Time was when man's relationship with his environment was a relatively simple two-dimensional one. Not yet having overcome the effects of gravity, the vertical dimension was denied him, while the available modes of transport generally limited his horizontal excursions to local forays. His interactions with the environment were pretty much unidirectional-that is, he passively accepted it.
The Defense Meteorological Satellite Program (DMSP) is man-aged within the Space and Missile Systems OrganizatiOn (SAMSO) (LA AFS, CA) of the Air Force Systems Com-mand. DMSP is an all blue-suit organization comprising: technical and management functions of the system provided by the Deputy for Defense Meteorological Satellite Systems, SAMSO, (LA AFS, CA); command and control functions provided by the 4000th Aerospace Applications Group, SAC, (OFFUTT AFB, NB); launch activities provided by the 10th Aerospace Defense Squadron, ADC, (Vandenburg AFB, CA); Logistics from AFLC; training from ATC; and Communications from AFCS. IMSP is a triservice program satisfying specific Army, Navy, and Air Force mission related requirements. The Air Force Global Weather Central, MAC, (OFF UTT AFB, NB) is the primary Air Force user of the satellite data.
The Defense Meteorological Satellite Program (DMSP) Block 5D Satellite comprises a primary sensor (the Operational Linescan System), a 5D spacecraft, and special meteorological sensors (see "The Defense Meteorological Satellite Program" in this issue for configuration details). This article provides a review of the optical subsystem of the primary imaging sensor specifying the unique and novel methods used to obtain near constant high resolution, multispectral, meteor ological data
The Defense Meteorological Satellite Program (DMSP) Block SD Satellite comprises a primary sensor (the OLS), a SD spacecraft, and special meteorological sensors (see the article "The Defense Meteorological Satellite Program" in this issue). This article provides a review of the optical subsystem and spectral characteristics of the special meteorological sensor H (SSH).
The scanning and telescope field of view requirements for making Earth Resources (ER) and Meteorological (MET) phe-nomena observations from a Synchronous Earth Observation Satellite (SEOS) have been defined. The equations relating spacecraft scan capability to user scan field of view requirements are given and evaluated using four different telescope fields of view. The tradeoffs between telescope field-of-view and user scan fields of view requirements are shown, and it was determined that a 0.6 degree by 1.2 degree telescope FOV is optimum for the SEOS telescope. It was shown that an internal scan as well as external scan is required to satisfy both ER and MET users.
A series of optical systems is considered for the Synchronous Earth Observatory Satellite (SEOS) and classified by field coverage. As field angle increases, so does utility, but the penalty is increased complexity, size, and weight. All-reflective optical configurations are required by the wide spectral range requiremnt and the 1.5-meter diameter equivalent area aperture size. A series of telescope designs has been developed to confirm design viability, to eliminate physical/ mechanical interference, and to generate preliminary envelope and packaging data. The optical designs were carried to the modulation transfer function (MTF) level. The range of field angles investigated varied from a few arc-minutes square to more than 7 degrees x 3 degrees. The configurations and comparisons of utility, performance, size, and weight are discussed, and impacts on the mission and subsystems are considered.
The stray radiation rejection requirements for the Synchron-ous Earth Observation Satellite telescope were determined and compared with estimated stray radiation rejection performance. It was found that normal baffle design practice and A/20 rms surface roughness on the mirrors is adequate to prevent stray light from limiting the telescope measure-ments as long as the sun is 10 degrees, or more, from the edge of the field of view for a baffle tube length to aperture diameter ratio of 6.
The earth resources sensing Multispectral Scanner (MSS) for the Landsat satellite has two versions; one with four spectral bands from 0.5 to 1.1 um, and one with five bands, the added band being 10.4 to 12.6 pri. This paper describes optical design and performance. The instrument uses a flat, object-space scanning mirror of near linear motion, with a sensitive optical position monitor to detect mirror angular position. The 22.9-cm aperture telescope images the scene on an array of fiber optics, which dissect and transmit the scene energy to photomultiplier tubes detecting in Bands 1, 2, and 3, and silicon photodiodes detecting Band 4. Band 5 energy passes the fiber optic assembly and is reimaged on a radiatively cooled mercury cadmium telluride (HgCdTe) detector. Bands 1 through 4 are calibrated by an internal lamp and by the sun. Band 5 employs an internal blackbody and a cold refer-ence which is a self-view of the detector. The orbiting four-band scanner is furnishing data registered to better than 50-m band-to-band and resolving 80-m repetitive pattern over a 185-km swath width from 907-km altitude. Over a year's time, radiance measurements have shown less than 2% variation.
