South Pole Weekly Report, January 18, 2009

The current IceCube population stands at 47. String numbers 2 and 83 (1st Deep Core String) were added to the IceCube array this week for a total of 16 deployed this season. Drilling of the 17th hole (hole 37) was completed, SPATS pinging was accomplished, and string installation was well underway as of Sunday evening (January 18). All surface to DOM cables are now on-site to complete 19 strings. Plans are underway for shutting down systems, winterizing the drill, and redeployment dates have been pulled forward in anticipation of completing 19 holes ahead of schedule.

P. Hulth explains the IceCube project to Prince Albert of Monaco

This week we completed 3 more holes, having started drilling hole 2 (hole 15) around midnight on Sunday, January 11 and completing hole 37 (hole 17) around noon on Sunday, January 18. In between, the drillers took a well-earned two days off to prepare for the final few holes of the season. The drill equipment continues to perform reliably. We have had to replace one more hose section this week. A problem with some static discharge caused the failure of one network card on the computer but more seriously, took out the communications cards on all of the seven motor controllers in one of the towers. We had replacement cards and installed them in time so as not to affect drilling. These card replacements on the drives caused the load cells to begin giving strange readings: deflecting to full scale. After many hours of attempting to diagnose the problem, including replacing the complete set of load cells and amplifiers from the other TOS, we eventually discovered that the new network cards required the installation of an inline resistor in order to convert the 4-20mA load cell signal to a voltage.

Further updates to the motor controller programming were undertaken in order to detect load spikes on the hose and slack on the drill cable and to stop the drill in case either of these situations takes place. The changes have been tested and were successful, subsequently stopping one hose load spike.

The week also included a visit from the Prince of Monaco who toured the SES, the TOS as well as the ICL. He appeared very interested in what we were doing and spent a more than a half-hour at the drill camp before moving on to the ICL. We completed firn drilling for all of this season's holes.

The automated firn drill software is currently being tested and seems to be performing well. We hope to fine-tune the software on some of next season's holes, which we plan to start drilling on Monday or Tuesday. Given the current rate of progress, we expect to complete drilling the remaining two holes around Thursday, January 22 and to begin winterizing the drill immediately after that.

This week reported zero reportable injuries and no new incident reports marking over 77 days on the ice without a reportable injury.

Two Ice Cube strings were installed last week, String 2 on January 13th and String 83 (L) on January 14th. String 2 included a dust logger run while String 83, the first of six Low Energy/Deep Core (LE/DC) strings, contains 60 high energy DOMs mostly at 7 meter spacing. A third string deployment, String 37, began on Sunday, January 18.

The first LE/DC Surface Junction Box (SJB) was successfully deployed into the oversized pit dug for it. All patch cables have been pulled into the ICL for all strings to be deployed this season and all deployed strings have passed quick connector tests (QCT) and wet connector tests (WCT) and are connected to the DOM Readout (DOR) cards. In the upcoming week, winterization of the ICL will begin in earnest as more than 180 DOMs will be moved into the ICL next week along with Optical Module Lab (OML) Do Not Freeze (DNF) materials. The snow ramp to the ICL will be removed later in the week after all drill heads are stored in the ICL. A final cleanup and inventory is scheduled for the end of the week.

Prince Albert of Monaco signing a DOM before it descends on String 11

This week saw the last South Pole Acceptance Test, SPAT21. Thanks to the volunteers who helped hookup and unhook DOMs. SPAT21 provided 60 DOMs for string 37, 3 DOMs for the buffer, and failed one DOM with sustained high dark rates. There are enough DOMs in the buffer for strings 26 and 17, the final two of the season. Season-end procedures are going smoothly, including OML shutdown and finding winter storage for about 250 DOMs.

We started to remove the DOM holders in the IceTop tanks, removing the DOM holders in the following 12 stations: 6, 12, 19, 27, 36, 13, 20, 28, 37, 10, 4, and 5. Seven stations remain and we expect to finish this work by Monday.

All systems have been running smoothly in the ICL. Because of the leap second discrepancy in the timing signal from the GPS feeding the SPS, we decided to install a spare GPS, Tier 1 fan-out, and another antenna. The antenna was installed on the ICL roof, and the GPS unit and fan-out hardware were installed in Rack 6. We will decide in the next few days when to switch to the new GPS. With the conclusion of DOM testing this week and in preparation to winterize IceCube operations, the DOM testing hub and supporting electronics were moved from the OML to the ICL. The last on-ice member of the Data Systems team arrived on Saturday and will be working on the Hierarchical Storage Management (HSM) and Iridium upgrades.

We changed the amplifiers on the surface antennas of the digital radio extension, calibrated the antenna response and the cable time-delays, putting them in final configuration for the summer. We calibrated the first Digital Radio Module (DRM). We were able to detect the RICE transmitter this morning.

Twelve strings have now been turned on, and we have had 720 communicating DOMs. One pair of IceTop DOMs (on station 13) had communication problems. We determined that there was 200mV peak-to-peak crosstalk on the quad (each IceTop DOM works normally when its partner is off). The crosstalk is believed to exist in the surface cable, and we believe a simple workaround is to swap the problem quad with the quad for the IceTop freeze control unit (the freeze control unit only uses one of the wire pairs).

The IceCube GPS is one-second behind actual time, due to a mistaken firmware addition of a leap second on December 30 (leap second additions during leap years seem to cause a lot of problems, and an international commission is talking about banning them). We installed a second GPS unit in the adjoining rack, and now IceCube has a hot-swappable backup GPS unit (otherwise it would take hours to install and start using a replacement GPS unit, in the event of problems). In the near future we will be switching IceCube over to the correct time (this requires coordination with AMANDA).

Prince Albert of Monaco skied to the South Pole as part of a visit to 26 different bases throughout Antarctica. He successfully turned on string 11.