A novel autonomous and portable Celestial Inertial Navigation System (C-INS) is proposed for unmanned surface vessels (USVs). The C-INS is capable of developing and maintaining accurate and continuously updated positional awareness on the Earth's surface without the use of GPS. It seamlessly fuses robotic guided ultra-precise astro-imaging with Earth inertial sensing capabilities to achieve Assured Position, Navigation, and Time (APNT). The C-INS has a mobile observatory that integrates: 1) a Robotic Gimbal Machine (RGM) guided astro-imaging unit that has a full range of freedom to point a telephoto imaging payload to any targeted azimuth and altitude direction with a ~0.01 arcsec angular resolution. The RGM is agile, versatile and programable, providing advanced imaging capabilities for precise celestial and vision navigation; and 2) a RGM North and Latitude Sensing Unit (NLSU) that operates a set of ultra-sensitive Fiber Optic Gyros (FOGs) to measure the Earths rotation. For North-finding, the RGM rotates a FOG to align the FOGs sensing axis with the northing meridian plane of the horizontal coordinate system of the observatory. Similarly, for Latitude determination, the RGM actuates a FOG to recognize its positioning to the Earths center. The high-performance FOGs combined with the accurate pointing knowledge provided by the RGM gives the NLSU azimuth and latitude accuracy of sub 1 arcsecond accuracy for the USV, as well as the northing and easting speeds with a 1Hz data rate. Whenever a star becomes invisible because of time or weather, CCU automatically performs dead reckoning with the NLSU to maintain the position determination. Because the four intrinsic PNT parameters that NLSU senses have extremely low drift, without random walk, the dead reckoning is capable of maintaining the position fix within a FOM = 2 accuracy level for up to 72 hours. The C-INS allows USVs to navigate and understand their precise location on the Earth in a fully passive manner without electromagnetic emissions or needing to receive external radar, AIS, or GNSS transmissions. The absolute positioning accuracy that the system can achieve is a direct result of NGIT's R&D and innovation in aerial imaging and mapping. Over the past 15 years, NGITs principals have provided NASA and the DoD ultra-precise gimballed aerial hyperspectral, multispectral, thermal and optical mapping systems.
Benefit: As part of its 30 year plan, the Navy is moving to a fleet architecture based on the Distributed Maritime Operations (DMO), which pairs greater numbers of smaller ships with fewer large manned ships. The smaller ships, many of which will be unmanned surface vessels (USVs), enable the fleet to be adaptive to new threats and situations, sustain damage with less human cost, and better adapt to ongoing changes and needs. Without crewed backup, autonomous ships are much more reliant on their onboard sensing capabilities. The ships need to understand where they are, not only for their own safety in navigating charted obstacles and international boundaries, but also so that they can communicate warnings and detected threats with each other with the precision necessary for the fleet to present a unified response. The key technology underlying the coordination of the distributed fleet is GPS, which is vulnerable to jamming and spoofing. NGITs system ensures that autonomous ships understand exactly where they are, even in the face of GPS degradation or unavailability. The need for a ships location service to perform with 100% uptime and reliability spans not just USVs, but also manned ships. Navy sailors frequently have to perform under pressure for long periods of time with little sleep, performing duties that encompass not only navigation, but also upkeep on the weapons systems as well as threat detection and monitoring. NGITs system gives the ships captain the knowledge the ships operation is resilient to the jamming, spoofing or malfunctioning of GPS, and that overworked sailors will not have to be dedicated to performing backup navigation such as sextant use. Finally, there may be Special Forces units who need to operate under the utmost stealth, and they may need to jam RF signals including GPS in order to disrupt the communications and situational awareness of an adversary as they make an approach. NGITs system allows them to maintain precise location awareness and direction while denying GPS to others in the same area. The commercial shipping industry carries 90% of the worlds trade, yet operates with margins as low as one percent. The industry is coping with this in a few ways: 1) Charting fuel efficient routes via GPS, 2) Lowering the manned count aboard ships, and 3) developing autonomous and semi-autonomous ships. All of these require the ability for ships to trust their location information, which is currently reliant on GPS. There have been a number of incidents the past few years where jamming and spoofing have affected ships, including incidents around Russia, North Korea and the Suez Canal. Due to the advent of software-defined radios, jamming and spoofing can be performed for as lows as hundreds of dollars. For the shipping industry to maintain operational efficiency and not have to resort to traditional navigation, ships need a backup system to indicate when jamming is occurring and provide an alternate location fix.
Keywords: Observatory, Observatory, gimbals, Autonomous Instrument, Maritime Star Tracker, Inertial navigation, Robotics, celestial navigation
