Satellite Servicing: A History, the Impact to the Space Force, and the Logistics Behind It

Published March 29, 2021
By Capt Joshua J. Garretson, USAF

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Introduction

Satellite servicing is an important emerging technology not only to industry and National Aeronautics and Space Administration (NASA), but also to national security. Servicing technology should be of key interest for the United States Space Force (USSF) to research, and serviceability should be an even greater requirement pushed by the United States Space Command. The ability of spacecraft to be upgraded, inspected, re-orbited, and refueled while remaining in-situ could not only change space operations but also significantly lower the cost and schedule of placing satellites in orbit. The strategic benefits of satellite servicing are great, and it will play a crucial role in maintaining space superiority over our adversaries.

The importance of satellite servicing in future space environments is one reason why the 2020 Space Capstone Publication calls out sustainment as apart of Space Mobility and Logistics (SML). The publication states plainly that,

“Orbital sustainment and recovery is another important application of SML. Already demonstrated in the commercial sector, orbital sustainment will allow military space forces to replenish consumables and expendables on spacecraft that cannot be recovered back to Earth. Orbital sustainment will also enable spacecraft inspection, anomaly resolution, hardware maintenance, and technology upgrades. Orbital recovery allows for the recovery of personnel or military equipment from the space domain. This includes objects such as reusable space-craft or launch boosters.”^¹

This commitment to advancing satellite servicing, or what the capstone publication refers to as orbital sustainment, shows that the USSF knows its importance to keeping space dominance. There are multiple servicing paradigms that the USSF can consider including human based servicing or robotic based. This paper will review the history of satellite servicing for those unfamiliar with the concept first. This is in order to develop an understanding of its need and where it is at currently. There won’t be any specific servicing paradigms to discuss, but there will be a discussion on the effects it will have on USSF acquisitions—as well as a look at several different generalized logistical paradigms like in-situ resources and large-scale earth-based logistics.

Background
History of On-Orbit Satellite Refueling, Repair, and Upgrading

Figure 1. SolarMax Servicing, 1984^²²

Satellite servicing actually has been a concept since the 1960’s when it became pretty clear that once a satellite was up in orbit, it was impossible to service with the technology at the time. It stayed a concept for academia and space agencies to ponder over for several decades. The first organization to successfully service a satellite on-orbit was NASA. The very first servicing mission was for the SolarMax research satellite in 1984.^² This manned mission, seen in Figure 1, used a space shuttle to obtain the satellite for on-orbit servicing. In ’84, the New York Times summed up the mission as, “a new era of the human enterprise in space.” The New York Times, in the same piece, stated that NASA viewed the mission as, “a critical demonstration of equipment and skills that could have broad future applications for refueling and servicing orbiting craft and for assembling structures such as a manned space station.”^³

The most successful set of servicing missions were completed on the Hubble Space Telescope starting in the 1990s to correct for a spherical aberration in the optical path, and also to update electronics and sensors on the telescope. Like the SolarMax repair, these missions were manned using the space shuttle program. The shuttle would launch with the needed tools and components to service the Hubble, match the Hubble’s orbit, use the robotic arm on the shuttle to grasp the Hubble, and then the crew could service the satellite. After servicing, the Hubble would be released, and the shuttle would return to Earth. This was done five times in total.^⁴ After the fourth servicing, NASA realized the importance of the work done and its usefulness in servicing other satellites in the future. After this realization, all the experience on the Hubble servicing team was transferred into the new Satellite Servicing Capabilities Office.^⁵ This office eventually changed its name and mission several times. In 2020, it was reorganized again into NASA’s Exploration and In-Space Services projects division, also known as NExIS.^⁶

Since the last servicing mission on the Hubble, the focus in satellite servicing has switched to make it more cost effective and take the human element out. The NASA organizations that came before NExIS made strides in automating the demonstrated different procedures in servicing. Following the same steps that the crewed shuttle missions did, NASA has tried to automate navigation and orbit matching, docking, and actual servicing using robotics. There have been more than a dozen technology demonstrators launched to test the automation of these processes. Below is a list of just a few:

