Each GOTO system can point independently, whilst each unit telescope (UT) has a fixed orientation on themount so all 8 must be pointed at once. Each UT's pointing is offset from the others to cover the adjacent area of sky, with a small overlap between them. This results in each GOTO system acting as a single large telescope with a very widefield of view (FoV).[2]
TheAndromeda Galaxy, with an overlay showing the field of view of a single GOTO unit telescope.Relative positions of each unit telescope in a single GOTO system.
The UTs are ASA H400Newtonian telescopes, each with an aperture of 400mm and a focal length of 960mm (f/2.4).[2] Attached to each telescope is a focuser,filter wheel, and a Finger Lakes Instrumentation (FLI) ML50100 camera,[2] based on theOnsemi KAF-50100 CCD sensor.[6] The fastfocal ratio of f/2.4 and large image sensor result in a relatively large field of view, with each GOTO system having a total FoV of approximately 40 square degrees,[2] around 200x the area of the full Moon in the sky. The fast focal ratio also means that only a small amount of time is needed to observe each area of the sky, with each visit requiring only 3 minutes of exposure time.[2]
GOTO utilisesdifference imaging to identify changes of existing objects and the appearance of new transients.[7] Images of the sky are matched to previous observations of the same region, finding the difference between these two images will show only the changes in the new image. Sources within these difference images can then be detected automatically. Using difference imaging in this way produces many thousands of candidate sources per image, the vast majority of which areartefacts of the processing and not real transients.[8][9] GOTO utilises aconvolutional neural network based 'real-bogus' classifier to identify which sources are likely to be real.[9]
GOTO's typical mode of operation when not performing a follow-up campaign is to survey the entire visible sky. As there are sites located in both the northern and southern hemispheres, the visible sky for GOTO is all areas which are visible at night from anywhere on the Earth. If both sites have good weather conditions the entire visible sky can be observed every 2–3 days.[2]
Total (line) and monthly (bar) count of transients discovered by GOTO between 2020 and September 11 2024.
The first phase of GOTO's development was the deployment of a prototype system located at the planned site of the northern node, consisting of four unit telescopes on a custom-built mount.[7] The prototype system was deployed during the secondLIGO-Virgo Collaboration (LVC) observing run (O2), achieving first light in June 2017[7] with its official inauguration on July 3, 2017.[3]
The prototype system was active during the first half of the third LVC observing run (O3a), which ran between April and October 2019.[14] During this time GOTO was able to respond to gravitational-wave events and begin observing within one minute of alerts being received (if the source region was visible).[15]
In late 2019 funding was awarded to expand the network with two full GOTO systems a duplicate site in Australia.[16] In 2020 the first full system of the northern node was being deployed, with the second system planned for early 2021 and the Australian site planned for later that year.[17]
The deployment of the second northern system was completed in August 2021[18] and, despite delays due to the2021 volcanic eruption, the full northern node was completed in December 2021 with the upgrade of the prototype to the final hardware configuration.[19]
By the end of 2022 the site for the second GOTO node (GOTO-S) had been prepared at Siding Spring Observatory (SSO) and the two domes installed.[20][21] In May 2023 it was announced that both systems at SSO had been successfully installed.[22]
As of April 1, 2025, data from GOTO has been used in the discovery of 2,092 astronomical transients, of which 311 have been classified as supernovae and two as tidal disruption events.[23][24][25]
Kilonova Seekers is acitizen science project on theZooniverse platform designed to assist GOTO in identifying real astrophysical transients.[26] Volunteers are shown transient detections from GOTO, alongside a reference GOTO observation and the difference between the two, and asked whether they believe it to be a real detection. If a source reaches an 80% consensus, and has at least 8 votes, an alert is sent to the GOTO team for further investigation.[27]
As of January 31, 2025, there have been over 2 million classifications made via Kilonova Seekers by over 3200 volunteers. In total over 158,000 possible sources have been completed as either real or bogus.[28]
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