CENAP Infoline - no 151

Magazine Overview

Title: CENAP-INFOLINE
Issue: NR.151
Date: 18. Februar 2002
Publisher: CENAP-INFOLINE
Country: Germany
Language: German

This issue of CENAP-INFOLINE, a supplement to the CENAP-Report focusing on UFOs, details the upcoming launch of the European Space Agency's (ESA) Envisat satellite. The article highlights Envisat as Europe's largest, most expensive, and most sophisticated satellite, designed for comprehensive environmental monitoring.

Envisat: Europe's Environmental Sentinel

The lead article, "ESA-SATELLIT ENVISAT VOR START" (ESA Satellite Envisat: Ready for Launch), introduces Envisat as a source of European pride. Its mission is to circle the Earth 14 times daily, providing extensive coverage for environmental monitoring and climate change analysis. The satellite is tasked with measuring and analyzing greenhouse gases, identifying environmental offenders, tracking ocean currents, observing algae growth, and keeping a close watch on the ozone hole. The article emphasizes that this mission comes at a critical time for understanding environmental changes.

Advanced Technology and Precision

Envisat is equipped with ten state-of-the-art instruments capable of detecting subtle changes in natural processes and human-induced activities on land, in water, and in the air. This data will enable scientists to develop robust models for climate change and potentially improve predictions for events like earthquakes, volcanic eruptions, and floods. The satellite's ability to repeatedly observe the same location allows for the correction of measurement errors, enabling it to detect millimeter-level changes in the Earth's surface, such as the sinking of Venice or the uplift preceding a volcanic eruption.

Orbit Control and Instrument Capabilities

The article stresses the need for high precision in Envisat's orbit. Sørensen, identified as the ground segment manager, explains that maintaining the satellite's precise trajectory is crucial, and extensive simulations have been conducted to address potential issues. A key instrument highlighted is the Synthetic Aperture Radar (ASAR), which can detect oil spills of just a few hundred liters on water surfaces, identify deforestation in rainforests, and even spot small oil slicks at sea. The satellite operates at a speed of nearly 20,000 kilometers per hour, making precise aiming essential.

Operational Challenges and Redundancy

Maintaining Envisat's orientation in space is a complex task, influenced by various gravitational fields, residual atmosphere, and solar wind. The satellite is equipped with approximately 50 independent onboard computers that automatically manage its flight attitude using gyroscopic instruments and magnets. Sørensen emphasizes that maintaining orientation is a matter of survival for the satellite. In the event of a deviation from its planned orbit, it would be immediately detected through instrument readings or a drop in solar panel power.

Data Processing and Distribution

Envisat generates a massive amount of data, with its two main storage units capable of holding 160 Gigabits, which would overflow within hours. Therefore, the satellite transmits its data to Earth every orbit when passing over the ESA ground station in Kiruna, Sweden. A second station in Svalbard, Norway, serves as a backup. The telecommunications satellite Artemis, positioned in high Earth orbit, acts as a relay, providing a longer contact window for data transfer. Data is then sent to the ESA data processing center, ESRIN, in Frascati, Italy. Over its lifetime, Envisat is expected to collect a petabyte of data, equivalent to the hard drive content of one million home PCs. Software experts have developed numerous programs to efficiently process and disseminate this information.

Scientific and Economic Applications

Envisat's data will be made available to thousands of scientists, engineers, institutions, and industries. It will aid in understanding the oceans, atmosphere, and biosphere, assist public authorities and companies in disaster preparedness and environmental protection, and help international organizations monitor natural catastrophes and global environmental issues. The data will be processed at six data centers across Europe (England, Germany, Italy, France, Sweden, and Spain) to ensure consistent information and secure long-term archiving. While raw data is available quickly, verified data requiring error analysis may take up to a month to be released, coinciding with Envisat's return to the exact same orbital position for measurement confirmation.

Scientific institutes involved in the mission receive data at cost price, provided it is used for scientific purposes and published openly. This collaboration has fostered a large Earth observation community. The issue also notes that the next generation of environmental satellites is expected to be significantly smaller.

Specific Applications and Future Outlook

Envisat's data has significant economic potential, with analysts suggesting that environmental observation could become a sector comparable to satellite navigation. Applications include helping ships avoid stormy waters and ice, identifying areas with high plankton content to prevent improper ballast tank filling, and providing data for regional forecasts of extreme UV radiation or toxic algae blooms. The article concludes by mentioning that the Envisat team is already working on the next generation of environmental satellites, which will be much smaller. The data managers in Frascati and the space controllers in Darmstadt face a decade of work, but Sørensen describes it as "everyday's work."

Recurring Themes and Editorial Stance

The magazine consistently emphasizes the technological advancement and scientific importance of the Envisat mission. There is a strong focus on the precision, complexity, and potential benefits of Earth observation satellites for understanding and mitigating environmental challenges and climate change. The editorial stance appears to be one of admiration for European technological achievement and a belief in the critical role of such missions for scientific research and global well-being. The publication also highlights the collaborative nature of space missions and data sharing among scientific institutions.