The Solar Backscatter Ultraviolet and Total Ozone Mapping Spectrometer (SBUV/TOMS) experiment scheduled for launch on NIMBUS G is an expanded capability version of the Backscatter Ultraviolet (BUV) instrument, which has been providing useful data for deducing ozone vertical profiles since its launch aboard the NIMBUS-4 satellite in April 1970. Evaluation of the BUV data has led to a number of design changes on the SBUV/TOMS that will improve our knowledge of the global stratospheric ozone distribution. The BUV instrument sounded ozone in the nadir direction only, and under certain orbital conditions the data were influenced by charged particles in the earth's radiation belts. The SBUV/TOMS instrument has a wider wavelength range, a cross-course mapper, and special provisions for minimizing the effects of space radiation. The BUV instrument is a double (tandem) Ebert-Fastie spectrophotometer measuring spectral intensities at 12 wavelengths from 2555 A to 3398 A with a 10-A bandpass. The SBUV is similar in design to the BUV. It features a state-of-the-art double monochromator that maximizes throughput while providing good wavelength resolution, accuracy, and very high stray-light rejection (106). The TOMS is an ozone mapping system utilizing a close replica of the first monochromator of the SBUV.
The radiation field measurements using a polarimeter and a multispectral radiometer can be used to infer the equivalent optical parameters of aerosol particles. The importance of this experiment lies in the fact that radiative effects of particulates can be calculated without ambiguity if these effective parameters are known. In addition to providing illustrative examples of the derivation of atmospheric parameters from radiation measurements, a critical discussion of the implications underlying these model calculations are given so that the physical significance and the usefulness of these experi-ments can be better appreciated.
The FLD-ll is a computing photometer that determines and displays real-time values of the luminescence and reflectance coefficients of scenes within its field of view. It senses luminescence by limiting the spectral bandwidth of the received energy to the spectral half-bandwidth of a Fraunhofer line-an absorption feature in the solar spectrum-by means of a. solidetalon Fabry-Perot filter. The Fraunhofer lines of interest are generally very narrow (less than 0.1 nm) and are appreciably reduced in intensity from the continuum. The FLD-II can operate from either helicopter or fixed-wing air-craft. The sensitivity of the instrument permits detection of the luminescence of <0.3 ppb of rhodamine WT dye at the 589.0-nm Fraunhofer line. The FLD-II can perform the fol-lowing functions: (1) remote tracking of fluorescent dyes for the study of current flow and rate of dispersion in large bodies of water; (2) detection of oil spills and leaks; (3) de-tection of the luminescence of in vivo chlorophyll of stressed vegetation in order to identify geochemical anomalies in the soil and the onset of crop disease; and (4) detection and mon itoring of pollutants that exhibit an inherent luminescence, such as effluents from phosphate processing plants, laundry detergents containing luminescent brighteners, lignin sulfo nate (a pulp mill effluent waste product), and others. This paper presents both details of the airborne FLD (optical system) and it's extension to an orbiting imaging system with applications to earth resources studies.
The advent of multispectral remote sensing in the 1960s1 evoked interest in its possible application as an acquisition tool, providing information needed to produce topographic and special-purpose thematic maps for civil and military use. Subsequently, the U. S. Army Engineer Topographic Laboratories initiated a program to investigate optimization of this technology by studying the options and tradeoffs. In the course of the investigation, it was determined that the per-formance characteristics of existing multiband cameras and multispectral scanners were unacceptable for evaluating the full potential of multiband imagery for mapping applications for several reasons. With conventional multi-lens and multi-camera photographic systems,293 the primary shortcomings became evident when additive color techniques4 were employed to display the spectrally separated images. The additive color display requires the superposition of several images, projected through spectral filters (nominally red, green, and blue) to exhibit color and false color renditions of a recorded scene. Severe restrictions on the permissible relative distortion between images must be imposed if high-quality displays are to be achieved. The difficulties encountered in shutter synchronization, boresighting, and lens matching are inher-ent sources of relative distortion which must be overcome to obtain coincident, spectrally isolated imagery using conventional camera systems. On the other hand, multispectral scanners, while avoiding some of the distortion problems, lacked resolving power. In order to avoid the limitations imposed by existing equipment, it was decided that a high-performance, experimental multiband camera would be built to provide input imagery for the evaluation. The goal would be to obtain multispectral imagery with minimum relative distortion and maximum resolution for display using additive color techniques.
