ESA Science & Technology - SMART-1 Impact Flash and Debris: Crash Scene Investigation

"The successful capture of the SMART-1 impact from Earth raised substantial interest in the astronomical community (professional and amateur) to reanalyse available data, to reobserve the impact site and to share the result worldwide as a family," says Pascale Ehrenfreund , ground based campaign coordinator, after catching up with some sleep.

Where did SMART-1 impact the Moon?

"From the various observations and models, we try to reconstruct the movie of what happened to the spacecraft and to the Moon," says ESA SMART-1 Project scientist Bernard Foing. "For this lunar 'Crash Scene Investigation', we need all Earth witnesses and observational facts."

The SMART-1 impact took place on 3 September on lunar orbit 2890 at spacecraft time 05:42:21.759 (time of generation of last received packet). The JIVE radio telescope from Hobart Tasmania measured a loss of signal at 05H42:22.394 UTC.

These times are remarkably in agreement with the SMART-1 flight dynamics predictions of 3 Sept 05:42:20 UTC, with coordinates longitude 46.20 West, latitude 34.4 South.

This is also in agreement with the coordinates newly derived from the position of the infrared flash observed at CFHT.

Extensive data processing is underway to specify the topography of the impact site.

From preliminary analysis of the topographic stereo and SMART-1 earlier maps, the satellite should have hit the Moon in the ascending slope of a mountain of height about 1.5 km above the Lake of Excellence plain.

What happened?

To determine what part of the flash comes from the lunar rock heated at impact or from volatiles released by the probe, it is important to have measurements in several optical and infrared bands, in addition to the CFHT observations at 2.12 microns.

From a detailed analysis of the CFHT infrared movie of the variations after the flash, a cloud of ejecta or debris travelling some 80 km in 130s, has been detected by observer Christian Veillet.

"It seems that some ejecta or debris made it across the mountain, that is good news to search for the ejecta blanket," says Bernard Foing, "We might also see the firework expansion of gas and debris from the spacecraft that has bounced after impact."

Some SMART-1 campaign amateurs may have observed the optical flash in their own data and have spotted a possible afterglow in the movie posted soon after impact. We call for observers to search for the crater and ejecta blankets from SMART-1, in particular using visible or infrared imagery, or even to look at spectroscopic anomalies at the impact site.

We call all observers for sending their reports, and thank also the media for some 1000 news stories that helped to engage so many people in the SMART-1 adventure.

Contact information:

Bernard H. Foing
ESA SMART-1 Project scientist
Bernard.Foingesa.int

Pascale Ehrenfreund
Leiden University
SMART-1 ground-based impact campaign coordinator
Pascalestrw.leidenuniv.nl

Note

Five radio telescopes involved in the SMART-1 observations and coordinated by the Joint Institute for VLBI (Very Long Baseline Interferometry) in Europe (JIVE), are: the Medicina (INAF) 32-metre antenna in Italy, the Fortaleza (ROEN) 14-metre antenna in Brazil, the German-Chilean TIGO (BKG) 6-metre antenna in Chile, the Mount Pleasant Observatory of the University of Tasmania (Australia) and the Australia Telescope Compact Array (CSIRO).

SMART-1 impact observation campaign involved a core of participating telescopes, including: the South African Large Telescope (SALT), the Calar Alto observatory in Andalucia, Spain, the ESA Optical Ground Station (OGS) at Tenerife, Spain, the TNG telescope in La Palma, Canary Islands, Spain, the CEA Cariri observatory in Brazil, the Argentina National Telescope, the Florida Tech Robotic telescopes at Melbourne FL and Kitt Peak, MSFC lunar meteor robotic telescopes, Houston 1m, Big Bear Solar Observatory, MDM telescopes at Kitt Peak, NASA IRTF, the Canada-France-Hawaii Telescope, the Japanese Subaru Auxiliary telescopes on Hawaii, the ODIN space observatory.

We acknowledge also support from Nottingham University, and USGS. We shall report later on data sent by other observatories that joined the campaign.