Short for Laser Imaging Detection and Ranging, LIDAR is used for a variety of mapping, distance and speed measuring tasks. It is a key feature in unmanned vehicles, like the SpaceX Dragon spacecraft. SpaceX and NASA worked with Advanced Scientific Concepts (ASC) to design DragonEye, the 3D Flash LIDAR Space Camera developed for the Dragon.
While a DragonEye LIDAR sounds like a subplot to a James Bond movie, it is what the Dragon spacecraft uses to approach and position itself to dock with the International Space Station. Laser precision comes in handy when trying to attach the 1.3-meter hatch of the Dragon to the football-field-sized space station which travels at an astounding speed of 4.71 miles per second. Once the Dragon capsule passes the R-Bar, it has to preform a series of staggered maneuvers to gradually approach the ISS Keep out Zone, a 200-meter border around the ISS, and get ready for the Canada Arm to grab it at 10-meters out.
So how this space camera work? It’s a scanning digital camera, of sorts, that generates a 3D diagram or map. Similar to a digital camera it has an image sensor that measures in pixels, in this case 128 x 128, and can capture up to 10 frames per second. Each pixel on the array is independently triggered which allows for 16,324 points of data to be collected. The image sensor is powered by a 3D engine so these data points generate a point cloud (looks like a super detailed 3D connect-the-dots) or a realtime video stream. The scanner works by sending a laser pulse through a beam spreader toward the object it is scanning. The light from the laser acts as a camera flash by lighting the object for the camera lens and helps focus the image of the object onto the pixel array. A single laser pulse is sent for every frame captured so if viewing video from the DragonEye, 10 laser pulses would be fired every second to capture video. The laser also measures distance from an object by recording the time it takes the beam to bounce back to the camera from the object.
All of that capability is contained in a space about half the size of a shoe box. And speaking of laser fast, the DragonEye was built, from concept to final hardware, in ten months. The DragonEye, the first 3D Flash LIDAR camera in space, was first flown on the Space Shuttle Endeavor in July 2009.
It was put to the test, along with SpaceX mission control, during the NASA COTS 2/3 Mission in May 2012. DragonEye was receiving different data than the onboard thermal imager, the other device used by Dragon’s guidance systems. It was discovered that the LIDAR was picking up stray reflections from the Japanese Kibo lab on ISS. With Dragon in a holding pattern, SpaceX uploaded new software that narrowed the view of the pixel array allowing Dragon to successfully position itself to be grappled by the Canada arm and be berthed to the ISS.
What about the name? It is assumed SpaceX was able to choose the name DragonEye since the device was designed for them but ASC also has a product named TigerEye, which is a portable LIDAR.
This is the third article in a series building up to the next SpaceX CRS mission currently scheduled for March 1, 2013 at 10:10 am EST.