The case is made that the 21st century will be the epoch of precision cosmology. It is realistic to expect that many of the standard cosmological parameters will be determined with high precision. This will require detailed and convincing understanding of the astrophysics of the objects used in the determinations.

The VSA is a 14-element aperture-synthesis telescope for mapping structure in the Cosmic Microwave Background which is now being commissioned at the Teide Observatory, Tenerife. It operates at frequencies between 26 and 36 GHz, with a bandwidth of 1.5GHz. Its elements track the sky, providing fringe-rate discrimination of any instrumental effects such as antenna cross-talk or ground radiation. The instrument incorporates a single-baseline interferometer comprising two large (3.7m) dishes, which is used to provide concurrent (and same frequency) pointed flux measurements of point sources in the VSA fields, the positions of these source having been obtained previously from survey observations made with the Cambridge Ryle Telescope at 15 GHz. The VSA is now completing its commissioning programme and it will start routine observations in September 2000.

The Cosmic Background Imager (CBI) is an instrument designed to make images of the cosmic microwave background radiation and to measure its statistical properties on angular scales from about 3 arc minutes to one degree (spherical harmonic scales from l ˜ 4250 down to l ˜ 400). The CBI is a 13-element interferometer mounted on a 6 meter platform operating in ten 1-GHz frequency bands from 26 GHz to 36 GHz. The instantaneous field of view of the instrument is 45 arcmin (FWHM) and its resolution ranges from 3 to 10 arcmin; larger fields can be imaged by mosaicing. At this frequency and resolution, the primary foreground is due to discrete extragalactic sources, which are monitored at the Owens Valley Radio Observatory and subtracted from the CBI visibility measurements.

The instrument has been making observations since late 1999 of both primordial CMB fluctuations and the Sunyaev-Zeldovich effect in clusters of galaxies from its site at an altitude of 5080 meters near San Pedro de Atacama, in northern Chile. Observations will continue until August 2001 or later. We present preliminary results from the first few months of observations.

We describe the design and current status of the Degree Angular Scale Interferometer (DASI), a compact cm-wave interferometer operating at the Amundsen-Scott South Pole research station. With 20-cm diameter primary antenna elements operating over the frequency range 26 − 36 GHz, DASI is optimized to measure the power spectrum of the cosmic microwave background radiation (CMBR) over the multipole range 140 − 920, (corresponding to scales of 25′ − 2°.6), as well as make high-sensitivity maps of the microwave sky. The telescope was built at the University of Chicago and deployed at the South Pole during the 1999-2000 austral summer.

This paper presents results obtained with the Jodrell Bank - IAC two-element 33 GHz interferometer, located at the Teide Observatory on Tenerife, which is designed to measure the level of the Cosmic Microwave Background (CMB) fluctuations on angular scales of 1° and 2°. The result from a maximum likelihood analysis of observations taken at Dec +41° of δTl = 63+7-6μK at l = 208 ± 18 is comparable with those of Boomerang and Maxima. The contribution of possible foreground contaminants are considered.

In preparation for Very Small Array (VSA) observations we have surveyed the first three VSA fields at 15 GHz using the Ryle Telescope in Cambridge, finding 217 sources with flux density greater than ˜ 20 mJy over 178 deg2. This is the highest radio frequency at which a survey has been done that is relevant to the issue of radio source contamination in CMB experiments. Our results show that source fluxes, and indeed the existence of many sources, cannot be predicted at 15 GHz by extrapolation from lower frequency. The spectra and variability of the sources and their implications for CMB experiments at cm-wavelengths are discussed.

BOOMERanG has recently resolved structures on the last scattering surface at redshift ˜ 1100 with high signal to noise ratio. We review the technical advances which made this possible, and we focus on the current results for maps and power spectra, with special attention to the determination of the total mass-energy density in the Universe and of other cosmological parameters.

We have developed a balloon-borne experiment to measure the Cosmic Microwave Background Radiation anisotropy on angular scales from ˜50° down to ˜20′. The instrument observes at frequencies between 150 and 690 GHz and will be flown on an Antarctic circumpolar long duration flight. To greatly improve the experiment performance, the front-end of the experiment is mounted on the top of the balloon. With high sensitivity, broad sky coverage, and well-characterized systematic errors, the results of this experiment can be used to strongly constrain cosmological models and probe the early stages of large-scale structure formation in the Universe.

A combined technique using the maximum-entropy method (MEM) and the mexican hat wavelet (MHW) to separate and reconstruct the physical components of the microwave sky is presented. We apply this method to simulated observations by the ESA Planck satellite in small patches of the sky. The reconstructed maps of the CMB and foregrounds are improved as compared to those obtained with MEM on its own. Moreover, more accurate point source catalogues are produced at each observing frequency. This technique may also be extended to deal with other multifrequency CMB experiments, including all-sky data.