Molecular beam epitaxy has been applied as a technique for growing low carrier concentration, single crystal thin films of lead-tin-telluride suitable for fabrication of infrared detect-ors in the wavelength region of 3 to 14 um. Lead-tin-tellur-ide photodiode detectors with background-limited performance in the 8 to 14 pm band at 77°K have been fabricated. Twenty-five element linear arrays of lead-tin-telluride detect-ors have been fabricated and flip-chip bonded to an alumina substrate.
In order to optimize the lighting geometry of deep-sea camera systems, theoretical expressions have been developed for determining the loss of contrast due to backscatter. These expressions indicate that significant gains in area coverage result from increasing light-camera separation up to distances on the order of 10 m. This large a lateral separation is not practical for a towed system, so the LIght BEhind Camera technique was used. Field tests indicate that the LIBEC sys-tem has a better than 2 : 1 range advantage over the previously used equipment which had a 1 m lateral separation.
The capability of high-resolution microdensitometers is cur-rently limited by the inability to focus accurately and to maintain focus under dynamic conditions. This paper describes a device for establishing and maintaining submicrometer focus tolerances under dynamic operating conditions that would normally result in gross defocus. The device utilizes pneumatic operating principles in a closed-loop feedback system. The precision and repeatability of establishing the focal position is such as to virtually eliminate the need for visually obtaining best focus. The manual through-focus positioning traditionally done by the operator is eliminated. The focus position is established through a gauge indicator needle that is positioned in submicrometer increments from slightly above the target surface to 20 micrometers below. The system is capable of dynamically maintaining focus over a range of more than 150 gym, and it can accommodate object thick-nesses of up to 1/4 inch. Since the pneumatic servo system employs an air nozzle, it not only provides automatic focusing, but also a film hold-down method that was determined to be the best of a number of possible candidates.
A technique of holographic interferometry yielding a one-order-of-magnitude increase in sensitivity over conventional techniques is described. The method, based on the superposition of a calibrated quarter-wavestep motion on the motion to be detected, is designated as step-biasing. The sensitivity improvements are due to a reversal of the brightness distribu-tion, so that vibrating points appear lighter, nodal points darker. A theoretical discussion of the technique, as applied to the detection of vibration by time-average holographic inter-ferometry, is offered and experimental verification with a 30A peak amplitude of vibration is presented, together with comparison with conventional techniques. The method was originally devised for application to real-time holographic interferometry. This is done easily, yielding the same sensitivity improvement.
The rotation of a shaft is sometimes measured by detecting the position of a narrow beam of light, reflected by a mirror rigidly mounted to the shaft. For small angles of rotation, a centering detector can be used to determine the position or the change in position of the beam. One type of centering detector is comprised of two photo-detectors each having the shape of a hemi-disc. These hemi-discs are placed close to each other so that their straight edges are aligned parallel. If a radially symmetric beam of light is incident on two such detectors with equal sensitivity, their electrical output signals will be of equal magnitude when the beam center coincides with the geometric center of symmetry of the pair. If the beam is displaced, the detector outputs are no longer equal, and the unbalance is related to the magnitude of the displacement.
The next series of articles discusses the applications of fluorescence techniques to environ mental analysis. This approach is of particular interest because of its ability to respond to trace constituents in the atmosphere. The present article discusses the basic concepts of fluorescence. Subsequent articles will (a) cover the advantages and drawbacks of the tech nique, (b) compare it to other light scattering analytical methods, and (c) discuss practical applications of this approach.