A variety of conventional and remotely sensed data for the 25 million acre California Desert Conservation Area (CDCA) have been integrated and analyzed to estimate range carrying capacity. Multispectral classification was performed on a digital mosaic of ten Landsat frames. Multispectral classes were correlated with low level aerial photography, quantified and aggregated by grazing allotment, land ownership, and slope.

Remote sensing is being used with increasing frequency in the development of geologic maps and in the exploration process. Spectral data from airborne and spaceborne multispectral scanners provide information on rock type and vegetation stress, important in geologic applications. Emphasis is now being placed on direct identification of materials rather than discrimination among geologic units. To do this, higher spectral resolution systems with wider spectral coverage than currently available are required. Imaging spectroscopy in the 0.4 - 14 μm region appears to be the answer.

An airborne spectroradiometer system developed at Columbia University has been providing new spectral data for use in remote sensing for natural resources. The system has been improved by addition of a solid state silicon detector array, and has been extended into the infrared by addition of a 64 element lead sulfide detector array. The infrared data in the 2000 to 2500nm region especially holds large potential for mineral and oil exploration.

A near-infrared mapping spectometer is included in the science complement of the Galileo Mission, which will explore Jupiter and its satellites in the mid-1980s. The objectives of the infrared mapping spectrometer experiment are to map compositional units on the surfaces of the Jovian satellites and to characterize the mineral content of these units. For Jupiter's atmosphere, this experiment will investigate such areas as cloud properties and the spatial and temporal variability of minor species. The instrument consists of a telescope, a plane grating spectrometer, a Si and InSb detector array, and a passive radiative cooler. The spectral range is 0.7 - 5.2 μ, covered with a resolution of 0.025 μ. A wobbling secondary mirror in the telescope provides one dimension of spatial scanning, while the other dimension is provided by motion of the spacecraft scan platform.

Throughout the Viking Mission which extended from July of 1976 through July of 1980, more than two Mars years, spectral and photometric observations were made using some complement of the four, paired camera systems, two on the surface and two in orbit. Results of these studies have enabled definition of the probable composition and texture of the surface, grossly and at high resolution; determination of optical properties of the atmosphere from two vantage points and under varying conditions; and overall, a better understanding of the Martian environment.

A novel design for a high-resolution imaging system which includes on-board data editing and optical navigation, suggests high quality images can be acquired from spin-stabilized spacecraft oriented towards high velocity, short duration planetary missions ("Probes"). The approach to designing imaging systems requires that mission objectives be met within the physical and fiscal constraints imposed by the spacecraft and mission design. Severe constraints imposed on a Comet Halley probe (for example, 57km/sec encounter velocity with a small, 10km diameter, object coupled with a great uncertainty in encounter time and distance, were overcome by innovative use of existing technology. Such designs suggest that 3-axis stabilization or non-spinning platforms are not necessary to acquire high resolution, high quality planetary images.

The Thematic Mapper (TM) is a multispectral earth resources sensor intended for application on NASA's Landsat D spacecraft. The performance requirements and design features of the TM have been presented previously in a number of papers. This paper will briefly review the performance requirements and the design features of TM; it will then deal in some depth with the problem of registration between spectral bands. A major performance feature of TM is its multispectral capability and the associated ability of the system to perform tasks involving classification. Registration of these spectral bands is primarily dependent on the ability of the scan mirror to provide a highly linear scan profile. This ability is presented in detail, along with a description of the phenomena causing deviations from linearity. Experimental data documenting the performance of the scan mirror are presented along with a technique of real time compensation for nonlinearities.

An instrument concept that uses solid-state array imaging has been developed for a future land observing system. The design concept is responsive to a variety of use needs and provides improved capabilities over the planned Landsat Thematic Mapper. A comparison of the differing approaches to the instrument design was made, resulting in the selection of a concept which uses a spectrograph coupled to a line-array imager to provide simultaneous spatial and spectral resolution. The design provides an inherent solution to the problem of achieving precise registration among the spectral bands. Data processing on the focal plane is used to select the spectral bands and their band widths. Onboard capabilities include radiometric correction, selection of instantaneous field-of-view and swath width, and data compression.

The general system design considerations that motivated the architecture of a programmable signal processor are presented. They include: accommodation of multiple I/O channels, high throughput, ease of programming, low absolute parts count and stand alone operation. The specific design requirements and the approach to the signal processing for an Imaging Interferometer Sounder are also discussed.