US Air Force: Experimental Spacecraft System: included XSS-10, launched in January 2003, and XSS-11, launched in April 2005. Both of which demonstrated autonomous orbit matching.^⁷
Demonstration of Autonomous Rendezvous Technology (DART): a NASA project launched in 2005 that was meant to demonstrate a number of technologies including orbit matching and rendezvousing. DART unfortunately collided with the satellite it was meant to rendezvous with due to a sensor malfunction.^⁸
Orbital Express: A DARPA program, with partnership from the Air Force and NASA, was designed to demonstrate autonomous refueling and servicing. Orbital Express was composed of two satellites that launched together on STP-1 in 2007. NEXTSat was to demonstrate a modular and serviceable design while its partner ASTRO was to demonstrate refueling and on-orbit upgrades. After a successful autonomous rendezvous and docking, ASTRO successfully fueled and swapped out a battery on NEXTSat. The flight computer on ASTRO was also successfully changed. To date, this has been the most successful autonomous space servicing demonstration.^⁹
Robotic Refueling Mission (RRM): a phased program by NASA’s NExIS division to research and demonstrate robotic technologies; not just on-orbit refueling, but other servicing as well. The RRM is being done on-board the international space station (ISS). It especially focuses on satellites not designed to be serviced. Phase 1 completed in 2013 and Phase 2 in 2016. A suite of tools and techniques have been tested over the years.^¹⁰

With the goal of making autonomous satellite servicing a reality, several key technologies have emerged that can not only be applied to servicing but other areas. Such technologies include robotic arms, autonomous satellite navigation, autonomous rendezvousing, and sensor suites that can detect problems with satellites like fuel leaks. All of the previous missions have established a great advantage for the United States to lower the cost of space acquisition and operations but more work is still needed before on-orbit servicing can take place regularly.

Current Efforts

On-orbit satellite servicing has historically been a government funded effort, but like many other space activities over the past several years industry has started to increase their presence in the area. Industry has just as much need to service their satellites as NASA and the USSF does. The first industrial need for satellite servicing came from the telecom industry. Due to the quick pace of technology development, once a telecom satellite is placed in orbit the telecom technology on board quickly becomes irrelevant. This drives the price of these satellites up since the industry is always needing to launch updated satellites. Some industry efforts currently underway include:

Airbus’s O.CUBED SERVICES: This program is focusing on eventually servicing GEO Telecom fleets. There is a vehicle named SpaceTug that attaches to satellites with a booster and re-orbits. There is also a focus on orbit clean-up services that will remove active debris.^¹¹
Astroscale’s ELSA-d: a satellite that will provide a comprehensive set of services for customers including re-orbiting, inspection, and magnetic capture of tumbling satellites. The capture of satellites in weird orientations or tumbling has never been demonstrated before. The Japan based company is expecting to launch ELSA-d in late 2020.^¹²
Northrup Grumman’s (NG) Mission Extension Vehicle (MEV): the most mature satellite servicing company is NG’s subsidiary SpaceLogistics, formally known as Orbital ATK. The MEV program started under Orbital ATK and has reached several stages of success under NG. They are currently working with Intelsat to provide services that include re-orbiting. There is an effort to add a robotic arm capability called the Mission Robotics Vehicle (MRV) which will add additional servicing capabilities to MEV.^¹³

There are a dozen small businesses working this problem as well. One problem in this field is a lack of industry standards and organization. This is the reason why DARPA seeded an organization called the Consortium for Execution of Rendezvous and Servicing Operations (CONFERS). This organization will be industry led with the goal to leverage best practices that have been developed in government and industry. It also aims to generate standards for on-orbit servicing and rendezvous and proximity operations.^¹⁴ This CONFERS is also starting a Global Satellite Servicing Forum to exchange technical information. Along with initializing CONFERS, DARPA is developing their own servicing vehicle based off their previous success with Orbital Express. The Robotic Servicing of Geosynchronous Satellites (RSGS) program has the goal to perform servicing on satellites currently in GEO. Figure 2 shows an artist’s conception of the RSGS. The vision for RSGS is for DARPA to develop a modular toolkit of hardware and software for use on board a privately developed commercial partner’s spacecraft.^¹⁵

Figure 2. Robotic Servicing Vehicle from DARPA's RSGS program.^²³

Other current projects currently on-going in the government include NASA’s OSAM program and the Phase 3 of the RRM on-board the ISS. OSAM or On-Orbit Servicing, Assembly & Manufacturing takes servicing one step further. OSAM’s goal isn’t just to demonstrate refueling or component replacement, but also to set industry standards, and assemble components in space. It’s planned to demonstrate the satellite called RESTORE-L, which is under the OSAM program, by using a robotic arm to grasp and refuel a government satellite, assemble a new communications antenna, and manufacturing a 10-meter beam. NASA also hopes to push industry to adopt OSAM’s robotic grappling and refueling valve features.^¹⁶ The OSAM program is the latest step towards on-going satellite servicing operations. The impact of which could lead to repercussions to both the Space Force’s operations and acquisitions processes.

