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arXiv · 2606.31793

Modeling of the diffuse background produced by the Vera C. Rubin Observatory M2 baffle scattered light

Alessio Taranto·Gabriele Rodeghiero·Luca Rosignoli·Aashay Pai·Alex Drlica Wagner·Elana K. Urbach·Fritz Muller·Eli S. Rykoff·Hannah M. M. Pollek·John Andrew·Douglas R. Neill·Parker Fragelius·Tomislav Vucina·Christopher W. Stubbs·Robert H. Lupton·Lee S. Kelvin·Kate Napier·Jacqueline Seron Navarrete·Travis Lange·Andrew P. Rasmussen·Aaron Roodman·Chuck F. Claver·Joshua E. Meyers·Anastasia Alexov·Keith Bechtol·Brian Stalder·R. Lynne Jones·Leanne P. Guy·Tiago Ribeiro·Erik Dennihy·Bruno C. Quint·Aaron E. Watkins·Alysha B. Shugart·Lukas Eisert·Kevin Fanning·Marina S. Pavlovich·Yijung Kang·Hye Yun Park·Paulo Lago·Kris Mortensen·Paulina Venegas Salas·Minhee Hyun·Karla Pena Ramirez·David Sanmartim·Qianjun Hang·Gonzalo Aravena·Kshitija Kelkar·Carlos A. L. Morales Marin·Danica Zilkova·Eric J. Christensen·Yusra Alsayyad·William O'Mullane·Enrico Giro·Rodolfo Canestrari·Sandrine J. Thomas·Kevin A. Reil·Claudio H. Araya Cortes·Roberto Tighe·Holger Drass·Pablo Zorzi·Massimo Brescia
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Abstract

The Vera C. Rubin Observatory, with its unprecedented field of view and fast focal ratio, will survey the entire sky every 3.5 nights. This unique capacity requires dealing with off axis light that can produce stray light artefacts on the images. The secondary mirror (M2) baffle restricts the light that reaches the LSSTCam detector and it contributes to shaping the inner edge of the telescope optical pupil. This work studies the contribution to the background from the light scattered by the M2 baffle itself. The evanescence of this feature, together with the challenge of isolating it from the sky background, led to the necessity of performing in dome tests using a Collimated Beam Projector (CBP), normally used for calibration purposes. To complete the analysis, in addition to the in dome tests, an on sky observational campaign was conducted. This campaign employed both stellar targets and the Moon as illumination sources in order to determine the actual energy associated with the feature. The test data have been retro fitted thanks to the combination of ray tracing simulation, CBP and on sky data to infer the intensity and spatial distribution of the background scattered light within the different LSSTCam filters. We quantified the on sky impact of scattered light from the M2 baffle, both for light coming from bright and red stars and from the Moon. We also developed an approximate relation to transform the in dome measurements into predictions of on sky behavior. This transformation was achieved by comparing the illumination footprint produced by an off axis star with that generated by the CBP and by mapping the stellar Spectral Energy Distribution (SED) onto the CBP's set of discrete wavelengths. Finally, we extrapolated the scattered light behavior of the Moon to stellar sources, in order to build a compplete description of the M2 baffle contribution over the full range of magnitudes.

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Alessio Taranto, Gabriele Rodeghiero, Luca Rosignoli, Aashay Pai, Alex Drlica Wagner, Elana K. Urbach, Fritz Muller, Eli S. Rykoff, Hannah M. M. Pollek, John Andrew, Douglas R. Neill, Parker Fragelius, Tomislav Vucina, Christopher W. Stubbs, Robert H. Lupton, Lee S. Kelvin, Kate Napier, Jacqueline Seron Navarrete, Travis Lange, Andrew P. Rasmussen, Aaron Roodman, Chuck F. Claver, Joshua E. Meyers, Anastasia Alexov, Keith Bechtol, Brian Stalder, R. Lynne Jones, Leanne P. Guy, Tiago Ribeiro, Erik Dennihy, Bruno C. Quint, Aaron E. Watkins, Alysha B. Shugart, Lukas Eisert, Kevin Fanning, Marina S. Pavlovich, Yijung Kang, Hye Yun Park, Paulo Lago, Kris Mortensen, Paulina Venegas Salas, Minhee Hyun, Karla Pena Ramirez, David Sanmartim, Qianjun Hang, Gonzalo Aravena, Kshitija Kelkar, Carlos A. L. Morales Marin, Danica Zilkova, Eric J. Christensen, Yusra Alsayyad, William O'Mullane, Enrico Giro, Rodolfo Canestrari, Sandrine J. Thomas, Kevin A. Reil, Claudio H. Araya Cortes, Roberto Tighe, Holger Drass, Pablo Zorzi, Massimo Brescia. 2026-06-30. Modeling of the diffuse background produced by the Vera C. Rubin Observatory M2 baffle scattered light. https://arxiv.org/abs/2606.31793

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