status reports 20-March-2019 10:21:54

No. 22 - 2000 hours of electric propulsion operations

28 April 2004

The spacecraft is now in its 278th orbit, in good status and with all functions performing nominally. The new thrusting strategy is well in progress with thrust arcs around perigee for about one third of every revolution. Presently the thrust arcs last for about 13 hours of every 36 hour-orbit. The thrust duration will increase to 18 hours when the orbital period reaches about 50 hours in one and half month.

In this phase of the mission, the electric propulsion system is again at the centre of our attention, as the main purpose is now to increase the apogee of the orbit to get closer to the Moon. The performance of the engine is still very good. At 16 April 2004, the engine had cumulated a total ON time of about 2000 hours, consumed about 32 kg of Xenon and imparted to the spacecraft a velocity increment of about 1440

Orbital/Trajectory information

The osculating orbital elements are periodically computed by the ESOC specialists. These elements define the so called "osculating orbit" which would be travelled by the spacecraft if at that instant all perturbations, including EP thrust, would cease. So it is an image of the situation at that epoch. In reality the path travelled by the spacecraft is a continuous spiral leading from one orbit to another. The most recent osculating elements are as follows:

EPOCH (UTC) 2004/04/26 07:21:36.5

Elements WRT Earth (J2000)
Pericentre Distance (km)

22 742.301469

Apocentre Distance (km)

90 145.336906

Semi Major Axis (km)

56 443.819188



Inclination (deg)


Asc. Node (deg)


Arg. of Pericentre (deg)


True Anomaly (deg)


Osc. Orbital Period (h)


In this diagram the osculating orbits at launch (GTO) and at different times are plotted. It can be seen that since the electric propulsion is again being operated, the last orbit is substantially modified. Especially the height of the apogee is dramatically increased due to the perigee thrusting strategy. 

Since the start of the mission, the electric propulsion system has changed the orbital parameters as follows:

  • The semi major axis from 24 626 km to 56 443 km
  • The perigee altitude from 656 km to 16 364 km
  • The apogee altitude from 35 880 km to 83 767 km
  • The orbital period from 10 hours 41 minutes to 37 hours and 4 minutes

Contact Points

Giuseppe Racca
SMART-1 Project Manager
Keplerlaan 1- 2200 AG Noordwijk, The Netherlands

Bernard H. Foing
SMART-1 Project Scientist
Keplerlaan 1- 2200 AG Noordwijk, The Netherlands


Last Update: 18 May 2004

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