The NASA Ames Research Center has developed a unique approach that permits any fixed or moving platform (e.g., aircraft, ships, tanks, automobiles, etc.) to accurately point to and open loop-track, an optical or electromagnetic device at a stationary or moving target without feedback from the target.
The Inertial Pointing and Positioning System (a.k.a. Blind Pointer) will continuously update for finite duration with an accuracy that corresponds closely to closed-loop tracking systems. The invention permits blind pointing of any celestial or terrestrial target with known coordinate positions. For example, ships at sea can point and open-loop track antennae at satellites for television reception, and aircraft can point sensors at terrestrial targets with known coordinates. Furthermore, this technology offers a cost-effective alternative to complex three-dimensional position encoders by offering a simplified inertial solution.
The Blind Pointer currently employs equipment commercially available from several sources, assembled in a unique setup, coupled with an existing Inertial Navigation System (INS), Global Positioning System (GPS) and unique computer software to coordinate the system's functions. The Blind Pointer consists of a second-generation, laser-gyro based INS integrated with a GPS receiver in a relatively small package. Traditionally, for example, an airborne telescope would be positioned by strapping down an INS to the aircraft and pointing the telescope relative to the aircraft's known angular orientation using encoders. Instead, the Blind Pointer straps the INS to the telescope itself. In effect, the telescope flies in inertial space, independent of the airframe. This method simplifies coordinate transformations and eliminates position encoder implementation and accuracy problems. Additionally, the INS gyros can double as the telescope's (or other platform's) stabilization instrument while providing the measurements for additional kinematics command generation.
Identification of Components and Mode of Operation
The Blind Pointer consists of two major components: an INS and a computer. The inertial measurement system-such as a Litton LN-100G INS-mounts directly on the telescope, rather than a remote location on the airframe. The INS monitors telescope terrestrial position and geodetic attitude and points the telescope to stellar objects with known astronomical coordinates-Right Ascension (RA) and Declination (DEC). This is accomplished with a PC-compatible computer interfaced to an INS with GPS-corrected position, telescope attitude, Universal Time data, and a series of transformation equations with control logic developed and converted into software to process the INS outputs into telescope command angles in the navigation coordinate frame.
During normal operation mode, an operator inputs the RA and DEC of a celestial target into the Blind Pointer computer. The Blind Pointer computes the aircraft heading and issues the new heading command to the autopilot. After the aircraft flight path is corrected to the desired heading, the Blind Pointer commands the telescope to the proper elevation, cross-elevation, and line of sight (LOS) angles, resulting in the designated celestial target appearing in the telescope's focal plane field of view for stellar object acquisition and track.
History
The Blind Pointer was developed for the Stratospheric Observatory For Infrared Asronomy (SOFIA), which houses a telescope aboard a Boeing 747. Its purpose is to accurately point to and open-loop track celestial targets without visual or optical feedback. The Blind Pointer accomplishes this task by employing an INS updated by the GPS as the sensor measurement system. The measurements are combined with the coordinate transformation equations and control-logic algorithms under computer control to form the telescope blind pointer commands. Furthermore, it computes an aircraft heading for the autopilot, generating flight paths for celestial target acquisitions. Modifications can be made to adapt the Blind Pointer to other applications as well.
The patent (#5,809,457) for the Blind Pointer was issued to NASA on September 15, 1998.
Points of Contact
The Inertial Pointing and Positioning System was developed by Robert Yee at the NASA Ames Research Center. He can be contacted through the following methods:
Robert Yee
Blind Pointer Project Leader
Mail Stop 244-30
NASA Ames Research Center
Moffett Field, CA 94035-1000
Phone: (650) 604-4122
Fax: (650) 604-1094
Email: ryee@mail.arc.nasa.gov
Phil Herlth is the Technology Commercialization Manager contact at Ames Research Center for the Blind Pointer. He can be contacted through the following methods:
Phil Herlth
Commercial Technology Office
NASA Ames Research Center
Mail Stop 202A-3
NASA Ames Research Center
Moffett Field, CA 94035-1000
Fax: (650) 604-1592
Email: pherlth@mail.arc.nasa.gov
Resources Available
The following documents have been produced regarding the Blind Pointer:
The method employed by the Kuiper Airborne Observatory (KAO) relies on a dead reckoning (no GPS correction) INS strapped to the airframe, rather than the telescope. Therefore, pointing to a designated celestial target requires computing the proper telescope attitude relative to the airframe. The KAO algorithms are based on the navigation triangle rather than celestial coordinate transformation equations driven with GPS time and position, precise INS attitude, and uncorrupted with airframe errors.
Benefits of the Blind Pointer
The Blind Pointer is different from previous systems in its field since it incorporates the mounting of an INS onto a telescope, rather than the aircraft or moving platform. In addition, it uses GPS-corrected time, position, and attitude information to ensure greater accuracy. Furthermore, the celestial coordinate transformation equations and control-logic algorithms developed for the Blind Pointer eliminates costly position encoder implementation and accuracy problems.
Potential Commercial Uses
Potential Industries