Guest Science Projects

ASKAP Guest Science Projects (GSP) are observational programs that require modest amounts of observing time to complete, that take advantage of ASKAP’s capabilities to enable scientifically interesting experiments, and which do not overlap unduly with approved Survey Science Projects (SSPs). 

GSPs should not duplicate SSPs (the data from which are made publicly available through the CSIRO ASKAP Science Data Archive immediately upon validation). Prospective GSP proposers are expected to familiarize themselves with the SSPs science goals and strategy summarised here before submitting. Proposals may be rejected if they are deemed to overlap unduly with the science goals of any approved SSP. 

GSPs may overlap SSP fields but must have some clearly distinguished science goal and characteristic (such as observing frequency or sensitivity limit). Survey Science Teams (SSTs) are not excluded from proposing for Guest Science Time, but such proposals should not be an extension of an existing SSP (for example, to cover a greater Declination range). The scope of the SSPs will be managed within the framework of their ongoing annual review process. While ASKAP is primarily a survey telescope due to its wide instantaneous field of view, GSPs may be submitted for a single object when there is another requirement for the unique capabilities of ASKAP.

In recognition of the importance of completing ASKAP’s main surveys within 5 years, and in keeping with the recommendations of the Review of ASKAP Survey Science Projects (RASSP), the amount of time offered for GSPs will be limited to 300 hours per year (150 hours per Semester), though this may be reviewed after the first 12 months. 

GSPs can be Non A-priori Assignable (NAPA) proposals with clearly-defined trigger criteria, but do not include override requests such as Target of Opportunity observations which will follow the same procedure as the other ATNF instruments here. 

Proposals submitted under the Guest Science Program will be assessed for scientific merit and ranked by the ATNF Time Assignment Committee (TAC) in the usual way. The process will follow the existing timeline for calls for proposals, OPAL submission deadline, TAC meeting dates and notification of outcomes. The technical feasibility of GSPs will be assessed by the ASKAP Senior System Scientist, seeking advice as required. Proposals assessed to be technically infeasible, of prohibitive complexity or which otherwise unduly impact the approved SSPs will not be accepted. The Senior System Scientist may also make recommendations to the TAC on whether a proposal overlaps unduly with an existing SSP, or other GSP proposal. Accepted proposals will have their OPAL cover sheets and observation tables published in OPAL, as is done for the other ATNF facilities. Scheduling of approved proposals will be done autonomously based on the field selection and observing mode specified in the proposal. 

ASKAP datasets are generally released to the public via the data archive (CASDA) without any proprietary period. A request for a proprietary period for GSP observations will be considered only under exceptional and compelling circumstances, up to a maximum of 12 months from the observation. 

In the following sections, this User Guide outlines the capabilities of ASKAP, provides an overview of the Survey Science Projects, describes how proposals are submitted and reviewed, and summarises how observations are conducted, processed, and the data made available.

Observing modes for Guest Science Proposals

The Australian SKA Pathfinder (ASKAP) radio telescope is an array of thirty-six 12 m diameter antennas, situated at Inyarrimanha Ilgari Bundara, the CSIRO Murchison Radio-astronomy Observatory in Western Australia. ASKAP uses Phased Array Feed (PAF) technology to form 36 beams, providing an instantaneous field of view of 31 square degrees at 800 MHz, reducing to 15 square degrees at 1700 MHz. As a two-dimensional array, with baselines ranging from 22 m to 6.4 km, ASKAP has excellent snapshot imaging capability and a 10 arcsec resolution at 1 GHz. This, combined with 288 MHz of instantaneous bandwidth and a unique third axis of rotation on each antenna, gives ASKAP the capability to create high dynamic range images of large sky areas very quickly. ASKAP is primarily a survey telescope, and nine Survey Science Projects (SSPs) have been allocated time to conduct surveys covering a range of science over a five-year period, with observations starting in late 2022.

Being a survey telescope, ASKAP is designed for autonomous operations in pre-defined modes with high efficiency. GSP observations, like SSP observations, will be fully specified in advance, then scheduled autonomously and dynamically by the automated scheduler SAURON based on the identified constraints. The data will be calibrated, processed, and archived according to a pre-defined processing template, chosen from an existing and well-tested set (unless there is a strong case for adjusting any of the parameters). Proposers will be notified when their data products are available in the science data archive, CASDA. Recipients of data will be required to submit a short validation report after being granted access and before the data can be released and used for science. If the data are not fit for science, they can be rejected and will be automatically re-observed. In such cases, it is important to describe the problem in CASDA’s validation notes or direct communication with the operations team to ensure the issues can be rectified.

