On-orbit satellite servicing, considered as a niche technology, has a vast array of benefits and challenges. It is fast coming up as a transformative and disruptive capability that provides operators with unprecedented flexibility and resilience for their space assets.
- The iconic Landsat 5, which successfully set the new Guinness World Records title for ‘Longest-operating earth observation satellite’, outlived its three-year design life, to deliver high-quality, global data of Earth’s land surface for 28 years and 10 months, before it was decommissioned in 2013. Imagine it lasting forever!
- ISRO launched IRNSS-1A satellite in 2013, which was the first in the seven-satellite constellation to provide regional navigation services to India and its neighboring countries. In 2016, ISRO had to discard the satellite altogether and launch a replacement when all the three rubidium atomic clocks onboard IRNSS-1A failed. Imagine a robotic arm changing the clocks instead!
Imagine dumping your car when it runs out of fuel or develops a snag on the highway. Imagine throwing away your television set if a fuse goes off. Imagine abandoning your house if the pipelines are leaking. We don’t do any of that, right? We call relevant service providers to fix the problems.
If everything can be refurbished and serviced, why not satellites?
Of course, they can be. Here’s how. On-orbit satellite servicing entails servicing, refueling, repairing, and even upgrading satellites that are in orbit. The major components here include an advanced spacecraft with a specialized toolkit and robotic arms for capturing, interacting with, and manipulating a client, software for managing semi-autonomous servicing tasks, and an advanced sensor suite for careful rendezvous and proximity operations.
Though still a niche technology, on-orbit servicing is fast coming up as a transformative and disruptive capability that provides operators with unprecedented flexibility and resilience for their space assets.
The capability is the gateway to an entirely new infrastructure for earth observation, communications, space exploration, space travel, and habitats, and integral part to build a better world.
The application area of on-orbit satellite servicing is very broad where each application area has its own importance based on scientific, economic, strategic, and societal benefits. Repair and maintenance of the satellites in space keep a unique and valuable asset operational, essentially improving it beyond its design lifetime or the reliability of its subsystems. It improves overall mission robustness and offers a unique capability to improve risk posture through post-launch operations.
“On-orbit satellite servicing is an exciting new area and a great technological transformation in the space sector. The technology will not just impact geospatial domain but can be used for all satellites. It is a great capability that will elongate the life of some very expensive satellites,” says Robert Zitz, Senior Vice President & Chief Strategy Officer, SSL, a Maxar Group Company.
SSL is a pioneer in satellite servicing, and its sister company Canada-based MDA (then known as Spar Aerospace) built the Canadarm for the Canadian Space Agency way back in 1980s. Today, Canadarm2 plays a key role in station assembly and maintenance on the International Space Station. Launched to the ISS in 2001, the Mobile Servicing System, Canadarm’s technical name, moves equipment and supplies around the station, supports astronauts working in space, and services instruments and other payloads attached to the space station and is used for external maintenance.
When did it all begin?
The first in the list is Skylab. Launched in the year 1973, Skylab was NASA’s first space station and also the first human satellite servicing endeavor. In the mission, the parasol was successfully deployed that restored an acceptable thermal configuration saving the mission.
A similar operation was carried in the year 1984 to extend the life of Solar Maximum Mission. Solar Maximum Mission was launched on February 14, 1980. After nine months of its launch, it was observed that the satellite’s attitude control system had stopped working. On April 10, 1984, the satellite was captured by the Shuttle’s RMS arm, and was sent back to orbit when the problem was solved by astronauts.
The most eminent among on-orbit satellite servicing is the famous Hubble Space Telescope. Launched in the year 1990, HST was developed by NASA in collaboration with European Space Agency. After the launch, some optical flaws were observed in Hubble’s primary mirror. Along with this, Hubble also encountered thermally tempted “jitter” or shaking from its solar arrays during orbital sunrise and sunset. Both these glitches were resulting in blurred images. To fix the problem, NASA initiated a striving program to restore the capabilities through astronaut servicing. In this servicing mission, Corrective Optics Space Telescope Axial Replacement (COSTAR) was installed to restore the observatory by replacing the High-Speed Photometer instrument to correct the faulty vision. In 20 years of Hubble Space Telescope mission, many such unexpected issues arose which were more than just changing hardware designed to be serviced. Each of these repairs required accessing interfaces that were not designed for servicing but were fully successful accomplished.
Today, thanks to technology advancements and miniaturization, on-orbit repair and refurbishment have reached a point where it can be employed on a varied number of satellite systems even without human presence, as against early days when astronauts were required to aid the servicing station in space. For instance, when the Solar Maximum Mission developed some problems, mission specialists George Nelson and James Van Hoften had make a space travel to repair it.
