Overview of Improved Limb Atmospheric Spectrometer (ILAS) instrument design, band selection studies, and operation plan is described. The ILAS is a solar occultation instrument onboard ADEOS spacecraft with two grating spectrometers: one is for measurement for O₃, HNO₃, NO₂, N₂O, H₂O, CH₄ CFC11 and CFC12 in the infrared band (850-1610cm^-1, 11.76µm-6.21m), and another is for aerosols, temperature and air density measurement in the visible band (753-784nm, O₂ atmospheric A band). The ILAS will observe the ozone layer over high-latitudes (N55-70, S63-87) regions with a high vertical resolution (2km) for a period of 3 years after launch in 1996.

This paper applied the polarimetric filtering principle to Synthetic Aperture Radar (SAR) image sets in three possible polarimetric radar channels and compared the resultant imagery. The polarimetric radar channels in consideration here are Co-Pol, Cross (X)-pol, and Matched (M)-pol channels. Each channel has its own polarimetric characteristics for imaging. Using the formulation of the contrast enhancement factors based on the Stokes vector formalism, polarimetric enhanced images for three channels are shown using NASA JPL DC-8 AIRSAR data sets (CC0045L, Bonanza Creek, AK/USA). It is shown that the optimally enhanced Co- and X-Pol channel images play a decisive role in imaging in a complex featured background.

SEASAT synthetic aperture radar (SAR) echoes from the sea show beautiful images of storms over the ocean. However, the mechanisms by which such storm images are created have not yet been revealed very well. The core of these images is usually an echo-free hole which is attributed to the damping of the radar-detectable short gravity waves by the intense rain in the storm core. The bright area surrounding the core is believed to be caused by strong winds diverging from the downdraft which is collocated with the intense rain. The outer boundary of the bright area has been found to be associated with the classical gust front. During the Tropical Ocean Global Atmosphere/Coupled Ocean-Atmosphere Response Experiment (TOGA/COARE), continuous observations of rain by shipborne radars were carried out. One image of JERS-1 SAR taken in this period contains storms that were within the observation area of a shipborne radar. The SAR image and the rain-radar image are compared. Even though the signal-to-noise ratio of the SAR image is very low, there is good correspondence between heavy rain areas and some of the dark areas in the SAR image. The boundary of a rain-induced dark area is found to correspond approximately to the radar reflectivity factor (Z-factor) of 35dBZ or 5.5mm/h of rain.

Data reduction method for the earth-satellite-earth laser long-path absorption measurements of atmospheric trace species using the Retroreflector in Space (RIS) on the Advanced Earth Observing Satellite (ADEOS) is described. In the RIS experiment, atmospheric absorption will be measured with single-longitudinal-mode pulsed CO₂ lasers and their second and third harmonics. High-resolution absorption spectra are measured by using the Doppler shift of the return beam which is caused by the satellite movement. Vertical profiles of O₃ and CH₄ are retrieved from the measured absorption line shapes with the inversion method. Also, column contents of CFC12, HNO₃, CO₂, CO, N₂O are derived by the least squares method with assumptions on the relative vertical profiles. Errors in the measurement were evaluated by computer simulation.

The Bidirectional Reflectance Distribution Function (BRDF) is an intrinsic measurement of directional properties of the earth's surface. However, the estimation of the BRDF requires many remote sensing measurements of a given surface target from different viewing angles. In addition, a good atmospheric correction scheme is a prerequisite for such an attempt. The airborne POLDER sensor measures successively reflected radiation by terrestrial surfaces in a framed image form at different viewing angles during a single airplane pass, like taking snap-shot pictures. A specially improved atmospheric correction algorithm which is applicable to a framed image data by POLDER sensor is presented. The observed reflectance images taken successively by the airborne POLDER at slightly different viewing angles are converted to a series of surface albedo images by applying our atmospheric correction algorithm. Then, the BRDFs for three surface covers, namely, "River Water," "Forest," and "Rice Field," are estimated by using successive albedo images. It is found that the BRDF for "River Water" follows Lambert law at both 550nm and 850nm. It is also found that the BRDFs for "Forest" and "Rice Field" follow Lambert's law at 550nm, but they follow an anisotropic reflection law at 850nm and fitting parameters for their BRDFs are presented.

Physical and optical parameters within the atmosphere-ocean system have been retrieved by a multiple scattering analysis of the reflectance and degree of linear polarization data measured by the airborne POLDER sensor in Medimar campaign in 1991. Assuming an atmosphere-ocean system with a Cox-Munk type rough sea surface model, the theoretical reflectance and -degree of linear polarization were computed by the doubling and adding method for several different models. In this study the retrieval was made by assuming a fixed refractive index of the aerosol particles, i.e., N_r=1.33-0.0i. We obtained several important results in this study as follows:
1) By comparing computed results with the observed data at 0.85m, we rejected the oceanic type aerosol model and found Junge type aerosol model with its index range of 4.0v4.5 as an appropriate model for aerosols at the observation time.
2) The reflectance data analysis in the perpendicular plane rejected an isotropic Cox-Munk model, but it indicated that an anisotropic Cox-Munk model should be used in the sea surface wind field retrieval.
3) The surface wind speed was estimated to be 10.0m/secV15.0m/sec with an best estimate of V=12.5m/sec, which agrees with the observed wind speed of V=14.4m/sec. The range of the water column reflectance was also estimated to be 0.025r_wc0.045 from Medimar reflectance data at 0.45m.
4) Further study should be made for other refractive indices of the aerosol particles. More refinement of the present multiple scattering code to include upwelling polarization components from below the sea surface is also necessary.

