Gary A.P. Horsham and George R. Schmidt

Glenn Research Center, Cleveland, Ohio

James H. Gilland

Ohio Aerospace Institute, Brook Park, Ohio

Establishing a Robotic, LEO-to-GEO Satellite

Servicing Infrastructure as an Economic

Foundation for Exploration

NASA/TM—2010-216937

November 2010

AIAA–2010–8897
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Gary A.P. Horsham and George R. Schmidt

Glenn Research Center, Cleveland, Ohio

James H. Gilland

Ohio Aerospace Institute, Brook Park, Ohio

Establishing a Robotic, LEO-to-GEO Satellite

Servicing Infrastructure as an Economic

Foundation for Exploration

NASA/TM—2010-216937

November 2010

AIAA–2010–8897

National Aeronautics and

Space Administration

Glenn Research Center

Cleveland, Ohio 44135

Prepared for the

Space 2010 Conference and Exposition

sponsored by the American Institute of Aeronautics and Astronautics

Anaheim, California, August 30 to September 2, 2010
Acknowledgments

The authors extend thanks to the following NASA personnel who contributed to this paper by providing a leadership framework, 

conducting workshops, and/or sharing opinions about the strategic business/technology future and potential of the emerging 

commercial in-space satellite servicing industry: Mr. Doug Comstock, Mr. Charles Miller, and Mr. David Huntsman, HQ;

Dr. Bruce Webbon, ARC; Dr. Phillip Abel, Dr. Lynn Anderson, Dr. David Chato, Mr. Randall Furnas, Dr. Geoffrey Landis,

Mr. Calvin Ramos, and Dr. Mary Zeller, GRC; Mr. Frank Cepollina, Mr. Benjamin Reed, Mr. Brian Roberts, Mr. Theodore 

Swanson, and Dr. Harley Thronson, GSFC; Mr. Edgar Zapata, KSC; Mr. John Dorsey and Dr. Judith Watson, LaRC; and

Mr. David Smitherman and Dr. Philip Stahl, MSFC. In addition, the authors also extend thanks to the following industry and 

academia personnel: Dr. David Kang, MDA, and Dr. David Akin, UMD.

Available from

NASA Center for Aerospace Information

7115 Standard Drive

Hanover, MD 21076–1320

National Technical Information Service

5301 Shawnee Road

Alexandria, VA 22312

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

Level of Review: This material has been technically reviewed by technical management. 

This report contains preliminary fi ndings, 

subject to revision as analysis proceeds.
NASA/TM—2010-216937 1 

Establishing a Robotic, LEO-to-GEO Satellite Servicing 

Infrastructure as an Economic Foundation for Exploration 

Gary A.P. Horsham and George R. Schmidt 

National Aeronautics and Space Administration 

Glenn Research Center 

Cleveland, Ohio 44135 

James H. Gilland 

Ohio Aerospace Institute 

Brook Park, Ohio 44142 

Abstract 

The strategy for accomplishing civilian exploration goals and objectives is in the process of a fundamental shift 

towards a potential new approach called “Flexible Path.” This paper suggests that a government-industry or publicprivate partnership in the commercial development of low Earth orbit to geostationary orbit (LEO-to-GEO (LTG)) 

space, following or in parallel with the commercialization of Earth-to-LEO and International Space Station (ISS) 

operations, could serve as a necessary, logical step that can be incorporated into the flexible path approach. A LTG 

satellite-servicing infrastructure and architecture concept is discussed within this new strategic context. The concept 

consists of a space harbor that serves as a transport facility for a fleet of specialized, fully- or semi-autonomous 

robotic servicing spacecraft. The baseline, conceptual system architecture is composed of a space harbor equipped 

with specialized servicer spacecraft; a satellite command, communication, and control system; a parts station; a fuel 

station or depot; and a fuel/parts replenishment transport. The commercial servicer fleet would consist of several 

types of spacecraft, each designed with specialized robotic manipulation subsystems to provide services such as 

refueling, upgrade, repair, inspection, relocation, and removal. The space harbor is conceptualized as an ISS-type, 

octagonal truss structure equipped with radiation tolerant subsystems. This space harbor would be primarily capable 

of serving as an operational platform for various commercially owned and operated servicer spacecraft positioned 

and docked symmetrically on four of the eight sides. Several aspects of this concept are discussed, such as: systemlevel feasibility in terms of ISS-truss-type infrastructure and subsystems emplacement and maintenance between 

LEO and GEO; infrastructure components assembly in LEO, derived from ISS assembly experience, and transfer to 

various higher orbital locations; the evolving Earth-to-orbit (ETO) capability to deliver humans and cargo to LEO 

for assembly purposes; system architectural definition, optimal orbital parameters, mass estimations, delta velocity 

(V) estimations, power and propulsion options, and assessments of various critical technologies. Large-scale, 

robotic, LTG satellite servicing is considered as an essential economic pre-condition and next parallel or sequential 

step on the road toward exploration beyond LEO. Such a step might produce the necessary pre-requisite economic 

value that can be used by future decision makers to justify further investment in exploration beyond LEO. 

I. Introduction1

The modern world remains extremely dependent on thin strings of several hundred civil, military, and 

commercial spacecraft/satellites currently stationed in space. They provide a steady stream of commerce, defense, 

and knowledge data. This dependency will in all likelihood increase significantly during this century. A major 

disruption of any kind in these essential systems and networks could be socially, economically, and politically 

catastrophic, on a global scale. The development of a space-based, robotic servicing economy could be useful in 

mitigating this growing risk, from an efficiency and security standpoint. This paper attempts to suggest what makes 

sense to invest in next for the logical, economic development of Earth orbit—i.e., after ISS completion. It 

incorporates results from recent NASA studies in 2010 to understand the barriers and challenges faced by U.S. 

industry and the formulation of a commercial business case (Refs. 1 and 2). It also expands on the results of early 

2000s advanced market research and analysis studies (Ref. 3) that sampled the opinions of several satellite industry 

executives and presents these results within a broad policy context. 

 1

This paper presents a revised strategic context and update of Reference 3 and includes a preliminary assessment and 

discussion of various key technologies. 
NASA/TM—2010-216937 2 

The concept of a “Space Harbor”2

 (Fig. 1) that 

serves as the central component of a national, 

space-based or on-orbit/in-space, robotic or 

automated servicing infrastructure is introduced as 

the next logical step for United States leadership 

in space. This is viewed as a reasonable and 

appropriate follow-on to the development of 

expendable launch vehicles (ELVs) and satellites 

in the 1950s and 1960s, the Space 

Shuttle/partially reusable launch vehicle (PRLV) 

in the 1970s and 1980s, and the International 

Space Station (ISS) in the 1980s, 1990s, and 

2000s. Large-scale experience in LTG 

spacecraft/satellite servicing and protection by 

robotic means is assumed to be a “stepping-stone” 

toward the development and preservation of the 

large scientific exploration facilities and humanrobotic exploration systems that are envisioned by 

NASA for operation beyond GEO. A balanced, 

return on national investment strategy for space, 

focused on the provision of enhanced 

national/homeland security for increased 

protection (from orbital debris and other threats), 

national economic/industrial expansion for 

increased revenue, and national scientific 

exploration for increased knowledge creates a 

strong goal in alignment with the new National 

Space Policy of the United States (Ref. 4). 