The first successful end-to-end robotic satellite servicing was performed by Defense Advanced Research Projects Agency (DARPA) in 2007 when two systems — Autonomous Space Transport Robotic Operations (ASTRO) vehicle and a prototype modular NEXT-generation serviceable Satellite (NEXTSat) — were launched. ASTRO and NEXTSat were designed keeping on-orbit servicing in mind.
Till date, the International Space Station (ISS) is unarguably the perfect example on-orbit robotic satellite servicing, with robots playing a significant part in the space station’s construction, maintenance and operations.
Why adopt the technology?
On-orbit satellite servicing leaves little room for satellite failures. The idea facilitates cheaper and faster development of satellites and enables repair missions which extend the life expectancy of the spacecraft by replacing damaged blocks or those run out of fuel. Old satellites can even be refitted for new missions that help to reduce space debris and the cost of launching new systems.
”The vision for on-orbit servicing and assembly is to create a robust and resilient space ecosystem that drives humanity toward a new era of space exploration, ultimately lowering the cost of access to space, and helping to build a better world,” says Richard White, President, SSL Government Systems. The technologies resulting from the development of this capability are critically important to accelerating innovation for the NewSpace economy, enhancing national security, bolstering economy, and enabling next-generation space missions, he adds.
The tools and methodologies developed to enable these successes apply equally well to a broad range of customer satellites. In the near future, the benefits of on-orbit satellite servicing will become increasingly imperative as the longings in space increase and the price and achievability of major projects become commensurately more challenging. On-orbit satellite servicing validates how to successfully use nominal mission planning, preplanning for contingencies, in-situ contingency assessment, and detailed simulation tools to help ensure success. On-orbit satellite repair mechanism will also decrease space debris, and as Dr Peter Swan, President of International Space Elevator Consortium, says, will have a remarkable business growth in the GEO orbit region.
How the technology works?
For on orbit-servicing, a service spacecraft is built with robotic arms. These arms are just like human arms, and in case of a satellite developing a snag, the servicing spacecraft is made to approach it, grab it, pull it close, and repair or exchange the faulty part with a toolkit it is carrying. If a satellite runs out of the fuel, similar technology is used to refuel it.
“The actual servicing process changes depending on the design, orbit, and needs of the client spacecraft, but generally include rendezvous and gentle capture of the client, completion of servicing tasks using the servicer’s robotic arms and toolkit, and then release of the client within a few days,” explains White. The client continues to operate during most on-orbit servicing procedures.
An important question that comes up here — can all satellites be serviced on orbit or do they need to be assembled in a specific way? Dr Swan feels it will be difficult to replace or refuel currently-existing satellites that were not built specifically for on-orbit servicing. “It is a very difficult task as all those attributes will have to be designed in and built,” he adds.
However, SSL is now developing a technology which can service every satellite in the orbit. “Servicer designed by SSL will be compatible with most government and commercial spacecraft that are currently in orbit, even those not designed to be serviced in space,” emphasizes White.
That being said, SSL envisions some of the future satellites to be heading in the direction of standardized and modular architectures, with external plug-in interfaces. This would facilitate both planned and unplanned upgrades, modifications and repairs, for changing missions and technology updates.
In the near future, many government and private missions are gearing up to fully demonstrate these technologies in orbit. NASA is coming up with Restore-L as one of its kind. Zitz reveals the US space agency has signed a contract with SSL to build Restore-L which will refuel the aging Landsat 7 remote sensing satellite launched back in the year 1999.
Orbital ATK, the commercial spaceflight provider is also in the game but with a marginally different approach. The Robotic Servicing System designed by the company is Mission Extension Vehicle (MEV). MEV will dock a satellite and will also provide attitude control, station keeping and end-of-life disposal.
What are the challenges?
Every technology comes with a challenge and so does on-orbit satellite servicing. Since satellite servicing entails few new technologies, the key challenge lies in integrating communication system with regard to distance increase between the satellite repair system and ground station. In such a case, it becomes tough to locate and then rendezvous dock spacecraft that has to be serviced. The path to this goal requires a strong system engineering approach to combine the available technologies, tools, and procedures to overcome which brings together some economic challenge. Maintenance or upgrade without any technical glitch means launching a new satellite to replace something that may have a fully functional set of subsystems which increases their cost. The real economic challenge lies in determining the value of servicing like comparing the cost of a servicing mission to the cost of replacing the failed satellite as well as the potential returns from the serviced satellite.
The space segment is expanding at a fast pace. Every day numerous satellites are being shot in the space, some of them are destined for long distance and due to any glitch abandoning those satellites is a huge loss. Retiring satellites because of failure also create a lot of space junk. On-orbit satellite servicing comes as a magic solution to these issues, and could go onto become the base of future economic development of space, delivering increased benefits from space to the world.