Discussion
Possible Impacts to Space Force Acquisitions

Space acquisition models currently have evolved from classical hardware acquisitions. They have evolved to meet the heavy upfront test and early costs of satellites. This large focus on the early life cycle of the system stems from the fact that sustainment on satellites in currently impossible. Figure 3 is a comparison of life cycle costs of typical systems and space vehicle systems. The early life cycle focus also forces longer acquisition timelines. A program manager could stay on the same project for an entire career before seeing a successful launch of a system. In fact, in a 2019 report the government accountability office found that budgets of satellite segments usually are higher than original estimates, even sometimes double, and schedules can run over by years.^¹⁷ This has become very clear as the US revamps their space systems to stay ahead of our adversaries. This is one of the arguments those that supported an independent space service made; an independent service could regulate the acquisitions process more and can get control of costs and schedule. This is also an argument for satellite servicing.

Figure 3. Life Cycle Cost Comparisons Between Traditional & Satellite Acquisitions.^²⁴

The servicing of satellites could totally change the current satellite segment acquisition model. First, let’s discuss the impact of mission extension. The possibility of extending the life cycle of a satellite will put more focus on post milestone C, specifically sustainment and disposal. Sustainment of satellites will change all three areas of cost, schedule, and performance of systems and even the acquisition model used. The ability to bring satellites and debris back to Earth also allows for low cost from recycling. Let us discuss the impacts of cost, schedule, and performance:

Cost: In 2009, AFRL did some preliminary research into on-orbit servicing on constellations and its effects on baseline costs.^¹⁸ They split their study into several cases and looked specifically at LEO and GEO orbits. Their results show throughout their cases that using servicing on only one satellite is not useful. Cost effectiveness increased when developing a servicing program for a constellation of satellites though. Each case studied showed that if a constellation had at least two serviceable failures that the servicing program was cost effective because of need to build and launch two replacement satellites. As the USSF starts to embrace a more small-sat, large constellation approach, it seems servicing will become an even more cost-effective mean to keep constellations working. Once more, the results also showed that servicing constellations at GEO are more cost effective than other orbits due to the higher launch costs of getting satellites out to GEO. Figure 4 below shows just one of the simulation results in the report ‘Cost Effectiveness of On-Orbit Servicing.’ The research didn’t consider the possible cost savings of in-situ resource mining and manufacturing which is a part of a specific servicing paradigm. It also didn’t investigate the lower costs in the initial baseline of the constellation from the lower need of reliability being overly important in the design of the constellation.

Figure 4. Results of Case 4 at GEO from Cost Effectiveness of On-Orbit Servicing.^²⁵

Schedule: The ability to sustain spacecraft on-orbit opens up the ability to compress schedules as well. One of the key reasons why satellite acquisitions take so long to get to initial operational capability is because so much design and testing needs to be done to make the system as reliable as possible. This reliability requirement is both a curse and a blessing. It gives space systems a low rate of failure but also extends early life cycle processes out over long periods. Having a lower threshold for reliability is one way of decreasing the schedule to a more manageable timeline.
Performance: Satellite serviceability also opens the door to agile like space acquisitions. An initial operation capability could be designed, tested, and launched. Once in orbit and performing operations other components could be designed, tested, and launch to supplement or add capabilities to the system. This component like system would also have higher serviceability and hence reliability wouldn’t be compromised. The speed to having better performing components like faster computers and better communications would be decades faster than the current status quo.

Logistical Considerations

While the need for serviceability is well understood, and the capability to do it is fast approaching, there are other aspects of it not being given much attention. One of those is the logistics behind servicing. The question has been theorized and some have developed theoretical logistic trains for NASA and industry. This section will look at those trains and theorize a path forward for the USSF.

There are four logistical trains to consider for on-orbit servicing. Those four include in-situ fuel, terrestrial fuel, in-situ resource mining and manufacturing, and terrestrial manufacturing. Table 1 shows the major pros and cons for each.

