Cluster (satellite)

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Cluster is a satellite project by ESA and NASA to research the earth's magnetosphere , the earth's magnetic field . The program, consisting of a group of four identical satellites, suffered a setback in 1996 with the false start of the first Ariane 5 rocket , but has been in operation with reserve satellites since summer 2000.

Mission overview - 4 satellites

Cluster satellite during the test phase

The satellites operated in the network examine the earth's magnetic field , which shields the planet from the solar wind . Clusters 5 to 8 measure three-dimensional data of collisions of the solar wind with the earth's magnetic field, the time course and the resulting interactions in space. The latter often lead to northern lights , but can also cause severe radio interference and even electrical failures.

German institutes are responsible for two of the eleven instruments in each satellite; German scientists were involved in two others . In addition to sophisticated measurement technology , a special challenge of the mission is models to improve the forecast for the so-called space weather , i.e. the disturbances from solar wind.

The satellites have an approximately cylindrical shape (290 × 130 cm) and spin stabilization in the inertial space (15 revolutions per minute). Their solar cells provide an electrical output of 224 watts for operation and radio communication . The satellites were assigned the SCID (Spacecraft ID) from 90h to 93h for the active satellites, 94h for the reserve device and 95h to 96h for the simulators by the World Data Center for Satellite Information .

False start in 1996 and naming of the specimens in 2000

During the first flight of Ariane 5 on June 4, 1996, the four satellites (provisional names FM1 to FM4 ) were supposed to be launched, but due to a bug in the flight software taken over from Ariane 4 , the rocket went off course after launch, began to break up and finally blew itself up after 36.7 seconds.

Four more FM5 to FM8 were built by the beginning of 2000 . A replacement satellite and several replacement instruments from the original mission were used to keep costs down. On the occasion of the successful start on July 16, 2000, the winners of the naming competition for the cluster satellites were announced at the European Space Control Center (ESOC) in Darmstadt . Out of more than 5,000 submissions, the decision was made in favor of the proposal from an Englishman who is an enthusiastic dancer: the four satellites will in future be called Rumba , Salsa , Samba and Tango .

Starts in July and August 2000

On July 16, 2000, two of the four new probes were launched with a Soyuz Fregat rocket from the Russian spaceport Baikonur and reached a preliminary orbit 90 minutes later. Originally an almost simultaneous launch with the German mini satellite CHAMP (from Plesezk ) was planned, but this was delayed by a day. 90 minutes after take-off, the engines of the Fregat stage were ignited again to lift the satellites into a parking orbit of 240 × 18,000 km. A little later, the ESA ground station Kiruna in Sweden reported the successful orbit maneuver and the decoupling. Salsa and Samba reached their final orbit of 19,000 to 119,000 km with a 57 hour orbit on their own drive during the next few weeks .

The second cluster pair was launched about three weeks later on August 9th. This time, however, not everything worked right away: the third stage of the Soyuz Fregat did not produce enough power and put the Fregat upper stage with the cluster satellites in a lower orbit than planned. But the Fregat saved the mission - because it was filled with excess fuel, it was able to reach the planned orbit and successfully deploy the satellites.

The four cluster satellites can work in different constellations , depending on the magnetic field structure to be examined . The fuel for the orbit maneuvers makes up more than half of the take-off weight of the probes (650 of 1200 kg each).

The mission was extended to December 2018, and then to the end of 2022 in November 2018 Template: future / in 2 years.

Constellation at the end of 2003

In December 2003 the four clusters formed a tetrahedral structure with a mutual distance of about 200 kilometers, which can be increased to several thousand kilometers. The polar orbits of the four satellites are strongly elliptical (heights 19,000 to 119,000 km). The instruments on board each satellite can record a wide variety of magnetic effects from many regions of the earth's magnetic field:

  • Measurements of charged particles
  • Measurement of electric and magnetic fields
  • Interactions between the solar clouds of high-energy particles, the earth's atmosphere and the magnetic field.

To this day, rumba , salsa , samba and tango have fully met the expectations placed in them.

Chinese "Double Star" 2003

Two Chinese double-star research satellites are to cooperate with the cluster system in the future - albeit from lower orbits: On December 27, 2003, at 20:23 (CET), the first of two satellites, resulting from a cooperation between ESA and of the People's Republic of China . The two identical satellites TC-1 and TC-2 have a mass of 330 kg and are the first Chinese magnetosphere satellites. They were designed and built in China and were equipped with eight measuring instruments of Chinese origin. The launch took place with launch vehicles of the Langer Marsch 2C type, the measurements of the Double Stars should take 12 to 18 months.

The European contribution to this mission are eight other instruments, seven of which are cluster counterparts (reserve instruments or inexpensive duplicates). In addition to the economic advantage, similar instruments on several satellites are also technically and scientifically interesting: they allow conclusions to be drawn about the function and give a multidimensional picture of the magnetic field surrounding our planet.

In contrast to the relatively high-flying cluster satellites, the double-star duo of the China National Space Administration (CNSA) will come close to the earth within 550 and 700 kilometers respectively on their elliptical orbits. While TC-1 is to orbit in a relatively equatorial orbit - which will still be inclined by 28.5 degrees to the equator - TC-2 will orbit the earth in a polar orbit.

literature

  • CP Escoubet, CT Russell, R. Schmidt (Eds.): The Cluster and Phoenix Missions. Kluwer, Dordrecht 1997, ISBN 0-7923-4411-1

Web links

Individual evidence

  1. ↑ ESA: Two-year extensions confirmed for ESA's science missions. November 22, 2016, accessed January 6, 2017 .
  2. ^ ESA: Extended Life for ESA's Science Missions. November 14, 2018, accessed December 20, 2018 .