The Atmospheric Chemistry Experiment (ACE) is the mission selected by the Canadian Space Agency for its new science satellite, SCISAT-1. Dr. Peter Bernath of the University of Waterloo is the ACE Mission Scientist, and ABB is the industrial contractor for the development of the ACE primary instrument. The ACE primary instrument is an infrared Fourier Transform Spectrometer (FTS) coupled with an auxiliary 2-channel visible and near infrared imager. The FTS, operating from 2.4 to 13.3 microns, will measure at an unapodised resolution of 0.02 cm-1 the infrared absorption signals that contain information on different atmospheric layers to provide vertical profiles of atmospheric constituents. Its highly folded design results in a very high performance instrument with a compact size. The imager will monitor aerosols based on the extinction of solar radiation using two filtered detectors at 1.02 and 0.525 microns. The instrument also includes a suntracker, which provides the sun radiance to both the FTS and the imager during solar occultation of the earth’s atmosphere. In order to meet all science objectives, the instrument line width of the ACE-FTS has to be smaller than 0.028 cm-1. There are however different instrument function contributors affecting the width and the symmetry of spectral lines. These contributors are related to effects inherent to the instrument. This paper will describe these different effects and their impacts on the instrument line shape (ILS). Results obtained during the ILS characterisation of the flight model will be presented. A short description of a correction algorithm is also discussed.
The Atmospheric Chemistry Experiment (ACE) is the mission selected by the Canadian Space Agency for its next science satellite, SCISAT-1. ACE consists of a suite of instruments in which the primary element is an infrared Fourier Transform Spectrometer (FTS) coupled with an auxiliary 2-channel visible (525 nm) and near infrared imager (1020 nm). A secondary instrument, MAESTRO, provides spectrographic data from the near ultra-violet to the near infra-red, including the visible spectral range. In combination the instrument payload covers the spectral range from 0.25 to 13.3 micron. A comprehensive set of simultaneous measurements of trace gases, thin clouds, aerosols and temperature will be made by solar occultation from a satellite in low earth orbit. The ACE mission will measure and analyze the chemical and dynamical processes that control the distribution of ozone in the upper troposphere and stratosphere. A high inclination (740), low earth orbit (650 km) allows coverage of tropical, mid-latitude and polar regions. This paper will describe the metrology scheme, based on an IR laser diode, as well as algorithms that are needed to fully calibrate, along the wavenumber axis, the spectra measured by the ACE instrument.
The Cross-track Infrared Sounder (CrIS) is part of the National Polar-orbiting Operational Environmental Satellite System (NPOESS) series of polar-orbiting spacecrafts. The CrIS sensor forms a key component of the larger Cross-track Infrared/Microwave Sounding Suite (CrIMSS) and is intended to operate within the context of the CrIMSS architecture. The CrIS instrument is a Michelson interferometer infrared sounder covering the spectral range of approximately 3.9 to 15.4 microns. CrIS provides cross-track measurements of scene radiance to allow the calculation of temperature and moisture vertical distributions in the Earth's atmosphere. We present sensor data record (SDR) level 1B algorithms that are needed on ground in order to produce meaningful data meeting all requirements of the NPOESS CrIS instrument. Level 1B data are made of geolocated, radiometrically and spectrally (spatial frequency) calibrated spectra with annotated quality indicators. CrIS SDR algorithms include, among others, radiometric calibration with phase error correction, interferometer fringe count error handling and correction of the instrument line shape (ILS) distortion.
The Atmospheric Chemistry Experiment (ACE) is the mission selected by the Canadian Space Agency for its next science satellite, SCISAT-1. ACE consists of a suite of instruments in which the primary element is an infrared Fourier Transform Spectrometer (FTS) coupled with an auxiliary 2-channel visible (525 nm) and near infrared imager (1020 nm). A secondary instrument, MAESTRO, provides spectrographic data from the near ultraviolet to the near infrared, including the visible spectral range. In combination, the instrument payload covers the spectral range from 0.25 to 13.3 micron. A comprehensive set of simultaneous measurements of trace gases, thin clouds, aerosols and temperature will be made by solar occultation from a satellite in low earth orbit. The ACE mission will measure and analyze the chemical and dynamical processes that control the distribution of ozone in the upper troposphere and stratosphere. A high inclination (74°), low earth orbit (650 km) allows coverage of tropical, mid-latitude and polar regions.
This paper will describe level 1 algorithms that are needed on ground in order to produce meaningful data meeting all requirements of the ACE FTS instrument. Level 0 data are as downlinked from the spacecraft. Level 1A data are decoded (CCSDS, bit trim) interferograms from individual acquisition channels. Level 1B data are made of spectrally (spatial frequency) calibrated transmittances with annotated quality indicators. Some key ACE FTS L1B algorithms include, non-linearity characterization/correction, robust interferometer fringe count error handling, spectral calibration from Solar reference lines, transmittance computation with phase error correction, and correction of the instrument line shape (ILS) distortion.
We report on the results of the system simulation software written at Canada-France-Hawaii Telescope, to predict and optimize the performance of our adaptive optics bonnette presently under construction. The individual simulation elements, atmospheric simulator, curvature sensor, bimorph mirror and control loop, are reviewed with an emphasis on the basic properties of curvature sensors. Optimization of the extra-focal distance parameter and its consequences are discussed. We then present results of whole system simulations, and quantify the main sources of error. Some results, including noise, are reported. In a second part, we present our view of modal control and detail the construction of the modal basis. We also report briefly on modal gain optimization.
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