|status reports||21-September-2018 18:04:22|
No. 17 - Ion Engine Switched Off and Commissioning Begins
04 February 2004
The spacecraft is now in its 207th orbit, in good status and with all functions performing nominally. As in previous weeks, the ion drive has only generated thrust around the perigee point to fine-tune the altitude of the apogee point. This strategy has produced a noticeable increase in apogee height, see plot below, which is necessary to minimize the duration of eclipse periods that will occur during March.
The total cumulated thrust so far is more than 1705 hours, consuming 27.1 kg of Xenon, has provided a velocity increment of about 1220 ms-1 (equivalent to 4392 km per hour). In this period the electric propulsion engine's performance, periodically monitored by means of the telemetry data transmitted by the spacecraft and by radio-tracking by the ground stations, have been nominal.
The spacecraft subsystem continue to function well despite the known problem of the hot star trackers. This can overload the star tracker computers, because in these conditions they "see" many more stars and the search for the correct constellation becomes heavier. In one case this overload caused a loss of synchronisation between the star tracker time with the spacecraft time.
The software patch, required to recover from the flame-outs, has been prepared and will be uploaded to the spacecraft as soon as the electric propulsion engine is operated again.
After four months of continuous travelling through the Earth's radiation belts the electric propulsion engine was switched off on 30 January. The engine will remain dormant for a period of three weeks to allow the instrument teams to switch on and test their instruments.
After the last SMART-1 Science and Technology Working Team (STWT20) at ESOC, 15 January 2004, the payload operation preparation activities have accelerated between PI teams, project, STOC and ESOC.
On 29 January, between 20:00 and 21:19 UT, images of the first quarter moon were taken through several filters. The result is a small, but impressive, image revealing, clockwise from the top: Mare Serenitatis, Mare Tranquillitatis, Mare Fecunditatis and Mare Nectaris, with Mare Crisium also visible near the limb.
The result is very encouraging as the spacecraft is still over 300 000 km from the Moon. The camera appears to have survived its journey through the high radiation environment with no apparent reduction in performance. Taking images is also an excellent test of the pointing ability of the spacecraft.
EPDP and SPEDE
Planned Instrument Activities
5 - 10 February 2004
11 - 18 February 2004
19 - 20 February 2004
Planned Spacecraft Activities
The ESOC specialists periodically compute the osculating orbital elements. 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. Therefore, 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:
Displayed in the plot are the osculating orbits at launch (GTO) and at different times throughout the mission. Since the start of the mission the electric propulsion engine has changed the orbital parameters as follows:
Bernard H. Foing
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