A flash-lidar sensor tested at the space station may guide Orion to noncooperative targets
Astronauts on the space shuttle Endeavour's final flight tested an optical navigation device that may help the Orion capsule make its first approach to a target in space, whether it is the International Space Station (ISS), an asteroid or another celestial body.
In the Sensor Test for Orion Relative Navigation Risk Mitigation (Storrm)maneuver last May 30, STS-134 Commander Mark Kelly flew back toward the ISS after undocking, following an approach like the one that Orion would use if it ever needs to dock with the station. Tucked into the payload bay was an advanced flash lidar that illuminated the looming station 30 times a second with an eye-safe burst of laser light. The lidar was part of a Vision Navigation Sensor (VNS) that resolved features on the station at ranges of 5.7 km (3.5 mi.) down to 7 meters (23 ft.) from the reflected laser light, and provide data that can be used to guide Orion or another spacecraft toward a target.
“It basically provides you a 3-D image of the target, so you'll see, for example, the particulars on the actual docking mechanism itself on station,” says Howard Hu, manager of Orion system performance and analysis at. “It's not like a picture, but it gives you a 3-D image, and it's fantastic in how it can replicate, because it gives you that surface differentiation.”
Storrm was conceived and developed under the old Constellation program, when Orion's first flights were to be to the space station. With the crew-transport role for the ISS shifted to commercial vehicles, and Orion's managers aiming at targets beyond low Earth orbit, the flash-lidar approach remains relevant because the target does not need to be rigged with special reflectors or be cooperative in other ways for the system to work.
Instead, the VNS generates a sort of 3-D image of a target for its algorithms to digest, based on the varying strengths of the reflections returning from different points on it. That means it can work with pretty much anything, whether manmade or natural.
“We're looking at hazard avoidance for lunar landing,” says Hu. “If you want to avoid a particular bad spot as you get closer on the surface of the Moon, the lander can flash that lidar, and it gives you an image, and it can discern big boulders, big craters, things like that, and that allows you to steer yourself kind of like a target vehicle, to the surface and land safely.”
For Orion itself, that could mean an asteroid. President Barack Obama has set a goal of reaching an unspecified near-Earth asteroid with Orion by 2025, and ongoing work with the Storrm package at's Space Operations Simulation Center is aimed in part at that potential mission. There the sensor is “flown” on a robotic platform toward mockups of a planetary surface, with craters and boulders, as well as toward an ISS docking port (see photo).
Hu's team continues to analyze the 500 gigabytes of data generated by the Storrm test, which also “shadowed” Endeavour's navigation system as it flew a standard shuttle approach to the ISS at the beginning of its mission. That work will not be finished until the summer, more than a year after the data were generated, because of the need to pace Orion development in line with tight budgets.
“It'll be phased to when we need to be rendezvous-and-docking with something,” says Mark Geyer,'s Orion program manager. “The great thing about that lidar system and why we picked it so many years ago [is that] it can also be used for landing, for determining landing clearances and stuff.”
In an operational system, the software that Johnson Space Center is running on the ground will be included in the sensor package in space, generating navigation solutions on board an Orion or any other spacecraft using it.
“We're fleshing it out,” says Geyer. “It actually feeds forward to many exploration plans. It could be used on a lander; it could be used on other things, too.”
While the lander application is in the future,is already developing a common docking mechanism for Orion and any commercial vehicles that need it, working with the international docking standard published by the ISS partnership in 2010.
The new system would combine elements of NASA's electromechanical Low Impact Docking System (LIDS) and Russia's Androgynous Peripheral Attach System (APAS), with standard diameters and docking functions. The idea is to have a standard docking interface, including the “capture envelope” that governs rate of approach and the force needed to make a connection.
“We're building to the standard that we put out, and we're seeing if we missed anything in the standard,” says William Gerstenmaier, associate administrator for human exploration and operations. “It's not a set of build-to requirements. It's not a specification in the typical way we specify hardware. It's like a USB interface. It says, 'here's where the pins are; here's what kind of signals can go across those pins,' but we don't specify much more than that.”
Plans call for a flight test of the system before the commercial crew vehicles begin flying to the ISS in 2017. The system could also be used on Orion, which retains its role as a backup station crew transport in case the commercial companies do not deliver. Gerstenmaier says NASA could either provide docking mechanisms like the one on Orion as government-furnished equipment to private companies that need them, or let the companies build their own to the international standards.