Labsphere, Inc. in conjunction with NASA GSFC and Genesis Engineering Solutions Inc., has developed an innovative, vacuum compatible, calibration spectro-radiometric illumination source with a highly uniform large-area rectangular flat panel active area. This device features a uniquely shaped diffuse integration geometry to achieve high uniformity over a large active output area while maintaining a smaller and more robust overall form-factor when compared to previous designs or integrating spheres. A new liquid-cooled hybrid quartz-tungsten (QT) and light emitting diode (LED) source module has been engineered to provide direct-in-vacuum reference illumination over the full dynamic range and spectrum of the VIIRS instrument’s optical bands during pre-launch testing. The first unit has been demonstrated to meet its requirements using ambient technology and a fully-vacuum-compatible second unit is planned to allow testing in thermal vacuum (TVAC) campaigns. This technology is flexible and capable of meeting the needs of many other instruments/missions requiring this type of test/calibration capability.
In this work, we describe an improved thermal-vacuum compatible flat plate radiometric source which has been developed and utilized for the characterization and calibration of remote optical sensors. This source is unique in that it can be used in situ, in both ambient and thermal-vacuum environments, allowing it to follow the sensor throughout its testing cycle. The performance of the original flat plate radiometric source was presented at the 2009 SPIE1. Following the original efforts, design upgrades were incorporated into the source to improve both radiometric throughput and uniformity. The pre-thermal-vacuum (pre-TVAC) testing results of a spacecraft-level optical sensor with the improved flat plate illumination source, both in ambient and vacuum environments, are presented. We also briefly discuss potential FPI configuration changes in order to improve its radiometric performance. Keywords: Calibration, radiometry, remote sensing, source.
This work describes the development of an improved vacuum compatible flat plate radiometric source used for characterizing and calibrating remote optical sensors, in situ, throughout their testing period. The original flat plate radiometric source was developed for use by the VIIRS instrument during the NPOESS Preparatory Project (NPP). Following this effort, the FPI has had significant upgrades in order to improve both the radiometric throughput and uniformity. Results of the VIIRS testing with the reconfigured FPI are reported and discussed.
In this work, development of a fiber-optically coupled, vacuum-compatible, flat plate radiometric source applicable to the characterization and calibration of remote sensing optical sensors in situ in a thermal vacuum chamber is described. The original flat plate radiometric source configuration’s performance was presented at the 2009 Berlin SPIE. Following the original effort, design upgrades were incorporated in order to improve radiometric throughput and uniformity. Results of thermal and radiometric performance, with incorporated upgrades, of a flat plate illumination source in a temperature-controlled vacuum chamber operating at liquid nitrogen temperature are presented. Applications, including use with monochromatic tunable laser sources for the end-to-end system-level testing of large aperture sensors, are briefly discussed.
A gradual, but persistent, decrease in the optical throughput was detected during the early commissioning phase for the
Suomi National Polar-Orbiting Partnership (SNPP) Visible Infrared Imager Radiometer Suite (VIIRS) Near Infrared (NIR)
bands. Its initial rate and unknown cause were coincidently coupled with a decrease in sensitivity in the same spectral
wavelength of the Solar Diffuser Stability Monitor (SDSM) raising concerns about contamination or the possibility of a
system-level satellite problem.
An anomaly team was formed to investigate and provide recommendations before commissioning could resume. With few
hard facts in hand, there was much speculation about possible causes and consequences of the degradation. Two different
causes were determined as will be explained in this paper. This paper will describe the build and test history of VIIRS, why
there were no indicators, even with hindsight, of an on-orbit problem, the appearance of the on-orbit anomaly, the initial
work attempting to understand and determine the cause, the discovery of the root cause and what Test-As-You-Fly (TAYF)
activities, can be done in the future to greatly reduce the likelihood of similar optical anomalies. These TAYF activities are
captured in the “lessons learned” section of this paper.
Thomas Koch, Duane Bates, James Bell, Roger Hoelter, Craig Kent, Steven Kus, David La Komski, John Leonard, John Mehrten, Jay Neumann, David Rogers, Thomas Wolverton
KEYWORDS: MODIS, Calibration, Space operations, Instrument modeling, Long wavelength infrared, Interfaces, Contamination, Electromagnetism, Photonic integrated circuits, Control systems
A key milestone in NASA's Mission to Planet Earth project was achieved with the completion of Environmental Qualification testing of the Protoflight Model (PFM) Moderate Resolution Imaging Spectroradiometer (MODIS) instrument. Completing this task paved the way for MODIS to be integrated onto the EOS AM spacecraft which is to be launched as the keystone of the EOS system. Qualification of the PFM MODIS instrument required conducting an extensive test program in four different test facilities. Accomplishing environmental qualification testing, while meeting the stringent contamination and operational requirements for the MODIS instrument, required us to address a variety of issues and tasks. The main tasks included: developing special ground support test equipment, developing special tenting and handling equipment to protect the instrument from being contaminated during off-site environmental vibration an electromagnetic compatibility testing, designing and developing a state-of-the-art thermal-vacuum test chamber, and defining detailed test operations to fully characterize the instrument's electrical, optical and mechanical performance before, during and after each environmental test sequence. Selected penalty test were streamlined for characterizing the instrument whenever design changes or improved test techniques were incorporated to ensure all requirements had been met while maintaining a fully qualified instrument.
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