The photographic recording of high-voltage electric fields is accomplished in several ways, and it is variously called by several names as well, including radiation-field photography, electrography, high-voltage photography, klydonography, corona-discharge photography and most recently, Kirlian photography.
The atmosphere has been a subject of interest and concern throughout history. In the form of clouds, winds, and storms, it affects the lives of people in fundamental, obvious ways. In ways of which we are less conscious, it provides protective and stabilizing functions; for example, the ozone filters out ultra-violet radiation, which, in the present evolutionary state of the human species, would do serious harm to our health. In addition, the earth's radiation balance is affected by the composition of the atmosphere. Consequently, with our consumptive practices and increasing abilities to intrude upon its natural condition, the possibilities of long-term, accumulated harmful effects are in evidence.
The spin scan camera was first flown on ATS-1 from 1966 to 1973 to continuously monitor the global atmospheric circulation. Later, modified versions with improved sensor capabilities were flown on ATS-3 and SMS. Today, the GOES series of spin scan cameras is in regular operational use. The value of the spin scan camera as a dependable meteorological workhorse requires proper functioning of the entire camera system, composed of four main elements: a) a spinning spacecraft whose highly stable and predictable motions generate a time divisible precision scan and therefore a metric image; b) a telescope having both on-axis image quality and a wide field of view; c) a data chain which in-corporates duty cycle improvement and uses the spacecraft as a communication link to distribute the image data to users; and d) image display and analysis techniques which permit organizing a large number of images in the time domain and efficiently selecting and measuring data of greatest importance.
This paper describes the goals and performance characteristics of the LIMS radiometer to be flown on the NIMBUS G spacecraft scheduled for launch into a polar orbit in 1978. Radiance measurements are made of gases (03, H2 0, NO2 , HNO3 , and CO2) that are key elements in the nitrogen ozone photochemistry, which is crucial to an understanding of the natural processes controlling the ozone distribution in the atmosphere. The earth limb is scanned and imaged with an optical system designed for compatibility with a two-stage solid-cryogen cooler. Six different bandpass (Hg,Cd)Te detectors are cooled with solid methane to 65 K. The detected outputs are demodulated and low pass filtered before being multiplexed and digitized with a 12-bit A/D converter. The primary LIMS data output is in the form of a highly multiplexed serial digital word at 4 K bps rate. Every LIMS word transmitted from spacecraft to ground control contains data from each radiance channel and pertinent housekeeping functional performance data. Inversion algorithms are used to operate on the CO2 limb radiance profiles which determine the vertical temperature distribution. Along with the measured radiance profiles in the other spectral bands, this inferred temperature profile is used to calculate the vertical distribution of NO2, H2 0, 03 , and HNO3. Profiles are determined with 1 and 2 km resolution over altitudes of 10 km to 80 km.
The lidar (laser radar) technique of remotely observing atmospheric structure and composition is now ready for use on a space vehicle. Progress in lidar technology has led to the development of high performance, light-weight, compact and highly reliable basic systems. These could ensure successful mapping of clouds and aerosols by elastic backscattering and offer high promise of opening up a range of more sophisticated observations using wavelength-specific techniques (resonant scattering, differential absorption and Doppler). The Spacelab program provides an ideal facility for initiating and exploring this concept, since it makes possible development on a short-trip, minimum-investment basis. The goals, philosophy and rationale of a proposed program to accomplish the first use of lidar in space are described, and details are provided of the specific observations proposed and of the necessary instrumentation. Using a solid-state neodymium laser, frequency doubled to drive a tunable, doubled dye laser, energy could be transmitted at a range of wavelengths (1060 nm, 589 nm, 530 nm and 279.6 nm). With simple wavelength-discriminating photometric detectors the system could be used to detect returns from particles (cloud and dust) or Na atoms or Mg+ ions. The value of a capability to make such observations is noted in terms of their meteorological and aeronomical significance.
The differential-absorption lidar (DIAL) technique is recognized worldwide as being a sensitive and long-range method for making remote measurements of gases. This article summarizes the research performed at SRI on the infrared DIAL. A deuterium fluoride lidar was used for the remote measurement of integrated concentrations of HC1, CH4 , and N2 0 in a sample chamber between the lidar and a topographic target. A CO2 lidar was employed for range-resolved measurements of ambient water vapor using radiation backscattered from naturally occurring aerosols. Also, integrated concentrations of ambient ethylene were measured using a CO2 lidar system, and good agreement was obtained between lidar and in situ measured concentrations. Calculations indicate that range-resolved concentration profiles can be obtained for many gases at a range of 10 km using commercially available components.
High resolution infrared spectroscopy is a very useful technique for remote sensing of atmospheric constituents. From an aircraft it is possible to use emission or absorption spectroscopy to measure total quantities of constituents above the aircraft or profiles at altitudes below the flight. The adaptation of a commercial high resolution (0.06 cm-1) Fourier transform infrared spectrometer for use in absorption spectroscopy on a jet aircraft is described, emphasizing methods of dealing with the difficulties of the aircraft environment. Atmospheric constituents with concentrations less than one part per billion can be measured.