Satellite servicing is defined in this paper as the 

offering of services to owners or operators that 

involve the direct manipulation of on-orbit 

hardware or assets for the purposes of refueling, 

upgrade, repair, inspection, relocation, removal, etc. 

The aforementioned NASA studies have resulted in the preliminary definition of five near-term “commercial inspace servicing” market sectors: (1) Propellant Transfer and Depot/Storage; (2) Satellite Servicing (i.e., Repair, 

Maintenance, Refueling, etc.); (3) Orbital Transportation/Transfer; (4) On-orbit Assembly; (5) Orbital Debris 

Removal/Mitigation. This paper presents a discussion of the long-range prospects for spacecraft/satellite servicing 

and protection by robotic means (i.e., by teleoperated remote control and/or full-autonomy) as a common 

government-industry strategy for the logical, systematic development of space beyond LEO. 

Two key premises underlie this paper. Firstly, in the latter half of the 20th century, the feasibility of a LEO 

humans-in-space-centered space operations program was tested. The results-to-date indicate that the real and 

perceived benefits of having people in space need to heavily outweigh the risks inherent in transporting, keeping 

them there, and returning them to the Earth. Space, in terms of the LTG economic operations zone, or the beyond 

GEO exploration zone, appears to be the domain of semi- (i.e., teleoperated) and fully-autonomous (i.e., artificially 

intelligent) robots. Secondly, any major strategic/long-range exploration agenda will remain politically vulnerable 

and unsustainable without the establishment of a viable economic foundation. 

This paper offers a vision and definition of a logical and rational future state, stepping stone, or intermediate 

destination point that takes into consideration the present space-related social, technological, economic, 

environmental, political, and scientific context of the United States. It suggests the notion of the full-fledged 

development of a space-based/on-orbit infrastructure that can support the creation of a robust, in-space, robotic 

satellite servicing enterprise. Such a capability could significantly augment and benefit NASA’s exploration plans 

and begin the process of establishing an economic foundation to enhance sustainability and affordability of deeper 

 2

The term “Space Harbor” was conceived as an appropriate, functional metaphor for the concept being introduced in this 

paper. Subsequent research revealed that the early 1980s Space Station Task Force, Concept Definition Team, had originally 

applied this metaphor to the LEO, human-tended, space station concept.

Figure 1.—Notional “Space Harbor” with 16 servicer 

spacecraft at a sub-GEO location. 
NASA/TM—2010-216937 3 

space investments and activities into the future. The lack of an economic foundation can be considered the missing 

pre-requisite that has resulted in the failure of past exploration pronouncements to take hold—i.e., from the 1989 

space exploration initiative (SEI) to the 2004 Vision for Space Exploration (VSE). The new national space policy, 

which is interpreted as a formalization of the “Flexible Path” or “Flex Path” approach (Ref. 5), emphasizes the need 

for a real and significant involvement of private commercial interests and international partners—beginning now 

and extending indefinitely into the future. It is possible that vigorous, White House level emphasis on these critical 

success factors will lead to a new national and international paradigm or mindset shift needed for real sustainability. 

Five sections follow this introduction. Section II, discusses the LTG infrastructure system concept and how it 

might fit within a logical space development framework. Section III presents a notional assessment of the LTG 

system construction and operation, with a focus on electric propulsion and technology, and robotic communications 

and control. Section IV discusses the emerging satellite servicing industry and national investment within an 

historical context; the status of the commercial satellite industry; and then offers a high-level roadmap for potential 

forward action through a government-commercial partnership. Section V assesses alignment with the new national 

space policy. Finally, Section VI offers a concluding statement. 

II. LEO-to-GEO Infrastructure System Concept 

Figure 2 (shown in the previous section) presents a high-level, LTG satellite-servicing infrastructure concept.3 At 

the heart of this concept is a space harbor that serves as a “basing” facility for a fleet of market specialized 

automated servicing and protection spacecraft (SASPS). This fleet could consist of several spacecraft, each one 

specially built to provide a service in one market segment such as: refuel, upgrade, repair, inspection, relocation, 

removal, threat interception, threat neutralization, etc. (Fig. 3). The space harbor is considered to be octagonal in 

shape with docking stations for each servicer spacecraft positioned symmetrically on four of the eight sides. The 

baseline, conceptual system is composed of the following: 

1. Two Space Harbors each equipped with 16 specialized servicer spacecraft. (Fig. 1) 

2. A satellite command, communication, and control (C3

) system 

3. A Fuel Station (Depot) (Fig. 4) 

4. A Parts Station (Fig. 5) 

5. A Fuel/Parts Replenishment Transport 

Figure 6 shows a notional servicing mission to a GEO communications satellite. With autonomous rendezvous 

and docking interface and other standards accepted internationally, these servicer spacecraft could conceivably be 

built, owned and/or operated by numerous private companies from any country in the world—somewhat similar to 

today’s commercial satellites model. The goal of this logic would be to build a strong “economic foundation” with 

the aim of achieving economic ROI in support of NASA’s beyond-GEO exploration strategy. 

The LTG region is currently the only accessible, extraterrestrial region with both near and far-term civil, 

military, and commercial development potential. The initial exploitation of this potential began with the 20th 

century installation of numerous communications satellites and other spacecraft in orbits throughout the region. The 

Van Allen radiation belts dominate the region and produce a very harsh environment that challenges the 

survivability of both humans and machines. Several key technology areas such as low temperature and radiation 

tolerant electronics, laser/optical communications, and space robotics, are all at medium-to-high levels of maturity. 

In this regard, the LEO-to-GEO domain is perhaps also the only accessible region in space with any reasonable 

potential for achieving increasing relevance and value to the economy of the United States and the world during the 

21st century. 

Figure 7 depicts the stepwise progression of space systems and capabilities development from ELVs and 

satellites in the 1950s and 1960s, to the shuttle/PRLV in the 1970s and 1980s, then to the ISS in the 1980s, 1990s, 

and 2000s. The next logical step in early 21st century U.S. (and international) space strategy should perhaps focus 

on establishing a “spacecraft harbor or carrier”-centered, national infrastructure. Progress in this systematic manner 

would establish a strong economic and experiential foundation upon which the planned exploration strategy beyond 

LEO and GEO can be built.

 3

This concept was formulated in 2003 and published in Reference 3. If feasible and cost effective, policy changes could result 

in system establishment during the first or second quarter of the 21st century.
NASA/TM—2010-216937 4 

Figure 2.—A LTG robotic servicing architecture concept can be a logical, systematic follow-on capability to the ISS. 