Many of the thermal imaging systems used by the Department of Defense for battlefield surveillance, fire control, and target acquisition are constructed using standardized "Common Module" components. This paper describes a method of modifying a Common Module thermal imaging system such that it can also be used as a spectrometer for 7.5 to 11.5 micrometer radiation. A discussion of the spectrometer spectral filter, optics, electronics, sensitivity, and resolution is included. Example spectra taken in the laboratory and in the field are given along with a description of the digital technique used to identify spectra collected with the instrument.

Linear and area arrays are being used increasingly in spectroscopic, astronomical, and military applications. The unaided array is a powerful detector by itself, but when coupled to an image intensifier tube its spectral range and sensitivity can be greatly extended. We have constructed several types of intensified linear self-scanned array instruments which include various image intensifiers, demountable linear photodiode array assemblies, power supplies, readout electronics, and controls. For example, the use of a high gain tube permits operation in the photon counting mode for astronomical and low-light-level spectroscopic applications. The tubes can be electronically gated to suppress unwanted background or to isolate the main burst from a pulsed radiation source. Instruments having windowless tubes can now be provided to extend the spectral range far into the vacuum-UV region. The intensified array can provide spectroscopic information rapidly and in a form suitable for a computer. In our prototype instruments, photons from a phosphor within the tube are coupled from the tube module to an external array module with fiberoptic coupling. It is also possible to generate the signal using electron bombardment of a specially prepared array mounted within the tube (self-scanned Digicon), and the relative merits of the two approaches will be briefly discussed.

We propose a new design of a hard X-ray and soft gamma-ray telescope spectrometer in the energy domain of 30 keV to 200 keV with reasonable spatial, temporal, and energy resolution for possible space flight missions. This design incorporates a Uniformly Redundant Array (URA) mask in the front end and the Low Intensity X-ray Imaging Scope (Lixiscope) developed in our laboratory as the imaging spectrometer. Using a newly acquired intensifier tube with a digitizing anode, preliminary results indicate that such a complete hard X-ray and soft gamma-ray telescope spectrometer system is indeed feasible.

A dual-input radiometer with matched modulation transfer functions is described. The two MTF's are defined by the form of the two entrance pupils, one of which is annular and the other of which is circular. The radiometer switches alternately between the two pupils by means of a set of polarizing corrpenents. by detecting only the resulting fluctuations in the image, the lower spatial frequencies in the object scene are suppressed. Preliminary measurements of the suppression characteristics as a function of spatial frequency are presented.

Some novel optical approaches to spatial clutter rejection have recently been proposed. Applications include the detection of small objects near larger or brighter emissions and the detection of dim targets against spatially structured backgrounds. This paper presents a mathematical comparison of the performance of conventional optics with that of a tailored optical transfer function approach. The analytic approach used in this paper follows that of Fried and Williams (1977) whereby the root mean square clutter leakage through the sensor is calculated in terms of the power spectral density of the background, the optical system transfer function and the detector transfer function. Attention is given to point source moving targets.

In this paper it will be seen that an aberration corrected holographic diffraction grating can function as the sole optical component in a spectrograph. The use of such a grating has shown that over a flat focal plane, resolution was maintained. In the examples described, two gratings were tested; one of which operated in the range of 2000-8000Å, the other 4000-8000Å, each range distributed over 25mm. Resolution was found to be constant up to lmm on each side of the optical axis perpendicular to dispersion, permitting spatial resolution with wavelength. The device is reviewed in terms of its applications in astronomy and analytical spectroscopy.

Using the selective modulation interferometric spectrometer (SIMS) as a tunable filter is proposed. This tunable filter can have a large optical throughput and a resolving power on the order of a few thousand. A basic explanation of the operation of this filter is given with an emphasis on the similarities and differences between it and a Fourier spectrometer. Several equations that have been found to be particularly useful in designing, operating, and calibrating this filter are presented. The construction and operation of a tunable filter prototype are reported.

A study approach used to define optical tunable filter requirements while operating as an integral part of a satellite-based earth looking IR telescope is presented. The key to the study methodology is a high fidelity, dynamic, end-to-end simulation which generates realistic mission inputs and relates these inputs to system performance as a function of the sensor/filter design parameters. A modular simulation design approach is used which permits the interface of new or existing mission data base inputs. Sensor models relate the mission inputs to the sensor output. Mission models include dynamic targets with their time-correlated spectral radiant intensity and corresponding line-of-sight spectral radiant back-ground. The apparent target spectral radiant intensity contrast and background spectral radiance are computed at the sensor. Sensor models include the optics, optical tunable filter, the staring focal plane array (FPA), point spread function/FPA convolution and detector electronics. Detail design requirements for the filter are selected by exercising the simulation under different mission conditions with different selected optical filter parameters. Analysis of these data provides the inputs for selecting the filter design requirements and an optimum control strategy which can be used for adaptable tunable filter control. Initial results show the importance of spectral agility in an optical filter. It is shown that, in addition to sensor performance dependence on filter design, the spectral band and bandwidths are sensitive not only to the mission/sensor conditions but also to the spectral region selected for the operational system. Examples of data are presented to help demonstrate the analysis procedure and include (1) impact of filter efficiency; (2) system performance vs optical filter parameters; and (3) system performance vs atmospheric conditions.