There have been many developments on neural network research, and ability of a multi-layered network for classification of multi-spectral image data has been studied. We can classify non-Gaussian distributed data using the neural network trained by a back-propagation method (BPM) because it is independent of noise conditions. The BPM is a supervised classifier, so that we can get a high classification accuracy by using the method, so long as we can choose the good training data set. However, the multi-spectral data have many kinds of category information in a pixel because of its pixel resolution of the sensor. The data should be separated in many clusters even if they belong to a same class. Therefore, it is difficult to choose the good training data set which extract the characteristics of the class. Up to now, the researchers have chosen the training data set by random sampling from the input data. To overcome the problem, a hybrid pattern classification system using BPM and Kohonens feature mapping (KFM) has been proposed recently. The system performed choosing the training data set from the result of rough classification using KFM. However, how the remotely sensed data had been influenced by the KFM has not been demonstrated quantitatively. In this paper, we propose a new approach using the competitive weight vectors as the training data set, because we consider that a competitive unit represents a small cluster of the input patterns. The approach makes the training data set choice work easier than the usual one, because the KFM can automatically self-organize a topological relation among the target image patterns on a competitive plane. We demonstrate that the representative of the competitive units by principal component analysis (PCA). We also illustrate that the approach improves the classification accuracy by applying it on the classification of the real remotely sensed data.

A new method is proposed for realizing a flexible change detection which is free from the limitation that multitemporal images must have the same spectral bands whose center wavelength and bandwidth are identical. As spaceborne multispectral scanners are continuously improved for performance and new scanners do not necessarily have the same spaectral bands for observation, this limitation is a serious obstacle for detecting long term temporal change. The proposed method removes this limitation by using an image normalization technique based on multiple regression analysis. The method is successfully applied to actual remotely sensed multitemporal images.

The wavelet transform provides information both in the spatial domain and in the frequency domain because of its inherent nature of space-frequency analysis. This paper presents a classification result of synthetic aperture radar image obtained by JERS-1 based on the discrete wavelet transform. This paper points out that the wavelet analysis has yielded a fine result in texture classification compared to a conventional method with less computation time.

This paper discusses and evaluates an effect of cell level FEC (Forward Error Correction) capability on error-free (i.e. reliable) IP multicast service over ATM networks. In the error-free IP multicast service, every receiver is delivered IP packet from the sender synchronously. Without applying the FEC policy, the expected IP packet error/loss probability becomes large, when the number of multicast receivers is large. For example, when the cell error/loss probability of each ATM data-link segment is 10^-6 and the number of receivers is 10³, the IP packet error/loss probability observed at the sender is about 0.5, which means that about 50% of IP packet sent from the sender will be subject to retransmission. One possible solution would be using the intermediate multicast-TCP entities, that terminate TCP protocol, among the sender and the receivers. However, this approach requires the additional entities within the network and can not provide the ordered message delivery for a multipoint-to-multipoint communication. On the contrary, with applying the FEC policy, the expected IP packet error/loss probability is dramatically reduced. Therefore, an error-free IP multicast service can be provided with a simple architecture, even when the number of multicast receiver is large, e.g. 10⁵. For example, when the cell error/loss probability of each ATM data-link segment is 10^-6, the packet error/loss probability observed at the sender is less than 10^-2 even for 10⁶ receivers. Finally, even when the cell error/loss probability of ATM data-link segment is large, e.g. 10^-3, the IP multicast service without the FEC policy can not apply even for 10 receivers. However, the IP multicast with the FEC policy can apply upto few hundred of receivers.

We propose a distributed operation system platform for optical cable networks. This distributed platform is an extension of the previously proposed platform for a flexible cable network operation. The concept of the unit platform has been proposed for the distributed operation system platform. By using this concept, we discuss the system upgrade including the connection to other operation systems. We use an object-oriented software technology for designing the distributed operation system platform. The prototype system has been constructed using C++ programing language and the evaluated results are shown.

This paper investigates the problems which inhibits the use of today's WDM networks. These are propagation delay, packet processing overhead, bit & frame synchronization, and tuning latency. So far, these problems, especially propagation delay, have been ignored in most performance analysis papers. They have always hindered network designers, but they are magnified by the order of magnitude increase in speed of optical communications systems as compared to previous media. This paper examines the impact of the propagation delay on the performance of WDM protocols with variations in the number of channels, packet length and system size, specifically in two reservation based protocols with control channels and two pre-allocation protocols without the control channels. Also the impact of three delay factors (packet processing overhead, bit & frame synchronization and tuning latency) are studied with different propagation delay parameters. In reservation protocols, each node has one agile transmitter and two receivers; one of them is fixed and the other one is agile. The fixed receiver continuously monitors the control channel, receives all control packets, and updates their own status tables in order to track the availability of the other nodes as a target and data channels to avoid the destination collisions and the data channel collisions, respectively. In pre-allocation protocols, each node has a tunable transmitter, a fixed or slow tunable receiver, and its own home channel to receive the packets. The performance of this protocol is evaluated through the discrete-event simulation in terms of the average packet delay and network throughput.

An analytical framework to study the nonuniformity in geographical distribution of the traffic load in low earth orbit satellite communication systems is presented. The model is then used to evaluate the throughput performance of the system with direct-sequence packet spread-slotted ALOHA multiple-access technique. As the result, it is shown that nonuniformity in traffic makes the characteristics of the system significantly different from the results of uniform traffic case and that the performance of each user varies according to its location. Moreover, the interference reached from users of adjacent satellites is shown to be one of the main factors that limit the performance of system.