It would require a government-led initiative, preferably spearheaded by a transformational, civil-militarycommercial partnership. This would help build a sturdy economic foundation or building block for space 

development and exploration. (“X” indicates an unknown quantity, which can be determined and optimized via an 

analysis that takes into consideration the orbital debris and radiation belt environments). 

 

Figure 3.—Notional servicer spacecraft. Figure 4.—Notional fuel station. 

 

LEO-to-GEO Infrastructure System Concept 
NASA/TM—2010-216937 5 

Figure 5.—Notional parts station. 

Figure 6.—Notional servicer spacecraft performing a 

servicing mission on a GEO communications 

satellite. 

Figure 7.—The next logical step in early 21st century US (and international) 

space strategy should perhaps focus on establishing a “spacecraft harbor 

or carrier”-centered, national infrastructure following the NASA STS and 

ISS investments. 
NASA/TM—2010-216937 6 

III. System Construction and Operations 

As discussed in Section II, the large-scale, robotic, LTG satellite-servicing infrastructure concept consists of a 

“space harbor” for a fleet of SASPS. One version of a potential space harbor is considered to be octagonal in shape 

with docking stations for each servicer spacecraft positioned symmetrically on four of the eight sides. The core 

space harbor subsystem of the LTG satellite servicing infrastructure system is conceptualized based on the U.S. ISS 

heritage. It is notionally constructed from ISS-P3/P4 truss assembly elements (length = 13.8 m; width = 4.8 m).4

 The 

two shorter parallel sides each contain 3 sections, the two longer parallel sides each contain 

6 sections, and the four remaining 45 angled sides each contain 4 sections. This would result in a notional length of 

160 m and width of 119 m. Construction of the LTG infrastructure is planned for a circular, co-planar “space harbor 

assembly orbit,” at a safe, close LEO distance in the vicinity of the present ISS orbit. The following assumptions 

underlie this concept: 

1. An ISS-truss-type infrastructure and subsystems can be effectively and efficiently emplaced and 

maintained between LEO and GEO. 

2. Components of this infrastructure can be assembled in LEO (in a similar manner to the ISS), as 

necessary, and then transferred to various higher orbital locations. 

3. An efficient and effective Earth-to-orbit (ETO) capability will be available to deliver humans and cargo 

to LEO. 

A complete pre-phase A feasibility study of this concept would entail the following analyses: 

A. Basic analyses: 

1. System-level feasibility 

2. Architectural definition 

3. Cost analyses 

B. Supplementary analyses: 

1. Optimal orbital parameters: X1, X2, X3 (see Fig. 2) 

2. Mass estimations 

3. Delta V estimations 

4. Comparison of chemical and electric systems 

5. 3D Modeling and Simulation 

6. Critical technologies 

 Telerobotics, On-orbit Assembly/Disassembly, Inter and Intra-Orbital transfer and Insertion, 

Autonomous Rendezvous and Docking, Low Thrust Electric/Chemical Propulsion, Power 

Generation and Energy Storage, Low Temperature/Radiation Hardened Electronics, High Data 

Rate Communications, Broadband Satellite Communications, Cryogenics, In-Space Fuel Transfer 

and Storage, etc. 

A preliminary assessment of electric propulsion operations and the technological state-of-the-art (SOA) are 

discussed in the two sub-sections below. 

LTG satellite servicing operations are envisioned to be conducted from an optimized sub-GEO location that will 

be determined by taking into consideration radiation and debris environments, and other factors—such as time-torendezvous. Operations will involve telerobotic or supervised autonomy control of servicer spacecraft by operators 

on the ground. The satellite command, communication, and control subsystem requirement would not require any 

new hardware to be launched and would instead rely on existing commercial communication satellite assets already 

in service at GEO. An overview of in-space robotics communications and control operations is presented in the 

Appendix. 

A. Electric Propulsion Operations 

Routine in-space servicing might eventually consist of a series of established orbiting stations housing remote 

specialized automated servicing and protection spacecraft or servicer spacecraft. The servicer spacecraft will require 

adequate mobility to reach the target satellite client population, as well as possible derelict debris craft that must be 

removed. This introduces a complex optimization problem, dealing with the proper staging orbits, the optimal 

propulsion system parameters, the number of servicer spacecraft, and the allowable number of trips per servicer 

spacecraft, which are all free parameters to be determined. 

 4

http://en.wikipedia.org/wiki/Integrated_Truss_Structure#P3.2FP4.2C_S3.2FS4_truss_assemblies
NASA/TM—2010-216937 7 

Figure 8.—Notional orbital transfer options for 

multiple node LTG servicing infrastructure. 

In contrast to orbit transfer, which only primarily deals with transportation to a given orbital altitude and 

inclination, servicing will require rendezvous to the specific orbital altitude, inclination, and true need, problem or 

anomaly of the spacecraft to be serviced. The initial need or anomaly, and altitude of the servicing nodes, in 

combination with the trip time required for orbital transfer, will determine the vehicle that can rendezvous in the 

minimum time. A greater number of vehicles will yield lower propellant requirements, at the expense of additional 

hardware launched and maintained to the service orbit. A graphical example of the trades inherent is shown in 

Figure 8. This depicts a scenario with six space harbors located at a high basing orbit, servicing a satellite at an inner 

orbit. While multiple servicer spacecraft can reach the client spacecraft, only one can be done with the minimum 

propellant. Equivalently, one other spacecraft can reach the client in the minimum time. These trends hold true for 

the opposite case, in which the clients are at a higher orbit, such as GEO, than the space harbors. 

A Hohmann transfer is the minimum V trajectory, which requires a 180 elliptical transfer between orbits. This 

type of transfer is labeled in Figure 3. For a Hohmann transfer between geosynchronous orbit and a 500 km orbit, 

the trip time would be 5 days using high thrust propulsion. This timing would have to be taken into consideration for 

determining the service vehicle to launch in order to minimize propellant. Shorter trip times would result in 

increased propellant requirements, and a different staging location for the service vehicle. 

In the case of electric propulsion, the trade space extends to the variation in travel time due to the propulsion 

system power, specific impulse (Isp), and efficiency. Trip time affects the time to rendezvous, which then identifies 

the optimum service location from which to launch the service vehicle. An iterative approach to infrastructure 

design using electric propulsion requires taking the effects of power levels, and power and propulsion system 

masses, into the relationship. For electric propulsion orbital transfer, the orbit-to-orbit V is a function of the 

circular orbits of the initial (V1) and final (V2) orbits: 





 



   iVVVVV

2

2 Cos 21

2

2

2

1

2 (1) 

However, the above relation does not include the requirement to rendezvous at a specific point on the orbit, 

which will determine the choice of space harbor from which to launch a servicer spacecraft. 

The trip time for the low thrust is dependent on the on board power system and the thruster performance. An 

example of this sensitivity is shown in Figure 9, where trip times from the space harbor to various lower orbits are 

shown as a function of power. Trip times are significantly lower than chemical, at the same power lever, for the full 

range of powers. The benefit, of course, is the increased payload capability for multiple rendezvous/servicing 

operations. Not included in this initial sensitivity study is the effect of Isp on the trip time. In addition, the actual 

delivered payload (i.e., servicing/refueling equipment and supplies) has not been identified; both the power and Isp

will affect this number. 
NASA/TM—2010-216937 8 

Figure 9.—Orbit transfer trip time sensitivity of low thrust systems to power level and space harbor 

orbital altitude. 

