Navigation Aid Supplies Information to Help Satellite's Research

A key navigation aid from Northrop Grumman Corporation is supplying attitude reference, or satellite orientation, information critical to NASA's Aura Earth Observing System (EOS) satellite and to a key scientific instrument aboard it. Precise satellite orientation information will facilitate Aura's mission to answer questions about changes in the Earth's environment and climate changes.

Aura was launched July 15 from Vandenberg Air Force Base, (CA).It is on a six-year journey that will help answer questions about changes in the Earth's life-sustaining atmosphere. Science operations will begin approximately three months after launch, with all onboard scientific instruments becoming operational in stages over the following three months.

"In addition to supplying information for the spacecraft stabilization system, our space inertial reference unit (SIRU) also supplies information to the primary mirror stabilization system of the tropospheric emission spectrometer aboard the spacecraft," said Alexis Livanos, vice president and general manager of Northrop Grumman's Navigation and Space Sensors Division.

The spectrometer will make the first global measurements of tropospheric ozone as it measures atmospheric infrared radiation. It will measure tropospheric carbon monoxide, methane, nitric acid, water vapor, and nitric oxide. Other instruments aboard Aura will measure gases such as bromine oxide, volcanic sulfur dioxide and aerosols as well as ultraviolet radiation, and special products such as chlorofluorocarbons.

Aura is the third of five satellites launched by NASA for its first EOS series, following Terra and Aqua, which are already in orbit. Several of the EOS satellites will fly in formation to coordinate observations made by different instruments on the various satellites. Both Aqua and Aura were built by Northrop Grumman's Space Technology sector of Redondo Beach, Calif. and contain the company's SIRU.

The SIRU utilizes Northrop Grumman's exclusive hemispherical resonator gyros.The inherent high reliability, high performance, radiation tolerant features of the gyros and the dual redundant features of the SIRU makes this the ideal inertial reference unit for long-term missions such as Aura.

The hemispherical resonating gyro utilizes a thin-walled quartz shell that is energized by an electrical field to produce an imperceptible vibration pattern within itself.This pattern is electrically sensed and used to determine the gyro's output parameters. The vibration is so minute that it creates virtually no internal stress and fatigue effects, leading to its unmatched reliability. Northrop Grumman is the exclusive producer of the gyros, which to date have accumulated more than 4.5 million hours of operation in more than 50 systems in space without a mission failure.

FMI: www.northropgrum.com