Ketao Liu

US Patent:

6339734, Jan 15, 2002

Filed:

Feb 22, 2000

Appl. No.:

09/510136

Inventors:

Ketao Liu - Cerritos CA
David S. Uetrecht - Palos Verdes CA

Assignee:

Hughes Electronics Corporation - El Segundo CA

International Classification:

G06F 1700

US Classification:

701 13, 244164

Abstract:

A method, apparatus, article of manufacture, and a memory structure for compensating for instrument induced spacecraft jitter is disclosed. The apparatus comprises a spacecraft control processor for producing an actuator command signal, a signal generator, for producing a cancellation signal having at least one harmonic having a frequency and an amplitude substantially equal to that of a disturbance harmonic interacting with a spacecraft structural resonance and a phase substantially out of phase with the disturbance harmonic interacting with the spacecraft structural resonance, and at least one spacecraft control actuator, communicatively coupled to the spacecraft control processor and the signal generator for inducing satellite motion according to the actuator command signal and the cancellation signal. The method comprises the steps of generating a cancellation signal having at least one harmonic having a frequency and an amplitude substantially equal to that of a disturbance harmonic interacting with a spacecraft structural resonance and a phase substantially out of phase with the disturbance harmonic interacting with the spacecraft structural resonance, and providing the cancellation signal to a spacecraft control actuator. The apparatus comprises a storage device tangibly embodying the method steps described above.

US Patent:

6771217, Aug 3, 2004

Filed:

Feb 20, 2003

Appl. No.:

10/371141

Inventors:

Ketao Liu - Cerritos CA
Paul C. Werntz - Long Beach CA

Assignee:

The Boeing Company - Chicago IL

International Classification:

H01Q 322

US Classification:

342368, 342173, 342465, 342442

Abstract:

A method and apparatus for determining and correcting for phased array mispointing errors, particularly those due to structural deformation, is disclosed. The method comprises the steps of receiving a signal from each of a plurality of signal sources at at least one receiving sensor disposed away from the phased array in a direction at least partially toward a receiver of a transmitted signal from the phased array, and determining the phased array pointing from the received signals. The apparatus comprises a receiving sensor for receiving a signal from each of a plurality of signal sources, the receiving sensor disposed away from the phased array in a direction at least partially toward a receiver of a transmitted signal from the phased array, and an array pointing computer for determining the direction of the phased array from the received signals.

US Patent:

6825806, Nov 30, 2004

Filed:

Jun 3, 2002

Appl. No.:

10/162465

Inventors:

Ketao Liu - Cerritos CA
Richard Fowell - Rolling Hills Estates CA
Rongsheng Li - Hacienda Heights CA

Assignee:

The Boeing Company - Seattle WA

International Classification:

H01Q 300

US Classification:

342359, 342354, 342355, 342358

Abstract:

Methods and structures are provided for reducing pointing errors of satellite antennas and for generating broad field-of-view satellite attitude acquisition patterns. In one method embodiment, satellite transmit beams have estimated pointing attitudes and are transmitted to overlap on a ground-based receiving terminal which has a known terminal location and which measures received signal strengths. Pointing errors of the transmit beams are then determined from the estimated pointing attitudes , the terminal location and the signal strengths and the pointing errors are subsequently reduced by revising the pointing attitudes. Other method embodiments utilize known signal-strength functions and antenna signals with known signal parameters such as frequencies and/or modulations.

US Patent:

6921048, Jul 26, 2005

Filed:

Jan 21, 2003

Appl. No.:

10/348663

Inventors:

Ketao Liu - Cerritos CA, US

Assignee:

The Boeing Company - Chicago IL

International Classification:

B64G001/38

US Classification:

244164, 244168, 244173

Abstract:

A method and system for minimizing the solar array sun tracking disturbance is disclosed. The method separates the North solar array wing stepping and South solar array wing stepping in time, and use the disturbance caused by one solar array wing to cancel the disturbance caused by the other solar array wing. It separates the step times of these two solar arrays by a half cycle of the array frequency excited by the solar wing drive stepping. Because of the symmetry between the North and South solar arrays, their disturbances cancel each other out.

US Patent:

7134630, Nov 14, 2006

Filed:

Aug 30, 2004

Appl. No.:

10/929844

Inventors:

Leonard A. Plotke - Los Angeles CA, US
Ketao Liu - Cerritos CA, US

Assignee:

The Boeing Company - Chicago IL

International Classification:

B64G 1/36

US Classification:

244171, 2441718, 2441713

Abstract:

A system and associated method for compensating for thermal deformation of a spaced-based structure having a spacecraft payload. The system including a beacon source coupled to a first spacecraft for transmitting a first signal and a beacon sensor coupled to a second spacecraft for receiving the first signal and providing measurement data derived from the first signal. At least one attitude sensing device is coupled to the second spacecraft for determining estimated spacecraft attitude data for the second spacecraft. A processor on the second spacecraft is configured to process ephemeris data of the first and second spacecraft, beacon measurement data, estimated spacecraft attitude data, and gimbal angular position data to estimate spacecraft structural deformation.

US Patent:

7242483, Jul 10, 2007

Filed:

Aug 12, 2004

Appl. No.:

10/917924

Inventors:

Ketao Liu - Cerritos CA, US
Cameron Massey - Hawthorne CA, US
Michael Nolan - Hermosa Beach CA, US

Assignee:

The Boeing Company - Chicago IL

International Classification:

G01B 11/24

US Classification:

356601, 356614, 3562371

Abstract:

A laser metrology system for estimating the deformation of a structure is provided. The system includes a plurality of laser beam position detectors distributed across a surface of the structure. Each laser beam position detector is intersected by a laser beam and is configured to determine the change in location of the intersection point in at least one dimension. By determining the change in location of the intersection point for each laser beam position detector, the laser metrology system can calculate the deformation of the structure that caused these changes in location.

US Patent:

7258306, Aug 21, 2007

Filed:

Sep 19, 2006

Appl. No.:

11/533165

Inventors:

Leonard A. Plotke - Los Angeles CA, US
Ketao Liu - Cerritos CA, US

Assignee:

The Boeing Company - Chicago IL

International Classification:

B64G 1/36

US Classification:

244171, 2441718, 2441713

Abstract:

A system and associated method for compensating for thermal deformation of a spaced-based structure having a spacecraft payload. The system including a beacon source coupled to a first spacecraft for transmitting a first signal and a beacon sensor coupled to a second spacecraft for receiving the first signal and providing measurement data derived from the first signal. At least one attitude sensing device is coupled to the second spacecraft for determining estimated spacecraft attitude data for the second spacecraft. A processor on the second spacecraft is configured to process ephemeris data of the first and second spacecraft, beacon measurement data, estimated spacecraft attitude data, and gimbal angular position data to estimate spacecraft structural deformation.

US Patent:

7414576, Aug 19, 2008

Filed:

Jan 25, 2007

Appl. No.:

11/627360

Inventors:

Ketao Liu - Cerritos CA, US

Assignee:

The Boeing Company - Chicago IL

International Classification:

H01Q 3/00
G01S 5/04

US Classification:

342359, 342368, 342442

Abstract:

A precision antenna pointing system and methods are disclosed. Antenna pointing error is determined by detecting RF signal phases at locations along the edge of an antenna reflector. A set of signal phase reference harnesses are used to compensate for harness induced errors. Furthermore, multiplexing is used to minimize electronics induced phase errors.