Dormant since 1857, Mount St. Helens Volcano in southwestern Washington stirred from its repose to erupt on March 27, 1980, following a week of premonitory earthquake activity. The eruption was the first in the conterminous United States since the 1914-1921 activity of Lassen Peak, California. The eruptive activity through May 17 was intermittent and relatively mild, but the accompanying seismic activity remained intense. On May 18, a catastrophic eruption, triggered by a magnitude 5.0 earthquake, produced a massive landslide/debris avalanche, a devastating lateral "blast," pyroclastic flows, mudflows, and an ash column that rose more than 20 km into the stratosphere. Winds carried the ash easterly, and more than 7 cm of ash was deposited locally in parts of eastern Washington. The landslide/debris avalanche and associated mudflows caused flooding of the Toutle and Cowlitz River valleys, which carried sediment as far as the confluence with the Columbia, where it choked off the channel to navigation. Smaller but significant explosive eruptions followed in May, June, July, August, and October, 1980, with lava domes being extruded in the crater following the June, August, and October eruptions. Subsequently in December 1980 and February 1981, lava domes were extruded without significant preceding explosive activity. Except for the latter two, each dome was partly or wholly destroyed by succeeding explosive events. Scientists expect similar activity to continue for months or years--possibly even decades. The Mount St. Helens eruptions severely tested the ability of scientists to respond swiftly and effectively in assisting public officials during a geologic disaster. At the same time, they shall continue to provide an unprecedented opportunity for the systematic investigation of volcanic phenomena, and hopefully, the insight to meet possible future eruptions there and elsewhere in the Cascade Range with equal success.

Following the volcanic eruption of Mount St. Helens on May 18, 1980, the surrounding area was obscured by varying amounts of clouds and ash for 30 days. A total view of the damaged area was needed immediately. This need was met within 3 days by acquiring high-altitude side-looking airborne radar imagery. This imagery was analyzed using only the char-acteristics of the radar returns in conjunction with preeruption high-altitude photography. The analyst was able to establish the areal extent of the changes in lakes, topography, and damage to timber caused by the eruption. The three radar condi-tion maps were compared to posteruption photography collected on June 19, 1980, and other damage condition maps. These comparisons show good agreement for both the boundaries between classes of damage and the types of damage defined by the radar imagery. A major factor in the total exploitation of the radar imagery was the availability of image analysts trained and experienced in interpreting the characteristics of radar returns from natural vegetation. This study shows that high-resolution radar data can provide important information on the damage to large areas when obscuration prevents the use of other types of imagery.

Lidar measurements of the worldwide movement of stratospheric aerosols produced by the 18 May 1930 eruption of Mount St. Helens are described. Ground-based and airborne measurements show that the layers below 20 km produced by this eruption moved in an easterly direction while those above 20 km moved in a westerly direction. The effluent at jet stream altitudes of 10-12 km circled the globe in about 16 days, and the effluent at 23 km (the highest altitude recorded) circled the globe in about 56 days. Mass calcu-lations, using backscatter-to-mass conversion models, indicate that approximately 0.5 x 106 metric tons of new stratospheric material was produced by this eruption. Even though this represents a 2008 increase in Northern Hemispheric aerosol, no significant long-term atmospheric temperature change should occur.

The explosive eruption of Mt. St. Helens on 18 May 1980 was monitored by infrared sensors aboard two U. S. Air Force satellites. Essentially continuous data are available following the initial sighting of the eruption cloud less than one minute after the earthquake which triggered the eruption. Dual monitoring permits triangulation so that both the horizontal and vertical development of the eruption can be determined with good temporal resolution. The sequence of events occurring early in the eruption can therefore be established.

The eruption of Mount St. Helens on May 18, 1980, and subsequent destruction of ap-proximately 593 square kilometers (229 square miles) of vegetation, clearly provided a unique opportunity for earth-oriented satellite remote sensing systems. Landsat, a relatively high resolution Multispectral Scanner (MSS) system, imaged Mount St. Helens both before and after its major eruption. Digital data have been used to create a damage assessment map and a change detection image. Several classes of timber damage and land cover modification have been developed. Acreages for each class have been tabulated.

