The Commission on Photometry and Polarimetry has a long and distinguished history in the IAU and its contributions to astronomy have been extensive and profound. Its efforts are centered on the issues of atmospheric extinction, photometric passbands, transformations among photometric systems, and calibration. Photometric and polarimetric techniques and standardization are essential tools in our exploration and investigation of astronomical objects and astrophysical quantities.

The past three-year period has seen steady efforts to collect large numbers of radial-velocity (RV) measurements, as well as important applications of radial velocities to astrophysics. Improvements in precision continue to be driven largely by exoplanet research. A workshop entitled “Astronomy of Exoplanets with Precise Radial Velocities” took place in August of 2010 at Penn State University (USA), and was attended by some 100 researchers from around the world. The meeting included thorough discussions of the current capabilities and future potential of the radial velocity technique, as well as data analysis algorithms to improve precision at visible and near-infrared wavelengths.

In Manchester, a WG was set up to work on the implementation of the 9th catalogue of orbits of spectroscopic binaries (SB9), superseding the 8th release of Batten et al. (1989) (SB8). SB9 exists in electronic format only. The web site http://sb9.astro.ulb.ac.be was officially released during Summer 2001. This site is directly accessible from the Commission 26 web site, from BDB (in Besancon) and from the CDS (at least).

The Commission was created in 2006, in response to an initiative by members of the international interferometry community, and as a natural expansion of the work of the earlier Working Group on Optical/Infrared Interferometry. At that time, optical interferometry had been in regular use in modern astronomy for approximately 20 years, primarily with first and second generation prototype and experimental facilities. Also at this time, the first observatory-scale user facilities were coming into operation at ESO, Keck, and CHARA.

The formal commissioning of the IRWG occurred at the 1991 Buenos Aires General Assembly, following a Joint Commission meeting at the IAU GA in Baltimore in 1988 that identified the problems with ground-based infrared photometry. The meeting justification, papers, and conclusions, can be found in Milone (1989). In summary, the challenges involved how to explain the failure to achieve the milli-magnitude precision expected of infrared photometry and an apparent 3% limit on system transformability. The proposed solution was to redefine the broadband Johnson system, the passbands of which had proven so unsatisfactory that over time effectively different systems proliferated, although bearing the same “JHKLMNQ” designations; the new system needed to be better positioned and centered in the spectral windows of the Earth's atmosphere, and the variable water vapour content of the atmosphere needed to be measured in real time to better correct for atmospheric extinction.

This triennium has seen a phenomenal investment in development of observational radio astronomy facilities in all parts of the globe at a scale that significantly impacts the international community. This includes both major enhancements such as the transition from the VLA to the EVLA in North America, and the development of new facilities such as LOFAR, ALMA, FAST, and Square Kilometre Array precursor telescopes in Australia and South Africa. These developments are driven by advances in radio-frequency, digital and information technologies that tremendously enhance the capabilities in radio astronomy. These new developments foreshadow major scientific advances driven by radio observations in the next triennium. We highlight these facility developments in section 3 of this report. A selection of science highlight from this triennium are summarized in section 2.

The IAU Working Group on Historical Radio Astronomy (WGHRA) was formed at the 2003 General Assembly of the IAU as a Joint Working Group of Commissions 40 (Radio Astronomy) and 41 (History of Astronomy), in order to: a) assemble a master list of surviving historically-significant radio telescopes and associated instrumentation found worldwide; b) document the technical specifications and scientific achievements of these instruments; c) maintain an on-going bibliography of publications on the history of radio astronomy; and d) monitor other developments relating to the history of radio astronomy (including the deaths of pioneering radio astronomers).

Originally, Division XI concerned itself only with high-energy astrophysics (in particular UV, X-ray and gamma rays), to which was later added the domain of lower-energy astrophysics where observations are generally performed from space (optical, infrared, submillimeter and parts of the radio spectrum). The Division also includes ground-based high energy gamma ray and cosmic ray experiments, gravitational wave, and Moon-based astronomical observations. The individual expertise of the present OC reflects primarily the UV and higher energy domains. However, since there are plans within the IAU to restructure divisions, we propose that, following the changes in the Divisional structure and renewal of the OC, the new members will be recruited to broaden the spectral range of research covered by the Division.

