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SMART-1 Closing in on the Moon

Status Report From: European Space Agency
Posted: Friday, December 10, 2004

image 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.Raccaesa.int

Bernard H. Foing
SMART-1 Project Scientist
ESA/ESTEC - SCI-SR
Keplerlaan 1- 2200 AG Noordwijk, The Netherlands
E-mail: Bernard.Foingesa.int

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