TABLE 1.—SUMMARY OF SOLAR ELECTRIC PROPULSION STATE-OF-THE-ART, 

TECHNOLOGY READINESS LEVELS, AND TECHNOLOGICAL CHALLENGES 

B. Electric Propulsion Technology 

Table 1 presents a summary of electric propulsion and solar power SOA, Technology Readiness Levels (TRLs), 

and technological challenges. 

Electric propulsion technology as an overall concept is currently at a TRL of 9, with routine use of ion and Hall 

thrusters on Earth orbiting satellites, and the successful flights of Deep Space 1 (ion), SMART1 (Hall), and 

Hayabusa (ion) beyond Earth orbit. These devices have operated at powers less than 5 kWe per thruster, which, 

based on initial results shown in Figure 4, may not be sufficient for timely servicing. 

The NASA developed NEXT ion propulsion system is at a TRL level of 5-6, with many of the components 

having gone through flight qualification testing (Ref. 6). This system is capable of operating at up to 10 kWe per 

thruster (Ref. 7) Laboratory Hall effect thrusters have been operated up to 100 kWe power levels, by both NASA 

(Ref. 8) and industry (Ref. 9). Key challenges remaining at the higher power levels are the power processing 

electronics and heat management of the overall propulsion system. Higher power systems are possible with further 

research (Ref. 10). 

Solar power has reached the 17 kWe levels on the Boeing 702 spacecraft (Ref. 11); however, the solar power 

systems are relatively massive for propulsion. More advanced power options include the UltraFlex and SLASR 

systems (Refs. 12 and 13). The UltraFlex array already has flight heritage for NASA science missions at low 

powers. Higher power, lightweight solar arrays using this technology have been considered in multiple NASA 

studies for planetary science missions using SEP. The structure, deployment, and space qualification of larger arrays 

remains the primary technology development effort. For more advanced arrays using high efficiency photovoltaics, 

the performance and manufacture of the cells remains a research topic. 

IV. Emerging LEO-to-GEO Satellite Servicing Industry Sector 

From a commercial point of view, the development and utilization of LTG space has been underway since the 

early 1960s. The satellite industry presently consists of a mix of integrated services and applications sectors that 

include: Communications, Remote Sensing, GPS/Navigation, Broadband, Direct Broadcast System/Digital Audio 

Radio System (DBS/DARS). The industry’s production sectors include: Ground Equipment, Launch Industry, 

Satellite Manufacturing, and Satellite Services. World satellite revenues (Ref. 14) as of June 2010 
NASA/TM—2010-216937 9 

Figure 10.—Satellite-servicing capabilities development investment profile. 

(Qualitative—Not to Scale) 

stood at $160.9 billion, up from $82.7 billion in 2004 for an average annual growth of 11.7 percent. This is a very 

positive trend that bodes well for the future of an industry that could be augmented by the advent of a satellite 

servicing capability that could result in lower industry risk, insurance premiums, and operating costs. 

Figure 10 shows a qualitative satellite servicing capabilities development investment profile. Investment peaked 

in the mid-to-late 1980s due to space shuttle operations related to satellite servicing. The practicality of a satellite in 

geostationary orbit was first envisioned in the 1940s. The satellite industry (in particular the “communications” 

segment) has contributed positively to international trade, and has become indispensable to the terrestrial national 

and global security and economic infrastructure. The satellite industry was effectively born in the early 1960s and 

became dominant during its “introductory” stage in the 1960s and 70s when copper wire cable technology (a 

nineteenth century technology that enabled long distance and transoceanic, telegraph communications) entered its 

decline. Now in its “mature” stage, satellite technology (i.e., transponders) is threatened by the 1980s and 1990s 

emergence of challengers in the form of optical fiber cable and terrestrial wireless technologies. In addition to the 

challenging U.S. export control environment, the emergence of serious challengers during maturity has prevented 

the industry from reaping healthy returns on its investment (Ref. 15). Most importantly though, perceived high risk 

and the accompanying high insurance premiums ranging from 10 to 30 percent over time (Ref. 16), have combined 

to negatively impact this sector’s market power. In December 2009, it was stated that the space insurance market 

had been very profitable over the last five years, and that this will inevitably lead to more competitive premiums for 

satellite operators.5

Figure 116

 presents an approximation of the evolutionary substitute/complementary telecommunications 

technology life-cycle market context within which in-space servicing emerged and could establish its niche (the 

thick line corresponds to the line in Fig. 10). It suggests that satellite and terrestrial technologies will become perfect 

complements and co-exist synergistically into the future. 

Within the last decade, there were several high-profile, beginning of life (BOL) satellite failures, which may 

have been salvageable if the nation and the world were in possession of a robust, space-based servicing capability. 

There are strong indications that operators may be willing to invest in a servicing mission at beween 25 to 

60 percent of total asset value, including launch cost, and that this fraction would tend to the high end of the range 

depending on proximity to BOL and the particular servicing objective.7

 If validated through further studies, then it 

would be mutually beneficial for government and industry to join forces and define a common, “build-launchoperate-service-protect” (BLOSP) strategy that expands this important industrial capability while opening up the 

development of space. The creation of a satellite or spacecraft servicing industry sector could be that initial, 

common strategy. 

 5

http://www.allbusiness.com/insurance/aviation-insurance-spacecraft-satellite/14534089-1.html

6

Global market presence provides a qualitative picture of the relative impact, influence, and dominance a complementary or 

substitute technology/system has had in the global marketplace over time. Market presence can perhaps be quantified by 

determining the actual industry capitalization of each respective technology. Further quantitative analyses of this sort would 

increase the fidelity and accuracy of this qualitative picture. That was beyond the scope of this study. 7

Reference 3, Appendix B, Question 16
NASA/TM—2010-216937 10 

Figure 11.—Approximation of the evolutionary telecommunications technology life-cycle 

market context within which in-space servicing emerged and could establish a niche. 

The existence of a thriving satellite industry offers an excellent opportunity for effective implementation of a 

government-industry, space-based, economic growth and capital infrastructure expansion strategy. Standardization, 

however, appears to be the key to any economic expansion of this industry due to its inherent cost-effectiveness.8

 If 

standardization were to become an industry practice, new markets and private capital investment could ignite and 

propel the integrated, civil, military, and commercial development of LTG to a new level of performance. Another 

cost-effectiveness factor is international cooperation for cost sharing, especially where common goals and objectives 

are found. Although not as economically efficient as standardization, in the near-term, “uncooperative” satellite 

servicing technologies/capabilities are under development and will probably be applied first to effectively jump-start 

the new industry. 

