February, 2008....J. Dana Hrubes...updated February 29, 2008 , 0002 GMT

last plane 
The remainder of the summer people board the last LC-130 aircraft
for the season leaving winter polies isolated for 8-1/2 months

(photo by keith vanderlinde)

February is a month of transition for winterovers. It is an exciting time as the last of the summer people board the aircraft for the final flight from Pole for 8-1/2 months, leaving us in total isolation. (2 photos by Keith Vanderlinde)    last plane rotating      last plane waving goodbye for 8-1/2 months   No matter how many times I have wintered, the beginning of the 8-1/2 months of winter still gives me the same strange feeling I got the first time.

In one of the last flights was the arff, the aircraft rescue and firefighting vehicle. It was shipped back to McMurdo station for the long winter, since we don't need it and it will be too cold to operate it anyway.    arff and firefighter     arff      

Immediately after the last plane left on February 14th, winter preparations began. We have to prepare the station for the long dark winter. We pulled up fuel lines that were used to fuel the station for winter, we removed all the aircraft skiway flags (that's about 6 miles worth), we installed flaglines to all of the off-station science buildings that are visited every day, each of us stored away caches of extreme cold weather (ECW) clothing off-site in case of a devastating fire, we man-hauled tons of food and cargo up to the elevated station, and we all moved into our winter rooms.    I'm augering hard ice for flags (4 photos by steffen richter)     augering ice     installing flag       I'm returning with fresh battery for auger     steff installing a flag    

I am setting up my winter room. I got a good one because of my South Pole ice time to date... over 3 years and 6 months..   I have several computers and an iridium pager so I can monitor and control the telescope from my room and be paged if selected parameters go out of range, meaning I would have to put on my ECW and walk the mile to the telescope any time of the day an emergency occurs. If you look at my website from 2001 and 2004 you can tell that the living conditions have improved significantly from the old days in the dome, although I miss living there. After many years of living in darkness, I have optimized my selection of mini-lights for my room and I have decided that purple and orange are optimum for maximum cheeriness and well being.   room-1     room-2    I also have a nice office to perform my station science leader duties.  station science leader office   office with a view of the geographic south pole  

I also have another nice office and a building with workshops to work in at the Dark Sector Laboratory(DSL), where I work with Keith, overlooking South Pole Telescope (SPT), our large 10 meter microwave telescope. DSL/SPT is a mile from the main station.     DSL-SPT-office      
in front of the primary microwave mirror
I am standing on the ground shield in front of the 10 m (33 ft) primary
microwave mirror
February was also a big month for the South Pole Telescope. In the last several weeks before station closing, the Berkeley and Chicago teams worked around the clock to warm up the secondary and receiver cryostat, open up the receiver and replace some of the bolometer (sensor) wedges in the hope to increase the sensitivity and signal to noise ratio of the already much improved sensor array. It was a risky venture, given the time left before station closing, but it was accomplished and the results are very good.      

We are now ready to start the observing season armed with the best Cosmic Microwave Background (CMB) detector ever.  It was tight getting the receiver back together, mating it with the secondary cryostat, pumping the whole subsystem down to about 1 x 10-7 Torr and then cooling it down in time to test it before February 14th, the closing date of the station. The cooldown process takes almost 5 days and the result is a sensor array that is cooled down to 0.26 Kelvin, just 1/4 of a degree Celsius above absolute zero. This low temperature is necessary to detect the very weak low temperature 150 GHz microwave signal at a respectable signal to noise ratio. After the cryostat and receiver was assembled, most of the team was needed to perform the arduous task of lifting, securing and connecting hundreds of cables to this 3000 lb mass.
   telescope showing the heated receiver cabin     another view of telescope showing cabin for receiver   I'm installing a new pulse tube cooler into the receiver cryostat with brad, the cryostat designer       preparing to lift receiver and secondary mirror cryostat into cabin     preparing to lift(you can see the microwave window in the roof of the cabin)      begin cryostat lift     team up in cabin ready to receive cryostats     lifting cryostat-1   lifting cryosat-2   lifting cryostat-3    mounting cryostat to optical bench    connecting pulse tube cooler helium lines

