SMART-1 approach to lunar polar orbit, November 2004

Read about ESA's moon probe at the web site of the prime contractor, the Swedish Space Corporation.

Approach trajectory

The image below shows the trajectory and attitude of the spacecraft as it was captured by the Moon. The graph was produced by the Swedish Space Corporation using data from ESOC. Click on the image to see sharper version.Red line, elelectric thruster = on, green line = truster off. The spacecraft passed its first perilune at 1748 UT on 15 November after having turned on the electric thruster at 0524 UT on 15 November,

Image of the far side

On 12 November SMART-1 took an image of the Moon's north pole and the illuminated far side.The craters in the red ellipse in the SMART-1 image below are easy to recognize. (Photo: ESA, Space-X, Space Explortaion Institute).

The same feature can be seen in this photo atlas image where the image centre is at 80 degrees north and 180 west. The phase of the Moon is about 3 days from ”new”. Crater d’Alembert is a recognizable feature.

Atlas image from:


Comparison with other unstable lunar orbits

It is interesting to quote from Jonathan McDowell's Space Report for Nov 18 2004:

The European SMART-1 probe made its third lunar resonance gravity assist on Oct 12 and on Oct 26 was in a 173339 x 298835 km x 20.6 deg deep Earth orbit. The continued gravitational effect of the Moon raised the orbit until lunar capture on Nov 15. On Nov 11 the spacecraft finally passed through the weak stability boundary region at the Earth-Moon L1 point, where small changes to the probe's path result in large alterations to its final orbit, and where the orbit becomes better described as Moon-centered rather than Earth-centered. The probe reached perilune on Nov 15 at 1748 UTC and entered a 4962 x 51477 km orbit around the Moon inclined at 81 degrees to the lunar equator.

This is the most loosely bound lunar orbit ever achieved, with its highest point close to the Earth-Moon gravitational boundary - the US record-holder Explorer 35 in 1967 had an apolune of only 7800 km, while the 1990s Japanese probes Hagoromo and Hiten had apolunes of 22000 and 49400 km respectively; the Apollo missions  went directly to low orbits with apolunes of only 300 km.

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