Submitted by Bryan Gaensler, Canadian SKA Science Director
(Cassiopeia – Autumn/Automne 2015)
Updates on the Square Kilometre Array (SKA) will now appear regularly in Cassiopeia. For more frequent and more detailed info, please subscribe to the Canadian SKA email list, at SKA email list.
International SKA Activities
The rebaselining process for the SKA has now concluded. The outcome is that the first 10% of the SKA (« SKA1 ») will now consist of two components: SKA1-Mid in South Africa (0.35-14 GHz), and SKA1-Low in Australia (50-350 MHz), each of which will have spectacular scientific capabilities in its own right. Construction on SKA1 is planned to commence in 2018, with science operations to begin in 2023.
Canada is one of 10 member countries of the SKA Organisation, and is represented on the SKA Board of Directors by Greg Fahlman (NRC) and Bryan Gaensler (U. Toronto). The Board most recently met in March 2015 (Jodrell Bank) and July 2015 (Cape Town), with the year’s final meeting scheduled for November 2015 (Jodrell Bank). The SKA member organisations held a separate meeting in April 2015, at which they voted to site the permanent headquarters of the SKA at Jodrell Bank.
« Canada and the SKA » Workshop, Toronto, Dec 10-11, 2015
Canada is an active participant in both SKA technology development and SKA science programs, as described in detail below. This meeting will be an opportunity for the Canadian community to assess its main interests and activities for the SKA and its pathfinders, and to identify areas for synergy and coordination. For more details and to register, visit SKA Workshop.
The Murchison Widefield Array (MWA) will be holding its annual project meeting in Toronto immediately preceding the SKA workshop, over Dec 7-9, 2015. Canada is in discussions with the MWA Board about joining the MWA project and participating in the MWA upgrade path. The Canadian astronomy community is invited to to learn about the MWA and its capabilities, and to identify future areas for participation and collaboration. See MWA Meeting for more information.
SKA Engineering Meeting, Penticton, Nov 9-13, 2015
For the last number of years the SKA Project has held a week long all-hands engineering meeting at one of the member countries: 2013 was in Manchester, 2014 was in Fremantle, and 2015 is in Penticton! See SKA Engineering Meeting for more information.
The SKA science case went through a complete update in 2014, and has now been published in two large volumes. The entire science case (around 2000 pages) or individual chapters can be downloaded from SKA Books.
SKA science activities are advanced through several science working groups, as listed at SKA Working Groups. Anyone interested in joining a SKA science working group should contact Bryan Gaensler (email@example.com). New ideas and new faces are very welcome!
The first SKA Key Science Workshop was held in Stockholm over August 24-27, 2015. Seven members of the Canadian astronomy community attended, covering expertise in five science working groups. Summaries of the resulting activities are as follows:
- Tim Robishaw (NRC), Jeroen Stil (U. Calgary) and Bryan Gaensler (U. Toronto) participated in the « Magnetism » science working group, which seeks to reveal the evolution of magnetic fields over cosmic time via sensitive broadband polarisation surveys of the sky. Significant progress was made in two key areas during the Stockholm meeting. First, the magnetism group was able to distil a wide range of competing ideas into two core thrusts: « Origin and Evolution of Magnetic Fields in Large Scale Structures », focused on studying the polaristion of the diffuse Universe including clusters, filaments and the intergalactic medium, and « Origin and Evolution of Magnetic fields in Galaxies », targeting magnetism in compact individual sources such as galaxies and AGN. Second, the Stockholm meeting proved to be a superb opportunity to hold discussions with other working groups on commensality. Most groups have needs for large surveys, requiring in excess of 10,000 hours each. Since scheduling all this observing time is impractical, there is a crucial need to identify similar observing programs that can be conducted simultaneously. The magnetism group has a need for two separate wide-field surveys with SKA1-Mid, in both bands 1 and 2. We were able to identify numerous areas of commenality with the Continuum, HI, Our Galaxy and Cosmology working groups, suggesting that it may indeed be feasible to meet the ambitious science goals of all parties.
- Doug Johnstone (NRC) represented Canadian interests in both the « Cradle of Life » and « Our Galaxy » working groups. The Cradle of Life key science focuses on dust evolution in protostellar disks, an investigation into prebiotic materials around forming stars, and searches for extraterrestrial intelligence. The Our Galaxy group is newly estabished, and is so far focusing on key science interests around formaldehyde absorption (as a measure of dense molecular gas), radio stars, and the HI galaxy. Both groups spent much time discussing possible commensality with other teams. In particular, the Our Galaxy group began more detailed discussions with the Magnetism working group on the overlap science of Galactic Magnetism, an area of Canadian strength.
- During the workshop, two major projects were highlighted by the Our Galaxy science working group: a moderately deep Galactic midplane survey (largely aimed at spectral lines) and a shallower but much wider Galactic plane plus bulge survey (the latter championed by G. Sivakoff). Both of these would provide unmatched sensitivity at high spatial resolutions and be done at sufficiently high radio frequencies (5 GHz and above) that would detect both non-thermal and thermal sources. There also appeared to be a consensus across multiple working groups for a deep Galactic Centre project, also at the same radio frequencies. These projects have great synergy with Canadian interests and expertise, especially given past plane surveys led by our community.
