A key sensor for the National Polar-orbiting Operational Environmental Satellite System (NPOESS) passed one test, and is poised for further tests, prime contractor Northrop Grumman Corp. [NOC] announced today.

The Visible Infrared Imager Radiometer Sensor (VIIRS) passed Ambient Electro-Magnetic Interference (EMI) testing performed by subcontractor Raytheon Co. [RTN].

Testing at Raytheon facilities in El Segundo, Calif., verified VIIRS operates in a space-like configuration without emitting or being susceptible to electro-magnetic signals that could interfere with the spacecraft or other sensor operations.

Comprehensive vibration testing is expected to start this month. Next year, the flight instrument will be subject to thermal vacuum testing, which will last for several months. During this time, VIIRS will be subjected to thermal cycles typical of the space environment.

News of progress comes after some members of Congress have criticized cost increases and the removal of some sensors from NPOESS.

"Northrop Grumman, Raytheon and our government customer have been working together closely to resolve technical issues on this sensor," said Dave Vandervoet, vice president of the Northrop Civil Systems Division. "Completion of ambient EMI testing is a significant achievement and paves the way for us to move forward with the final environmental tests on this flight unit for delivery to the NPP spacecraft."

Northrop is the prime contractor for NPOESS, leading an industry team under a government contract to the NPOESS Integrated Program Office and headed by a tri-agency group of the Department of Defense, Department of Commerce, and NASA.

Some lawmakers have said that is part of the problem, having three agencies attempting to lead the NPOESS program.

The flight unit cryoradiator completed component level thermal vacuum testing and ambient testing earlier this year to demonstrate technical performance and has the capacity to withstand the space environment. The sensor engineering development unit passed all planned environmental tests under a previous phase of development for the program.

VIIRS will collect visible/infrared imagery and radiometric data on the atmosphere, clouds, Earth radiation budget, clear-air and/water surfaces, sea surface temperature, and ocean color, as well as low-light visible imagery. The sensor will offer dramatic and unprecedented spatial, spectral, and radiometric performance improvements compared with current operational capabilities, according to Northrop.

"This is an important milestone that further validates the technical performance of the VIIRS instrument, which will provide critical new capabilities in weather forecasting, disaster response and warfighter planning," said Brian Arnold, Raytheon Space Systems vice president.

The VIIRS flight unit will be integrated onto the NPOESS Preparatory Project (NPP) spacecraft acquired by NASA. NPP is the precursor for NPOESS and will provide technical risk reduction and data continuity between NASA’s scientific Earth Observing System (EOS) satellites, Terra, Aqua, and Aura, and the operational NPOESS system.