A. Status of In-Space Satellite Servicing Industry 

The capability to service satellites began with the demonstration of the first U.S. extravehicular activity (EVA) 

on the Gemini 4 mission in June 1965. The technological development of human/robotic satellite servicing has been 

pursued since the1970s and came to a high point with a series of capability demonstrations (see Fig. 5). With the 

advent of the space shuttle space transportation system (STS) in 1981, satellite servicing, as a discipline, formally 

entered the public’s consciousness. 

In April 1984, the term “satellite servicing” was introduced with the retrieval, repair, and redeployment of the 

Solar Maximum Mission (SMM) satellite. The STS 41-D SMM satellite-servicing mission was very successful. 

Shortly after, in October that same year, astronaut, on-orbit refueling was demonstrated. In November 1984, the 

Westar and Palapa communications satellites were captured and returned to Earth. Space robotics, a key enabling 

technology for satellite/spacecraft servicing received considerable international and U.S. government investment 

during the 1980s, from the Canadian robotic manipulator system (RMS) for the STS and ISS, to a formal NASA 

space telerobotics program. The European Space Agency (ESA), led by the German Space Agency (DLR), has 

continued significant development of telerobotic/satellite servicing technologies. 

Compared to 1980s spending levels, the development of U.S.-led, robotic, space-based servicing technology 

development entered a period of virtual dormancy throughout the 1990s. This was perhaps largely attributable to 

downsizing of the space station program and the general restructuring of the entire United States space program and 

aerospace industry (Ref. 17). There has been a reversal of this trend since 2004 when preparations began at NASA 

Goddard Space Flight Center (GSFC) for a robotic servicing mission to the HST—Servicing Mission (SM)-4. 

Although the planned, teleoperated HST-SM-4 was abandoned in favor of an astronaut-servicing mission, which 

was successfully completed in 2009, NASA retained and enhanced its robotic technology development capabilities 

 8

Aggregated finding from Industry Briefings presented to the NASA Office of the Chief Technologist, Commercial In-Space 

Servicing Working Group, July 2010; and, Reference 3, Appendix B, Questions 8, 18, 19.
NASA/TM—2010-216937 11 

and has been developing several “last-mile” technologies such as refueling valves that would allow refueling of 

uncooperative satellites. 

Government-led, civil and military development of satellite servicing capabilities have progressed to the point 

where it is appropriate to assess the technical feasibility of a robust, large-scale, robotic, LTG servicing 

infrastructure. NASA GSFC is developing telerobotic systems for servicing scientific spacecraft such as the current 

HST. This capability is considered extensible to telerobotic LTG satellite servicing. DARPA’s past (2007) Orbital 

Express/ASTRO and current Front-end Robotics Enabling Near-term Demonstration (FREND) programs have 

provided and will provide, respectively, several important demonstrations. The goal of the FREND program is to 

develop, demonstrate and fly robotic manipulator technologies designed to allow interaction with geosynchronous 

orbit (GEO)-based military and commercial spacecraft, extending their service lives and permitting satellite 

repositioning or retirement. 

Between 1984 and 1990, NASA’s attention was focused on the development of a “commercial” satellite 

servicing facility (SSF) and a flight telerobotics servicer9

 (FTS) as major business components of the core space 

station system. The SSF was abandoned, however, for three apparent reasons: (1) inherent incompatibilities with the 

space station’s microgravity environment requirements; (2) the lack of a compelling business case; and, (3) severe 

space station program budgetary shortfall problems. Nonetheless, there are strong indications that satellite operators 

would support the creation of a robust, servicing infrastructure in space.10

The lack of an ability to close the business case continues to plague present-day established and entrepreneurial 

companies that have continued to invest in the development of commercial satellite servicing capabilities. In 2010, a 

foreign company became the first to announce publicly that it had closed the business case on the design of a GEO 

refueling servicing capability and would plan to have its first flight demonstration in 2013. Around the same time, 

the DLR announced that it was granted the authority and would be funded by the German government to 

demonstrate a satellite servicing capability. In addition, a second foreign company has been very active in the 

development of a reboost and relocation servicer spacecraft that can operate on existing, nonstandardized, 

uncooperative spacecraft. This strong foreign/international interest and investment combined with the results of the 

NASA 2010 “International Workshop on On-Orbit Satellite Servicing,” suggest the potential for a governmentsupported, commercial, international race-to-market between 2010 and 2015. This workshop and follow-on studies 

have identified several American companies that are actively engaged in these pursuits, but are being held at bay by 

several significant barriers and challenges (discussed in the Part B). 

B. Government-Commercial Partnership 

Figure 12 presents a high-level roadmap that could result in the establishment of a LTG infrastructure by 2025, 

driven by a government-industry or public-private partnership, and commercial industry strategic and international 

alliances. 

It is in the long-term interest of NASA, DoD, and other governmental entities, to build and sustain a healthy 

commercial space/satellite industry. The U.S. and global economies will remain heavily dependent on a ring of 

roughly 300 geo-stationary commercial satellites. In the future, military reconnaissance, Global 

Positioning/Locating Systems (GP/LS), and Communications, Navigation, and Surveillance/Air Traffic 

Management (CNS/ATM) applications systems will probably increasingly populate medium and low Earth orbits. 

Planning is underway in all sectors, civil, military, commercial and industrial to coordinate a strategy for the 

future. There is a growing interest within both the defense and commercial sectors in the development of a robotic, 

satellite-servicing sector, along with various high-risk satellite technologies - such as laser/optical systems. This 

prospect appears ideal as both a necessary capability and a potential economic foundation to support NASA’s longrange exploration objectives. 

Commercial, robotic, in-space servicing is expected to find an initial foothold or market in GEO11. As mentioned 

earlier, the key to this and any space market was identified as standardization. If satellite/spacecraft manufacturing 

 9

NASA decided to develop a $288-million Flight Telerobotic Servicer in 1987 after Congress voiced concern about 

American competitiveness in the field of robotics. The FTS would also help astronauts assemble the Space Station, which was 

growing bigger and more complex with each redesign. Martin Marietta and Grumman received $1.5-million study contracts in 

November 1987. Martin Marietta received a $297-million contract in May 1989 to develop a vehicle by 1993. The Bush 

Administration briefly tried to commercialize the FTS project in early 1989. The contractors objected since the FTS had no 

commercial customers. The FTS was then combined with the Orbital Maneuvering Vehicle into the Robotic Satellite Servicer 

concept. (Source: http://www.astronautix.com/craft/flivicer.htm) 10Reference 3, Appendix B, Questions 12, 13, 14, 15.

11Reference 3, Appendix B, Question 20
NASA/TM—2010-216937 12 

Figure 12.—Notional high-level roadmap for the systematic realization of a 

LTG satellite-servicing infrastructure by 2025—a civil-to-commercial 

transition strategy for major sub-systems. 

were standardized (i.e., component interfaces, dimensions, etc.), as a result of market forces or government 

regulation, then it is conceivable that the (Earth orbit) market for spacecraft/satellite servicing (and protection) could 

rapidly grow into the hundreds of billions of dollars. This could become a thriving industry with no real limits to the 

growth-stage, given the potential for development and deployment of serviceable (Earth-Moon or Sun libration 

points) exploration and other spacecraft. 

