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This paper describes a space-qualified optical memory device for application in the Columbus Attached Laboratory. The unit is based on a MIL-standard CDdrive leading to a cost-effective design with full compatibility to commercial CD-ROM. The system is extendable to CD-MO (Rewriteable) and CD-I (CD Interactive). Paper presented at Eindhoven IEEE Student Branch Symposium "Elektrotechniek in de Ruimtevaart", 22 april 1993."

After surveying tele-education systems and technology, this study describes the design of a tele-education system which is particularly suitable for the extension of the educational facilities of universities to remote communities. The study is focused on the application of third-world small-scale institutes like the University of the Netherlands Antilles (UNA), Curasao, which is used as a case. On the basis of the specific requirements, limiting conditions, and constraints, a PC-based system has been developed, with as much functionality as possible implemented in software. Interactive media considered are low frame-rate video, audio, and the communication of text, graphics, handwriting, and still pictures via a shared screen. A fast and effective low-frame rate video coding scheme is presented. It achieves acceptable image transfer times for application in real-time tele-education services, where the bandwidths are small to moderate and where a requirement exists for implementation based on standard microcomputer equipment without dedicated hardware. This method includes a novel approach to entropy coding: Modified Tunstall Coding, an improvement of Tunstall's variable-to-fixed-length coding algorithm. It is an attractive choice for software implemented entropy coding in the event of limited alphabet sources with a low entropy. Further, a number of improvements of telewriting systems is proposed in relation to tele-education services, concerning a colour-fill facility, an efficient coding algorithm and a method which supports editing of existing pages. To reduce end-to-end delays of compound pages for the purpose of tele-education, a method referred to as pretransfer is developed. It employs periods of low channel utilisation during the session for automatic transmission of these pages. The above mentioned techniques and solutions have been incorporated in the design of a tele-education system appropriate for narrow bandwidths. The development and implementation of this interactive real-time PC-based multimedia system is described. An initial version was involved in a classroom experiment at the UNA. From the evaluation results it may be concluded that the multimedia concept developed meets the recjuirements and is a viable approach to tele-education in the specific situations aimed at in this study.

Data storage devices each providing 260 MB non-volatile "random access memory will be used in the Data Management Systems of the Russian and the European Modules of the Space Station. The National Aerospace Laboratory NLR, and Signaal Special Products have jointly developed these Mass Storage Devices (MSD) based on commercial Winchester disks. For increased reliability, these MSDs contain two separate disk cartridges with identical data contents. An intelligent latch-up protection system has been incorporated to safeguard the drives against destmction due to radiation effects. This protection mechanism has been validated by tests in a proton beam facility.

Industrial and other organisations in the Netherlands are active in both the preparation for and the promotion of the broadcasting of HDTV. There has also been a start to research into "spin-off" specialised applications which could also benefit from the superior picture resolution; an example Is telescience. Already in 1991, RAI (I) has conducted the first HDTV demonstrations using OLYMPUS for short-term broadcasts with both analogue and digital transmission techniques. In the next two years, more regular HDTV transmissions will become both desirable and practicable, with contributions from various countries including the Netherlands. One of the major objectives of these demonstrations will be to bring HDTV to the general public and other "users" in a progressive way. This study firstly explores the options for specifically Dutch HDTV demonstrations with OLYMPUS. Secondly selects specific preparatory initiatives.

This document describes the results of research activities related to critical issues of the FA^ffi mission, carried out by NLR. FAME constitutes a dedicated infrastructure, consisting of a space segment and a ground segment, for the global monitoring of forests. The space segment is a single-mission satellite carrying a Synthetic Aperture Radar sensor. Recorded SAR data are transmitted directly to the ground over a low-rate data channel and received by multiple low-cost end-user stations. The work covered by this report comprises the following subjects: • Applicability of operational and future payloads for global forestry monitoring. • Data rate reduction techniques. • Orbit analysis.

Effective global forest monitoring can be achieved by means of Earth Observation techniques. The most promising technique in this respect is the synthetic aperture radar (SAR) technique. Due to the high percentage of cloud cover in tropical and temperate regions SAR offers excellent opportunities to monitor the forests. Requirement studies in the past have discovered that requirements from users focus on five aspects: the availability of data, the accessibility of data, the affordability of data, the timeliness of data and thematic aspects. On the basis of these requirement aspects a concept was developed which emphasises an end-to-end small space mission approach. This approach is characterised by a complete integration of the groundand space segment, rather than treating them separately. The concept is based on two key-elements: decentralised, low-cost reception and processing capabilities and a low-frequency SAR. This paper presents the initial concept, and its elements, based on work performed within the National Space Technology Programme.

Effective global forest monitoring can be achieved by means of Earth Observation techniques. The most promising technique in this respect is the synthetic aperture radar (SAR) technique. Due to the high percentage of cloud cover in tropical and temperate regions SAR offers excellent opportunities to monitor the forests. Requirement studies in the past have discovered that requirements from users focus on five aspects: the availability of data, the accessibility of data, the affordability of data, the timeliness of data and thematic aspects. On the basis of these requirement aspects a concept was developed which emphasises an end-to-end small space mission approach. This approach is characterised by a complete integration of the groundand space segment, rather than treating them separately. The concept is based on two key-elements: decentralised, low-cost reception and processing capabilities and a low-frequency SAR. This paper presents the initial concept, and its elements, based on work performed within the National Space Technology Programme.

This paper describes the conceptual design of a synthetic aperture radar (SAR) sensor operating at P-band frequency (435 MHz). It is part of the FAME (Forest Assessment and Monitoring Environment) initiative for the realisation of a global operational end-to-end service to allow forests to be monitored at national and sub-national level. The system will cover all the global forest areas at least three times a year, providing timely information on deforestation and forest degradation processes at a resolution of 50 - 100 m. SAR processing and product generation are fully decentralized activities carried out by low-cost end-user stations. For standardisation and cost reasons the SAR data downlink is compatible to the NOAA HRPT link, with a data vthroughput capacity of 614 kb/s. This limited data rate imposes a hard constraint on the instrument requirements. In order to achieve sufficient radiometric resolution, data buffering as well as data compression and basic SAR processing on-board the satellite are foreseen.