	Pros	Cons
In-Situ Fuel	Significantly lower costs Ability to sustain a cislunar constellation long term New economic sector worth trillions	Decade away Needs moon base
Terrestrial Fuel	Current infrastructure in place	Costs roughly $4k per kilogram to get to LEO and more for GEO Higher needs on Earth
In-Situ Mining & Manufacturing	Significantly lower costs Ability to sustain a cislunar constellation long term New global economic sector worth trillions	Decades away from mining Need moon base or asteroid for mining Decade away from manufacturing
Terrestrial Manufacturing	Current infrastructure in place	Costs roughly $4k per kilogram to get to LEO and more for GEO

Table 1.

Terrestrial fuel and manufacturing: These are the traditional methods of finding materials on Earth, building and processing on Earth, and launching the fuel or components to an orbit. These trains have been very costly and have historically precluded space travel to wealthy, more developed nations.

In-situ fuel: This method of obtaining fuel involves mining the moon, or another body, for water. Some of this water will be saved for other purposes like human consumption but most will go to a processing center. The center will use electrolysis to separate the water in hydrogen and oxygen which can be used for fuel. Since the moon’s gravity is much weaker than the Earth’s, the cost of moving the fuel off the surface of the moon to a place in orbit is low. This ability will require some sort of moon base, be it automated or manned, and is at least a decade away from reality. After leaving the moon, the fuel will most likely be stored in a fuel depot. These depots could be at several different orbits, or even earth-lunar Lagrange points, depending on needs. Refueling servicing satellites will then be able to acquire the needed fuel at the depot, travel to a satellite that needs the fuel, and transfer it over.^¹⁹

In-situ mining and manufacturing: The process of gathering the mining materials from astronomical bodies and then use those materials for in-situ manufacturing is farther off than any other logistical train. In-situ manufacturing itself though could soon be a reality on the lunar surface and even on-orbit vehicles. This has been heavily researched by NASA and recently industry. Both In-situ mining and manufacturing could generate markets worth trillions of dollars which is why some risk adverse companies have been researching ways to do this. NASA sees this logistical train as a requirement for mankind to explore the solar system which is why they also have been exploring and supporting industry.^²⁰

Recommendation: The USSF should rely heavily on NASA and industry in the logistics of servicing, while at the same time leading the effort to stand up in-situ logistical trains. This is not only the most cost-effective means but has also been a proven means. Before the Falcon 9 rocket, the cost per launch was quadruple of what they are with the Falcon 9 at $95 million per launch. SpaceX says costs can be lowered further to $30 million per launch when all possible reusable components are used.^²¹ The dire need to push launch vehicle reusability was there but wasn’t seen until SpaceX saw it because they themselves couldn’t afford to launch. Left to its devices, the Air Force would have never gotten to reusable lower stages using their own acquisition processes. It could be said though that both NASA and the Air Force supported SpaceX in its endeavor, and then reaped the reward. The need to establish in-situ logistical trains is becoming evident not only for space exploration but because the economic incentive is that of a possible gold rush on steroids. The USSF should advertise this and push for American industry to expand their view to in-situ resource utilization. There should be a large-scale effort by the USSF to organize and share information between industry and NASA. They need to create an environment of innovation and open up industries minds to the possibility.

Impacts to the USSF Mission and Warfighter

What does all of this mean for the warfighter, you might ask? It is true that the biggest impact of satellite servicing will be on USSF acquisitions, but there will be great impact on space operations? Servicing can bring new forms of space domain awareness with its capability to perform not only close up spacecraft inspections, but also the ability for robotic servicing vehicles to grasp and re-orbit other vehicles and debris. It could change space cyber operations by introducing more secure computers to vehicles well before traditional acquisitions could. It will revolutionize orbital warfare by giving space warfighting units the ability to disable adversary satellites without causing more space debris and furthermore collect that satellite for our own use. Finally, satellite serviceability will more smoothly change the systems operators use. Brand new satellites won’t even be branded new as their technology in some form could have been placed in older satellites before their end-of-life. This emerging technology will disrupt how the USSF will do both acquisitions and operations.

Conclusion

Satellite servicing is an important technology for the future of space supremacy. Its history is short but explains the need of this capability. From the ability to refuel and re-orbit spacecraft to on-orbit upgrades and inspection, a servicing satellite can revolutionize space. It will change space acquisitions for the better for by lowering lifecycle costs by billions while prolonging system lives and increasing performance. It will also make rapid space acquisitions a reality and the norm. It could solve many problems with space acquisitions in a time that needs solutions to get a leg up on near peer adversaries. The logistics behind it is complex and requires effort but the rewards of increased space superiority, solar system exploration, lower costs, and possibility of the largest economic market in recent history speak for themselves. The technological advancement made to realizing a satellite servicing vehicle also brings rewards to space operations and warfighting as well with new ways to disrupt adversary systems. Overall satellite servicing is an important emerging technology not only to industry and NASA, but also to the national security.

