Clover is a UK-led experiment to measure the Bmode polarization of the cosmic microwave background. The instruments are currently under construction and deployment to the Pampa La Bola site in the Atacama Desert is planned for 2010. It consists of two 2-m class telescopes feeding background limited imaging arrays of ~100 dual polarization pixels at each of 97, 150 and 225 GHz. The waveguide and antenna fed TES bolometers are limited by unavoidable photon noise from the atmosphere, and read-out using NIST’s time domain multiplexing scheme. The entire instrument has been designed for exceptionally low systematic errors in polarization measurements, which has necessitated novel designs for the instrument optics, horn arrays, OMTs and detector feeds, as well as careful development of the scan strategy, field location and data analysis methods. The experiment aims to measure the polarization of the CMB with an angular resolution of 5.5′ − 8′ across 1000 deg2 of sky(angular multipole range 20 < l < 1000) to a sensitivity of 8 μK-arcmin after foreground cleaning. If all systematics are adequately controlled this will allow the detection of the primordial B-mode CMB anisotropies down to tensor to scalar ratios of 0.03, as well as providing extremely accurate measurements of the CMB temperature, E-mode polarization, and B-mode lensing polarization. Detecting or constraining the level of the primordial B-mode signal will allow constraints to be placed on the energy scale of inflation, providing an unprecedented insight into the physics of the early Universe. We describe the current status of the Clover project, including the current instrument design and construction status, and the development of the novel technology involved.

We give a description of the design, construction and testing of the 30 and 44 GHz Front End Modules (FEMs) for the Low Frequency Instrument (LFI) of the Planck mission to be launched in 2009. The scientific requirements of the mission determine the performance parameters to be met by the FEMs, including their linear polarization characteristics. The FEM design is that of a differential pseudo-correlation radiometer in which the signal from the sky is compared with a 4-K blackbody load. The Low Noise Amplifier (LNA) at the heart of the FEM is based on indium phosphide High Electron Mobility Transistors (HEMTs). The radiometer incorporates a novel phase-switch design which gives excellent amplitude and phase match across the band. The noise temperature requirements are met within the measurement errors at the two frequencies. For the most sensitive LNAs, the noise temperature at the band centre is 3 and 5 times the quantum limit at 30 and 44 GHz respectively. For some of the FEMs, the noise temperature is still falling as the ambient temperature is reduced to 20 K. Stability tests of the FEMs, including a measurement of the 1/f knee frequency, also meet mission requirements. The 30 and 44 GHz FEMs have met or bettered the mission requirements in all critical aspects. The most sensitive LNAs have reached new limits of noise temperature for HEMTs at their band centres. The FEMs have well-defined linear polarization characteristcs.

CℓOVER is a multi-frequency experiment optimised to measure the Cosmic Microwave Background (CMB) polarization, in particular the B-mode component. CℓOVER comprises two instruments observing respectively at 97 GHz and 150/225 GHz. The focal plane of both instruments consists of an array of corrugated feed-horns coupled to TES detectors cooled at 100 mK. The primary science goal of CℓOVER is to be sensitive to gravitational waves down to r ~ 0.03 (at 3σ)in two years of operations.

C. E. North, B. R. Johnson, P. A. R. Ade, M. D. Audley, C. Baines, R. A. Battye, M. L. Brown, P. Cabella , P. G. Calisse, A. D. Challinor, W. D. Duncan, P. G. Ferreira, W. K. Gear, D. Glowacka, D. J. Goldie, P. K. Grimes, M. Halpern, V. Haynes, G. C. Hilton, K. D. Irwin, M. E. Jones, A. N. Lasenby, P. J. Leahy, J. Leech, B. Maffei, P. Mauskopf, S. J. Melhuish, D. ODea, S. M. Parsley, L. Piccirillo , G. Pisano, C. D. Reintsema, G. Savini, R. Sudiwala, D. Sutton, A. C. Taylor, G. Teleberg, D. Titterington, V. Tsaneva, C. Tucker, R. Watson, S. Withington, G. Yassin, J. Zhang

We describe the objectives, design and predicted performance of Clover, which is a ground-based experiment to measure the faint “B-mode” polarisation pattern in the cosmic microwave background (CMB). To achieve this goal, clover will make polarimetric observations of approximately 1000 deg^2 of the sky in spectral bands centred on 97, 150 and 225 GHz. The observations will be made with a two-mirror compact range antenna fed by profiled corrugated horns. The telescope beam sizes for each band are 7.5, 5.5 and 5.5 arcmin, respectively. The polarisation of the sky will be measured with a rotating half-wave plate and stationary analyser, which will be an orthomode transducer. The sky coverage combined with the angular resolution will allow us to measure the angular power spectra between 20 < l < 1000. Each frequency band will employ 192 single polarisation, photon noise limited TES bolometers cooled to 100 mK. The background-limited sensitivity of these detector arrays will allow us to constrain the tensor-to-scalar ratio to 0.026 at 3sigma, assuming any polarised foreground signals can be subtracted with minimal degradation to the 150 GHz sensitivity. Systematic errors will be mitigated by modulating the polarisation of the sky signals with the rotating half-wave plate, fast azimuth scans and periodic telescope rotations about its boresight. The three spectral bands will be divided into two separate but nearly identical instruments - one for 97 GHz and another for 150 and 225 GHz. The two instruments will be sited on identical three-axis mounts in the Atacama Desert in Chile near Pampa la Bola. Observations are expected to begin in late 2009.

We describe the objectives, design and predicted performance of Clover, a fully-funded, UK-led experiment to measure the B-mode polarisation of the Cosmic Microwave Background (CMB). Three individual telescopes will operate at 97, 150 and 225 GHz, each populated by up to 256 horns. The detectors, TES bolometers, are limited by unavoidable photon noise, and coupled to an optical design which gives very low systematic errors, particularly in cross-polarisation. The telescopes will sit on three-axis mounts on a site in the Atacama Desert. The angular resolution of around 8´ and sky coverage of around 1000 deg2 provide multipole coverage of 20

e-MERLIN is an upgrade to the MERLIN array of seven radio telescopes spread across England, which will increase its sensitivity by more than a factor or 30. The combination of muJy sensitivity with the 50-mas resolution already provided by the long baselines of MERLIN, will open new avenues of research for e-MERLIN. The huge increase in bandwidth is achieved by replacing the exiting microwave links with new optical fibre connections. To collect and correlate this wide bandwidth, new receivers, IF and sampling equipment, digital and optical transmission equipment and a new wideband correlator are being designed and constructed. This paper summarises the design goals, scientific objectives and implementation of e-MERLIN.