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NOAA 16, weather monitoring satellite, launched 21 September 2000
of the magnetosphere decreased and the spacecraft moved back inside the Earth's magnetic domain. Since then, the Cluster spacecraft have made regular measurements of the magnetopause. One of the earliest interesting discoveries has been the confirmation of the existence of waves along this ever-shifting boundary in space. "They are like waves that form on the surface of a lake when the wind is blowing" said Cluster Project Scientist, Philippe Escoubet. ''The Cluster spacecraft give us, for the first time, the size and speed of these waves". "Cluster has given us the first observational proof that these waves exist" said Dr Nicole Cornilleau-Wehrlin of CETP in Vellzy, Principal Investigator on the STAFF experiment. "Further studies will enable us to discover more about what happens and why". By late December 2000, the elliptical Cluster orbits carried the quartet of probes close to , the huge shock wave in near-Earth space. This bow shock, which lies some 100 000 km from the planet, forms when particles in the solar wind moving at more than 1 million kmlh slow to subsonic speeds after coming up against the Earth's magnetic shield. Cluster's battery of instruments is beginning to record in great detail what happens at this turbulent barrier. The gusts in the stream of solar particles caused the magnetosphere to oscillate and the bow shock to migrate through space, crossing and recrossing the Cluster spacecraft at irregular intervals. "This is the first time we have ever seen the bow shock in such remarkable detail" said Professor Andre Balogh of Imperial College London, the Principal Investigator for the FGM experiment on Cluster.
(19 miles per second). Further studies of the different data sets are expected to provide valuable new insights into the physical processes taking place in these key regions above the Earth's magnetic poles. "This is a very dynamic region, but it has only been studied previously by single spacecraft" said Dr Escoubet. ''This is why the Cluster measurements are so important. With four spacecraft, we can obtain the most accurate, three-dimensional view of what is happening around our planet".
Cluster and SOHO (the Solar and Heliospheric Observatory) make up the SolarTerrestrial Science Programme - one of the Cornerstones of ESA's Horizons 2000 longterm science plan. Together, they are playing key roles in international efforts to investigate the physical interaction between the Sun and Earth.
4.6. NOAA 16 Weather Monitoring Satellite, iaunched 21 September 2000 NOAA 16 is an American weather monitoring satellite carrying several atmospheric and weather monitoring instruments. The AVHRR·3 (Advanced High Resolution Radiometer) has six wavelength channels (0.58-0.68, 0.6251.00, 1.58-1.64, 3.55-3.93, 10.30-11.30 and 11.50-12.50 urn) of which the first three monitor the back-scattered solar energy, and the second three monitor the emissions from land, sea and clouds, all with a spatial resolution of 1.1 km. The HIRS-3 (High-resolution Infrared Sounder) monitors the atmosphere at 19 closely spaced channels so as to derive the vertical temperature profile up to an altitude of 40 km (25 miles). The AMSU-A and AMSU-B (Advanced Microwave Sounding Units) capture the microwave emissions, with unit A operating in 15 channels covering 23.8-89.0 GHz, and AMSU-B covering five channels of the 89·183 GHz band to derive the tropospheric water vapour profile. The SBUV-2 (Solar Backscatter Ultra Violet) instrument derives the ozone profile by monitoring the incident and backscattered radiation in 12 wavelength bands covering the 252-340 nm band. In addition to the atmospheric instruments, the spacecraft also carries a SEM-2 instrument to monitor kilovolt and megavolt electrons and protons. The data are stored onboard and transmitted over Fairbanks, AK and Wallops Island, VA.
Comparisons of spacecraft measurements will also be invaluable for in-depth studies of other parts of the magnetosphere. Of particular interest are the cusps - funnel-shaped gaps in the Earth's magnetic shield that guide electrified particles into the upper atmosphere. The first Cluster observations of the north polar cusp were made on 14 January 2001, when shifts in the solar wind caused the spacecraft to pass right through this narrow 'window' in the magnetic envelope at an altitude of about 64000 km. The EISCAT ground-based radar in Svalbard, which lay beneath the Cluster spacecraft at that time, confirmed the abrupt change in the position of the cusp. Preliminary analysis of data from Cluster indicates that the upper regions of the cusp were moving through space at around 30 km/s 24
(19 miles per second). Further studies of the different data sets are expected to provide valuable new insights into the physical processes taking place in these key regions above the Earth's magnetic poles. "This is a very dynamic region, but it has only been studied previously by single spacecraft" said Dr Escoubet. ''This is why the Cluster measurements are so important. With four spacecraft, we can obtain the most accurate, three-dimensional view of what is happening around our planet".
Cluster and SOHO (the Solar and Heliospheric Observatory) make up the SolarTerrestrial Science Programme - one of the Cornerstones of ESA's Horizons 2000 longterm science plan. Together, they are playing key roles in international efforts to investigate the physical interaction between the Sun and Earth.
4.6. NOAA 16 Weather Monitoring Satellite, iaunched 21 September 2000 NOAA 16 is an American weather monitoring satellite carrying several atmospheric and weather monitoring instruments. The AVHRR·3 (Advanced High Resolution Radiometer) has six wavelength channels (0.58-0.68, 0.6251.00, 1.58-1.64, 3.55-3.93, 10.30-11.30 and 11.50-12.50 urn) of which the first three monitor the back-scattered solar energy, and the second three monitor the emissions from land, sea and clouds, all with a spatial resolution of 1.1 km. The HIRS-3 (High-resolution Infrared Sounder) monitors the atmosphere at 19 closely spaced channels so as to derive the vertical temperature profile up to an altitude of 40 km (25 miles). The AMSU-A and AMSU-B (Advanced Microwave Sounding Units) capture the microwave emissions, with unit A operating in 15 channels covering 23.8-89.0 GHz, and AMSU-B covering five channels of the 89·183 GHz band to derive the tropospheric water vapour profile. The SBUV-2 (Solar Backscatter Ultra Violet) instrument derives the ozone profile by monitoring the incident and backscattered radiation in 12 wavelength bands covering the 252-340 nm band. In addition to the atmospheric instruments, the spacecraft also carries a SEM-2 instrument to monitor kilovolt and megavolt electrons and protons. The data are stored onboard and transmitted over Fairbanks, AK and Wallops Island, VA.
Comparisons of spacecraft measurements will also be invaluable for in-depth studies of other parts of the magnetosphere. Of particular interest are the cusps - funnel-shaped gaps in the Earth's magnetic shield that guide electrified particles into the upper atmosphere. The first Cluster observations of the north polar cusp were made on 14 January 2001, when shifts in the solar wind caused the spacecraft to pass right through this narrow 'window' in the magnetic envelope at an altitude of about 64000 km. The EISCAT ground-based radar in Svalbard, which lay beneath the Cluster spacecraft at that time, confirmed the abrupt change in the position of the cusp. Preliminary analysis of data from Cluster indicates that the upper regions of the cusp were moving through space at around 30 km/s 24