses (e.g., IEEE 1394, Mil-Std 1553, 

Switched Ethernet, SpaceWire) that could be involved in information transfer. Further complications 

are arising from translating between the various protocols that must be supported. 

In recognition of the growing problem, a new CCSDS activity concerned with Spacecraft On-board 

Interfaces (SOIF) has been established to define standard interfaces and a common reference model 

for future on-board LANS of unmanned spacecraft [10]. The standard will encompass many of the 

common on-board busses as well as the link, network, and transport protocols layers.. Protocols that 

handle asynchronous data, isochronous data, real-time data and multicasting of data will be 

developed, tested and implemented. Gateway functions between the underlying protocols will be 

defined. The activity is expected to reduce development costs and risk for the spacecraft itself. 

Emergence of a common or standardized addressing scheme at the subsystem or instrument level 

will also reduce the complexity of the overall Mars communication architecture and move towards 

improving end-to-end interactions by Earth-based scientists and mission operators. 

6. Conclusions 

The Mars communication architecture has been described for implementation in the near-, mid-, and 

far-term. These architectures were based on current activities that are defining future Mars missions. 

The communication architectures have been decomposed into five elements: the backbone networks, 

three proximity networks (orbiter to/from surface, inter-spacecraft, and Mars surface networks), and 

the spacecraft on-board LAN’s. These elements are then used to address the technologies required for 

the near to far-term architectures. Many of the technologies are already under definition and 

development in various research programs (e.g., [11]). These include microwave transmission devices 

NASA/TM—2001-210975 9
and antennas, cryocooled receivers and MMIC’s, high rate modem circuits, optical communication 

devices and systems, spacecraft/vehicle on-board LAN’s, and data movement protocols. 

The analysis also reveals the following technology gaps: 1) transparency to the application programs 

of the underlying communication protocols, 2) autonomous operation of the communication 

infrastructure, 3) efficient protocols for the inter-satellite and surface proximity links, 4) gateways 

based on common protocol standards and reference models between the architecture elements 5) high 

power microwave and optical sources, and 6) lightweight, large aperture antennas. 

7. References 

[1] Kul Bhasin, Jeffrey L. Hayden, Space Internet Architectures and Technologies for NASA 

Enterprises, 2001 IEEE Aerospace Conference, March 2001. 

[2] Loren P. Clare, Jonathan R. Agre, Tsun-Yee Yan, Considerations on Communications Network 

Protocols in Deep Space, 2001 IEEE Aerospace Conference, March 2001. 

[3] Internet Society IPN Special Interest Group, InterPlaNetary Internet Study, http://ipn.jpl.nasa.gov/ 

[4] R J. Cesarone, R. C. Hastrup, D. J. Bell, D. T. Lyons, and K. G. Nelson, “Architectural Design for 

a Mars Communications and Navigation Orbital Infrastructure,” Paper No. AAS 99-300, 

AAS/AIAA Astrodynamics Specialist Conference, Girdwood, Alaska, August 16-18, 1999. 

[5] CCSDS File Delivery Protocol (CFDP). Draft Recommendation for Space Data Systems 

Standards, CCSDS 727.0-R-3. Red Book. Issue 3. Washington, D.C., CCSDS, June 1999. 

[6] CCSDS Proximity-1 Space Link Protocol. Draft Recommendation for Space Data Systems 

Standards, CCSDS 211.0-R-2. Red Book. Washington, D.C., CCSDS, January 2000. 

[7] Bob O’Hara and Al Petrick, IEEE 802.11 Handbook: A Designer’s Companion, Standards 

Information Network, IEEE Press, New York, NY, 1999. 

[8] Bluetooth, http://www.bluetooth.net, 2000. 

[9] G. J. Pottie and W. J. Kaiser, Wireless Integrated Network Sensors, CACM, Vol. 43, No. 5, 

May, 2000, pp. 51-58. 

[10] CCSDS P1K Subpanel for Spacecraft On-board Interfaces (SOIF), 

ftp://ftp.estec.esa.nl/pub/ws/wsd/ccsds/ccsdsoif/. 

