• 1 Introduction
• 2 Comet 3I/ATLAS captured by Rubin
• 3 Changes to the Rubin Early Science programme
• 4 Bringing LSST:UK into focus
• 5 A new window onto the low-surface-brightness near-infrared universe
• 6 Fantasy Football – still time to enter
• 7 Forthcoming meetings of interest

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Introduction

The 2025 Rubin Community Workshop ran from 28 July - 1 August in Tucson and online (see group photo to right). The full agenda for the meeting is visible to all from the project.lsst.org website, but you must have been registered for workshop to access materials from the sessions from that site. Recordings can, however, be accessed via the Rubin YouTube channel. The main topic was the proposed change to Data Release 1 (and, possibly, Data Preview 2), which is discussed in a separate item below, but there is plenty of useful material to be found in the recordings of the other sessions.

Commissioning activities continue at the summit, although with time lost due to winter weather affecting progress with the Science Validation surveys and necessitating some changes to the plans for the remainder of SV time before on-sky observing pauses in mid/late-September for dome work. In particular, the Wide component of the SV survey observations will concentrate on a smaller (~750 sq deg) area, to ensure that there will be sufficient good quality data to test thoroughly the generation of prompt products in a mode similar to that to be used in the Wide-Fast-Deep survey, and they are likely to be restricted to the current griz filter set, as a problem with one of the filter slots precludes the inclusion of a fifth working filter at the moment.

Reports on progress with commissioning were included in a joint Construction Completion and Operational Readiness Review (CCR2/ORR1) held in La Serena in late July. The subsequent review, CCR3/ORR2, is scheduled for 22-24 October and its successful completion will mark the formal transition from construction to operations for the Observatory.

Closer to home, UK researchers looking ahead to the application of AI methods to LSST data analysis may be interested in the Turing AI Pioneer Interdisciplinary Fellowship scheme, which offers “opportunity is for established researchers from across UK Research and Innovation (UKRI) remit, without a background in core artificial intelligence (AI) research, who want to build domain relevant AI capability and develop advanced AI approaches to tackle a specific research challenge in their chosen field.” Projects are well funded (up to £2.1M over three years) and applications are due by 14 October, with a webinar on 11 September providing details of the scheme.

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Credit: R. Proctor

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Credit: RubinObs/NOIRLab/SLAC/NSF/DOE/AURA/A. Pizarro D.

 

 

Comet 3I/ATLAS captured by Rubin

The newly discovered Comet 3I/ATLAS, discovered by Asteroid Terrestrial-impact Last Alert System (ATLAS), was spotted by the Rubin camera during its commissioning phase.

The object was initially discovered on 1 July 2025 by ATLAS. In a happy coincidence, Rubin was collecting images of the part of the sky inhabited by the comet from 21 June to 7 July 2025. 

A new paper, NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/ATLAS (C/2025 N1), published on arXiv, reports on the observation and measurement of astrometry, photometry, morphology, and activity of 3I/ATLAS. Speaking on Radio 4's Today programme on 2 August, @Meg Schwamb co-chair of the LSST Solar System Science Collaboration, explained that it was a case of the telescope being in "the right place at the right time".

Changes to the Rubin Early Science programme

At the Rubin Community Workshop – primarily in the Science Advisory Committee open session – there was a discussion of a likely change to the plans for the Rubin Early Science programme. The bottom line is that, given the (staff and computing) resources needed to produce Data Preview 1 (DP1), the Observatory do not now think that they can follow DP2 (as originally planned) with a DR1 comprising data from the first six months of LSST observing and released ~12 months after the start of LSST observing.

So, the plan is to now not to have a data release based on the first six months of LSST data – so the first data release, presumably to be renamed DR1, would comprise the first year of LSST data and would appear ~24 months after the start of LSST observing – and there are a number of options being discussed as to how best to bridge the gap between DP1 and the new DR1.

The original plan was to have a DP2 in Spring 2026 that would comprise the Science Validation survey data plus whatever other science-quality data had been obtained during commissioning, but it is possible that plan could be changed. It is still expected that the SV surveys will be completed by late September, at which point on-sky observing will be paused for a period of a few weeks while some work in the dome is performed, so, in essence, the question is what should happen when on-sky observing starts again in late October and when should the data generated from that those observations be released.

A number of options are under discussion, including the following:

• release an SV-dominated DP2, as planned, and start the 10-year LSST as soon as possible

• start the 10-year LSST as soon as possible, but include the first few months of data from it in (a therefore delayed) DP2

• do more SV-like observations and include them in (a therefore delayed) DP2. Variants of that would include different fields in the additional SV-like observations - e.g., DESC would be keen to see the COSMOS field covered to depth, while others have argued for another Galactic field to expand the range of stellar densities covered to date, and others are likely to propose further fields with further scientific motivations.

• some people are keen to do whatever would maximise possible Rubin support of the O4 gravitational wave run (which could, itself, be extended)

• others are keen to increase the coverage of sky for producing template images for difference imaging, so that alerts can be produced from as wide an area as possible as early as possible after the start of the 10-year LSST.

The Science Collaborations have all been asked to produce their views on the different options, which will then be considered by the Science Advisory Committee and Rubin staff before a decision is made as to the way forward. Whatever that decision is, it will be possible to implement it quickly, so there is no need to make that decision immediately – and, indeed, one of the factors likely to influence the decision is the quality of the data obtained from the SV surveys, which will not be known until some time after the end of SV observations, in late September. So, it seems likely that the decision will be made during the period of dome closure.

We will not be making an LSST:UK response since, given the wide range of scientific interests within the LSST:UK consortium, it is very unlikely that there will be a consensus view within the UK as to the best way forward. Instead, all members of the UK LSST community are strongly encouraged to engage, if they haven’t already, with the debates going on within the Science Collaborations, as this is an important topic that will impact what early science our community is able to do with Rubin data in the next few years.

@Bob Mann

Bringing LSST:UK into focus

The newly launched In the Spotlight feature goes behind the scenes at LSST:UK to hear from team members as they talk about their work, their pathway into astronomy and more.

Showing that there’s no such thing as a typical scientist, this regular article will highlight the breadth of talent across the LSST:UK team, and aims to inspire others to follow in our team members' footsteps. First up are @Elham Saremi and @Roy Williams , whose interviews have been published on the LSST:UK website. Thank you to everyone who has responded so far – we’ll be working our way through the interviews so expect to hear from us soon!

Get involved

If you’d like to take part and are yet to be interviewed, fill out this simple webform and Communications Officer @Eleanor O'Kane will be in touch before publication to get final approval on your answers and request a picture.

@Eleanor O'Kane

A new window onto the low-surface-brightness near-infrared universe

@Elham Saremi and co-authors have recently had a paper accepted for publication in the journal Astronomy & Astrophysics: NASIM: Revealing the low surface brightness Universe from legacy VISTA data.

Ground-based exploration of the low-surface-brightness (LSB) Universe in the near-infrared has long been hindered by the intense atmospheric background, which overwhelms faint extended structures. Yet these wavelengths are vital for tracing old stellar populations that dominate galaxy outskirts, offering unique clues to their assembly and evolution. To tackle this challenge, Elham Saremi and collaborators have developed NASIM (Near-infrared Automated low Surface brightness reduction In Maneage)—a fully automated and reproducible reduction pipeline optimised for VISTA/VIRCAM data. 

NASIM incorporates advanced methods from the GNU Astronomy Utilities (Gnuastro) to eliminate large-scale artefacts and detector patterns while safeguarding diffuse emission essential for LSB science. Key innovations include an adaptive flat-fielding technique, a conservative sky subtraction strategy tailored to extended light, and weighted stacking with robust outlier rejection, producing clean reductions that retain even the faintest structures. 

Although applicable to all VISTA/VIRCAM surveys, this paper demonstrates the pipeline’s capabilities on the Ks-band dataset of the Euclid Deep Field South (KEDFS), also serving as LSST’s fifth deep drilling field. With NASIM, the reduction achieves a surface brightness depth of ~27.7 mag arcsec^-2 (3σ over 100 arcsec²); about 67 times deeper than 2MASS and 11 times deeper than the VISTA Hemisphere Survey. Looking ahead, NASIM is poised to become a cornerstone for near-infrared LSB studies, complementing missions such as Euclid, Roman, and ARRAKIHS, and enhancing LSST–VISTA data fusion pipelines. Its open and reproducible design sets a benchmark for reliable science in the era of large surveys. 

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Comparison between the standard VDFS-reduced VIDEO image (left, top) and the NASIM-processed version (left, bottom) for the field containing the NGC 895 galaxy. NASIM improves background uniformity, fully recovers the galaxy’s outskirts, and removes ghost-like residuals from bright sources. Zoom-ins highlight better treatment of both NGC 895 and the nearby dwarf galaxy LEDA 3098171. NASIM not only preserves LSB features but also maintains sensitivity to faint compact sources.

Read the paper: NASIM: Revealing the low surface brightness Universe from legacy VISTA data 

 

@Elham Saremi

Fantasy Football – still time to enter

There’s still time to assemble your squad for the LSST:UK Fantasy Football League – everyone is welcome.

Forthcoming meetings of interest

Dates, locations and links… The current list of forthcoming meetings is always available on the Relevant Meetings page. You may also wish to check information held on the LSST organisation website LSST-organised events and the LSST Corporation website.