Getting more out of our satellites
As deputy program manager of NASA’s Satellite Servicing Capabilities Office, Benjamin Reed leads a team working to create an era of re-use, assembly, and servicing to get more out of our satellites, and at ESC Boston on Thursday he laid out the plan to make that happen.
The cost of launching something into space is a major factor in the way satellites are designed. The median satellite costs about $250 million to build and almost half that to launch, so each one is carefully designed to be very reliable and takes years to build. That also comes at a cost.
“Every satellite is technologically obsolete the day it launches,” said Reed. “The paradigm of getting into space drives how we build satellites.”
The Hubble Space Telescope, launched April 24, 1990, is unique because it’s the only satellite that was designed to be serviced. In 1993, astronauts were able to repair a mirror and install new instruments.
“We used servicing as a force multiplier to get more value out of that initial launch,” said Reed.
The Hubble service success led to the creation of Reed’s team with a mission to design robots to service other satellites. They’re now working on technology to extend life, upgrade, and assemble satellites in space.
“The coup de grâce technology that we are looking for is the ability to assemble a satellite, an observatory large enough to find life on another planet,” said Reed.
The Restore-L servicer is the product of the SSCO vision, and it is set to launch in 2019 on a mission to service NASA’s Landsat 7 earth observation satellite.
“[Landsat] 7 is running out of fuel and may not last until Landsat 9 is launched, so we are going to use that as our candidate for this first servicing mission,” said Reed.
Artist's concept of Restore-L approaching Landsat 7. Source: NASA
The mission has five main technologies: relative navigation system, servicing avionics, robot arm and software, tool drive system and tools, and propellant transport systems. It will also have a unique set of challenges including tracking down a satellite in space going 16,500 mph and maneuvering the servicer to rendezvous with it.
“The autonomous rendezvous portion is incredibly difficult,” said Reed. “We need to match rates with it in three degrees of freedom, but we need to match its orientation in three degrees of freedom, so it’s a six degree of freedom problem.”
The next hurdle will be the autonomous grasping part, which will use a robotic arm with seven degrees of freedom to grab the satellite. Because the satellite wasn’t designed for service, there isn’t an obvious part of it to grab as it’s mostly covered in protective blankets and antennas. Then the refueling part involves cutting blankets and wires and removing caps robotically from the ground.
“That’s actually the easy part of it is the refueling,” said Reed. “Still hard, but relative to the first two, it’s not what’s making me lose my hair.”
The rendezvous system and robotic arm rely on SpaceCube, a cross-cutting, in-flight reconfigurable Virtex-5-based hybrid computing environment. There is also a camera positioning system that will provide video from the servicer.
“The astronaut telling us what they saw was really unbelievably valuable and impossible to replace with a robot, but we still need video to see what’s happening,” said Reed.
Testing and development for the mission is being done on the ground and on the International Space Station, where there is a robotic arm the team can use.
“We simply launch the tools and some other small things and practice on the Space Station for pennies on a dollar of what it would cost to do the work on a free-flying mission,” said Reed.
In August, NASA will launch Raven to autonomously track all the visiting vehicles coming from and going to the Space Station to demonstrate the real-time, relative navigation technology that Restore-L will require.
Beyond satellites, human exploration missions could be another area where servicing and robots can be of help.
“I have no idea what’s going to break on that journey to Mars, but something will,” said Reed. “You can’t launch enough stuff to just fly spares of everything, so you fly the ability to repair and replace, and instead of sending the astronauts outdoors every time something goes afoul to do a spacewalk to repair it, wouldn’t it be great if we could keep them inside where they’re safe and have the robot outside do the repair?”