Outside the United States there is a strong and growing interest in the establishment of satellite information 

networks to provide a variety of services ranging from global positioning to remote sensing. There is growing concern 

in the U.S. space industry that it is losing market share in the satellite manufacturing and launch vehicle services 

sectors. This is primarily being blamed on other countries’ subsidies to their emerging space industries. That being said, 

it is clear that the 21st century holds the promise of the potential emergence of a large international market for robotic, 

on-orbit servicing that would effectively dwarf the present global satellite industry. Europe, through the ESA is 

partnered with the U.S. in the construction of the ISS. ESA is also poised to expand its reliance on satellite networks in 

the future for emerging services such as navigation, telemedicine, high value asset tracking, etc. 

Like Europe, Japan has also engaged in long-range planning for 21st century space investments driven by both 

science exploration and commerce. There is also significant interest in space in the developing world. In addition to 

India as a new player in long-range space planning, the Chinese have made a strong commitment to future space 

investment. From Europe, to Japan, to China, to India therefore, it appears that during the early-to-mid 21st century, 

attention will increasingly be focused on significant development of satellite/spacecraft systems. Clearly, such 

systems will be spawned from the fertile and potent interests of nations driven by the quest for new knowledge, 

resources, and the fundamental need to prove the plurality of life in the universe. Based on the above indicators, it is 

reasonable to expect that the market for a future development of a robust, robotic, in-space servicing infrastructure 

will rest not only on the formation of a strong collaboration between U.S. civil, military, commercial and industrial 

concerns, but also on strong international cooperative interests. 
NASA/TM—2010-216937 13 

As mentioned previously, recent studies within NASA have resulted in the preliminary definition of the 

following five near-term “commercial in-space servicing” market sectors: (1) Propellant Transfer and 

Depot/Storage; (2) Satellite Servicing (i.e., Repair, Maintenance, Refueling, etc.); (3) Orbital 

Transportation/Transfer; (4) On-orbit Assembly; (5) Orbital Debris Removal/Mitigation. Table 2 shows the 

complete list of barriers and challenges faced by both established and entrepreneurial companies seeking to jumpstart the new, high potential, commercial in-space servicing industry. This study process identified the four highestpriority barriers and challenges facing each sector. The satellite-servicing sector had the following: (1) Investment 

Risk, (2) Market/Customer Risk; (3) ITAR/National Security Risk; and (4) Liability/Insurance Risk. NASA is 

currently planning to actively seek solutions to help U.S. industry eliminate/overcome these and other barriers and 

challenges. 

TABLE 2.—COMMERCIAL IN-SPACE SERVICING BARRIERS 

AND CHALLENGES IDENTIFIED IN NASA 2010 STUDY

The shift from a 20th century build-launch-operate-replace (BLOR)12 to a 21st century build-launch-operateservice-protect (BLOSP) mindset or philosophy for future civil-military-commercial space systems is considered an 

inevitability that might be justified on the basis of establishing a robust, cost-effective, space-based servicing 

infrastructure for 21st century spacecraft. Toward this end, entrepreneurial investment activity in this area has 

continued at a very low, self-supporting level. Given the considerable barriers and challenges involved, the 

establishment of a robust, in-space, robotic satellite-servicing industry sector should probably be catalyzed through a 

government-led initiative. This would stimulate commercial activity and evolve into a potentially strong economic 

foundation for space development and exploration, with perhaps numerous, unforeseeable, serendipitous economic 

development offshoots in space. In other words, this may be the way to achieve an economic, self-sufficient, space 

enterprise that can be used to reduce or minimize dependence on the public/tax-based component of investment in 

space development and exploration. 

Past studies13 on the economic viability of servicing for GEO, MEO, and/or LEO spacecraft have largely 

endorsed the prospects through analyses of its cost effectiveness compared to expendable satellites. Several studies 

and articles have focused on assessing the viability of discrete market segments (repair, refueling, etc.). As a 

comparison, commercial and other economic, social, and defense activities grew and expanded around the world as 

a result of highway and various, public and/or private capital infrastructure investments. Likewise, increasingly 

profitable in-space servicing and other market/business activities can be expected to emerge and thrive after a costeffective, government and/or industry-led, commercially operated infrastructure is established. 

V. Alignment With New U.S. Space Policy

The new National Space Policy of the United States, alluded to in Section I, continues the U.S. global leadership 

posture and contains several related goals, which clearly suggests that the new strategy for the development of space 

will involve an increasing dependency on privately funded commercial space activities and international 

cooperation. These goals are stated as follows: 

 12Reference 3, Appendix B, Question 1

13Reference 3—References: Sullivan, 2001; Madison, 1999; Levin, 1993; Space Systems Loral, 1990; Chenard, 1990; 

Higginbotham, 1987.
NASA/TM—2010-216937 14 

It will probably remain the responsibility of the United States to continue its leadership of the world in space 

throughout most of the 21st century. European and Asian countries are rapidly integrating and/or transforming their 

respective economies and thus might assume a significant share of space leadership and power later in this century. 

However, given current political and economic realities, it is becoming increasingly apparent that every step we 

propose to take in space, whether for exploration or development, must minimize and simultaneously reduce 

dependence on taxpayer dollars. The new U.S. space policy appears to embrace and fully recognize this reality in its 

strong and unambiguous promotion of commercial space and international cooperation as major factors for success in 

all space-related endeavors in the future. The LTG-related goals and objectives offered in this paper are also clearly 

aligned with and in support of this new policy. 

Over the last 52 years, since its inception, NASA has worked to realize national space policy and meet its statutory 

obligations.14 The agency has transitioned, developed and/or introduced various systems and technologies into civil and 

commercial use. This began with the transitioning of military expendable launch vehicle technologies during the late 

1950s and early 1960s, which culminated in the Apollo/Moon program success. NASA then graduated to partially 

reusable launch vehicle technology in the form of an ambitious shuttle STS program in the 1970s. Throughout the 

shuttle program, the agency amassed an impressive record of accomplishments by pushing back the boundaries of 

knowledge in the material sciences, life sciences, and biomedical and bioengineering disciplines. Much more remains 

to be accomplished, and with the advent of the International Space Station (ISS), the civil infrastructure development of 

LEO will continue to progress onward. 

In meeting its policy and statutory obligations, NASA also created the satellite industry. This industry has become 

one of the most critical capabilities of paramount, strategic military and economic importance to the purposes and 

objectives of modern, global civilization. In addition to several high-value scientific spacecraft such as the Hubble 

 14The National Aeronautics and Space Act of 1958. Section 102 (b) states that “The Congress declares that the general 

welfare and security of the United States require that adequate provision be made for aeronautical and space activities. The 

Congress further declares that such activities shall be the responsibility of, and shall be directed by, a civilian agency exercising 

control over aeronautical and space activities sponsored by the United States, except that activities peculiar to or primarily 

associated with the development of weapons systems, military operations, or the defense of the United States (including the 

research and development necessary to make effective provision for the defense of the United States) shall be the responsibility 

of, and shall be directed by, the Department of Defense; and that determination as to which such agency has responsibility for 

and direction of any such activity shall be made by the President in conformity with section 201(e).” Section 102 (c), requires 

NASA to “seek and encourage to the maximum extent possible, the fullest commercial use of space.” This is followed by Section 

102 (d) (1), which requires NASA to contribute materially to “the expansion of human knowledge of the Earth and of phenomena 

in the atmosphere and in space.”

