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Lunar Impacts Project
by Raffaello Lena (gibbidomine@libero.it)
 

Introduction:

The purpose of the Lunar Meteoritic Impact project is to coordinate and study the observation of lunar impact events. Several instances have occurred in the past where observers have observed flashes on the moon. The most recent examples include Dr. Leon Stuart's Lunar Flare of 1953 and the Leonid swarm of 11/18/1999.

Objectives:
--determine a classification of flashes using standard criteria.
--determine whether flashes are cosmic ray strikes on the CCD surface or true impact flashes.
-- find other ways to confirm that a recorded flash is of impact origin.
--coordinate observing activities during times of particularly promising meteor storms.
--coordinate and share information with other groups doing the same work.

Standard criteria:

In a previous paper (JALPO, vol 43.2, 2001), the GLR showed that camcorder-videotape systems may contain spurious 'flashes' that mimic lunar impact flashes. These were noted to originate from: readout noise, dark count, background noise, and other high energy sources (such as cosmic ray interactions with the CCD chip). These sources result in a variety of spurious forms on the videotape. We classified these as:

-single point spurious flashes (caused by cosmic rays, glints from satellites, etc.)
-multiple point spurious flashes (caused by defective reading cycle in the CCD chip)
-segment spurious flashes (caused by cosmic rays, etc.)
-faint spurious flashes (caused by readout noise, dark count, background noise, etc.)

Fortunately, the 'multiple point' and 'segment' spurious flashes are easy to distinguish from their unique morphology. However, our analysis of the 'single point' and 'faint' spurious flash revealed that their luminosity profile was identical to that of a star or an actual lunar impact flash. Fortunately, 'faint' spurious flashes are almost always within two standard deviations of the noise level, and so may be generally ruled out by setting criteria at five standard deviations above the noise level. However, the single point spurious flash cannot be differentiated from a lunar impact flash. Thus, an unconfirmed single point flash that is greater than five standard deviations above the noise level can only be suggestive of a lunar impact--but not conclusive. Confirmation of a lunar impact flash requires a second observer/recorder. Because some causes of spurious flashes may occur over a small distance (for example, the glint off a satellite), it is suggested that these observers be separated by a minimum of 20-30 km.

For these reasons, the criteria we established, and I am now using for lunar impact flashes, are as follows:

1. Flashes must be recorded by more than one observer, separated by not less than 20 km.

2. Flashes must have a S/N ratio greater than five standard deviations from the measured noise of the signal. This standard will also rule out faint true meteor flahes, unless they are confirmed by a second distant observer.

3. Flashes must have a 'single point' morphology.

Methodology:

At this point in the project, we have two objectives:

FIRST: we need to develop a methodology for confirming that a recorded flash is of impact origin. We will investigate this using the following methods:

1) Defocus the image slightly - any impact flash will be seen as a small blurred disk, but no cosmic rays.

2) Place a wedge shaped prism in front of the CCD - true bright impact flashes will have a spectra, cosmic rays will not.

SECOND: We need to develop a network of observers for simultaneous patrols in watching the lunar disk for impacts during particularly likely events (meteor storms). We will proceed with this as follows:

1) To have a network for general coordination of independent observers-recorders.

2) To post dates and times for likely impact events.

Final Comments:

I welcome any members who wish to participate in this joint ALS/GLR project. Please e-mail me.

This project will work by using the Internet as a communication platform in real time coordinating observing programs and events. Active international cooperation by individuals making regular systematic, simultaneous observations of the Moon continues to be my prime objective.

Being a new ALS Coordinator, I would like to take this opportunity to introduce myself. I am Raffaello Lena from Rome Italy. It is an honor for me to take this position and I will do my best to make this project significant for ALS and GLR group. A full collaboration with other Lunar Association and ALPO will be welcome.

References

- Eric Douglass, Francesco Badalotti, Giacomo Venturin, Raffaello Lena, and Guido Santacana. Observing for Lunar Flashes: Spurious vs. Real flashes. JALPO, 43.2, 2001


-Stuart, Leon H. (1956) A photo visual observation of an impact of a large meteorite on the moon. JALPO, 10, Nos 3-4.

-Maley, P.D. (1991) Space debris and a flash on the moon. Icarus 90.

-Rast, R.H (1991) The "moon" flash of 1985 May 23 and orbital debris. Icarus, 90.

- Circular IAU 7320 ( 7 december 1999)

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