SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Earth and atmosphere thermal emission spectra via Nimbus 4 Michelson interferometer, obtaining atmospheric temperature, humidity and ozone profiles
Performance of Michelson interferometer aboard Nimbus 4 satellite
Michelson interferometer onboard Nimbus 4 satellite for recording earth IR emission spectrum
The Michelson interferometer on Mariner 9 measures the thermal emission spectrum of Mars between 200 and 2000 per cm (between 5 and 50 microns) with a spectral resolution of 2.4 per cm in the apodized mode. A noise equivalent radiance of 0.5 x 10 to the minus 7th W/sq cm/ster/cm is deduced from data recorded in orbit around Mars. The Mariner interferometer deviates in design from the Nimbus 3 and 4 interferometers in several areas, notably, by a cesium iodide beam splitter and certain aspects of the digital information processing. Special attention has been given to the problem of external vibration. The instrument performance is demonstrated by calibration data and samples of Mars spectra.
The phase correction for a Michelson interferometer with misaligned mirrors in converging light is shown to give rise to a quadratic phase shift. In general, the calculation of a spectrum from the measured interferogram needs phase correction. Phase corrections have been well worked out for the cases of a linear phase shift and a phase that is slowly varying. The standard procedures for correcting calculated spectra need to be modified, however, to remove any phase errors resulting from misaligned mirrors.
A Michelson interferometer feed monitor system developed for Spacelab is described. The device is helium cooled and is to be used to measure far infrared radiation sources in space. Performance data and development sequence are presented.
The optical system, stepping control, phase and modulation depth, array detector, and directions sensor are described for a specialized type of Michelson interferometer which works at sufficiently high resolution to measure the line widths and Doppler shifts of naturally occurring atmospheric emissions. With its imaging capability, the instrument can potentially supply this data independently for each element of the 100 x 100 detector array. The experiment seeks: (1) to obtain vertical profiles of atmospheric winds and temperatures as functions of latitude by observing near the limb; (2) to acquire exploratory wind and temperature data on smaller scale structures in airglow irregularities and in auroral forms; and (3) to collaborate with other Spacelab experiments, such as barium cloud releases, in providing wind and temperature data.
The design and operation of an imaging Michelson interferometer-spectrometer used for near-infrared (0.8 micron to 2.5 microns) spectral imaging are reported. The system employs a rapid scan interferometer modified for stable low resolution (250/cm) performance and a 42 element PbS linear detector array. A microcomputer system is described which provides data acquisition, coadding, and Fourier transformation for near real-time presentation of the spectra of all 42 scene elements. The electronic and mechanical designs are discussed and telescope performance data presented.
Interferometer mirrors mounted on flexible spring strips. Mounts used in folded-beam Michelson interferometer designed to monitor pollutants at altitude of 40,000 meters.
Results of an orbital analysis and performance assessment of SAMSI (Spacecraft Array for Michelson Spatial Interferometry) are presented. The device considered includes two one-meter telescopes in orbits which are identical except for slightly different inclinations; the telescopes achieve separations as large as 10 km and relay starlight to a central station which has a one-meter optical delay line in one interferometer arm. It is shown that a 1000-km altitude, zero mean inclination orbit affords natural scanning of the 10-km baseline with departures from optical pathlength equality which are well within the corrective capacity of the optical delay line. Electric propulsion is completely adequate to provide the required spacecraft motions, principally those needed for repointing. Resolution of 0.00001 arcsec and magnitude limits of 15 to 20 are achievable.
A novel configuration is proposed for a Michelson interferometer spectrometer, which will be insensitive to tilts or displacements, and which employs separated inputs and outputs and double passing for higher resolution. The great advantage of such a compensated design is a relaxation of mechanical tolerances, which is especially beneficial for instruments in hostile environments. The Atmospheric Trace Molecule Spectroscopy project, which must work reliably after being subjected to the vibrations of a Space Shuttle launch, would benefit from the use of such an instrument.
The Solar Oscillations Investigation-Michelson Doppler Imager (SOI-MDI) for the SOHO (Solar and Heliospheric Observatory) mission is intended to investigate the solar interior using helioseismology techniques. The SOI program consists of a coordinated set of observations intended to address a set of science objectives, an MDI instrument, and a facility that will provide data reduction and analysis capability. The MDI instrument will take filtergrams to measure LOS velocity, line and continuum intensity, and LOS magnetic fields with both 4 and 1.2 arcsec resolution, The SOI study is designed to take advantage of the anticipated SOHO telemetry by organizining the observations into four programs: structure (at all times), dynamics (two months per year), campaign (eight hours per day, 10 months per year), and magnetic field (a few minutes per day).
