As we all know too well, building up a collaborative community around a software infrastructure is not easy. Besides recruiting enthusiasts to work as part of it, mostly for free, to succeed you also need to overcome a number of technical, sociological, and, to our surprise, some political hurdles. The ALMA Common Software (ACS) was developed at ESO and partner institutions over the course of more than 10 years. While it was mainly intended for the ALMA Observatory, it was early on thought as a generic distributed control framework. ACS has been periodically released to the public through an LGPL license, which encouraged around a dozen non-ALMA institutions to make use of ACS for both industrial and educational applications. In recent years, the Cherenkov Telescope Array and the LLAMA Observatory have also decided to adopt the framework for their own control systems. The aim of the “ACS Community” is to support independent initiatives in making use of the ACS framework and to further contribute to its development. The Community provides access to a growing network of volunteers eager to develop ACS in areas that are not necessarily in ALMA's interests, and/or were not within the original system scope. Current examples are: support for additional OS platforms, extension of supported hardware interfaces, a public code repository and a build farm. The ACS Community makes use of existing collaborations with Chilean and Brazilian universities, reaching out to promising engineers in the making. At the same time, projects actively using ACS have committed valuable resources to assist the Community's work. Well established training programs like the ACS Workshops are also being continued through the Community's work. This paper aims to give a detailed account of the ongoing (second) journey towards establishing a world-wide open source collaboration around ACS. The ACS Community is growing into a horizontal partnership across a decentralized and diversified group of actors, and we are excited about its technical and human potential.
A new solar flare spectral component has been found with intensities increasing for larger sub-THz frequencies,
spectrally separated from the well known microwaves component, bringing challenging constraints for interpretation.
Higher THz frequencies observations are needed to understand the nature of the mechanisms occurring in flares. A twofrequency
THz photometer system was developed to observe outside the terrestrial atmosphere on stratospheric balloons
or satellites, or at exceptionally transparent ground stations. 76 mm diameter telescopes were designed to observe the
whole solar disk detecting small relative changes in input temperature caused by flares at localized positions at 3 and 7
THz. Golay cell detectors are preceded by low-pass filters to suppress visible and near IR radiation, band-pass filters,
and choppers. It can detect temperature variations smaller than 1 K with time resolution of a fraction of a second,
corresponding to small burst intensities. The telescopes are being assembled in a thermal controlled box to which a data
conditioning and acquisition unit is coupled. While all observations are stored on board, a telemetry system will forward
solar activity compact data to the ground station. The experiment is planned to fly on board of long-duration
stratospheric balloon flights some time in 2013-2015. One will be coupled to the GRIPS gamma-ray experiment in
cooperation with University of California, Berkeley, USA. One engineering flight will be flown in the USA, and a 2
weeks flight is planned over Antarctica in southern hemisphere summer. Another long duration stratospheric balloon
flight over Russia (one week) is planned in cooperation with the Lebedev Physics Institute, Moscow, in northern
The solar submillimeter-wave telescope (SST) is the only one of its kind dedicated to solar continuous observations.
Two radiometers at 0.740 mm (405 GHz), and four at 1.415 mm (212 GHz) are placed in the Cassegrain focal plane of
the 1.5-m dish at El Leoncito high altitude site, San Juan, Argentina. The aperture efficiencies are close to design
predictions: 20% and 35% for 2 and 4 arcminutes beam sizes at 405 and 212 GHz, respectively. The positioner absolute
pointing accuracy is 10 arcseconds. Spectral coverage is complemented by ground-based mid-infrared telescopes
developed for high cadence observations in the continuum 10 micron band (30 THz), using small apertures and room-temperature
microbolometer cameras. Using the system, a new solar burst spectral component was discovered,
exhibiting fluxes increasing for smaller wavelengths, separated from the well known microwave component. Rapid sub-second
pulsations are common for all bursts. The pulsations onset times of appear to be connected to the launch times of
CMEs. Active regions are brighter for shorter submillimeter-waves. Mid-IR bright regions are found closely associated
with calcium plages and magnetic structures near the solar photosphere. Intense and rapid 10 micron brightening was
detected on active centers in association with weak flares. These results raise challenging difficulties for interpretation.
The concept of partially overlapping multiple beams, produced by focal plane arrays in large antennas, has been used successfully at mm-waves to detect instantaneously spatial positions of rapid spikes produced by solar flares. The technique has been used at mm-waves and was recently applied to the Solar Submillimeter-wave Telescope, which operates at 212 and 405 GHz. We present the basic description of the concept and the results obtained. New applications are being considered for shorter submm-IR wavelengths, with the use of focal plane arrays of bolometers, which spatial angular accuracy will strongly depend on the knowledge of the beamshapes of the individual beams produced.