In carrying out a fairly extensive amount of analysis of the expected performance of various types of signal processing schemes for detection of point targets with a mosaic sensor, we have observed that moving target detection in a cluttered background is so effectively accomplished by an MTI processor that there is virtually no additional help to be obtained from a spatial filtering processor. This does mean that in all cases tharget detection is assured by MTI signal processing methods. The target strength may be so low, or the clutter level so high that nothing can be done that will result in an adequate signal-to-clutter ratio. But in any case, what we have found is that the signal-to-clutter ratio obtained with MTI signal processing alone is much higher than the signal-to-clutter ratio obtained with spatial filtering alone, and that the combination of spatial filtering with MTI signal processing yields a signal-to-clutter ratio that is not noticeably better than that obtained with MTI signal processing alone. In the following we shall try to present an analytical basis for understanding why this is the case.

The development of efficient infrared acoustooptic materials along with techniques for growing these materials as large single crystals of good optical quality has extended the operating spectral range of acoustooptic tunable filters into the near and mid-infrared. As a result, it is now possible to construct compact, high-throughput infrared spectral analyzers controlled by microcomputers. We describe here the design and operation of such a filter, and discuss results of some tests of its application as an infrared gas analyzer.

The acousto-optic tunable filter is a solid state, electronically tunable device suitable for rapid-scanning spectrometer applications. The spectral resolution of the AOTF spectrometer is limited by the size of the acousto-optic crystal. This paper discusses techniques to increase the resolution of an AUTF spectrometer witnout losing its other inherent advantages, particularly its large optical tnroughput. Utilizing an AUTF in optical cascade with a scanning Fabry-Perot interferometer, resolvable bandwidth of 0.8/A was obtained at 3.39 microns.

Polarization interference filters that employ crystals with a strong dispersion of birefringence as the wave plates can provide a very narrow band pass width by using very thin crystal plates. If in addition, the birefringence is small, this filter can accommodate a very wide field-of-view. It is noted, in particular, that CdS exhibits a strong dispersion in the spectral regime between 5200 Å and 5400 Å, with a rate of dispersion that could provide a passband of only 1 Å with a filter structure of several millimeters thick. This paper investigates the properties of these filters. The results are presented and discussed.

In recent years we have been building tunable, narrow band, birefringent filters for the visible spectrum. These filters have bandpasses as narrow as 50 mÅ and can be tuned anywhere in the range 4500-7500 Å in less than one second. They operate over temperature ranges of more than 50°C with wavelength stability better than 5 mÅ. Wavelength stability and control are achieved by reference to a HeNe laser and precision temperature sensors under the control of a microprocessor system which tunes the filter to compensate for temperature variations. The microprocessor capability combined with some new ideas on birefringent filter construction can now enable even more flexibility and active contol of filter performance. Continuous control of passband width as well as location is possible. Real-time control of the shape of the entire visible spectral band for color balancing is now possible.

Honeywell has developed a spectrally agile infrared filter based on the dual tunable Fabry-Perot (DTFP) concept. A DTFP transmits broad or narrow spectral bands which are tunable over a large spectral range. Harmonic spectral transmission can be eliminated by maintaining staggered cavity orders. Several DTFP filters have been fabricated and tested. A closed-loop, capacitive control system is used to adjust plate alignment and spacing. DTFP transmission greater than 0.8 and drive and stabilization times of less than 4.0 milliseconds have been demonstrated. DTFP design considerations and experimental performance data will be discussed.

The large optical anisotropy of liquid crystal molecules is employed to realize an efficient, voltage tunable Fabry-Perot filter. Tuning has been demonstrated in both the visible and middle infrared. The small voltages required to tune over one free spectral range (FSR) result in a device having greater potential for designing filters having a larger range of FSRs, and therefore bandpass widths, than is possible for the solid electro-optic Fabry-Perot described in previous work.1 We show that for many commercially available liquid crystal materials, infrared operation is possible over wide regions where molecular absorptions do not occur.