Introduction

Commissioning update

Graham Smith

Recent outputs

Terry Sloan

Report

on ComCam commissioning run

As reported elsewhere, Rubin Observatory had its first on-sky observing run from October to December 2024 using ComCam (a smaller 9-chip version of the actual LSSTCam). I travelled to the summit from 20 November to 9 December to assist mainly with the Active Optics commissioning, spending 12 nights on the mountain and 5 at the Recinto (campus) in La Serena; weather was cloudless throughout.

During the run, roughly one quarter of the on-sky time was used for active optics testing, another quarter for various other technical tests (e.g. M1 support loops, exposure timing, stray light tests, fast-readout modes, etc) and about half for ‘early science’ observations on selected targets; the E-CDFS field was observed close to 10-year main survey depth in gri filters (shallower in u/z/y), while a number of other fields including 47 Tuc, Fornax dSph, a Euclid deep field and an ecliptic field were observed less intensively.

Unlike LSSTCam which has dedicated defocused wavefront sensor chips in 4 corners, ComCam does not: so, active optics ‘donut’ images were taken as ‘triples’, a sequence of three exposures with ComCam pistoned by -1.5mm, +1.5mm and 0mm from current focus position. (Here, the in-focus 0mm image is just a cross-check and does not enter the correction loop).
Similar to LSSTCam, the defocused donuts for selected stars, typically five per chip, are then analysed for wavefront aberrations, then these are input to a singular-value decomposition to derive a vector of corrections (hexapod offsets and mirror force patterns) which are sent to the telescope (see Megias et al, arXiv/2406.04656 for details).

Generally the active optics worked well, with all the image processing and coordinate rotations now sorted out; as long as the initial aberrations are not very large, the system generally converges to AO residual errors near 0.2 arcsec in two or three iterations. Some speed enhancements and robustifying against overlapping donuts or other glitches are still required, plus the wider field of LSSTCam will add new challenges.

For the telescope in general, the tracking is very precise, and slewing is quick even at the current 20% of full speed. Images with ISR-removed were available via USDF at about 30-second delay (obviously these are only 5% of full-size). There are various moderate issues including occasional TCS freezes, degraded rotator performance near the zenith, M1M3 force actuators faulting, and some suspected dome-seeing issues.

It is hoped that most of these can be improved before the real LSSTCam goes on-sky in April, so the coming year looks very exciting for Rubin.

Will Sutherland

Report from Rubin alerts and broker workshop: 14-15 January

Stephen Smartt

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LSST:UK in the news

The new year brought a spate of media interest in LSST:UK, with the UK’s involvement in Rubin highlighted on several major UK and global news outlets.

On 3 January, Catherine Heymans, the Scottish Astronomer Royal, was interviewed on Today, BBC Radio 4’s flagship news programme, about her perspective on Rubin. You can listen to the interview https://www.bbc.co.uk/sounds/play/m002694s ; go to 1.43:20

Catherine subsequently appeared on Sky News and BBC Scotland to talk about Rubin and LSST:UK, while the Today interview was featured on the BBC World Service Global News Podcast (go to 20.10).

Eleanor O'Kane

NSF DOE Vera C. Rubin naming convention

You may have noticed the use of the full name for Rubin – NSF DOE Vera C. Rubin Observatory – in official communications. The moniker reflects the funders, the U.S. National Science Foundation and the U.S. Department of Energy’s Office of Science.

When communicating about Rubin to an external audience, especially in text, please use the full name – NSF DOE Vera C. Rubin Observatory – in the first instance. After this, you can revert to a briefer style, e.g. Rubin or the Vera C. Rubin Observatory.

National Astronomy Week

National Astronomy Week (NAW) takes place on 1-9 February 2025. Drawing together the UK scientific, educational and astronomical communities, more than 250 events across the UK have been planned.

This year, the theme is Chasing the Moon, with telescope livestreams on the NAW YouTube channel, talks and stargazing events set to take place. A special show will screen at planetariums across the UK. Introduced by Catherine Heymans, the Scottish Astronomer Royal, the show will offer an immersive journey through the cosmos. Chris Lintott has also recorded a video to highlight some of the activities.

The event is supported by the Royal Astronomical Society, British Astronomical Association, Federation of Astronomical Societies, and Society for Popular Astronomy.  Previous NAWs have marked the return of Halley’s Comet, the close approach of Mars in 2003 and the 400th anniversary of the invention of the telescope.

Eleanor O'Kane

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.