First Light in Chile!

The POLARBEAR experiment on the Huan Tran Telescope achieved first light in Chile on January 10, 2012.

Pictures of the construction phase can be seen at:

http://bolo.berkeley.edu/polarbear/

The team is currently preparing the experiment for science observations in April, when weather conditions in Chile become suitable.

Top Photo: The Huan Tran Telescope (HTT) at 17,000 feet (51050 m) altitude.

Bottom Photo: Installing the 1284-bolometer focal plane. Hideki Mori (left) and Zigmund Kermish (right)

The Water Chiller

As Dan mentioned, I had the pleasure of draining the water chiller last week. Few have worked with the water chiller and come away clean. The water pump has as much power as a small lawn mower and can move a gallon of water in 2 seconds up 100 feet, which led to a fantastic disaster scene the first time we tested it in the lab.

For the past couple months we've been refilling the water chiller at about 2 gallons per week. The system is closed, so we were sure there was a leak. We were never able to find it though because you can't open the access panel with the exposed 1.5HP finger eating fan running inside.

Once it was open for draining, I toggled the manual bypass valve to try to get some of the last liquid out of the maze of pipes inside, and found this gem:


The manual bypass valve has a 1" long 1/16"wide crack running down the length of the body, which vomits a vile mixture of antifreeze and fungus water when toggled.

The other user accessible valve I needed, naturally, is also broken:
This valve shuts off the flow to the water pump, so that you can disconnect the device you're cooling water for. It now only closes to the point of the chiller drooling like an old dog.

Almost there

Since we stopped observation on August 22nd we've been reversing our work of the past year, taking pieces off the telescope and putting our gear back into boxes. It turns to be easier to take things apart than to put them together: in under two weeks we've gone from a fully operating instrument to a bare telescope with only mirrors and servos still attached. While Dave and I have been crawling all over the telescope, Ian and Tom have been going through the storage container, packing boxes and making sense of all the junk we've accumulated. Bryan was trying to work on data analysis so we made him drain the water and antifreeze from the chiller into jugs. Today we took apart the gantry, which was the last structure we're going to take apart ourselves.

To remove the various panels we had the telescope in birdbath position for a few days, and an overnight rain left this tree stump pattern on the primary. The Vertex guys are showing up in a little more than a week to handle the dis-assembly of the major pieces with the big crane as well as final preparations for shipping. We're in good shape for their arrival so we're taking a few days off this weekend.

HTT at JAO dedication

On Sunday, July 11th, nineteen members of Huan's family came out to the site for an official dedication of the Huan Tran Telescope at the James Ax Observatory. In their presence, we installed a plaque commemorating the project's namesake scientists.

Unwelcome Visitor

I almost stepped on a rattlesnake sunning himself next to our storage container. He then decided to hide under the container and we thought it wasn't a good idea to leave him there. Fortunately Bill knew exactly what to do:

Observations

Things are winding down in the field a bit - tomorrow we'll be briefly down to 5 people for a few hours between Aubra leaving and Hans arriving. The receiver, telescope and readout are behaving well enough now to keep things running with only a few people. We've already achieved many of the instrument demonstrating astronomical observations we planned to in California, including:

• Jupiter - the brightest point source in the sky at 150GHz, for mapping our beams and calibrating throughput
• Tau A, the crab nebula - A bright polarized source in the sky, for demonstrating and calibrating polarization sensitivity. Humans saw the supernova progenitor 1000 years ago.
  
• The Galaxy - We're observing this one the same way we'll observe the cosmic microwave background, but it's much brighter, so it has a fast turnaround time and acts as a dry run for science.
• Saturn, Mars, 3C279, J1229+0203, etc - An assortment of sources across the sky, planets and the brighter quasars, whose positions have been measured to exquisite precision using optical telescopes and interferometer arrays like CARMA. We measure where they appear to be in our telescope, and check that against where we know they actually are.
  

It's an exciting time to be analyzing data for Polarbear.

Hair cut

The moon is waxing gibbous again, which means the Polarbear receiver and I have been out in the field for nearly 2 months, and it's time for a hair cut. Thanks to Kam for picking up the shears in Bishop, and Dave for cleaning up the back and tolerating the mess I made of the bathroom.