After the destructive volcanic eruption of Mount St. Helens on May 18, 1980, there was a need for a quick response damage assessment. Timeliness of the information was emphasized because of the need to immediately devise land man-agement plans for timber sale operations, rehabilitation efforts, fire protection activities, and areas to be preserved. High-altitude color-infrared photography was collected during May and June by the National Aeronautics and Space Administra-tion (NASA) Ames Research Center (ARC). Interpretation of the photography plus a helicopter trip into the area provided the basis for the construction of 58 map-registered overlays within a 3-week period. These overlays depicted in detail the damage to timber resources, the transportation network, and the watershed. Using the 14 timber loss overlays, U.S. Department of Agriculture (USDA) Forest Service personnel were able to digitize cells depicting ownership, degree of damage, and the preeruption cover classes. These digitized data provided such informa-tion as the total area affected within and outside the national forest, total timber acreage destroyed and damaged, the sizes of timber destroyed, and the acreage of barren land both before and after the eruption. The hydrology and transportation overlays provided information for an alert system to locate areas needing in-depth studies. These problem areas were then studied in detail on low-altitude color photography so that potential erosion sites could receive preventive treatments and essential access roads needed for fire control and timber salvage could be repaired.

The Landsat-D systems offer several improvements in terms of observations from space for the Earth resource manager and scientists studying processes that occur on the surface of the Earth. The principal and new observing instrument, the thematic mapper (TM), will provide higher spatial resolution (30 m) than the radiometric observations provided from Landsats 1 through 3 (80 m), and, in addition, observations in new spactral bands (0.45 to 0.52, 1.55 to 1.75, and 2.08 to 2.35 micrometers) will be available. These characteristics in themselves are expected to offer considerable advantages in identifying crops and assessing the acreage and condition. Further advantages will also be realized in mineral exploration and land resource assessment efforts. The recently revised Landsat-D program calls for the launch of the first spacecraft (Landsat-D) in the third quarter of the 1982 calendar year with a multispectral scanner (MSS) on the spacecraft and a TM, if it is available. The second spacecraft (Landsat-D'), to be launched 12 to 15 months after Landsat-D, will include an MSS and a TM. The capability for processing the MSS data from Landsat-D should be operational by January 1983. The operational capability for processing TM data should exist in January 1985.

Throughout the world topographic maps are generally compiled by manually operated stereo plotters which recreate the geometry of two frame camera positions from which wide angle overlapping photographs were taken. Continuous imaging systems such as strip cameras, electro-optical scanners, or linear arrays (push brooms) also create stereo coverage from which, in theory, topography can be compiled. However, the instability of an aircraft in the atmosphere makes this approach impractical. The benign environment of space permits a satellite to orbit the earth with very high stability as long as no local perturbing forces are involved. A solid-state linear array sensor has no moving parts and creates no perturbing force on the satellite. Thus a linear array sensor in space promises to provide a new mapping tool. The importance of this concept should not be underestimated. The one dimensional data from linear array detectors lend themselves to digital processing and thus the concept of automated mapping in near real time can, in fact, become a reality.

The Orbiter Camera Payload System, the OCPS, is an integrated photographic system which is carried into Earth orbit as a payload in the Shuttle Orbiter vehicle's cargo bay. The major component of the OCPS is a Large Format Camera (LFC) which is a precision wide-angle cartographic instrument that is capable of produc-ing high resolution stereophotography of great geometric fidelity in multiple base to height ratios. The primary design objective for the LFC was to maximize all system performance characteristics while maintaining a high level of reliability compatible with rocket launch conditions and the on-orbit environment.

In order to fully understand the radar signature of different surface features and covers, observations must be acquired with a variety of sensor parameters (i.e., frequency, polarization, and incidence angle). This allows the selection of an appropriate set of sensors parameters which will provide the most information about the surface. The Shuttle Imaging Radar (SIR), which is planned by NASA for a series of flights in the 1984-86 time frame, will have the capability to obtain surface images at two frequencies (L-band and C-band), at multiple polarizations, and all incidence angles from near vertical to near grazing. The SIR will operate in the synthetic aperture imaging mode and provide digital images of the surfaces with a resolution of about 20 meters. As part of the SIR flights, a number of planned large-scale experiments will be conducted in the fields of geologic mapping, vegetation classification, land cover mapping, surface moisture measurements, and ocean surface observation.