“Energize competitive domestic industries to participate in global markets and advance 

the development of: satellite manufacturing; satellite-based services; space launch; 

terrestrial applications; and increased entrepreneurship. 

Expand international cooperation on mutually beneficial space activities to: broaden and 

extend the benefits of space; further the peaceful use of space; and enhance collection and 

partnership in sharing of space-derived information. 

Strengthen stability in space through: domestic and international measures to promote 

safe and responsible operations in space; improved information collection and sharing for 

space object collision avoidance; protection of critical space systems and supporting 

infrastructures, with special attention to the critical interdependence of space and 

information systems; and strengthening measures to mitigate orbital debris. 

Increase assurance and resilience of mission-essential functions enabled by commercial, 

civil, scientific, and national security spacecraft and supporting infrastructure against 

disruption, degradation, and destruction, whether from environmental, mechanical, 

electronic, or hostile causes. 

Pursue human and robotic initiatives to develop innovative technologies, foster new industries, strengthen international partnerships, inspire our Nation and the world, increase 

humanity’s understanding of the Earth, enhance scientific discovery, and explore our solar 

system and the universe beyond.” 
NASA/TM—2010-216937 15 

Space Telescope (HST) in LEO, there are presently around 300 commercial communications satellites in GEO. There 

are also several military reconnaissance and GPS satellites operating in MEO. Planning is underway in all sectors, civil, 

military, commercial and industrial, to establish new satellite networks in the future. In addition, NASA has plans for 

an ambitious exploration program that will require the installation of large scientific platforms throughout Earth-Moon 

space and beyond. It is becoming increasingly apparent that the total value of assets to be installed and operated in 

space during the 21st century, by either government or private interests, could be in the hundreds of billions of dollars. 

The magnitude of this potential investment implies that the capability to service spacecraft and satellites by robotic 

means will become increasingly economical, from a cost-effectiveness, asset value, revenue potential, and human 

safety or risk minimization standpoint. 

VI. Conclusion 

In-space, automated or robotic servicing (and protection) through a large-scale, on-orbit infrastructure is 

considered as a potentially viable industry or economic technology activity. Such activity might effectively and 

efficiently connect future space enterprise and space exploration with real economic growth contributions. Most 

importantly, economic growth contributions from the space sector are necessary to increase the relevance of space in 

the public mind. Given the magnitude and clear potential of this opportunity, it is possible that within the context of 

the new “flex path” space policy, the core, 21st century United States and international space strategies could be revectored toward the development of a LTG-and-beyond, robotics-centered stepping stone. The satellite industry is 

mature and ready to be incorporated into this strategy with the right incentives resulting from a government-industry 

partnership, and the integration of common civil, military, and commercial interests in eliminating/reducing the 

critical barriers and challenges to industrial growth and success. Preliminary assessments of robotic command, 

communications, and control, and electric propulsion operations provided encouraging indications. At a more 

fundamental level, the technical and economic feasibility in terms of BLOSP versus BLOR, technology readiness, 

in-space operations, and the start-up cost of a robust LTG infrastructure enterprise need to be examined in detail. 

NASA/TM—2010-216937 17 

Appendix15

In-Space Robotics Communications and Control 

Figure 13 presents the remote robotic operations latencies for several zones in space. Conventional orbital 

robotic operations, be it on the Shuttle or the International Space Station, rely on proximity teleoperations controlled 

by on-board astronauts. The Shuttle Remote Manipulator (SRMS) AFT Flight Deck Robotic Display and Control 

Station, has operated flawlessly on the Shuttle fleet for nearly 30 years, as well as the Robotic Workstation (RWS) 

for the International Space Station (ISS). The RWS (see Fig. 14) is the primary on-orbit operator interface for Space 

Station robotic elements and provides control and televised viewing of Space Station assembly and operations. The 

RWS was launched on STS-102 and delivered on-orbit in March 2001, and was brought into active service 

immediately. Since then it has been in almost continuous use. Both of these human-in-the-loop teleoperation 

systems have the advantage of real-time control and viewing. 

Figure 13.—Remote robotic operations latencies for several zones in space. 

Figure 14.—ISS robotic workstation. 

 15The information in this Appendix was obtained from Mr. Dan King, Director, Orbital Robotics, MacDonald, Dettwiler & 

Associates.
NASA/TM—2010-216937 18 

However, as new Exploration missions operate in an unmanned environment or are conducted over long 

distances, data communication latency becomes a significant problem and direct human-in-the-loop control may not 

be possible. Human in the loop control of manipulators is known to degrade when round trip communication 

latencies exceed roughly 0.25 to 0.5 sec. In the case of Mars missions, the data communication latency ranges from 

roughly twenty to forty minutes, exceeding a duration that would allow direct human-in-the-loop control of any 

kind. As a consequence, autonomous capabilities have to be introduced. The level of autonomy depends on the 

complexity of the operation, circumstances and environment under which it will be performed. 

For more recent robotic operations such as ISS robotics ground control, an approach called Remote Operation 

for Supervised Autonomy (ROSA) has been implemented. The same approach was implemented for DARPA’s 

Orbital Express Flight Demonstration flown in 2007. ROSA can provide astronauts and operators on the ground 

with the ability to choose the level of autonomy with which to instruct the system to perform an operation, and to 

permit the operator to generate Operations Scripts that seamlessly incorporate mixtures of high and low level 

commands within a single operation. An operations script can be generated any time prior to the operation. It will, in 

general, contain a mixture of goals or tasks and low level commands that control the operation. The use of goals to 

the greatest extent possible simplifies operations planning. In preparation for an operation the script and appropriate 

models are loaded. During execution the crew may view the operation. However, the crew need not directly control 

the execution, but maintains the ability to interfere as required. Since human operators can be involved in command 

and control, autonomous operations can be limited to very short operation at a time, significantly mitigating the level 

of risk involved. Architecturally ROSA consist of: 1) sensors to determine the external environment and system 

state, 2) a behavioral executor to guide operations, 3) an inference engine that invokes and terminates behaviors, 4) 

an intelligent operations supervisor that controls operations based on high level goals, and 5) a planning and 

cognitive modeling engine. ROSA has been demonstrated to be capable of effectively operating even with a 

communications latency of up to 7 to 8 sec. 