Captain Joshua Garretson

Captain Joshua Garretson (MS, Air Force Institute of Technology; BS University of Akron) is a developmental engineering officer in the US Space Force. He currently researches advance control systems for laser weapons at AFRL. He has served as a systems engineer in AFLCMC, studied systems for astronomical interferometry, and interests include next-gen space vehicle technology.

This paper was written as part of the SOS Air University Advanced Research (AUAR) elective, Ideas and Weapons section.

Notes

1 “Space Capstone Publication, Spacepower,” Headquarters United States Space Force, June 2020.

2 “On-Orbit Satellite Servicing Study Project report,” National Aeronautics and Space Administration, Goddard Space Flight Center, Goddard Space Flight Center, October 2010.

3 J. N. Wilford, “Space Crew to Attempt Historic Repair Mission (Published 1984),” The New York Times, 8 April 1984.

4 R. Garner, “About the Hubble Space Telescope,” NASA, 27 January 2015, http://www.nasa.gov/.

5 S. DeForest, “How NASA’s Approach to Satellite Repair Revolutionized Space Exploration,” Field Service Digital, 3 April 2019. https://fsd.servicemax.com/.

6 “NASA’s Exploration & In-space Services,” NExIS, https://nexis.gsfc.nasa.gov/.

7 “On-Orbit Satellite Servicing Study Project report.”

8 “On-Orbit Satellite Servicing Study Project report.”

9 “Orbital Express,” DARPA.mil, https://www.darpa.mil/.

10 “NASA Facts, Robotic Refueling Mission,” National Aeronautics and Space Administration, Goddard Space Flight Center, March 2013, [Online]. Available: https://nexis.gsfc.nasa.gov/; “NASA’s Exploration & In-space Services,” NExIS, https://nexis.gsfc.nasa.gov/.

11 “On-Orbit-Services,” Airbus, https://www.airbus.com/.

12 “End of Life (EOL) - Astroscale, Securing Space Sustainability,” Astroscale, https://astroscale.com/.

13 “SpaceLogistics,” Northrop Grumman, https://www.northropgrumman.com/.

14 “About – CONFERS,” https://www.satelliteconfers.org/.

15 “Robotic Servicing of Geosynchronous Satellites,” DARPA.mil, https://www.darpa.mil/.

16 “On-orbit Servicing, Assembly, and Manufacturing,” On-orbit Servicing, Assembly, and Manufacturing, https://nexis.gsfc.nasa.gov/; “On-Orbit Servicing, Assembly & Manufacturing Facts,” National Aeronautics and Space Administration, Goddard Space Flight Center, 2020, [Online]. Available: https://nexis.gsfc.nasa.gov/.

17 C. Chaplain, “Space Acquisitions, DOD Faces Significant Challenges as It Seeks to Address Threats and Accelerate Space Programs,” United States Government Accountability Office, Testimony GAO-19-482T, April 2019. [Online]. Available: https://www.gao.gov/.

18 T. Rexius, “Cost Effectiveness of On-Orbit Servicing,” Air Force Research Laboratory, Technical Paper AFRL-RZ-ED-TP-2009-270, June 2009. [Online]. Available: https://apps.dtic.mil/.

19 “ Commercial Lunar Propellant Architecture: A Collaborative Study of Lunar Propellant Production,” REACH, vol. 13, p. 100026, March 2019, doi: 10.1016/j.reach.2019.100026 ; “Want To Be A Trillionaire? Try Space Mining,” 19 October 2019. https://www.bloomberg.com/.

20 “Want To Be A Trillionaire? Try Space Mining.”

21 M. Sheetz, “Elon Musk touts low cost to insure SpaceX rockets as edge over competitors,” CNBC, 16 April 2020. https://www.cnbc.com/.

22 “NASA/Marshall Solar Physics,” https://solarscience.msfc.nasa.gov/.

23 “On-orbit Servicing, Assembly, and Manufacturing.”

24 “Why Is Space Acquisition Different,” DAU, December 2008, [Online]. Available: https://www.dau.edu/.

25 T. Rexius, “Cost Effectiveness of On-Orbit Servicing.”

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