The 11th, 12th, and 13th strings of the season were successfully deployed this week. Drilling has been going steadily. The strings typically reached target depth 10 h after the drilling was completed. Commissioning activities are increasing as more strings begin to freeze in. The safe production of deep ice holes and the subsequent string installation continue to be the focus of on-ice construction operations.
| IceCube Drilling and String Installation Plans | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| String (2007/08) | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
| Hole Location | 63 | 64 | 55 | 71 | 70 | 76 | 77 | 75 | 69 |
| String Installed | 12/08 | 12/1 | 12/16 | 12/19 | 12/22 | 12/24 | 12/29 | 12/31 | 1/3 |
| 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | |
| Hole Location | 60 | 68 | 61 | 62 | 52 | 44 | 53 | 54 | 45 |
| String Installed | 1/5 | 1/7 | 1/10 | 1/13 |
The IceCube population at the end of the week is 45, one below plan. The new arrivals this week enjoyed three extra days in McMurdo due to weather delay.
We have 17 Surface to DOM cables on the ice as well as enough DOMs to support 18 strings. The 18th cable is scheduled for delivery this coming week. A small number of additional DOMs coming in will go to next year's startup. We are planning only one strings worth of DOMs plus IceTop DOMs as an early season startup buffer (one less than originally envisioned).
This week was a short drilling week, starting with a day off on Monday and ending with a day off on Sunday. In between that time 2 holes were drilled.
Our original intention was to drill 3 holes then take a day off. However the replacement drill cable, which was spooled on the Monday, decided to suffer electrical failure after it was spooled so we decided to drill 2 holes "blind", then bring the day off forward by one hole and take the opportunity of that day off to replace the drill cable yet again with our final spare. This replacement is currently taking place as this report is being written. Once the cable is replaced, we will drill 3 holes then take a day off, then drill 2 more before the next day off.
The location of next season's Seasonal Equipment Site (SES) berm is currently being compacted and prepared for us to relocate the SES at the end of this season's drilling. We have started drilling some of next season's firn holes and intend to do 3 or 4 before we winterize the firn drill for the season.
We are currently still on schedule for drilling 18 holes, having achieved a hole turnaround of about 50 hours over the last few holes.
The crew appears to be in good health and good spirits are eager to complete the last 5 holes of the season.
We had a very good week in Deployment. Three strings were installed this week. String 68 went in on Monday, String 61 on Thursday, and String 62 was put in Saturday night. Strings 68 and 61 both deployed smoothly but String 62 was more troublesome. There were a large number of misplaced Yale Grips in the string which required the deployment crew to improvise and modify the installation. Twelve cases of misplacements by about 20 cm were reported by the team when the Deployment Logs were submitted at the end of the deployment.
The 28 IceTop tanks deployed this season continue to freeze-in nicely. A dual-axis inclinometer was deployed on String 68 to a depth of 2456 m and is reading properly. These devices will measure tilt changes of the strings to a precision of ~0.01 degrees in order to study the strain rate of the ice in the deeper portions of the array.
All three strings deployed this week passed the quad connectivity test as well as the wet connector test and are available to be commissioned. The final 6 surface cables were connected to patch panels and end-of-season planning has begun for winter storage in the ICL.
SPAT18 [South Pole Acceptance Test] (for string 62) went smoothly, all 64 DOMs passed. In SPAT19 (for string 52) we retested 8 DOMs with earlier problems. The fates of these three are yet to be decided, but 61 DOMs were good to deploy. In SPAT20 (for string 44) we saw suspiciously high currents from one pair of DOMs, this will be investigated further in a retest.
Network infrastructure upgrades were completed across the South Pole data System (SPS). The work primarily involved software upgrades and minor configuration modifications to layer 2 switching devices.
Maintenance and safety issues were addressed on the roof of the IceCube Lab (ICL). A broken heater unit was replaced inside the IceCube antenna enclosure. In addition, safety concerns raised by the presence of roof-top components of the South Pole Outdoor Test System (SPOTS) were mitigated via conventional securing techniques.
Three strings have been commissioned to date. 59 DOMs passed all 51 tests ("Beaver" is not testable). A total of 179 out of 180 DOMs passed the standard 24-hour TestDAQ data-taking test, which we run every year. The one bad DOM, 71-39, does not power up. This is the only DOM on the first three commissioned strings that is not usable.
Commissioning is currently on hold while we take a set of water data with string 62, which was deployed last night. The purpose of the data taking in water is to compare muon data in water with muon data taken with the frozen string. The idea is to test the current optical model of the refrozen ice.
There was one reportable safety incident this week. A driller was momentarily hit by a high pressure stream of hot steam during a heater venting operation. Despite the fact that he was wearing five layers of clothing, he suffered 2nd degree burns on his wrist (over an area the size of a half-dollar). He is continuing to work. Safety continues to be a top priority.
The Dedication of the new South Pole Station took place on January 12, 2008. A delegation of 24 distinguished visitors traveled to the South Pole for the Dedication. Earlier in the day, the U.S. flag was lowered over the Dome. Dr. Arden Bement, NSF Director, opened the ceremonies in the gym with an address to the visitors and the station personnel. The U.S. flag and the USAP flag were raised over the new station.
Later in the afternoon all visitors toured the station and the major science projects in 4 groups. The visit coincided with the installation of string 62 so that all visitors could witness the installation of the sensors in the ice.
This was a busy week for all of South Pole Station due to the Station Dedication that took place on Saturday, Dec 12th. In preparation for the dedication, an IceCube display was erected near the entrance to the station. A DOM was hung, along with a poster to give a brief introduction to IceCube.
Dr. Arden Bement, NSF director, while in the presence of several other very important people, presented National Science Foundation golf balls to Albrecht Karle, in recognition of the golf tournament played one week earlier (a tournament which was unfortunately won by the team representing the NSF).
IceCube participated in its 2nd Exploratorium webcast of the season on January 12. Albrecht Karle, Michelangelo D'Agostino, Jeannie Edwards and Edgar "Tex" Nielsen participated.