Both passive and active remote monitoring instruments, using discretely tunable infrared gas lasers and heterodyne receivers, have been used for measurements of ozone and other trace constituents in the atmosphere. A ground-based, solar heterodyne radiometer has been used in discrete spectral regions near 9.5 pm to measure altitude profiles of ozone in both the troposphere and stratosphere. Results indicate that this technique shows promise in providing calibration points for earth orbiting ozone measurement instruments. An airborne laser absorption spectrometer has been used to measure tropospheric ozone in two series of flights during the winter and spring of 1977, and these operations will be described here. Plans are also in progress to fly a balloon-borne heterodyne radiometer during the fall of 1977 in order to measure stratospheric trace species.
Infrared heterodyne spectroscopy provides a means of measuring the intensity profiles of individual rotation-vibration spectral lines with high sensitivity. Considerable effort has been expended on optimizing these instruments for remote measurements of gases in planetary atmospheres with the result that present generation spectrometers now are beginning to provide new and startling results on the planets. In this paper, the fundamental principles of laser heterodyne spectroscopy are discussed. Detailed considerations of the optical design and of the electronic design of the spectral line receiver are given. Representative results obtained with this spectrometer are discussed, including precision frequency measurements of NH3 (1)2 ) lines, detection of auroral emission from Jupiter, and measurements of terrestrial 03 and CO2.
A laser absorption spectrometer (LAS) is described which employs a wavelength tunable Pb 1-xSnxSe laser diode in conjunction with a multi-pass White cell. Absorption coefficients as low as 3 x 10-3 m-1 can be measured as a result of using a laser wavelength modulation technique to suppress noise in the detection system. This constitutes an improvement of several orders of magnitude in sensitivity compared with earlier reported applications of the direct absorption technique employing tunable diode lasers. The performance of the LAS is illustrated by describing the measurement of three gases commonly found in the atmosphere: SO2 and N2 0 with sensitivities of 1 ppb, and NH3 with a sensitivity of better than 0.1 ppb. The linearity of re-sponse and calibration of the instrument are also discussed in some detail.
The Atmospheric X-ray Emission Telescope (AXET) is designed to image and measure the spatial, temporal, and spectral distributions of x-ray aurorae produced in the upper atmosphere by precipitating energetic electrons. The bremsstrahlung produced x-ray radiation penetrates to stratospheric depths where it can modify ozone, conductivity, and other critical atmospheric parameters. Remote sensing of this radiation from topside will provide vital data on solar-terrestrial relationships and mechanisms that could help trigger tropospheric response to solar activity. The X rays also provide direct information concerning the dynamics of radiation belt processes within the magneto-sphere. AXET is designed to detect sources up to 50 keV and to image them below 25 keV by means of directionally sensitive proportional counters with passive collimators. It will be mount-ed in the space shuttle on a single, fixed platform designed to optimize viewing conditions for the anticipated orbits and as-pects of early Spacelab missions. A more sophisticated instru-ment is proposed for later missions when instrument pointing systems are available. This instrument concept is based on a two-dimensional spatially sensitive multiwire proportional counter with appropriate collimators, and will provide improved sensitivity and resolution.
An optical processor for direction independent differential operation a/ax + is/ay is described and feasibility studies for filter fabrication are reported. The resulting intensity distribution of the filter function can be generated by superimposing periodic time dependent pulse functions which modulate a writing beam (flying spot, monitor). Hence the filter transmission can be registered on a photographic film or by real time processing on an electro-coherent optical converter. This kind of filter generation allows changing the filter parameters with high speed, controlled by computer. The application of this processor to medical and biological images will be demonstrated.
This paper reviews the theory and the practical implementation of the selective modulation interferometric spectrometer (the SIMS). This spectrometer has an extremely large optical throughput, and it can scan the spectrum in real time while requiring no more signal processing than a chopped radiometer. Equations are presented which describe the relationship between design parameters and spectrometer performance. Practical design problems are identified, and some solutions to these problems are given.
Mode-locked laser techniques for obtaining spectroscopic information about ultrafast molecular processes occurring on a picosecond time scale are described. The results of picosecond measurements on several systems are presented as examples of the method. The advantages of employing two-dimensional vidicons and recently developed dispersive techniques to obtain time-resolved transient spectra with a single laser pulse rather than with multiple pulse techniques are discussed.
A description is given of the essential points of DIN 58185 Optical Transfer Function, in particular of the principles of OTF measurement, the necessary equipment and problems likely to be encountered during measurement. Items of special importance are incoherent illumination, linearity especially of the electronic system, and the existence of an isoplanatic region. These have to be checked before measurement. Other points of interest are the lowest spatial frequency for normalization, the selection of azimuth in the test pieces and the effect of auxiliary systems, insofar as these are used. When measuring phase, a distinction must be made between phase and distortion. Calibration should ensure that phase starts with a horizontal tangent. Information is given on the effect of veiling glare.
A unique, modern instrument is described for resolving and measuring fine detail and transient changes in the angular structure of underwater radiance fields. This instrument makes use of modern developments in photographic wide-angle lens design, random access image analyzers and digital engineering tech-niques to provide a versatile instrument for measuring and recording radiance distributions. An implementation of this instrument is described which was deployed for two months in coastal waters of southern California. Examples of data acquired are presented and illustrate the versatility and features of the underwater radiance scanner. Fundamental radiometric measurements can be accomplished rapidly with a high confidence in the data. The ability to record time varying phenomena and analyze the data statistically is shown. Also, near real time presentations of the data to the experiment director in the field are possible. Storage of all data on magnetic tape allows later pro-cessing by computer and display of the data in a wide variety of formats.