tech track papers
Categories: 2017, Space Technology Innovation
Evolving remote sensing missions present a growing need for satellite sensors with significantly enhanced measurement accuracies beyond current capabilities. For example, the on-board calibration needed for very precise (e.g., <1% radiance uncertainty), spectrally resolved IR radiances typically requires high-emissivity, ε (≥0.999) calibration blackbodies (BBs). The challenge is that conventional BBs have coating emissivities that are usually limited to ≈0.98. Additionally, they generally have complex geometries that create fabrication and coating non-uniformities which leads to radiance, emissivity, and temperature calibration uncertainties. Moreover, conventional BBs are typically large SWaP, which is not optimal for on-board calibration and can be very expensive. Thus, a first-order estimate of a conventional BB’s radiance uncertainty would total >2%, when the other sources of uncertainty and margin are included, failing to meet <1% radiance uncertainty requirement.
At Ball, our approach to enhance remote sensing missions beyond current capabilities is to leverage the unique optical properties of Carbon Nanotubes (CNTs) to develop advanced coatings that overcome the limitations of conventional BB coatings. We have developed “Flat-Plate, Extreme-ε (0.999), BB Calibrator” based on a Vertically Aligned CNT (VACNT). Key BB elements, such as the extreme-ε VACNT, have been verified for Ball by NIST to be ≈0.999. Extreme-ε provides a significantly reduced BB radiance uncertainty by minimizing the radiance error due to the radiation reflected from the BB’s background environment. Additionally, the flat-plate simplifies instrument design, is optimal for on-board calibration due to its low SWaP, and it eliminates the fabrication and coating difficulties associated with the complex geometry of conventional BBs. This paper summarizes the results of our design, characterization and plan for implementing the technology on a small satellite platform with a micro-bolometer sensor.
Author: John FlemingTopic: Space Technology Innovation
Advanced On-Board Calibration of Space Systems Using a Carbon Nanotube Flat-Plate BlackbodyDownload File