- Gregory Sivakoff (U. Alberta) and Michael Rupen (NRC) participated in the « Transients » working group, of which Rupen is co-chair. The transients group is focused on the study of variable sources on time scales from milliseconds to decades, encompassing sources as varied as exoplanets, accreting binary stars, supernovae, and tidal disruption and gravitational wave events. The group currently is working to ensure that the basic design and policies of the SKA make variable astronomy as accessible and as productive as possible, in areas ranging from commensal observations to cadenced scheduling to data access. We are also discussing the most important large-scale science which should be done with the SKA in the first few years of operations, with current candidates including searches for fast radio bursts, a wide-ranging program on explosive accretion-powered events, and a survey of the variable radio sky.
- Kristine Spekkens (RMC) participated in the HI working group. The HI group had a productive set of meetings during the Key Science Workshop. The meeting participants began the process of developing key science projects that would attain the highest-priority SKA1 science objectives for this field: resolving the HI distributions in galaxies out to redshifts as high as z~0.8, high spatial resolution studies of the interstellar medium in the local universe, and multi-resolution mapping of the interstellar medium in our own Galaxy. While survey definition work has just begun, it seems clear that a tiered blind HI survey using Bands 1 and 2 on SKA1-Mid, as well as targeted deep surveys of ~30 nearby galaxies and a shallower wide-field survey using Band 2 of SKA1-mid, will be the key observational components for achieving those science goals. Initial discussions with participants from other SWGs suggests that there is a strong potential for commensality with these surveys, allowing multiple science goals to be reached with the same set of observations. Commensal observing with additional surveys outlined by various SWGs could also afford exciting ancillary HI science, such as a search for HI absorbers out to high redshift. SKA1 is therefore poised to deliver transformation HI science through a variety of surveys.
SKA Technology Development
The Central Signal Processing (CSP) Consortium has completed a complicated downselection process, the outcome of which is that CSIRO will lead the SKA1-Low correlator/beamformer, while NRC Herzberg will lead the SKA1-Mid correlator/beamformer. Both of these are based on FPGA platforms. NRC Herzberg remains the CSP Consortium lead. NRC Herzberg is moving forward strongly on the powerMX FPGA platform (code-named Talon) for the SKA1-Mid correlator/beamformer, with prototyping activities well underway.
Within the Dish Consortium, the recommendation proposed for the downselect on the dish structure was to use the NRC Herzberg rim-supported composite reflectors. However, this recommendation fell short of the 2/3 assent required by the Dish Board, and a new panelised metal reflector design from Germany and China will be allowed to compete against the NRC Herzberg design. A final downselect is mandated by the SKA Office for Nov 2015. NRC Herzberg is working with Canadian industry partners to prepare a strong submission. The Dish Verification Antenna, « DVA1 », is continuing testing at DRAO, led by Lewis Knee and Tim Robishaw. Outstanding results have already been achieved using a prototype MeerKAT L-band feed. These results will form part of the downselect submission in Nov 2015. NRC Herzberg continues to lead the Single Pixel Feed digitiser sub-element, passing preliminary design review and preparing to build prototypes in stage 2. The re-baselining addition of Mid band 5 (4.6-13.8 GHz) has added work requiring higher speed samplers to maintain direct conversion. NRC Herzberg is collaborating with the ALMA high-speed sampler group led by U. Bordeaux, who are developing suitable high speed samplers. We are continuing are work on cryogenic low-noise amplifiers for single pixel feeds bands 1 and 2, and have delivered samples to Onsala and EMSS SA, respectively. These same amplifiers have been chosen for MeerKAT, and we are in full production with our industry partner Nanowave Technologies to deliver MeerKAT bands 1 and 2. We made a conscious choice not to bid for the new band 5 LNAs because of the large number of interested international partners. Our work on phased array feeds (PAFs) is continuing, although the re-baselining decision deleted SKA-Survey and the PAFs from SKA1. We are in discussion with CSIRO and ASTRON to form a new advance instrumentation program (AIP) consortium to continue work on PAFs for SKA. Our L-band PAF was recently equipped with the first room temperature CMOS LNAs from U. Calgary and achieved a hot/cold test system temperature of 20 K. We are working on a full prototype to be tested on DVA1. We are continuing work on our cryogenic PAF and have moved our concept design to band 4 (2.8-5.2 GHz). We will produce a prototype, again for testing on DVA1.
Within the Telescope Manager (TM) Consortium NRC-Herzberg is playing a supporting role to NCRA India to develop standards for the local monitor & control (LMC) software architecture. A standard based on Tango has been developed, and is being ratified for use by all the other consortia.
The SKA’s Science Data Processor (SDP) team is designing the flow of data from the SKA correlator to individual astronomers. A group of Canadian universities and the CADC are working on the SDP design and implementation. The SDP underwent a design review at the beginning of 2015 and the requirements for the SDP are becoming concrete. However, it remains an open question as to whether regional data centres will be used for the SKA. If so, the Canadian team hopes to establish a North American centre in Canada.
ACURA Advisory Council on the SKA
The Association of Canadian Universities for Research in Astronomy (ACURA) coordinates activities and discussion on the SKA through the ACURA Advisory Council on the SKA (AACS). Amongst the goals of AACS are to promote and advance Canadian participation in the SKA project, coordinate participation among universities, NRC, and industry in SKA pre-construction work packages, and to define a role for Canadian scientific participation and leadership in the SKA.
The AACS meets approximately 4-5 times per year. Details and minutes of meetings will be posted on the Canadian SKA WWW site (see below). For further information or to propose AACS agenda items, please contact the AACS Chair, Bryan Gaensler (firstname.lastname@example.org).
Canada SKA WWW Site
A new Canadian SKA WWW site is currently under development, with the aim to launch this site in time for the Canadian SKA workshop in December 2015 (see item above). The site will be fully bilingual, and will provide detailed information on Canadian SKA activities for the public, for government, for industry, and for the astronomy community.