April, 2005....J. Dana Hrubes...updated April 30, 2005 , 0500 GMT

One of the first visible auroras of the winter is seen reflecting its light from the geodesic dome during a full moon.

April at the Pole - darkness, stars, auroras, satellites

April is an exciting month as the veil of eternal darkness descends upon us resulting in beautiful skies full of stars, planets, auroras and numerous satellites orbiting high enough to reflect the sun to the polar plateau.  The polar twilight is about over now with the sun nearing 18 degrees below the horizon so we no longer have a hint of the sun.    last hint of the sun at the geographic pole marker   
The moon is visible about 2 weeks out of every month at the pole.    moon rise     moon over the new station    
Winter means not only beautiful skies, but periods of windy weather, poor visibility, and drifts of snow to shovel at my doors, particularly the back door of my Cusp Science Laboratory on the first floor of Skylab, which is now about 40 feet below the polar plateau.  I have some plywood to deflect some of the drifting snow this year and I am having some success in reducing my shovel time.    skylab door looking out      looking into the doorway    

Even though we are almost at a minimum of solar activity on the 11 year solar cycle, aurora activity has been quite good.
aurora over the new station in moonlight        aurora with the moon        twisted aurora   

aurora over the dome       aurora over the dome - 2     

aurora over the SETI telescope - 1         aurora over the SETI telescope - 2       aurora over the SETI telescope - 3         

aurora - 1     aurora - 2     aurora - 3       aurora - 4      aurora - 5     

Another interesting phenomenon here at the South Pole is the ability to view Iridium flares about every 9 minutes. Iridium flares are caused by the satellites that are used for the Iridium communication system. We use iridium phones here at the South Pole. There are 66 Iridium satellites divided into six polar planes (not exactly over the poles, but close); each plane has 11 operational satellites, so there is at least one above the horizon everywhere on earth. Since they are polar orbiters and they all cross near the pole, one satellite of each of the six orbital planes passes over the pole every nine minutes and eight seconds. The 11 of each orbital plane are equally spaced so ~9 minutes, 8 seconds times 11 gives about a 100 minute orbit around the earth for each. I have taken photos of the same satellite on successive orbits! Only one of the six planes flares here during a flare period. When the sun is in the right position, these periods of flaring at magnitude -8 (very bright) of one of the six orbital planes can last up to an entire day with a flare every 9 minutes. Most satellite watchers and photographers are envious of us at the Pole because the frequency of flaring is reduced significantly the further you get from the poles. We have another orbital plane flaring to magnitude -8 again on May 10th. There are also a few of these satellites, as spares, in slightly lower parking orbits, so at rare times you may see a double iridium flare as I did two weeks ago when I was walking to the dark sector and fortuitously saw two identical flares side by side.     http://www.iridium.com        iridium flare information  

The three flat antennas that face the Earth's surface are like mirrors and the satellite goes by and then makes a big bright flare as it reflects the sun, as bright as magnitude -8 or -9, when the conditions are right. You can see the satellites when they are not flaring of most of the 6 planes here in their orbits if they are not shadowed by the earth, but you have to carefully look for them, because they are normally only about magnitude +6 which is not very bright. At the Pole, when the conditions are right, each satellite of a particular plane of 11 satellites will flare when it is in the right spot to specularly reflect sunlight to your observation point or swath. Computer programs can predict these flares down to the second so I synchronize my watch to GPS time and push the shutter on my camera about 5 to 7 seconds before the flare and take a 10 to 15 second exposure.

The satellite flares can be seen almost anywhere on Earth, but much less frequently when away from the geographic poles.     find out when iridium flares occur where you live    

An Iridium Flare appearing under Alpha and Beta Centauri, just to the right of the Southern Cross Constellation

Here are a few of the many Iridium flare photos taken on April 29th and 30th when the flares were very bright (magnitude -8), but the weather was windy with blowing ice crystals resulting in skies that were not very clear.
1) Iridium flare and a green laser beam pointing up into the sky. The laser is the NASA Lidar located in the Atmospheric Research Observatory which maps the cloud cover over the South Pole     
2) The Australian and American flags on the AASTO building.    
3) Iridium flare over the circular tower which is attached to the new elevated station building and houses the 92 steps from the under-ice tunnels to the first and second floor of the station.    
4) Close-up of an iridium flare over the circular tower which is attached to the new elevated station building and houses the 92 steps from the under-ice tunnels to the first and second floor of the station.    
5) The top of the SETI telescope tower with an iridium flare overhead.    
6) Iridium flare over the 4 story Skylab building.       
7) Close-up of the Iridium flare, the Southern Cross and Alpha and Beta Centauri.    
8) Iridium flare taken off the back deck of the elevated station under the orange illuminated overhead crane. 

Here are a few Iridium flare photos taken early on May 1st when the flares were not as bright (magnitude -2 or -3), but the weather was calm and the skies were crystal clear. You can see the difference it makes in the number of stars you can see and the length of the iridium trail. These were only 15 second exposures, so the Iridium trail is not complete.

Iridium flare over the Atmospheric Research Observatory (ARO)       

Iridium flare, the Southern Cross Constellation, Alpha Centauri, and Beta Centauri        

Iridium flare and a faint aurora over the Skylab Building    

Iridium flare under the closest star to the Earth, Alpha Centauri, only 4.35 light years away
As far as work, I have been very busy this winter with the 11 projects which I am taking care of here.  With that many projects, something is always requiring extra attention.    repairing the inverter on the VLF transmitter     

I still enjoy walking the 2-1/2 miles each day to reach all of my project buildings: the Atmospheric Research Observatory (ARO), the SETI telescope building (AASTO), the VLF transmitter building and Skylab.     walking route        See my February, 2004  page for more details.

Finally, a good luck salute to the Space Shuttle Crew on STS-114 from South Pole Station    

NEXT MONTH:  more lights in the sky   

       A Real-Time Photo of South Pole Station as Seen from the ARO Building (live when satellite is up)

       A Comprehensive South Pole Web Site by Bill Spindler

     Winterover Web Pages (Bill Spindler's List)