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Abstract LSST Camera CCDs produced by the manufacturer e2v exhibit strong and novel residual charge images when exposed to bright sources. These manifest in images following bright exposures both in the same pixel areas as the bright source, and in the pixels trailing between the source and the serial register. Both of these pose systematic challenges to the Rubin Observatory Legacy Survey of Space and Time instrument signature removal. The latter trail region is especially impactful as it affects a much larger pixel area in a less well defined position. In our study of this effect at UC Davis, we imaged bright spots to characterize these residual charge effects. We find a strong dependence of the residual charge on the parallel clocking scheme, including the relative levels of the clocking voltages, and the timing of gate phase transition during the parallel transfer. Our study points to independent causes of residual charge in the bright spot region and trail region. We propose potential causes in both regions and suggest methodologies for minimizing residual charge. We consider the trade-offs of these methods including decreasing the camera's full well and dynamic range at the high end. The voltage scheme in the main camera was altered to address this effect accordingly. 

Ground-based astronomical surveys such as the much anticipated Vera C. Rubin Observatory Legacy Survey of Space and Time (LSST) [1] face new challenges due to the increasing number of satellites in Low and Medium Earth Orbit (LEO & MEO). With hundreds of thousands of artificial satellites likely to be launched in the near future as estimated by the IAU CPS, satellite trails in astronomical images will become frequent enough to require some form of mitigation. Limiting the maximum brightness of artificial satellites to below 7th magnitude is one of the proposed means to reduce satellite impact on Rubin data, which prevents the most severe systematic errors and widespread data loss in LSST camera sensors [2]. Glints caused by satellites and space debris are also expected to pollute LSST alerts [3].Brighter objects may require active satellite-avoidance scheduling schemes such as investigated by Hu et al. [4]. The IAU Centre for the Protection of the Dark and Quiet Sky from Satellite Constellation Interference (IAU CPS) in cooperation with the Aerospace Corp. is currently developing online services with global API access, such as SatChecker that enable satellite-avoidance [5,6].  However, dodging satellites would effectively decrease observing time in large sky surveys such as the LSST. In this contribution we report updates on satellite brightness mitigation efforts including technologies developed by both satellite constellation operators to darken their constellations as well as new IAU CPS tools for astronomers intended to help tackle this challenge. We also discuss the potential satellite constellation related losses in Solar System Object (SSO) discovery based on recent Sorcha simulations [7].Acknowledgments: The authors acknowledge support from the National Science Foundation through the award Collaborative Research: SWIFT-SAT: Minimizing Science Impact on LSST and Observatories Worldwide through Accurate Predictions of Satellite Position and Optical Brightness NSF Award Numbers 2332736 and 2332735. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the National Science Foundation.References:  [1] Ivezić, Ž., et al. (2019) “LSST: From science drivers to reference design and anticipated data products.” The Astrophysical Journal 873.2 : 111. [2] Tyson, J.A. et al. (2020) “Mitigation of LEO satellite brightness and trail effects on the Rubin Observatory LSST,” The Astronomical Journal, 160(5), p. 226. [3] Tyson, J.A., Snyder, A., Polin D., Rawls, M.L. and Ivezić Ž. (2024) Expected Impact of Glints from Space Debris in the LSST. The Astrophysical Journal Letters 966, no. 2 : L38. [4] Hu, J.A. et al. (2022) “Satellite constellation avoidance with the Rubin Observatory Legacy Survey of Space and Time,” The Astrophysical Journal Letters, 941(1). [5] IAU CPS SatChecker (https://satchecker.readthedocs.io/en/latest/fov.html), accessed 2025 May 2. [6] Skinner, M. A., Coursey, C.D., and George, E.R. (2023). Dark and Quiet Skies: A predictive technique to mitigate the impact of satellite reflections on astronomical observatories. 74th International Astronautical Congress (IAC), Baku, Azerbaijan, 2-6 October 2023. [7] Schwamb, M. et al. “Sorcha: A Solar System Survey Simulator for the Legacy Survey of Space and Time”, The Planetary Science Journal (in press). 

We examine the simple model put forth in a recent note by Loeb regarding the brightness of space debris in the size range of 1–10 cm and their impact on the Rubin Observatory Legacy Survey of Space and Time (LSST) transient object searches. Their main conclusion was that “image contamination by untracked space debris might pose a bigger challenge [than large commercial satellite constellations in Low-Earth orbit].” Following corrections and improvements to this model, we calculate the apparent brightness of tumbling low-Earth orbit (LEO) debris of various sizes, and we briefly discuss the likely impact and potential mitigations of glints from space debris in LSST. We find the majority of the difference in predicted signal-to-noise ratio (S/N), about a factor of 6, arises from the defocus of LEO objects due to the large Simonyi Survey Telescope primary mirror and finite range of the debris. The largest change from the Loeb estimates is that 1–10 cm debris in LEO pose no threat to LSST transient object alert generation because their S/N for detection will be much lower than estimated by Loeb due to defocus. We find that only tumbling LEO debris larger than 10 cm or with significantly greater reflectivity, which give 1 ms glints, might be detected with high confidence (S/N > 5). We estimate that only one in five LSST exposures low on the sky during twilight might be affected. More slowly tumbling objects of larger size can give flares in brightness that are easily detected; however, these will not be cataloged by the LSST Science Pipelines because of the resulting long streak. 

Abstract The apparent brightness of satellites is calculated as a function of satellite position as seen by a ground-based observer in darkness. Both direct illumination of the satellite by the Sun as well as indirect illumination due to reflection from the Earth are included. The reflecting properties of the satellite components and of the Earth must first be estimated (the Bidirectional Reflectance Distribution Function, or BRDF). The reflecting properties of the satellite components can be found directly using lab measurements or accurately inferred from multiple observations of a satellite at various solar angles. Integrating over all scattering surfaces leads to the angular pattern of flux from the satellite. Finally, the apparent brightness of the satellite as seen by an observer at a given location is calculated as a function of satellite position. We develop an improved model for reflection of light from Earth’s surface using aircraft data. We find that indirectly reflected light from Earth’s surface contributes significant increases in apparent satellite brightness. This effect is particularly strong during civil twilight. We validate our approach by comparing our calculations to multiple observations of selected Starlink satellites and show significant improvement on previous satellite brightness models. Similar methodology for predicting satellite brightness has already informed mitigation strategies for next-generation Starlink satellites. Measurements of satellite brightness over a variety of solar angles widens the effectiveness of our approach to virtually all satellites. We demonstrate that an empirical model in which reflecting functions of the chassis and the solar panels are fit to observed satellite data performs very well. This work finds application in satellite design and operations, and in planning observatory data acquisition and analysis. 

Abstract We presentSLIDE, a pipeline that enables transient discovery in data from the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST), using archival images from the Dark Energy Camera as templates for difference imaging. We apply this pipeline to the recently released Data Preview 1 (DP1; the first public release of Rubin commissioning data) and search for transients in the resulting difference images. The image subtraction, photometry extraction, and transient detection are all performed on the Rubin Science Platform. We demonstrate thatSLIDEeffectively extracts clean photometry by circumventing poor or missing LSST templates. We identified 29 previously unreported transients, 12 of which would not have been detected based on the DP1DiaObjectcatalog.SLIDEwill be especially useful for transient analysis in the early years of LSST, when template coverage will be largely incomplete or when templates may be contaminated by transients present at the time of acquisition. We present multiband light curves for a sample of known transients, along with new transient candidates identified through our search. Finally, we discuss the prospects of applying this pipeline during the main LSST survey. Our pipeline is broadly applicable and will support studies of all transients with slowly evolving phases.