[11] High Rate Data Delivery, NASA TAP, http://hrdd.grc.nasa.gov 

NASA/TM—2001-210975 10
This publication is available from the NASA Center for AeroSpace Information, 301–621–0390.

REPORT DOCUMENTATION PAGE

2. REPORT DATE

19. SECURITY CLASSIFICATION

 OF ABSTRACT

18. SECURITY CLASSIFICATION

 OF THIS PAGE

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources,

gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this

collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson

Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.

NSN 7540-01-280-5500 Standard Form 298 (Rev. 2-89)

Prescribed by ANSI Std. Z39-18

298-102

Form Approved

OMB No. 0704-0188

12b. DISTRIBUTION CODE

8. PERFORMING ORGANIZATION

 REPORT NUMBER

5. FUNDING NUMBERS

3. REPORT TYPE AND DATES COVERED

4. TITLE AND SUBTITLE

6. AUTHOR(S)

7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES)

11. SUPPLEMENTARY NOTES

12a. DISTRIBUTION/AVAILABILITY STATEMENT

13. ABSTRACT (Maximum 200 words)

14. SUBJECT TERMS

17. SECURITY CLASSIFICATION

 OF REPORT

16. PRICE CODE

15. NUMBER OF PAGES

20. LIMITATION OF ABSTRACT

Unclassified Unclassified

Technical Memorandum

Unclassified

National Aeronautics and Space Administration

John H. Glenn Research Center at Lewis Field

Cleveland, Ohio 44135–3191

1. AGENCY USE ONLY (Leave blank)

10. SPONSORING/MONITORING

 AGENCY REPORT NUMBER

9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES)

National Aeronautics and Space Administration

Washington, DC 20546–0001

Available electronically at http://gltrs.grc.nasa.gov/GLTRS

September 2001

NASA TM—2001-210975

AIAA–2001–289

E–12829

WU–755–1B–00–00

16

Advanced Communication and Networking Technologies for Mars Exploration

Kul Bhasin, Jeff Hayden, Jonathan R. Agre, Loren P. Clare, and Tsun-Yee Yan

Unclassified -Unlimited

Subject Categories: 32 and 17 Distribution: Nonstandard

Prepared for the 19th International Communications Satellite Systems Conference and Exhibit sponsored by the American Institute of

Aeronautics and Astronautics, Toulouse, France, April 17–20, 2001. Kul Bhasin and Jeff Hayden, NASA Glenn Research Center;

Jonathan R. Agre, Loren P. Clare, and Tsun-Yee Yan, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove

Drive, Pasadena, Calfornia 91109. Responsible person, Kul Bhasin, organization code 6100, 216–433–3676.

Next-generation Mars communications networks will provide communications and navigation services to a wide variety of Mars science vehicles

including: spacecraft that are arriving at Mars, spacecraft that are entering and descending in the Mars atmosphere, scientific orbiter spacecraft, spacecraft

that return Mars samples to Earth, landers, rovers, aerobots, airplanes, and sensing pods. In the current architecture plans, the communication services will

be provided using capabilities deployed on the science vehicles as well as dedicated communication satellites that will together make up the Mars

network. This network will evolve as additional vehicles arrive, depart or end their useful missions. Cost savings and increased reliability will result from

the ability to share communication services between missions. This paper discusses the basic architecture that is needed to support the Mars Communications Network part of NASA’s Space Science Enterprise (SSE) communications architecture. The network may use various networking technologies such

as those employed in the terrestrial Internet, as well as special purpose deep-space protocols to move data and commands autonomously between vehicles

at disparate Mars vicinity sites (on the surface or in near-Mars space) and between Mars vehicles and earthbound users. The architecture of the spacecraft

on-board local communications is being reconsidered in light of these new networking requirements. The trend towards increasingly autonomous

operation of the spacecraft is aimed at reducing the dependence on resource scheduling provided by Earth-based operators and increasing system fault

tolerance. However, these benefits will result in increased communication and software development requirements. As a result, the envisioned Mars

communications infrastructure requires both hardware and protocol technology advancements. This paper will describe a number of the critical technology needs and some of the ongoing research activities.

Advanced communication; Networking technologies; Mars exploration