Our group has several ambitious goals for the WMRS Barcroft station: Acquisition of CMBR (Cosmic Microwave Background Radiation) anisotropy data from the BEAST telescope; installation and operation of a sensitive CMBR Polarization experiment in the Barcroft dome; planning for and securing funding for a larger, more aggressive CMBR polarization telescope (the Densely Instrumented MMIC Correlation Array Module or ‘DIMCAM’). In addition, we are doing extensive work preparing the site for these instruments in terms of infrastructure (communications, power handling (UPS, surge protection, power distribution), 24/7/365 automated weather monitoring, and physical facilities). We made major progress in all these areas during 2001.
CMBR anisotropy and CMBR polarization anisotropy are probes of processes and structure in the early universe. CMBR Anisotropy measurements constrain the processes by which structure could have formed, the nature and distribution of matter in the universe, and the small number of cosmological parameters which describe the universe as a whole, including the Hubble constant, the cosmological constant and the average density of the universe. CMBR anisotropies may be polarized by several processes: measuring the polarized component of CMBR anisotropies should allow us to separate out otherwise degenerate models, as well as distinguish the characteristic imprint of primordial gravitational waves on the structure of the early universe.
Starting in late 2000 and early in 2001 (January), we brought the main components of the BEAST (Background Emission Anisotropy Scanning Telescope) to Barcroft. Through the winter season and into the early summer we made many trips to Barcroft so that by July, the following were accomplished:
View of the BEAST garage during observations, 2-15-02
Garage: We modified one of two available Barcroft garage structures by cutting a portion of the roof, raising it and mounting it on rails to allow it to roll open. This allows the telescope to view the sky without being moved out of the building. The roof is actuated with an industrial garage door opener, and has been working in all seasons at Barcroft (including during a trip in February 2002). Much of the success of this work rested on the ingenuity, skill and hard work of WMRS staff (Rick Masters and Dave Trydahl).
Power Handling: One of the challenges of working at Barcroft turned out to be power line problems. We lost several computers and some data acquisition equipment to power line surges before we acquired and installed appropriate power conditioning hardware, including ferro-resonant transformers and high capacity UPSs (Uninterruptible Power System). We have had no problems since installing these systems. In addition to this we contracted an electrician/carpenter to install new breaker panels and appropriately sized circuits in both garages and the dome.
Telescope: The BEAST telescope was originally designed to make measurements from a high altitude balloon, for periods of up to 10 days. We made extensive modifications to the system to allow extended observations from the ground and assembled the telescope at Barcroft in the garage. By late July we had the system operational, with full time data taking commencing in early August. To date we have around 200 Gbytes of Cosmology data from Barcroft and we are in the process of analyzing it.
Map made from Two days of beast data. Top panel shows full map (the measured area is about 3000 square degrees, the center of the panel is the north celestial pole).Extra noise in the upper left quadrant is from data missing due to bad weather. Bottom panel is a closeup of this map showing some point sources, the Cygnus A radio galaxy is at the center of the panel.
Weather and site monitoring: During the summer we installed a weather station, downloading weather data by hand during normal operations of the telescope. During our recent trip to Barcroft (Feb, 2002) we set the system up to automatically send data to UCSB via the STARBAND satellite internet link. At the same time we installed a webcam for visual record of the site conditions when personnel cannot be there. (http://moseisley.deepspace.ucsb.edu ). In addition to this we were able to borrow a standard NRAO ‘tipper’, an automated instrument for measuring atmospheric opacity. This standardized instrument allows direct comparisons among millimeterwave/infrared observing sites. We operated the tipper from early September thru late October. We were fortunate to have the tipper loaned to us by A. Beasley of the OVRO, and we hope to borrow that one or another one for longer term measurements of the site. For the time period measured, Barcroft was comparable to Mauna Kea, considered one of the best IR observing sites in the world.
Dome Refurbishment: We have been working to upgrade the dome facility in preparation for bringing the first generation polarimeter telescope to Barcroft. This includes upgrading the power systems as describe for the BEAST garage, strengthening the telescope support pedestal, replacing weatherstripping, insulating the instrument room, and upgrading the dome control system to allow computer control of the door and azimuth. This work will be completed in the early part of the Summer, 2002 , in time to install the telescope.
