Radio telescopes hear last signal from SMART-1

This short animation shows the SMART-1 carrier radio signal in the last moments of the spacecraft's life, as detected by the Australia Telescope Compact Array (CSIRO) radio station on 3 September 2006.

The signal stopped at 07:42 CEST (05:42 UT), when the spacecraft hit the Moon. Other radio telescopes involved in tracking the probe - the German-Chilean TIGO (BKG) 6-metre antenna in Chile and the Mount Pleasant Observatory of the University of Tasmania (Australia) - also heard SMART-1's final signal. The Medicina (INAF) 32-metre antenna in Italy and the Fortaleza (ROEN) 14-metre antenna in Brazil were not in view of the spacecraft at the time of impact, but complemented the observations during the last orbit.

Starting in spring 2006, these radio measurements provided extremely precise tracking of SMART-1.

The animation shown here presents a time resolution of 5 seconds (i.e. the signal is presented every five seconds). However the radio observations were done with a very high accuracy, on a millionth-of-a-second time resolution. This time span corresponds to a 2-centimetre motion of the spacecraft.

The signal shown in the animation (the peaks) is the result of the interference between a radio signal received directly from SMART-1 and its reflection from the Moon's surface.

In parallel to these radio observations, the Radio Science Receiver of the SMART-1 KaTE/Ka-band experiment received on Earth the last signal from the spacecraft at 07:42:25 CEST (05:42:25 UT), through the NASA Deep Space Network radio station 'DSS13' in the California Desert.