ASKAP’s technical capabilities and observing modes evolve over time. Detailed information about the modes being offered in any given semester will be released with the call for proposals, available online:

https://www.atnf.csiro.au/observers/apply/avail.html

Each mode has an associated beam footprint, which may be a square-packed arrangement (maximum field of view but higher sensitivity variation across the field), or a close-packed arrangement with less sensitivity variation, but a slightly smaller field of view. Longer integrations would most likely be done as a set of observations with the above parameters and deposited into the archive as individual observations of the same field, with combination being the responsibility of the proposer. ASKAP treats each observation of a field as a unique scheduling block for the purpose of observing, processing and archiving. 

In this early stage of GSPs, we will not be offering modes that have yet to be fully validated by the SSTs. These include zoom modes, joint deconvolution and (u,v) grid storage. We understand that the above restrictions may not encompass all science cases, but for this first round of GSPs we want to limit the number of variables by offering well tested modes. If you have a compelling need to create a different configuration, please discuss it with the ASKAP Operations team. 

ASKAP’s continuum sensitivity yields an RMS noise level of about 200 uJy/beam at 900 MHz in 15 minutes of observing time. With longer 10-hour observations the RMS noise level drops to about 20 uJy/beam. Detailed system information can be found elsewhere on this site.

The Rapid ASKAP Continuum Survey provides an example of ASKAP’s typical resolution and snapshot image quality, showing good sensitivity to extended emission. Longer integrations will better sample the (u,v) plane and should exhibit even better characteristics. We can observe fields up to about +40 Dec, although with diminishing time above the horizon further North. 

As noted above, GSP observations will be dynamically scheduled on the telescope alongside SSP fields, taking into account constraints and priority. GSP contact points will be automatically notified when an observation is added into the observing pool and when the processed data arrives in CASDA. The ASKAP Observation Management Portal (OMP) offers a visual insight into the observation database and can be used by proposers of GSPs to check the metadata associated with any observed data for their projects. 

Submitting a Guest Science Proposal via OPAL

ASKAP GSPs will follow the same process as existing ATNF facilities with proposals submitted via ATNF’s online proposal system OPAL (https://opal.atnf.csiro.au/login). All authors listed on the proposal must have a registered OPAL account in order to submit and view ASKAP GSPs. Users without an existing OPAL account can register by completing the registration form at https://opal.atnf.csiro.au/register. This OPAL account can also be used to access data through CASDA.  

All proposals are required to submit a cover sheet, observations table and science justification. Tools for creating cover sheets and observations tables for ASKAP GSPs can be found on the OPAL homepage. In addition to title and author information the cover sheet must contain a scientific abstract as well as a clear and concise outreach statement that should be aimed at someone with limited astronomy background knowledge. Optional fields give proposals the ability to add limited additional information that should be shared with the TAC and any requested scheduling constraints. The observations table allows users to upload a source list and set observing parameters via a dropdown menu.  

There are three different proposal types available for ASKAP GSPs:  

• Standard proposals: observing projects requiring less than 400 hrs for the whole project (including any future time requests). As described above, approved ASKAP GSPs will be added to the pool of available observations and scheduled autonomously if required observing constraints are met (e.g. minimum number of antennas available).  

• Non A-Priori Assigned (NAPA) proposals: for a well-defined set of observations in response to a trigger which is unpredictable in time (and therefore cannot be specified in advance). 
• Large proposals: Observing projects with a total time request larger than 400 hrs, often spread over multiple semesters. Large projects must also include additional information in the science justification includinga description of team roles/contributions, data analysis and timeline plans, data validation plans, and a recommended public outreach plan. 

For NAPAs with low triggering probability and Large Projects that require small increments of observing time over multiple semesters the TAC can assign pre-graded status for the following semester. Users have the option to request pre-graded status in the proposal in which case a clearly stated time-request breakdown per semester should be included.  

More details on using OPAL can be found in the OPAL Users guide: https://www.atnf.csiro.au/observers/docs/opal/guide.html#AboutOPAL 

The Science Justification

The science justification is uploaded as a pdf with a strict page limit of 3 pages inclusive of figures and references (5 pages for Large Projects). The science justification should be written in clear English and aimed at a non-expert in the field. The justification should include: 

• A summary of the background and any previous observations showing why the topic is important; 
• Detailed and specific science goals – e.g. test a particular hypothesis; 
• An explicit statement about how the proposed observations will address the science goal(s); 

• A clear description of the source selection criteria with a quantitative justification of the sample size; 
• A quantitative estimate of expected flux density and required signal-to-noise. A sensitivity calculator for ASKAP can be found at  https://www.atnf.csiro.au/people/Keith.Bannister/senscalc/askap.html ; see also considerations around weighting as explained in the Observation Guide. 
• A clear technical justification outlining the observational parameters and why ASKAP is best suited to carry out these observations. 

For future Semesters, any proposal that is a resubmission should also include: 

• A report on observations to date, particularly from previous semesters which have not yet been published.
• A detailed response describing how the TAC comments from previous semesters have been addressed. 