Polarimeter: The instrument being readied for the dome consists of three (3) receivers: one ‘delta T’ at 90 GHz, one polarimeter at 40 GHz, and one polarimeter at 90 GHz. The receivers are cooled to 20 Kelvin with a mechanical cooler and coupled to a second copy of the BEAST telescope optics. This instrument will be dedicated to making a small but very sensitive map of CMBR polarization fluctuations near the North Celestial Pole. The receivers are ready and being integrated to their electronics, while the telescope sytem is being integrated separately. All elements should be tested together in Santa Barbara by mid May, ready for Barcroft sometime in June.
Polarimeter Recievers and Polarimeter Telescope Frame and Rotation Stage.
We made major progress towards making Barcroft usable by our students by having one of the ‘garages’ refurbished into a comfortable laboratory. This provides a controlled comfortable environment for the students, most of the computers and test equipment, even in the harshest conditions at Barcroft in February. WMRS staff also helped significantly in setting up this lab.
DIMCAM is our name for a large format array of correlation Polarimeters, specially designed detectors for measuring CMBR polarization. We submitted two major proposals the the National Science Foundation to support this specific project development, decisions will be made later this year. In the meantime, design work and planning continues, assuming a good outcome for the proposal.
Reliable communications with reasonable bandwidth are critical to the success of our program, from simple interactions debugging instruments over the phone, downloading test data during observations, remote monitoring of the site for weather and atmospheric conditions, all the way to potential remote operation of the telescope via the web. Three systems brought up to Barcroft are making a huge difference to how we can work there:
Our efforts at Barcroft have been funded from a variety of sources, all of which have been very important to our success to date. In addition we have applied for significant funds from NSF to support future work. We have made a summary of the totals in the other part of this report, here we outline how the different sources contribute.
NASA Balloon program
Our NASA funds have been the primary support up to the start of our work at White Mountain. We developed and flew the BEAST telescope on NASA grants. The spare optics and much of the instrument infrastructure for the polarimter depend heavily on our previous work on the NASA payload. Without all this investment there would be no telescopes to site at Barcroft.
NASA/ESA Planck Surveyor
Planck is a second generation CMBR space mission we are involved in. While NO Planck funds have been spent on WMRS work, there has been very significant technology transfer. The receivers being used for the polarimeter were developed with JPL collaborators (T. Gaier, M. Seiffert) based very directly on the Planck receivers, and using the same devices from TRW. These are state of the art receivers with state of the art devices and performance, and could only be available to our program through our extensive collaboration with JPL on the Planck and BEAST programs.
Compass is a joint venture with the University of Wisconsin, Madison and the University of Miami. It has been funded by NSF extragalactic astronomy for several years, looking for polarization anisotropy in the CMBR from a site in Wisconsin. The collaboration plans to move the operation and future instruments to Barcroft due to the superior observing conditions. The 3 element polarimeter described above is part of this collaboration.
NSF Extragalactic,NSF MRI-DIMCAM
These two proposals to the NSF include our COMPASS collaborators and detail the large format polarimter array we plan to install at Barcroft.
We have an active collaboration with researchers at INPE (the Brazilian Space Agency). For the past year they have been providing significant amounts of support in the form of hardware contributions, totaling $100,000. These contributions range from very sensitive angle resolvers to state of the art custom electroformed microwave feedhorns.
All of the work described above could not have been accomplished without the enthusiastic support of the WMRS staff and management. Both Dave Trydahl and Mike Morrison (outgoing and new managers respectively) made sure we had what we needed to accomplish our work. Rick Masters has been tremendously helpful with advice, winter transport and logistical support as well as his work on the buildings. J. Szewczak’s work on the internet link has been much appreciated, and we look forward to taking full advantage of it. In addition all the OVL and Barcroft summer staff were enthusiastic and helpful, with normal logistics and helping hands for the students and staff. We’re all looking forward to a long and productive collaboration.