As part of an effort to learn more about the upper atmosphere and how it is linked to the weather experienced each day, NASA and NRCC are jointly sponsoring the Wide Angle Michelson Doppler Imaging Interferometer (WAMDII) Mission. WAMDII will measure atmospheric temperature and wind speed in the upper atmosphere. In addition to providing data on the upper atmosphere, the wind speed and temperature readings WAMDII takes will also be highly useful in developing and updating computer simulated models of the upper atmosphere. These models are used in the design and testing of equipment and software for Shuttles, satellites, and reentry vehicles. In making its wind speed and temperature measurements, WAMDII examines the Earth's airglow, a faint photochemical luminescence caused by the influx of solar ultraviolet energy into the upper atmosphere. During periods of high solar flare activity, the amount of this UV energy entering the upper atmosphere increases, and this increase may effect airglow emissions.
The Solar Oscillations Investigation (SOI) developed the Michelson Doppler Imager (MDI) to investigate the properties of the solar interior using the tools of helioseismology and of the photosphere and corona using more conventional techniques. The fundamental goal is to understand the Sun by determining its structure and observing its dynamics. The basic observables, velocity, intensity, and magnetic field, are computed on board from up to twenty 1024 by 1024 filtergrams made each minute. Subsequent analysis will extend the region to be explored downward into the solar interior and upward into the corona. While the instrument is dedicated to producing an uninterrupted series of helioseismology data, several magnetograms will be made each day and special eight hour campaigns are being developed to address specific scientific questions, some in coordination with other SOHO (Solar and Heliospheric Observatory) instruments.
A new, compact Fourier Transform Michelson interferometer (FTUV) with an apodized resolving power greater than 300,000 at 300 nm, high throughput and wide spectral coverage has been developed. The objectives include atmospheric spectroscopy (direct solar absorption and solar scattering) and laboratory spectroscopy of transient species. In this paper, we will briefly describe the prototype FTUV instrument and the results of preliminary laboratory investigations of OH and ClO spectra in emission and absorption.
MINT is a Michelson interferometer designed to measure the thermal emission from the earth at high spectral resolution (2/cm) over a broad spectral range (250-1700/cm, 6-40 mu m) with contiguous 3-pixel wide (12 mrad, 8 km field of view) along-track sampling. MINT is particularly well suited for monitoring cloud properties (cloud cover, effective temperature, optical thickness, ice/water phase, and effective particle size) both day and night, as well as tropospheric water vapor, ozone, and temperature. The key instrument characteristics that make MINT ideally suited for decadal monitoring purposes are: high wavelength to wavelength precision across the full IR spectrum with high spectral resolution; space-proven long-term durability and calibration stability; and small size, low cost, low risk instrument incorporating the latest detector and electronics technology. MINT also incorporates simplicity in design and operation by utilizing passively cooled DTGS detectors and nadir viewing geometry (with target motion compensation). MINT measurement objectives, instrument characteristics, and key advantages are summarized in this paper.
This report presents the results of a study of the instrumentation tolerances for a conventional style Michelson stellar interferometer (MSI). The method used to determine the tolerances was to determine the change, due to the instrument errors, in the measured fringe visibility and phase relative to the ideal values. The ideal values are those values of fringe visibility and phase that would be measured by a perfect MSI and are attributable solely to the object being detected. Once the functional relationship for changes in visibility and phase as a function of various instrument errors is understood it is then possible to set limits on the instrument errors in order to ensure that the measured visibility and phase are different from the ideal values by no more than some specified amount. This was done as part of this study. The limits we obtained are based on a visibility error of no more than 1% and a phase error of no more than 0.063 radians (this comes from 1% of 2(pi) radians). The choice of these 1% limits is supported in the literture. The approach employed in the study involved the use of ASAP (Advanced System Analysis Program) software provided by Breault Research Organization, Inc., in conjunction with parallel analytical calculations. The interferometer accepts object radiation into two separate arms each consisting of an outer mirror, an inner mirror, a delay line (made up of two moveable mirrors and two static mirrors), and a 10:1 afocal reduction telescope. The radiation coming out of both arms is incident on a slit plane which is opaque with two openings (slits). One of the two slits is centered directly under one of the two arms of the interferometer and the other slit is centered directly under the other arm. The slit plane is followed immediately by an ideal combining lens which images the radiation in the fringe plane (also referred to subsequently as the detector plane).
The variances of the quantum-mechanical noise in a two-input-port Michelson interferometer within the framework of the Loudon-Ni model were solved exactly in two general cases: (1) one coherent state input and one squeezed state input, and (2) two photon number states inputs. Low intensity limit, exponential decaying signal and the noise due to mixing were discussed briefly.