This paper examines the use of bi-static lidar to remotely detect the release of aerosolized biological agent. The detection scheme exploits bio-aerosol induced changes in the Stokes parameters of scattered radiation in comparison to scattered radiation from ambient background aerosols alone. A polarization distance metric is introduced to discriminate between changes caused by the two types of aerosols. Scattering code computations are the information source. Three application scenarios are considered: outdoor arena, indoor auditorium, and building heating-ventilation-air-conditioning (HVAC) system. Numerical simulations are employed to determine sensitivity of detection to laser wavelength and to particle physical properties. Results of the study are described and details are given for the specific example of a 1.50 μm lidar system operating outdoors over a 1000-m range.
An Advanced Land Imager (ALI) will be flown on the first Earth Observing mission (EO-1) under NASA's New Millennium Program (NMP). The ALI contains a number of key NMP technologies. These include a 15 degree wide field-of-view, push-broom instrument architecture with a 12.5 cm aperture diameter, compact multispectral detector arrays, non-cryogenic HgCdTe for the short wave infrared bands, silicon carbide optics, and a multi-level solar calibration technique. The focal plane contains multispectral and panchromatic (MS/Pan) detector arrays with a total of 10 spectral bands spanning the 0.4 to 2.5 micrometer wavelength region. Seven of these correspond to the heritage Landsat bands. The instantaneous fields of view of the detectors are 14.2 (mu) rad for the Pan band and 42.6 (mu) rad for the MS bands. The partially populated focal plane provides a 3 degree cross-track coverage corresponding to 37 km on the ground. The focal plane temperature is maintained at 220 K by means of a passive radiator. The instrument environmental and performance testing has been completed. Preliminary data analysis indicates excellent performance. This paper presents an overview of the instrument design, the calibration strategy, and results of the pre-flight performance measurements. It also discusses the potential impact of ALI technologies to future Landsat-like instruments.
The pre-launch measurements and test required for calibration and characterization of the advanced land imager (ALI), which will be flown on NASA's EO-1 mission, have been completed. The instrument level performance testing was conducted at MIT Lincoln Laboratory with the ALI in an operational environment. The overall calibration strategy, which includes both pre-launch and post-launch components, will be described in this paper. The fundamental sensor calibration data comprise five measurement categories: angular position in object space for each pixel; normalized spectral response functions; response coefficients; zero signal offsets; and modulation transfer functions. Performance and characterization test include measurements of noise, SNR, linearity, repeatability, image artifacts, stray light rejection, and cross-talk. An overview of the facilities, equipment, tests and results is presented here.
The ALI, which will be flown on the NASA New Millennium Program's EO-1 mission, has been completed and is being integrated with the spacecraft. The motivation for the EO-1 mission is to flight-validate advanced technologies that are relevant to next generation satellites. The ALI telescope is a reflective triplet design having a 15-degree cross-track field-of-view that employs silicon carbide mirrors. It incorporates a multispectral detector and filter array with 10 spectral bands that cover a wavelength range from the visible to the short-wave IR. The paper will describe the instrument and its operation, review test result, and suggest application to a future Landsat instrument.
Examination of future NOAA Geostationary Operational Environment Satellite (GOES) IR sounder requirement suggested replacing the present GOES I-M series filter wheel instrument with a high-resolution FTIR interferometer. NOAA and MIT Lincoln Laboratory initiated a design and test program replacement feasibility. In collaboration with NASA and ITT Aerospace, a brassboard-version GOES High-Resolution Interferometer Sounder (GHIS) developed under this pathfinder program was installed inside an earlier generation sounder at ITT Aerospace. This paper describes the suite of tests performed while operating the GHIS brassboard at room temperature inside the sounder. Results from the tests effort highlight key issues involved in characterizing FTIR interferometer performance for GOES sounder applications.
The primary instrument of the first Earth Orbiter satellite (EO-1) under NASA's New Millennium Program will be an Advanced Land Imager (ALI), with multispectral and imaging spectrometer capabilities. The principal motivation for this mission is to flight-validate advanced technologies which are relevant to the next-generation of Earth Science Systems Program Office science needs. The ALI telescope is a reflective triplet design employing silicon carbide mirrors with a 15 degree cross-track field of view. There are three imaging technologies in the ALI. The first is a multispectral panchromatic array with 10 spectral bands in the visible and near IR and short wave IR. The two additional imaging technologies are the Wedge Imaging Spectrometer (WIS) and the Grating Imaging Spectrometer (GIS) that each provides a continuous range of wavelength selections from 0.4 to 2.5 micrometers . Elements of the WIS and GIS were developed but due to budgetary and schedule constraints, and some performance issues, were not included in the flight assembly. The paper will present details of the ALI design and status.
Interim results of a current study on upgrading the GOES infrared Sounder are presented. Considered are a 15 cm diameter telescope to reduce instrument size and weight, use of a Fourier transform infrared (FTIR) interferometer for high spectral wavelength resolution, a small detector focal plane array operating at 65K, and combining the instrument with a microwave sounder. Retrieval performance improvement from the FTIR sounder is estimated.
Replacement of the sounder filter wheel in one of the clones of the GOES I-M satellite series with a Fourier transform infrared (FTIR) interferometer would improve retrieval performance and could be a pathfinder for technology employed in the next generation GOES series. Based on examination of an earlier proposal, NOAA decided to pursue the feasibility of such a FTIR replacement. The FTIR interferometer is to be as nearly a 'plug-in' replacement for the sounder filter wheel as possible. THis imposes some interesting and challenging optical, mechanical, and electronic constraints on the design and fabrication of the interferometer. This overview describes a brassboard design for a replacement FTIR interferometer and provides the background and the status of GHIS brassboard work-in- progress at MIT Lincoln Laboratory.