The Microwave Anisotropy Probe (MAP) satellite is scheduled to launch in mid-2001. MAP's goal is to produce a map of the anisotropy in the cosmic microwave background of unprecedented accuracy and precision. The guiding design principle has been the minimization of systematic effects. The instrument design and mapping strategy work in concert to take advantage of the unique opportunities afforded by deep space. We give an overview of the mission and compare the projected MAP error bars to recent measurements.

We present an overview of the European Space Agency's Planck mission, its scientific objectives and the key elements of its technical design. The current programmatic status of Planck within ESA's Scientific Programme, implementation plans, and near-term milestones are also addressed.

Jodrell Bank Observatory is responsible for the Front end modules (FEMs) for 30 GHz for LFI, with IAC being responsible for the hybrids and any phase switch. The University of Cantabria are responsible for the Back end modules (BEMs). Developments have been made to test prototypes both warm and cold for the FEMs. This is evolving towards flight hardware through an elegant breadboard phase EBB. Results of system performance show both white noise and 1/f characteristics.

Observations of cosmic microwave background in the range 10-90 GHz have revealed an anomalous foreground component well correlated with 12 μm, 60 μm and 100 μm emission from interstellar dust. As the recent cross-correlation analysis of WHAM Hα maps with the Tenerife 10 and 15 GHz maps supports an earlier conclusion that the emission does not arise from free-free radiation, the interstellar dust origin of it is left as the only suspect. Two competing models of this emission exist. The more favored at the moment is the spinning dust model, the other is the model that uses grains with strong magnetic response. In the spinning dust model the emission arises from rapid rotation of ultrasmall grains that have dipole moments, while in the other model magnetic grains emit due to thermal vibrations of magnetic dipoles. Both models predict the emission to be partially polarized and this emission can seriously interfere with the CMB polarization measurements. We discuss observational signatures that can be used to distinguish and eventually filter out the polarized component of the microwave dust radiation.

Recently completed Hα surveys of large portions of the sky can be used to create maps of the free-free intensity distribution at high Galactic latitude that are independent of the spectral fits to the CMB data. This provides an opportunity to test the accuracy of the spectral fitting procedures and to search for other sources of Galactic forground contamination that could be confused spectrally with the free-free, such as spinning dust grains. The Wisconsin Hα Mapper (WHAM) survey has sampled the sky north of declination −30° at about one degree angular resolution and has revealed that, except for a few isolated regions of enhanced emission, δTff (30 GHz) ≲ 30 μK at Galactic latitudes near 15°, decreasing to δTff(30 GHz) ≲ 4 μK at latitudes above 50°. Also in progress are Hα surveys that sample the sky at higher angular resolution.

We propose a technique for determination of the spectral parameters of the cosmological signal and pixel noise using observational data on CMB polarization without any additional assumptions. We introduce the notion of so called crossing points in the observational maps and derive the theoretical dependence of the total number of crossing points at different level of the polarization. Finally, we use the statistics of the signal in the vicinities of the singular points, where the polarization of the pure CMB vanishes to correct the final result.

We propose a novel method for the extraction of unresolved point sources from CMB maps. This method is based on the analysis of the phase distribution of the Fourier components for the observed signal and unlike most other methods of denoising does not require any significant assumptions about the expected CMB signal. The aim of our investigation is to show how, using our algorithm, the contribution from point sources can be separated from the resulting signal on all scales.

We have mapped the total sky brightness at 1465 MHz in two adjacent 60° declination bands with the portable 5.5-m parabolic reflector of the Galactic Emission Mapping (GEM) project, an on-going international collaboration to survey the radio continuum of the sky in decimeter and centimeter wavelengths. The observations were conducted from two locations, one in the USA and the other in Brazil, using a novel instrumental approach to overcome the well-known shortcomings of survey experiments. Our strategy consists of a 1-rpm rotating dish to circularly scan the sky at 30° from Zenith. The dish uses a rim-halo to re-direct the spillover sidelobes of its backfire helical feed toward the sky and the entire assembly has been enclosed inside a wire mesh ground shield in order to minimize and level out the contamination from the ground. The diffraction characteristics of this set-up have been successfully modelled and un-desired systematic striping across the observed bands has been carefully removed by a baseline propagation method which exploits the time-forward and time-backward intersections of the circular scans. The map displays nearly 300 hours of our best quality data taken with a HPBW of 5.4° at a sensitivity of 20 mK.

The main tools describing the formation of large-scale structure are reviewed. Detailed emphasis is given to the Cold Dark Matter model, since this appears to be a close match to observation. A consistent normalization that satisfies both CMB constraints and the cluster abundance requires Ωm ⋍ 0.35 for a flat universe and scale-invariant fluctuations. Discrepancies between observed galaxy power spectra and CDM predictions are discussed; a heuristic model for galaxy bias is proposed that potentially allows such scale-dependent bias to be understood.

This paper describes the goals, current status and some preliminary results from the 2dF Galaxy Redshift Survey. In particular we present the most precise measurement to date of the redshift-space distortion parameter, β ≡ Ω0.6/b = 0.39 ± 0.05. Combined with recent CMB anisotropy measurements, our results strongly favour a low-density universe.