Eyes on Autonomous Navigation

The farther NASA reaches out into the solar system and beyond, the more missions will need to function autonomously. Critical maneuvers require immediate onboard responses, and for smaller or more distant missions, communications bandwidth to Earth is stretched thin.

The Goddard-developed autonomous Navigation Guidance and Control (autoNGC) software system provides a fully autonomous framework for missions of all sizes, said Cheryl Gramling, Goddard’s mission engineering technology lead. Over the past year, investigators gave autoNGC an eye-opening infusion of optical navigation enhancements to improve autonomy for a variety of mission profiles.

“We are committed to performing missions autonomously when it comes to navigation, guidance and control,” Gramling said. “In optical navigation, for instance, autonomy means you don’t have to send images back to Earth for navigation processing, allowing communications bandwidth to be reserved for science products. Images are some of the highest-density data, and these spacecraft will be taking a lot of images for OpNav.”

Goddard innovators are currently working on multiple ways to improve or expand autonomy in space missions: including celestial OpNav capability to track moons, planets, and other bodies against background stars (See Page 9) and a panoramic navigation feature that makes sense of the Moon’s rocky horizon (Page 6), among other functions. Goddard’s Internal Research and Development, or IRAD, funding either enabled many of these technologies, or played a role in their early development.

The OSIRIS-REx spacecraft navigated to take a sample of asteroid Bennu’s surface autonomously using an onboard image software known as Natural Feature Tracking (NFT) – a form of optical navigation. NFT guides the spacecraft by comparing an onboard image catalog with real-time navigation images taken during descent, orienting the spacecraft by specific landmarks on Bennu. This navigation technique allows the spacecraft to accurately target small sites while dodging potential hazards.

At its heart, autoNGC works in the core Flight Software (cFS) environment, a standardized software solution for spacecraft operations designed to save each mission the cost and labor of reinventing their operating system. The autoNGC system incorporates a wide variety of cFS-compatible navigation hardware and technology, from measuring velocity through Doppler shifts in communications signals or onboard inertial sensors, to radar, lidar, or optical navigation using data from a variety of cameras. It could even use X-ray pulsar navigation – a concept developed out of the Station Explorer for X-ray Timing and Navigation Technology (SEXTANT) mission – to navigate deep space by tracking millisecond pulsars.

“We have a lot of different sensor compliments we can fuse together for the navigation solution,” Gramling said, not to mention guidance and control functions such as autonomous trajectory planning and closed-loop control systems.

“It also has different modes it can operate in depending on the mission phase and distance to the target,” she added. “As you get closer to your target, you can tune the system to improve the solution accuracy from better-resolution data: such as from a point cloud of lidar data returned on approach to an asteroid.”

The highlights in this issue of CuttingEdge reveal only the tip of the iceberg of opnav applications. Other ongoing adaptations being developed within the same cFS and autoNGC system architecture include: efforts to improve 3D imaging by lidar for steering, navigation, and hazard avoidance; developing an active wavelength scanning lidar for the Concurrent Artificially-intelligent Spectrometry and Adaptive Lidar System (CASALS) science lidar technology; improving optical navigation techniques

for future small-body sampling missions; improving combined optical and lidar navigation solutions for lunar landers; developing and testing a Space Qualified Rover Lidar (SQRLi) for use on planetary missions similar to the Mars Perseverance rover, and investigating how autoNGC could benefit future distributed space missions.

Scalability, adaptability, and a universal operating system for spacecraft make the combination of cFS, autoNGC, and optical navigation a powerful constellation to guide future deep space and planetary missions.