The next generation of instruments for planetary exploration will include advanced spectrometers and imaging systems. These instruments will take advantage of emerging charge coupled device (CCD) technology and synthetic aperture radar (SAR) development.

A computational model of the processes involved in multispectral remote sensing and data classification is being developed as a tool for designing smart sensors which can process, edit and classify the data that they acquire. By accounting for both stochastic and deter-ministic elements of solar radiation, atmospheric radiative transfer, surface and cloud reflectance, and sensor response, the model can be used to simulate and evaluate the performance of sensor spectral responses and concepts, data processing algorithms and topologies, and device performance characteristics for various tasks that might improve the efficiency of multispectral remote sensing. Typical tasks are editing of cloud cover and opaque haze, automatically correcting for atmospheric effects, and adaptively classifying data into land use categories and surface substances. Preliminary computational results are presented which illustrate the dependence of editing and classification errors on the selection of sensor spectral channels and data processing algorithms and topologies as well as on the natural variability of the atmospheric transmittance and surface reflectance. The results include an evaluation of the performance of three sets of spectral channels: the four Landsat D MSS and TM channels which are located in the visual and near-IR region, and the three channels which were proposed by Kondratyev et al for the survey of natural formations.

Future land observing satellites having multiple thematic mappers will produce data at rates of 100 to 300 Mbps. These rates, coupled with a high daily scene production rate, will require new and innovative approaches to ground processing. A consideration of future downlink rates and data volumes is made. Requirements specific to the future user community are discussed. Next, advanced technologies required to achieve an operational system in the 1985-1990 time frame are considered. Planned advances in the fields of communications, mass storage, bulk memories, and data processing are discussed. Utilizing advanced devices, a centralized data processing system capable of handling the 100 Mbps data rate is presented. New approaches, including a parallel pipelined calibration front-end, real-time brouse image production, a high bandwidth optical disk archive, regional image broadcast and massively parallel product production, are considered. A distributed system capable of handling the 300 Mbps data rate is next discussed. Designs are presented for a hub system and a regional processing center. Migration considerations involving the transition from a basic 100 Mbps centralized system to a 300 Mbps fully distributed system are discussed. Finally, the technological short falls expected in realizing a late 1980's implementation date are examined.

The Geostationary Operational Environmental Satellite (GOES-4) launched on September 9, 1980, carried an improved infrared radiometer to produce the first atmospheric soundings from geostationary orbit. An interactive system has been developed at NASA/Goddard Space Flight Center to receive data from this instrument in near real time and to perform interactive display and analysis of the 12 channel infrared imagery. The system is minicomputer based, and uses a menu approach to guide the analyst through spacecraft instrument programming, area and band selection, image acquisition, enhancement, analysis, and presentation of results. The system is interfaced via dual port disks to Goddard's Atmospheric and Oceanographic Information Processing System (AOIPS) for comparison of sounding results with parameters derived from conventional data and from time lapse analysis of visible and IR imagery from other geostationary satellites. The system hardware and software is being expanded to add capabilities for integration and assimilation of VAS data with data from other sources, comparison of severe storm observations from space with special ground network data, and for development of diagnostic models. This paper describes the configuration and operation of the VAS System hardware and software, and discusses the development of transportable software for extension to a distributed multiprocessor environment.

This paper summarizes an operational philosophy of the Tactical Radar Image Processing System (TRIPS). The basic areas covered in this paper are: (1) positioning and control of reference scene imagery; (2) unique radargrammetric least squares modeling to perform target coordinate derivation; (3) off-the-shelf automatic data processing (ADP) hardware to receive, buffer, and exploit the Synthetic Aperature Radar (SAR) data, and (4) all required data bases including a digital terrain matrix. The reconstructed SAR digital image will be received by a Data Base Processor (DBP) where it will be digitally compressed and stored. The receipt of a SAR scene puts a flag into a queue for the screening/interpretation console. When a console becomes available, the scene will be decompressed and sent to a virtual image refresh disc at the console. The console operator will be able to screen the image by roaming, rotation, zooming, or performing the classical digital image enhancements. When a target is detected, a corresponding subset of a reference image covering the target area will be selected. This subset will have ancillary parameters such that for each discrete pixel a latitude, longitude, and height can be computed. The reference scene will be precontrolled using the Defense Mapping Agency's Point Positioning Data Base (PPDB). The operator will transfer the target location to the reference image. A radargrammetric least squares adjustment will be performed resulting in a precise latitude, longitude, and height for the target along with an analytically derived accuracy figure. The Defense Mapping Agency's DLMS Terrain Data Base will be used for the height determination.