IAU Commission 5 (http://www.nao.ac.jp/IAU/Com5/) deals with data management issues, and its working groups and task group deal specifically with information handling, with data centers and networks, with technical aspects of collection, archiving, storage and dissemination of data, with designations and classification of astronomical objects, with library services, editorial policies, computer communications, ad hoc methodologies, and with various standards, reference frames, etc. FITS (Flexible Image Transport System), the major data exchange format in astronomy, has been standardized, maintained and updated by the FITS working group under Commission 5.

As earlier, the main activity of the Commission was performed by the Central Bureau for Astronomical Telegrams (CBAT), effectively directed by Dan Green. These three years were a difficult period for the Bureau and thus for the Commission because the Bureau unexpectedly had to move from the Smithsonian Astrophysical Observatory, its home since 1965, to the Harvard University's Department of Earth and Planetary Sciences. This move caused many serious administrative and logistical problems, effectively solved by the CBAT Director, Dan Green, and CBAT Director Emeritus, Brian Marsden. A great shock, not only for our commission but for the whole astronomical community, was Brian's death on November 18, 2010.

The main purpose of Commission 14 is to foster interactions between the astronomical community and those conducting research to provide data vital to reducing and analysing astronomical observations and conducting theoretical investigations. One way that the Commission accomplishes this goal is through triennial compilations on recent relevant research in astronomy, atomic, molecular and solid state physics, and related fields of chemical analysis. The most recent compilations appear in the accompanying set of Commission 14 WG Triennial Reports, which were produced by members of the Working Groups and the Organizing Committee of Commission 14.

This report summarizes laboratory measurements of atomic wavelengths, energy levels, hyperfine and isotope structure, energy level lifetimes, and oscillator strengths. Theoretical calculations of lifetimes and oscillator strengths are also included. The bibliography is limited to species of astrophysical interest. Compilations of atomic data and internet databases are also included. Papers are listed in the bibliography in alphabetical order, with a reference number in the text.

The current report covers the period from the second half of 2003 to the first half of 2011, bringing the Working Group's efforts up to date, and is divided into three main sections covering rotational, vibrational, and electronic spectroscopy. Rather than being exhaustive, space limitations only allow us to highlight a representative sample of work on molecular spectra. Related research on collisions, reactions on grain surfaces, and astrochemistry appear in the report by another Working Group. These also recount recent conferences and workshops on molecular astrophysics.

Research in atomic and molecular collision processes and spectral line broadening has been very active since our last report, Peach, Dimitrijević & Stancil 2009. Given the large volume of the published literature and the limited space available, we have attempted to identify work most relevant to astrophysics. Since our report can not be comprehensive, additional publications can be found in the databases at the web addresses listed in the final section. Elastic and inelastic collisions among electrons, atoms, ions, and molecules are included and charge transfer can be very important in collisions between heavy particles.

The ISO and Spitzer space observatories yielded a treasure trove of data on dust and ices covering dust grains. Now Herschel, and soon SOFIA and ALMA, will provide unprecedented views of the molecular world of the interstellar medium (ISM). It is on dust grains that key ISM molecules, such as hydrogen, formaldehyde, methanol, and water are formed. As a result of these new observations, there is a great need to know more about the interaction processes of atoms and molecules with dust grains. (The Proceedings of the 2010 NASA Laboratory Astrophysics Workshop (http://www-cfadc.phy.ornl.gov/nasa_law/) give a good view of recent accomplishments in the study of atom/molecule - solid interactions as well as other aspects of laboratory astrophysics.)

Commission 41 was created at the VIIth IAU General Assembly in Zürich in 1948. From an inauspicious start—Otto Neugebauer was appointed the first President in his absence, but proceeded to express his conviction that “an international organization in the history of astronomy has no positive function. . .my only activity during my term of service consisted in iterated attempts to resign”—the Commission quickly assumed a key role in the international development of the history of astronomy as an academic discipline.

In the triennium 2006–2009, the WG Archives promoted an action of recognition of the archival documents concerning the foundation of IAU. The pretext was given by the fact that the year 2009 was the 90th anniversary of the establishment of IAU and the WG considered worth to start checking the conditions of preservation and conservation of such documents, in view of the approaching centenary.

The Working Group on Historical Instruments (WG-HI) was founded by the members of Commission 41 at the 2000 Manchester IAU General Assembly with two main objectives: to assemble a bibliography of existing publications relating to historical instruments, and to encourage colleagues to carry out research and publish their results. Since then the concerns of the Working Group have expanded to include efforts to preserve and protect old astronomical instruments, observatories, and related sites as world cultural heritage and material evidence of the development of astronomy in different parts of the globe.