Active modelocking of multiple polariton lasers mediated by real time sensing offers novel capabilities for
optically based sensing. We outline a strategy based in part on short range polariton-polariton interactions
and in part on an actively managed external optical field coherent with each of the individual polariton lasers.
This actively managed coherent optical field is required to establish long range coherence between multiple
spatially distinct polariton lasers. Polariton lasers offer nonlinear behavior at excitation levels of a few quanta
of the optical field, time constants of picoseconds or less, and optical wavelength dimensions of individual
lasers. Achievement of useful long range, hundreds of meters, polariton based optical sensing appears
useful, but to require active cohering of arrays of polariton lasers. Continuous metrology and active control of
the system coherence offer unique opportunities for sensing approaching quantum limited operation. We
consider strategies and capabilities of sensing systems based on such arrays of spatially distinct, but
collectively coherent, polariton lasers. Significant advances in a number of technical areas over decades
appear needed to achieve such systems.
The goal of an imaging sensor with nearly constant response, constant image quality, with a focal plane array of pixels
whose overlap can be scaled, that can still provide a nearly hemispherical field-of-view has been demonstrated. The
topic of this paper is the optical design of just such a sensor. A flow down of these performance constraints to hardware
specifications is bounded by information theory, diffraction theory, plus practical matters that constrain the overlap of
focal plane arrays.
A set of performance goals for a sensor are the ability to observe features ≤25 μr features in size within a 45° scene
using >1 G pixels.
The Buchdahl dispersion model provides a rapidly converging polynomial form for describing the dispersion of refractive materials. Via this model, the dispersion of a material over the waveband of concern can be accurately characterized by a simple polynomial form, often out to only the second order. In this paper, the Buchdahl model is applied to hybrid refractive-diffractive achromats for both 3-5μm (MWIR) band and 8-12μm (LWIR) band. For each waveband, Buchdahl dispersion coefficients of IR materials and the diffractive optical element (DOE) are defined by optimally choosing the Buchdahl chromatic coordinate and best-fitting the Buchdahl model to the dispersion of materials and the DOE. The principles for selecting 1 to 2 IR materials combined with a DOE to produce hybrids achromatized at 3 and 4 wavelengths are discussed. A series of thin lens predesign examples are presented.
The full potential of current remote sensor technology is limited by the inability to correct biases once an exo-atmospheric remote sensor becomes operational. Even when the calibration is traced to the International System of Units, SI, and the instrument is performing within the operational envelope wherein it is calibrated, the problem exists and a Space Metrology Program is a potential solution to the problem. This paper discusses such a program, suggests a feasibility study to address the issues and recommends a plan of action.
Any operational instrument has a bias and reducing the magnitude of the bias can only be accomplished when an adequately accurate standard is accessible by the instrument while the instrument is in its operational environment. Currently the radiometric flux from the sun, the moon and the stars is inadequately accurate SI to provide a standard that is consistent with the remote sensor state-of-the-art technology. The result is data that is less accurate than it could be often leading to confusing and conflicting conclusions drawn from that data. Planned remote sensors such as those required to meet future program needs (e.g. the United States National Polar-Orbiting Operational Environmental Satellite System (NPOESS) and the proposed international Global Earth Observation Program) are going to need the higher accuracy radiometric standards to maintain their accuracy once they become operational. To resolve the problem, a set of standard radiometers on the International Space Station is suggested against which other exo-atmospheric radiometric instruments can be calibrated. A feasibility study for this program is planned.
The Traceable Radiometry Underpinning Terrestrial- and Helio-Studies (TRUTHS) mission offers a novel approach to the provision of key scientific data wtih unprecedented radiometric accuracy for Earth Observation (EO) and solar studies, which will also establish well-calibrated reference targets/standards to support other SI missions. This paper will present the TRUTHS mission and its objectives. TRUTHS will be the first satellite mission to calibrate its instrumentation directly to SI in orbit, overcoming the usual uncertainties associated with drifts of sensor gain and spectral shape by using an electrical rather than an optical standard as the basis of its calibration. The range of instruments flown as part of the payload will also proivde accurate input data to improve atmospheric radiative transfer codes by anchoring boundary conditions, through simultaneous measurements of aerosols, particulates and radiances at various heights. Therefore, TRUTHS will significantly improve the performance and accuracy of Earth observation misison with broad global or operational aims, as well as more dedicated missions. The providision of reference standards will also improve synergy between missions by reducing errors due to different calibration biases and offer cost reductions for future missions by reducing the demands for on-board calibration systems. Such improvements are important for the future success of strategies such as Global Monitoring for Environment and Security and the implementation and monitoring of international treaties such as the Kyoto Protocol. TRUTHS will achieve these aims by measuring the geophysical variables of solar and lunar irradiance, together with both polarized and un-polarized spectral radiance of the Moon, and the Earth and its atmosphere.