Finally, the South Pole Telescope (SPT) was tested and one of the first images taken to confirm its operation was to get an image of a well known galaxy cluster, AS1063. The detection and mapping of galaxy clusters using the Sunyaev-Zel'dovich effect
(SZE) is the main goal of SPT for the next two years. Once discovered and mapped, these galaxy clusters can then be viewed with optical telescopes to determine red shifting and thus distances and age of these massive entities.

coming soon
A preliminary CMB-SZE image map of
galaxy cluster AS1063 taken with SPT

For the first two weeks of winter since the summer team has left, Keith and I have been tweaking parameters on the refrigeration cycle. The bolometer array (sensor) is cooled down to about 0.25 degrees above absolute zero (0.25 Kelvin) using as series of helium coolers.  A pulse tube cooler takes us down to about 2.7 Kelvin and then a subsequent Simon Chase helium 10 cooler  allows us to take the bolometers and SQUIDs down to transition and superconducting temperatures as low as 1/4 degree Kelvin.  The entire cooling system is closed cycle and requires no transfer of expendable cryogens. The Simon Chase cooler is called a helium 10 cooler because the three stages, a helium 4 stage and two helium 3 stages adds up to 10.  Helium 3, with an atomic mass af about 3 is an isotope of standard helium 4 and its properties allow us to get to lower temperatures. We have been tweaking the refrigeration cycle in order to optimize the cycle time. During observation time, liquid helium 3 eventually all vaporizes and is collected in the charcoal adsorption devices. The helium is then recondensed as liquid by recycling (heating) the charcoal and driving off the helium, allowing it to condense at the the other end of the cooling stage. Minimizing the re-cycle time and maximizing the helium 3 vaporization time at 0.25 Kelvin before running out of liquid helium 3 results in the maximum CMB observation time. We are getting total cycle times on the order of 39 hours, although we would like to push it to 48 hours, in order to make the winterover's sleep cycle a bit more normal.
In addition, we have been running focus scans schedules sent to us in order to optimize the optical bench positions as a function of telescope orientation. The University of Chicago, Berkeley, Case Western Reserve and the other collaborators are working hard to send us focus scans, CMB scans and to troubleshoot every aspect of this complex instrument. Keith and I participate in two teleconferences per week with the entire team  (http://pole.uchicago.edu/) using the Iridium satellite system.

We have also had numerous mechanical issues to deal with which is typical in this harsh climate. It is still February and the temperature has already dropped to -67 F (-55C) and it will continue to drop over the next months to temperatures that can exceed -110 F(-80C) and that is the static temperature, not any wind chill nonsense.  Just this week, the 2000 lb optical bench failed to move to the correct position during a focus scan. The optical bench has 6 actuators driven by 6 servo motors and gear trains. One of the six actuators ceased moving, so Keith and I quickly aborted the current focus scan, docked the telescope and crawled up into the receiver cabin using the hydraulic man-lift. After 7 hours of troubleshooting and repair in this extremely tight space we fixed the actuator and got the telescope back in operation. The telescope was brought down by a 1/4-inch set screw that had loosened.
  one of the six servo motors and optical bench actuators     removing the servo motor       measuring the precise depth for the coupling       checking out the coupling repair      closing the 5000 lb roof after undocking the telescope    Other mechanical tasks included replacement of the rollers on the 5000lb rolling docking roof.    finishing replacement    on the roof

The mechanical aspects of the telescope are a diversion from the operation of the telescope with its many computers.    sweeping snow out of the primary mirror ground shield   
Some parting shots of SPT while the sun is still up.  SPT-1     SPT-2      SPT-3     many summer days are grey        

March: the sun sets and will not return for 6 months!

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)