An estimated pointing error of few to few tens of millidegrees can be achieved.
A spacecraft high-gain antenna (HGA) was designed with a sharp Vnotch in its far-field cross-pole pattern to determine the spacecraft pointing and attitude relative to the Earth receiving antenna station. The notch depth, relative to the antenna far-field main-lobe, varies with the off-boresight angle. By tracking the spacecraft from the observation antenna (on Earth for example), from rise to set (which is the usual way of tracking the spacecraft), or by performing boresight scans (in two orthogonal axes) against the spacecraft transmitting HGA and recording the received signal at the receiving antenna, determination of the spacecraft pointing and attitude errors can be computed with great accuracy. An estimated pointing error of few to few tens of millidegrees can be achieved with a V-notch concept.
The location and depth of the V-notch in the recorded data is used to determine the spacecraft attitude error (pointing in the cross-elevation) direction, while the depth of the V-notch is used to determine the spacecraft pointing errors in the elevation (up and down) direction (relative to the receiving antenna). As an example, for a spacecraft HGA whose co-pole is right circular polarized (RCP), a V-notch can be incorporated with advantages into its cross-pole, left circular polarization (LCP), thereby the diagnostics can be achieved without loss of telemetry tracking & command (TT&C), which is typically transmitted on the RCP channel. The end-to-end principle of this technology is described in the figure. These technology principles can be extended to other types of polarization and other features than a notch.
In accordance with Public Law 96-517, the contractor has elected to retain title to this invention. Inquiries concerning rights for its commercial use should be addressed to:
Innovative Technology Assets Management
Mail Stop 321-123
4800 Oak Grove Drive
Pasadena, CA 91109-8099
Refer to NPO-47041.