For ASKAP GSP proposals the science justification should also include a statement that the data does not currently exist in CASDA and will not be observed by any of the planned ASKAP Survey Science Projects (SSPs).  

The ATNF TAC now follows a dual-anonymous review process. All proposals must be written in a way such that authors cannot be easily identified. This includes referring to past projects by the proposal code rather than the PI, using numbered references to avoid self-citations, and avoiding phrases such as “our observations”. From the 2023OCT semester the TAC will adopt stricter penalties for proposals that do not adhere to the anonymous proposal guidelines, including automatic rejection for egregious cases.

Data processing

ASKAP observations will be automatically processed by the operational pipeline running on Setonix at the Pawsey Supercomputing Centre. There is usually no involvement from GSP members in the processing – the first contact the science team will have with the data is when it is archived in CASDA. 

The pipeline is controlled by a large number of potential user parameters. However, there are processing templates used by Survey Science Project observations that provide tested & demonstrated processing workflows, and GSPs are expected to make use of these. The templates are stored in a bitbucket repository https://bitbucket.csiro.au/projects/ASKAPSDP/repos/askap-sst/browse, to which access will be granted for successful GSP leads.  

Some modification of existing templates will be necessary due to changes in observation characteristics such as observing frequency or integration time. The expectation will be for GSP leads to interact with the Data Operations lead (and other Operations staff as necessary) to ensure the final template meets operational and science requirements. A template will need to be constructed and made available before any observation can be scheduled and executed. 

Data access

The online data archive CASDA is intended to be the astronomer’s primary interface to the telescope. Each scheduling block that is observed will be run through the ASKAPsoft processing pipeline with a set of parameters defined by the observing mode and science team requirements. Data produced by the pipeline will be uploaded to CASDA as “level 5” pre-release data. Files that pass quality control will be released as “level 6” data products and made available to the public for scientific use. Science teams are anticipated to do most of their analysis on products that may combine several scheduling blocks, using their own computing resources to access data from CASDA and produce “level 7” or value-added data products. These user-created products may also be uploaded to CASDA for archiving, upon request. 

All CASDA deposits include calibrated visibilities stored in a CASA Measurement Set with 1 MHz frequency resolution (we cannot store spectral line visibilities due to their size), a mosaicked continuum image covering the observed field, and a catalogue of sources found by the Selavy software package within the continuum image. Additional data products such as continuum cubes or spectral line cubes will be included as necessary, depending on the observing mode and processing parameters. Images at the individual beam level (that is, prior to mosaicking) are not archived. If your project has specific requirements for data products, or you would like to check the contents of the default deposit for a specific mode, please contact the ASKAP operations team. 

Data validation and proprietary periods

GSP data products will be uploaded to the science data archive (CASDA) upon completion of processing.  A deposit will trigger a VO event which is available online: 

https://casda.csiro.au/casda_data_access/observations/events

This is the fastest way to know when new data are ready for validation. There will be one deposit per scheduling block observed, which may contain multiple files and data types (image cubes, source catalogues, etc.). These deposits will be associated with the project code assigned to the GSP when it is first created in OPAL. The OPAL account of the GSP PI will automatically be granted permission to view the deposited data products in CASDA and add other CASDA users to their project. It is the responsibility of the PI or their delegate to submit a validation report (which will appear as a task associated with the user’s account in CASDA) for each scheduling block within one month of the deposit being made. For projects involving many scheduling blocks, we offer a scripted API-based validation scheme. Please contact the ASKAP operations team for further advice if this would be helpful for your project. 

Validation involves assigning a quality indicator to the data products. Typically, one indicator is assigned to all files in the deposit, but it is possible to assign individual quality indicators to each file if necessary. It is also possible to enter validation notes that describe anything of interest to astronomers using the data in future. These notes will be permanently associated with the files. Once the validation report has been submitted, the ASKAP operations team will either release the data (if it has GOOD or UNCERTAIN quality and there are no other considerations) or reject the deposit (if it has been marked as BAD). In cases where only some files are marked BAD, these individual files will be rejected, and the rest released. 

GSP applicants should note that unreleased data may not be used for scientific purposes, and doing so is a violation of the ASKAP publication policy which may lead to disqualification from future time allocation.  

If a deposit remains un-validated after one month, the ASKAP operations team may choose to conduct basic validation by comparing source characteristics to the RACS catalogues and release the data with our own quality assessment. Alternatively, if basic validation does not seem appropriate (in the case of spectral line data for example) we may choose to reject a deposit that remains un-validated for too long. 

As noted above, ASKAP data are generally released to the public via the CASDA archive without any proprietary period. Proprietary periods for GSP observations will be considered only under exceptional and compelling circumstances, up to a maximum of 12 months from the observation.