As orbital robotic missions become even more complex, the need for more capable robotic control ground 

stations arises. One particular example is in the area of robotic operations mission planning, training, monitoring and 

control. The current approach involves multiple teams at multiple sites performing primarily sequential tasks in the 

process. In addition, the current generation of robotic control stations is only capable of controlling one robot at a 

time and largely incapable of command and control of multiple robots active simultaneously while performing 

cooperative tasks. Such an approach will not be adequate to support anticipated future missions such as in-space 

assembly, maintenance and servicing of large spacecraft and infrastructure; and surface exploration and 

construction. Hence a logical next step is to develop a multirobot control ground planning, training, monitoring and 

control infrastructure. Such an approach will enable the control and oversight of multiple robots working 

cooperatively amongst themselves or in the presence of astronauts, as well as the efficient planning and training for 

safe operations. In addition, such a ground station concept will enable a more centralized approach to orbital robotic 

operations. 

Further into the future, a reasonable goal for autonomy in future human space exploration systems and 

operations is a range of autonomy rather than an absolute level. A system that supports variable and enhanced levels 

of autonomy is required. Autonomy will allow the crew to focus on key mission goals where man’s cognition, 

judgment, and experience provide the greatest benefit. Humans will be augmented and enhanced by: improved 

situational awareness, a system which supports variable levels of autonomy allowing operations to be defined in 

terms of simple high level goals where applicable, and the elimination of the need to perform routine operations. 

This will ultimately improve safety, increase efficiency, and reduce mission cost. 

References 

1. NASA Headquarters, “Commercial Space Workshop, Commercial In-Space Servicing Working Group Report,” 

July, 2010, URL: https://minx.arc.nasa.gov/minx/dsweb/View/Collection-12851 [cited 8 August, 2010]. 

2. NASA Goddard, “International Workshop on On-Orbit Satellite Servicing,” March 2010, URL: 

http://servicingstudy.gsfc.nasa.gov/ [cited 8 August, 2010]. 

3. Horsham, G.A.P., “Envisioning a 21st Century, National, Spacecraft Servicing and Protection Infrastructure and 

Demand Potential: A Logical Development of the Earth Orbit Economy,” NASA/TM—2003-212462. 

4. Obama Administration, “National Space Policy of the United States of America,” June 28, 2010. 

5. Review of Human Spaceflight Plans Committee, “Seeking a Human Spaceflight Program Worthy of a Great 

Nation,” October 2009. 

6. Gilland, J.H., “Commercial Electric Propulsion Implications for NASA Missions,” Presented at the JANNAF 

3rd Spacecraft Propulsion Subcommittee Joint Meeting, Orlando, FL, Dec. 2008. 
NASA/TM—2010-216937 19 

7. Patterson, M., Pinero, L., and Sovey, J., “Near-Term High Power Ion Propulsion Options for Earth- Orbital 

Applications,” AIAA Paper 2009-4819. 

8. Jacobson D., and Manzella, D., “50 kW Class Krypton Hall Thruster Performance,” AIAA Paper No. 2003-

4550. 

9. Busek Corp., “Busek Hall Thruster Demonstrates 20 kW Dual Mode Operating Capability,” 2010. 

10. Gilland, J., Fiehler, D., and Lyons, V., “Electric Propulsion Concepts Enabled by High Power Systems for 

Space Exploration,” IECEC Paper No. 22208, AIAA–2004–5690, 2nd International Energy Conversion 

Engineering Conference, Providence, RI August 2004. 

11. Spores, R. et al., “A Solar Electric Propulsion Cargo Vehicle to Support NASA Lunar Exploration Program,” 

IEPC-2005-320, Princeton, NJ, Oct. 2005. 

12. Eskenazi, M. et al., “Promising Results From Three NASA SBIR Solar Array Technology Development 

Programs,” NASA/CP—2005-213431, 2005. 

13. O’Neill, M. et al., “Stretched Lens Array (Sla) For Solar Electric Propulsion (SEP),” Presented at the 20th 

Space Photovoltaic Research and Technology (SPRAT XX) Conference September 25–27, 2007, Cleveland, 

Ohio. 

14. Futron Corporation for the Satellite Industry Association, “2010 State of the Satellite Industry Report,” June 

2010. 

15. Department of Commerce, International Trade Administration, “Flight Plan 2009: Analysis of the U.S. 

Aerospace Industry,” March 2009. 

16. Maléter, A., “Strategies to Mitigate High Satellite Insurance Premiums,” Satellite Finance, Issue 64, December 

2003. 

17. U.S. Aerospace Commission, “Final Report of the Commission on the Future of the United States Aerospace 

Industry—Anyone, Anything, Anywhere, Anytime,” November 2002. 
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Establishing a Robotic, LEO-to-GEO Satellite Servicing Infrastructure as an Economic 

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14. ABSTRACT

The strategy for accomplishing civilian exploration goals and objectives is in the process of a fundamental shift towards a potential new approach called “Flexible Path.” This 

paper suggests that a government-industry or public-private partnership in the commercial development of low Earth orbit to geostationary orbit (LEO-to-GEO (LTG)) space, 

following or in parallel with the commercialization of Earth-to-LEO and International Space Station (ISS) operations, could serve as a necessary, logical step that can be 

incorporated into the flexible path approach. A LTG satellite-servicing infrastructure and architecture concept is discussed within this new strategic context. The concept 

consists of a space harbor that serves as a transport facility for a fleet of specialized, fully- or semi-autonomous robotic servicing spacecraft. The baseline, conceptual system 

architecture is composed of a space harbor equipped with specialized servicer spacecraft; a satellite command, communication, and control system; a parts station; a fuel station 

or depot; and a fuel/parts replenishment transport. The commercial servicer fleet would consist of several types of spacecraft, each designed with specialized robotic 

manipulation subsystems to provide services such as refueling, upgrade, repair, inspection, relocation, and removal. The space harbor is conceptualized as an ISS-type, 

octagonal truss structure equipped with radiation tolerant subsystems. This space harbor would be primarily capable of serving as an operational platform for various 

commercially owned and operated servicer spacecraft positioned and docked symmetrically on four of the eight sides. Several aspects of this concept are discussed, such as: 

system-level feasibility in terms of ISS-truss-type infrastructure and subsystems emplacement and maintenance between LEO and GEO; infrastructure components assembly in 

LEO, derived from ISS assembly experience, and transfer to various higher orbital locations; the evolving Earth-to-orbit (ETO) capability to deliver humans and cargo to LEO 

for assembly purposes; system architectural definition, optimal orbital parameters, mass estimations, delta velocity (ΔV) estimations, power and propulsion options, and 

assessments of various critical technologies. Large-scale, robotic, LTG satellite servicing is considered as an essential economic pre-condition and next parallel or sequential 

step on the road toward exploration beyond LEO. Such a step might produce the necessary pre-requisite economic value that can be used by future decision makers to justify 

further investment in exploration beyond LEO.

15. SUBJECT TERMS

Orbital servicing; Spacecraft maintenance; Robotics; Telerobotics; Space commercialization; Commercial Spacecraft; International 

Space Station; Space platforms; Large space structures; Electric propulsion; Low Earth Orbit (LEO); Geosynchronous orbit 

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