The Image Processing Facility at the NASA/Goddard Space Flight Center utilizes High Density Tape Recorders (HDTR's) to transfer high volume image data and ancillary information from one system to another. For ancillary information, it is mandatory that very low bit error rates (BER's) accompany the transfers. The facility processes approximately 1011 bits of image data per day from many sensors, involving 15 independent processing systems that require the use of HDTR's. The original purchase of 16 HDTR's met state of art performance of 1 x 10-6 BER as specified. Later the BER requirement was upgraded in two steps: incorporation of data randomizing circuitry to yield a BER of 2 x 10-7; and further modification to include bit error correction capability to achieve a BER of 2 x 10-9. The overall improvement factor was 500 to 1. This paper provides the background, technical approach, and final results of these modifications. Also included are general discussions of the format of the data recorded by the HDTR, the magnetic tape format, magnetic tape dropout characteristics as experienced in the Image Processing Facility, head life history, and reliability of the HDTR's.

The Bausch & Lomb Zoom 500 Imagery Analysis Station is the first production unit designed as a system incorporating viewing optics and light table for the specific purpose of detailed photointerpretation of aerial photography. This system integrates the newest Zoom 500 high performance stereoscope with the latest in light table illumination systems, the high intensity ring illuminator, to provide a total system offering the ultimate in optical performance, illumination and human engineered operator comfort. The Zoom 500 Stereoscope was conceived and designed to supplement the Zoom 240 and has features which makes it especially appealing to the photointerpretation community. The light table was conceived around the high intensity ring illuminator, which provides an order of magnitude increase in illumination intensity over standard light tables, at a fraction of the power consumption. The Zoom 500 Imagery Analysis Station integrates these two into a modular system which, for the first time, addresses human factors engineering as a major design parameter. The resulting Zoom 500 IAS has proven to be a significant advance in the field of photointer-pretation.

Geo-based information Systems are developed to serve for land use or other area planning purposes. Digitizing data from existing maps provides the basic data base for these Systems. Although the data in Geo-based information Systems is very useful for the overall planning process that data is usually inadequate to be used in "Action" programs. Use of the Analytical plotter is described to input data, into a Geo-based system, that will be adequate for "Action" planning and implementation.

A computer-assisted photo interpretation research (CAPIR) system has been developed at the U.S. Army Engineer Topographic Laboratories (ETL), Fort Belvoir, Virginia. The system is based around the APPS-IV analytical plotter, a photogrammetric restitution device that was designed and developed by Autometric specifically for interactive, computerized data collection activities involving high-resolution, stereo aerial photographs. The APPS-IV is ideally suited for feature analysis and feature extraction, the primary functions of a photo interpreter. The APPS-IV is interfaced with a minicomputer and a geographic information system called AUTOGIS. The AUTOGIS software provides the tools required to collect or update digital data using an APPS-IV, construct and maintain a geographic data base, and analyze or display the contents of the data base. Although the CAPIR system is fully functional at this time, considerable enhancements are planned for the future.

In contrast to the traditional recording from high-altitude aircraft of Earth images directly onto film in their inherently continuous analog form, a Landsat Earth resources satellite samples the ground image brightness and records it on a digital, electronic medium. Although digitization incurs several extra steps in the reproduction of the imagery, it permits manipulation or enhancement of the data for special uses. For instance, image data enhancement techniques can be applied to partially restore contrast lost because of atmospheric luminance and scatter. More significantly, the digital-to-analog transfer function of the film recorder can be modified to simulate certain characteristics of other film types. Manipulation of a film's apparent gamma, relative speed, and linear-response region is easily accomplished by mapping the input data to a new distribution in real time using a hardware-implemented lookup table. To accomplish the desired photographic results, however, full cooperation and communication between photographic, electronic, and computer technologists is essential.