The annual Geminids meteor shower, scheduled to reach its peak on December 13 and 14, is slated to be the most intense shower of the entire year. This is also prime time for amateurs who enjoy bouncing their VHF signals off the ionized trails of these space rocks as they streak into our atmosphere. Known as meteor scatter, this communication technique takes advantage of temporary radio pathways that can span nearly 2000 miles. The week of December 10-16 is a good window for Geminid watching, but the night of Thursday, December 13 is the anticipated peak of the shower.

Geminids and Amateur Radio

Most meteor scatter activity takes place on 6 meters and 2 meters. Some amateurs use SSB or CW to make quick contacts during longer “burns,” while others rely on digital modes, primarily FSK441, which is part of the free WSJT software suite.

Meteor scatter is not as difficult as it may seem. On 6 meters in particular, it is possible to make contacts with just 100 W or less using modest antennas such as loops or dipoles. Meteor scatter on 2 meters and higher bands is best with directional antennas such as Yagis. The Ping Jockey Central website is a popular real-time gathering place for hams who want to arrange meteor scatter contacts, although many contacts occur entirely at random.

Activity during meteor showers takes place primarily in the late evening and early morning hours. Listen for brief bursts of signals, known as “pings,” on 50.125 and 144.200 MHz, SSB. The calling frequencies for FSK441 are 50.260 144.140 MHz.

Geminids and the Amateur Astronomer

According to NASA Meteoroid Environment Office Lead Bill Cooke, the 2012 Geminids will have a visitor. Comet Wirtanen, discovered in 1948, orbits the Sun every 5.4 years. This year marks the first time the Earth’s orbit will cross the comet’s debris field -- and coincide with the Geminids. Wirtanen is a Jupiter family comet, with a perihelion (closest point to the Sun) just outside the Earth’s orbit.

“Some computer models indicate that the Earth may pass near decades-old debris left behind by Wirtanen in mid-December, creating a new meteor shower,” Cooke explained. “In the most optimistic scenario, viewers could see as many as 10-30 meteors per hour radiating from a point in the constellation Pisces in the early evenings, sometime between December 10-15. This time period also includes the peak of the strong annual Geminid meteor shower, so skywatchers have a chance of a ‘meteor night’ after sunset on Thursday, December 13; meteors from the new shower (if any) will be visible in the early evening, with the Geminids making their appearance later on and lasting until dawn.”

The Geminids, which come around every December, were first observed shortly before the Civil War; when they first appeared, the shower was weak and attracted little attention. The Geminids appear when the Earth passes through debris from the extinct comet 3200 Phaethon, which astronomers long believed was an asteroid. This meteor shower is called the Geminids because it looks as if the meteors are coming from the constellation Gemini, while those from Wirtanen look as though they are coming from the constellation Pieces. By noticing which directions the meteors come from, skywatchers can distinguish which meteors are Geminids and those that are the meteors thought to be from Wirtanen. Cooke said the meteors from Wirtanen should be visible early in the evening, while Geminids should show up later.

Chat with NASA Meteor Experts

On Thursday, December 13 from 11 PM-3 AM EST (0400-0800 UTC December 14), meteor experts from NASA’s Marshall Space Flight Center will be available to answer questions via a late night web chat. There will be two ways to ask questions:

• NASA Chat: Use the NASA chat module. Simply enter your name and then ask your question.
• Ustream: Ask questions via the Ustream feed embedded on the chat page. Note that while the Ustream video feed will be active at dark, the experts will not be available to answer question in the social stream until 11 PM EST.

NASA will also provide a live Ustream feed of the Geminid shower via a camera mounted at NASA’s Marshall Space Flight Center in Huntsville, Alabama. Before the camera activates, viewers will see either pre-recorded footage or a blank box. The camera is light activated and will turn on at dusk.