Mission poster for NASA's Aqua satellite. Photo: NASA

TRW Inc. has completed the complex task of integrating all six science instruments onto the Aqua spacecraft, the second in NASA's series of Earth Observing System (EOS) satellites. TRW is building Aqua and its sister spacecraft, EOS Chemistry, under a contract managed by NASA Goddard Space Flight Center.

Aqua's instruments will take climate-related measurements of the atmosphere, cloud cover, precipitation, terrestrial snow cover and sea ice. Comprehensive measurements taken by the instruments will allow scientists to assess long-term environmental change, identify its human and natural causes, and advance the development of models for long-term forecasting.

"Aqua is on schedule to meet its late December 2000 launch date," said Fred Ricker, vice president and general manager, TRW Space & Laser Programs Division. "The upcoming environmental test phase will demonstrate the ability to meet our customer's stringent performance objectives on this program."

Environmental testing of the Aqua spacecraft is scheduled to begin this spring.

"Instrument integration was a painstaking process requiring great precision," said Brooks Vogt, TRW's EOS Common Spacecraft program manager. "We drew on our experience integrating more than 550 payloads to achieve alignments on the spacecraft platform within arc seconds (one arc second equals 1/3,600 degree). We maintained our production schedule by integrating each instrument as it was delivered to our production facilities, using simplified mounting devices.

An artist's concept of NASA's Aqua satellite in space. Photo: TRW

"We will perform the same procedure on EOS Chemistry, which we are building and integrating with a different set of instruments," Vogt explained. "Our spacecraft design accommodates a variety of payloads and can be easily adapted to the specific needs of any low-earth orbiting observation mission."

Aqua and EOS Chemistry are based on a modular, standardized spacecraft bus design that allows science instruments to be attached on a "mix and match" basis without making changes to overall spacecraft design or subsystem support requirements. The spacecraft have a six-year design life and will be launched from Delta 2 launch vehicles into sun-synchronous orbits. Aqua was formerly known as EOS PM.

To reduce the risk and improve quality on the EOS Common Spacecraft program, TRW developed an electronic engineering model of the spacecraft and a software development and verification facility. These and other risk-reduction efforts are intended to create a high-reliability and high-performance spacecraft bus.

Aqua and EOS Chemistry are space-based elements of NASA's Earth Science Enterprise, a long-term coordinated program to study the Earth as a single, global environment. Earth science data is already being used to study the connections among the Earth's air, water, land and life. Terra, the first spacecraft in the Earth Science Enterprise series, was launched in December 1999.

Aqua's instruments include the Atmospheric Infrared Sounder, built by Lockheed Martin Infrared Imaging Systems; Advanced Microwave Sounding Unit, built by Aerojet; Advanced Microwave Scanning Radiometer-EOS, built by Mitsubishi Electronics Corporation and provided by NASDA-Japan; Clouds and the Earth's Radiant Energy System, built by TRW; Humidity Sounder for Brazil, built by Matra-Marconi and provided by AEB-Brazil; Moderate Resolution Imaging Spectroradiometer, built by Raytheon Santa Barbara Remote Sensing.

TRW Space & Electronics Group builds communications, scientific and defense spacecraft for military, civil and commercial customers; produces, integrates and tests payloads; develops advanced space instruments; and integrates experiments into spacecraft. It is an operating unit of TRW Inc., which provides advanced technology products and services for the global automotive, aerospace and information systems markets.