Optical Physics Company
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Navigation Application
Current airborne platforms rely on double or triple redundant INS/GPS (inertial navigation system / global positioning system) devices for navigation as well as tracking and targeting.
If GPS becomes unavailable for any reason, the INS component of INS/GPS systems accumulates errors which degrade the accuracy of the system output. The longer the GPS signals are not available, the worse the error gets.
Celestial navigation is a much needed back-up for current navigation and targeting instruments that rely heavily on GPS.
Several platforms that are candidates for this technology are:
• Fighter aircraft
• Ground attack aircraft
• Next generation bomber
• Tier II and Tier II+ UAVs
• Airborne early warning and control aircraft
• ICBMs
• Cruise missiles
• Designators for laser guided weapons
Optical Celestial Navigation System
Celestial navigation is a centuries-old method whereby angles between objects in the sky (celestial objects) and the horizon are used to locate one's position on the globe. Celestial navigation in the past required a sextant, an almanac, and an accurate clock.
Optical Physics Company (OPC) has been building a modern day optical celestial navigation system (OCNS) using OPC’s interferometric star tracker which is far more accurate and reliable than a sextant. OCNS is a much needed back-up for current navigation and targeting instruments that rely heavily on GPS.
OPC's OCNS uses two or more star trackers to measure the star positions. An accurate horizon sensor is included which enables a complete geolocation capability without any a priori information.
The main advantages of the OCNS are itemized below:
•OCNS can be used independently of ground aids and GPS.
•OCNS has global coverage – land and sea.
•OCNS cannot be jammed.
•OCNS is passive and does not give off any signals that could be
detected by an enemy.
The OCNS data processing flow is shown at the top level below.
As shown, star trackers in the OCNS plus a precision clock allow accurate determination of all six degrees of freedom of the aircraft: Latitude, longitude, altitude as well as roll, pitch and heading.
The star field can be matched to a star catalog to find the celestial attitude (3-axis attitude in inertial space) of the aircraft. This 3-axis attitude is then combined with the horizon plane position and an accurate time measurement. Again, one can reference star catalog data and formulas for Earth orientation to pinpoint the exact latitude and longitude of the Earth coordinates directly below the aircraft.
One drawback of the technology is its reliance on an observable star field. OCNS operates best above weather and clouds although partial obscuration is acceptable. OCNS performance declines with decreasing altitude.
A field testable prototype has been designed. The prototype will be tested first in the laboratory environment. A field test is planned in preparation for transition. The field test is expected to involve mountain top testing at all hours of the day.