The DEEPSPACE 1-Team:
Dr. Karl-Heinz Glaßmeier
Dr. Günter Musmann
Dr. Falko Kuhnke
Dr. Ingo Richter
Dipl. Phys. Carsten Othmer
DS1 was launched successfully on October 24th, 1998 at Kennedy Space Flight Center, Cap Caneveral, Florida aboard a Delta 7326-9.5 Med-Lite rocket (for the first time). DS1 has a mass of 486 kg and contains 81 kg Xenon gas for the ion propulsion system. The primary mission objective was a rendezvous with the asteroid 1992 KD (now called Braille) on July 29th, 1999. The closest approach took place in a distance of 1.3 AU from the sun. This encounter was so close (about 25 km) to the asteroid as never ever reached by a satellite before to any celestial body. At this encounter the complete navigation as well as the flight and attitude conrtrol was managed by the new developped autonomous navigation system AutoNav. This system is based on a camera (MICAS), which scans and records the firmament, and a reference star data base for a realtime onboard evaluation of the precise position and the orientation of the spaceraft. Up to two days prior to the rendezvous the
ion propulsion system was used for spacecraft control; in the last 48 hours before the closest approach to the asteroid, however, 8 conventional thrusters (Hydrazin, 28 kg) were brought into action, to provide the possibility of quick direction corrections needed in certain cases.
During the complete cruise of DS1 our fluxgate magnetometer trnsmits precious magnetic field data. Within the scope of the DS1 Mission investigations take place, in how far it is possible to get scientic significant magnetic field data of the covered flight area, using an ion propulsion system equippped spacecraft. Special problems arise due to the ion current, which produces ist own magnetic field, and on the othe hand the movable ion beam focusing magnets , that show a temperature dependent magnetic disturbance field.
Magnetic field modells are created that contain all neccessary satellite parameteres to eliminate the disturbance components from the measured magentic field data.
The Ion Propulsion System
DS1 gets its thrust from a solar-electrical ion propulsion.
The power for the propulsion is supplied by the two solar arrays. The inert
gas Xenon, which is about 4.5 times heavier than air, is used to
produce the repulsion.
The gas in ionized in the enigine through ionization by collision . The ions are accellerated to a maximum ejection velocity of 110000 km/h by running through a potential difference of up to 1280 V. This process generates an effective thrust of about 90 mN. This corresponds to a pressure, that a piece of paper, lying on the hand, will apply to the hand . This thrust is in deed very low and would never be sufficient to launch a spacecraft from the earth, but as it can be kept over months (there is enough Xe gas for a 6000 h operation endurance) and thus provides a continous accelleration
amazing velocities can be reached. After the consumption of all the fuel DS1 will have perveived a relative velocity increase of about 15000 km/h. It is quite remarkable and should be mentioned that the ion propulsion generates about ten times more thrust than a conventional fluid or solid fuel rocket using the same amount of fuel. The ion engine has a diameter of 40 cm, is 40 cm long and has a weight of about 8 kg.
For the characterization of the plasma dynamics in the vicinity of the ion enigine a plasma simulation is developed at the Institute for Geophysics and Meteorology in cooperation with the Institute for Theoretical Physics and the Computation Center of the Technical University Braunschweig.
A high sensitive subminiatur vector fluxgate magnetometer was developed at the Institute for Geophysics and Meteorology. It has been designed for the extremely high requirements in space:
After the successful test phase the magnetometers were calibrated in Magnetsrode, the magnetic coil facility of our institute. The extensive test procedure of such a calibration contains: