This month’s gratuitous picture from the summit shows (at right) the M1M3 mass surrogate being washed. This took place on the maintenance level of the summit facility, as a prelude to it receiving a full-surface coating, using the same procedure, under vacuum and in the mirror coating enclosure, that will be applied to the M1M3 mirror itself in due course.

LSST:UK has operated a Pool Travel Fund since the start of Phase A in 2015, enabling those without travel funding from LSST:UK Science Centre (LUSC) grants to apply for support to attend LSST-related scientific and technical meetings. These awards are made by the Executive Group, primarily on the basis of anticipated scientific return, and have proven to be an effective way to help UK researchers engage with the international Science Collaborations. The Exec has decided that this scheme should be broadened slightly, to allow a fraction (<25%) of the Pool Travel Fund to be used to help support LSST-related scientific and technical meetings held in the UK, where, for example, hosting a meeting here would be more beneficial scientifically, and better value-for-money, than sending multiple attendees to a meeting that would otherwise take place in the US. The page on the LSST:UK wiki providing information about the Pool Travel Fund has been updated to include this updated policy, plus links to new application forms to apply for travel and meeting support.

March sees the return of online events run by the Rubin Community Science Team for Data Preview 0 Delegates. A series of these Rubin Science Assemblies will run through to early May, while the annual Rubin Data Academy will take place on 17, 18, 20 and 21 June.

Finally, we are delighted to announce that our very own @Stephen Smartt (right), the LSST:UK Project Scientist, has been awarded a Royal Society Research Professorship. These are very prestigious awards – Stephen’s was one of only two awarded across the whole of science for 2024 – intended both to recognise past achievements and to support future successes. Analysis, and follow-up, of LSST transients is a major element of the research programme that Stephen intends to undertake with support from this award, and we look forward to hearing about the fruits of this success in the coming years.

My focus was on three aspects of UK involvement in DM: contributing to Data Release Processing, running a Data Access Centre, and supporting UK science priority experiments. I also had a number of tasks/ questions from colleagues in the LSST:UK team to follow up on. I feel things are in good shape, and DM is working very well as a unit. There are still some challenges to the timeline to the start of Operations, with some details of Commissioning and Early Science still being finalise, but what is clear is that the telescope is going to be an amazing facility and the survey will keep astronomers busy for many years to come.

Being face-to-face also gave me a rare opportunity for some more sociable aspects of workshop participation. I particularly enjoyed my first experience of a board games evening and found a fellow retro-computing fan in the US-based team.

 It was also good to finally visit SLAC and learn more about the set-up of the US Data Facility. A particular highlight was a chance to see LSSTCam up close, as it is currently on site completing final testing, before being shipped to the summit in spring.

 From the UK, SLAC is easier to reach than Tucson, so I shall hope to have a few more opportunities to visit as we move into Operations and Early Science support.

A feature on the Rubin Observatory in The Guardian published earlier this month highlights how Rubin will expand our knowledge of the Universe.

@Aprajita Verma was interviewed for the feature, which underscores the UK’s role in processing around one quarter of the 60 petabytes of data set to be captured during the 10-year survey.

The article notes that with Rubin’s completion, Chile will become the leading destination of astronomical observation, generating about 70% of data seen from Earth by 2025.  

MNRAS has recently published an article by @Aaron Watkins and collaborators (including @Sugata Kaviraj and @Chris Collins) discussing the merits and pitfalls of different kinds of sky subtraction techniques.  The paper, Strategies for optimal sky subtraction in the low surface brightness regime, describes experiments using fully synthetic images to investigate three different techniques, two commonly used in low surface brightness surveys, another experimental.  

The study's results quantify the impact of undetected flux on sky models, which tends to bias estimated sky brightnesses high, risking over-subtraction of flux. If the sky is modelled with a complex function (for example, a high-order polynomial, or a spline interpolation), that over-subtraction can occur locally, leading to artificial divots surrounding extended objects like galaxies, or even objects which are simply located close together on the sky. However, the results demonstrate that when a simple model is used, and when proper care is taken to mask detected astronomical objects to low surface brightness levels, this bias can be reduced to negligible amounts.  

Even for a survey as deep as LSST, any sky subtraction technique traditionally used in low surface brightness surveys can still be applied safely, so long as empirical corrections are made for scattered light and undetected faint sources.

The paper justifies the recommendations Watkins and collaborators have proposed to LSST's data management (DM) team regarding the survey's pipeline sky subtraction. Working alongside DM, Watkins et al. found that the existing algorithm suffers from two problems: insufficient masking of low surface brightness flux, and too complex a sky model.  Following the paper's results, the team found that adjusting the algorithm to use a much simpler model, even without an improvement to the masking, proves very successful at minimising the impact of the sky subtraction on the flux of extended or clustered objects.  

In fact, a preliminary investigation suggests that the proposed revised algorithm might benefit more than just low surface brightness science: a number of DM's photometric quality metrics appear to improve slightly when the revised algorithm is used, compared to the default pipeline.  However, the full impact of the proposed change is still being investigated.

Examples of the synthetic images used to conduct the tests on sky subtraction routines, showcasing the kinds of model sources injected for four different experiment types.  

• Top-left panel shows a sparsely populated control field.  

• Top-right panel shows that same image, but convolved with an extended scattered light model derived from the Subaru Telescope's Hyper Suprime-Cam imager, to investigate the impact of that scattered light on sky models.

• Bottom-left panel shows an image simulating data processed through a typical low surface brightness optimised data reduction routine, in which that scattered light is subtracted from the stars (but not the galaxies).

• The bottom-right panel shows an image which includes models of many faint, high-redshift sources drawn from the New Horizon simulation, to investigate the impact of undetected faint objects on sky models (also known as extragalactic background light).

The second day of the conference was filled with tutorials to provide hands-on experience with current tools and in-development broker services. Both ALeRCE and Fink took centre stage with live broker demos reminiscent of a Silicon Valley Keynote address, reflecting the impressiveness of their development efforts.

Ideas exchanged
The middle of the week was reserved for scientific discussion and collaboration between the participants. The structure of the preceding days made way for a more relaxed environment where we pooled our ideas, searching for the next hot topic in transient astronomy, and discussions on how we can use LSST to spring these projects forward.

The final few days were dedicated to science talks. There was strong representation from the LSST:UK contingent, with @Philip Wiseman presenting his Ambiguous Nuclear Transients research, and Xinyue Sheng presenting her machine learning code, NEEDLE, and its deployment within the Lasair broker.

On the flight home, I reflected on what I learned during the past week. In isolation, the prospect of the full data stream from LSST is terrifying, however, the development efforts from the community were truly impressive. Now is the time to get involved, get ready, and to get excited about the start of LSST.

Many of you are probably already talking to people outside the LSST:UK sphere about the project. Maybe you’re blogging or posting about the project on social media – or would like to. We want to give researchers interested in telling new audiences about LSST:UK: the skills to spread the word.

We're looking to develop science communication skills in team members. This is an opportunity to gain useful skills while helping others – especially non-specialist audiences – understand the value of LSST:UK. The aim is to create a network of researchers who have the know-how to communicate the complexity and significance of LSST:UK and ignite interest in science and research.

The communications training schedule will be light touch, flexible and ongoing, guided by the skills and interests within the team. We’re looking for researchers with no experience to those who already engaged in science communication at any level.

The Communications Officer, @Eleanor O'Kane (email eokane@roe.ac.uk), will coordinate the training. We also have the considerable expertise of our Education and Public Engagement Officer @Chris Lintottwithin the project. Skills will include working with the media, communicating complex messages and understanding how to connect with different audiences.  

Training may be online and where possible we will work with institutional marketing and communication teams to deliver sessions. Sign up below if you’d like to learn more. Note that Consortium Board members who have previously responded to my requests about communications training do not need to respond.

As well as inspiring new missions, Rubin could also identify flyby opportunities for missions such as NASA’s Lucy, whose shape and orbit are represented in this image.

The latest science release from Rubin outlines how a discovery could trigger a space mission to a fast moving target.

The first space mission to launch before a primary target has been identified is already in development: the ESA/JAXA Comet Interceptor mission is due to launch with the ESA ARIEL spacecraft in 2029. A Rubin discovery could see the multi-element spacecraft directed to a long-period solar system comet or interstellar object passing by the sun for the first time.

@Colin Snodgrass, Mission Deputy Principal Investigator for the ESA/JAXA Comet Interceptor, comments: “LSST is expected to discover vast numbers of Solar System objects, but what is really exciting for me is that we expect to discover new comets approaching the Sun for the first time at much larger distances than we currently do. This will help us answer questions about how cometary activity works far from the Sun, where it is too cold for water ice to sublimate, and is also a key enabling technology that allowed us to propose Comet Interceptor.

“We expect to have years to react to a discovery instead of months, and while this is still too short a time to plan and build a space mission from scratch, it is enough to get the spacecraft into the right place at the right time from a parking orbit in space. LSST:UK will make an important contribution to this through the Adler system that we are developing in Edinburgh and Belfast, that will – along with other goals – flag comets that could be potential mission targets amongst the LSST discoveries.”