SMART-1 Closing in on the Moon
On 9 December 2004, at 08:57 UTC, SMART-1 started its 12th orbit around the Moon. After the first orbit started on November 15 at 17:47 UTC, the following perilune passages have taken place:
| Event | Day and Time (UTC) | Period (h) |
| Perilune Passage 1 | 15-11-2004 @ 17:47:38.762Z | 89 |
| Perilune Passage 2 | 19-11-2004 @ 11:01:02.127Z | 75 |
| Perilune Passage 3 | 22-11-2004 @ 14:29:38.449Z | 69 |
| Perilune Passage 4 | 25-11-2004 @ 11:36:11.520Z | 59 |
| Perilune Passage 5 | 27-11-2004 @ 22:42:28.011Z | 59 |
| Perilune Passage 6 | 30-11-2004 @ 01:59:00.054Z | 51 |
| Perilune Passage 7 | 01-12-2004 @ 23:25:21.011Z | 46 |
| Perilune Passage 8 | 03-12-2004 @ 16:05:27.002Z | 41 |
| Perilune Passage 9 | 05-12-2004 @ 05:08:18.135Z | 37 |
| Perilune Passage 10 | 06-12-2004 @ 15:08:27.116Z | 34 |
| Perilune Passage 11 | 07-12-2004 @ 22:40:07.437Z | 31 |
| Perilune Passage 12 | 09-12-2004 @ 04:08:57.443Z | 29 |
From the above it can be seen that the period of the orbit is continuously reduced due to the thrust provided by the electric propulsion system, which reduces the semi-major axis and hence the orbital period.
Since the first start of the electric propulsion engine in the gravitational field of the Moon on 15 November at 05:23 UTC, it has been working well and has fired 20 pulses with a total ON time of 333 hours.
The following table shows the last activities of the electric propulsion engine:
| Event | Day and Time (UTC) | Duration (s) |
| EPP Start | 03-12-04 @ 03:18:33.000Z | 68306 |
| EPP End | 03-12-04 @ 22:16:59.000Z | 0 |
| EPP Start | 04-12-04 @ 09:13:08.000Z | 8983 |
| EPP End | 04-12-04 @ 11:42:51.000Z | 0 |
| EPP Start | 04-12-04 @ 16:49:09.000Z | 67185 |
| EPP End | 05-12-04 @ 11:28:54.000Z | 0 |
| EPP Start | 05-12-04 @ 20:32:52.000Z | 8182 |
| EPP End | 05-12-04 @ 22:49:14.000Z | 0 |
| EPP Start | 06-12-04 @ 03:27:37.000Z | 62096 |
| EPP End | 06-12-04 @ 20:42:33.000Z | 0 |
| EPP Start | 07-12-04 @ 04:59:52.000Z | 7456 |
| EPP End | 07-12-04 @ 07:04:08.000Z | 0 |
| EPP Start | 07-12-04 @ 11:17:21.000Z | 58287 |
Orbital/Trajectory information
The following osculating orbital elements have been determined by a tracking campaign:
|
EPOCH (UTC) 2004/12/04 10:37:47.3 Elements WRT Moon and its equator of date |
|
| Pericentre Distance (km) |
5 454.925035 |
| Apocentre Distance (km) |
20 713.095288 |
| Semi Major Axis (km) |
13 084.010162 |
| Eccentricity |
0.583085 |
| Inclination (deg) |
83.035497 |
| Asc. Node (deg) |
239.659898 |
| Arg. of Pericentre (deg) |
291.239623 |
| True Anomaly (deg) |
180.000986 |
| Osc. Orbital Period (h) |
37.304959 |
In the below diagram the 9th lunar orbit is compared to the first one. It shows the influence of the firings of the electric propulsion system on SMART-1’s lunar orbit:
- the semi-major axis has decreased by 11 132 km
- the perilune height has decreased by 139 km
- the apolune height has decreased by 22 125 km
- the orbital period has been reduced by 56 hours
SMART-1 first and ninth lunar orbit
Contact Points
Giuseppe Racca
SMART-1 Project Manager
ESA/ESTEC – SCI-PD
Keplerlaan 1- 2200 AG Noordwijk, The Netherlands
E-mail: Giuseppe.Racca
esa.int
Bernard H. Foing
SMART-1 Project Scientist
ESA/ESTEC – SCI-SR
Keplerlaan 1- 2200 AG Noordwijk, The Netherlands
E-mail: Bernard.Foingesa.int
