James Blake charts the evolution of the orbital debris environment and reviews efforts to make operations more sustainable

We present the commissioning results and first scientific observations from the newly installed TWIST (TWenty Inch Survey Telescope) observatory – a 50 cm telescope equipped with an sCMOS (scientific complementary metal-oxide-semiconductor) camera providing a $36.1\times 24.1$ arcmin$^2$ field of view – housed in the former enclosure of the Super Wide Angle Search for Planets-North (SuperWASP-North) facility. We conducted a 67-night, 199-d baseline white-light monitoring campaign centred on the globular cluster M3 aimed at characterizing stellar variability within the cluster while also assessing the photometric performance of the newly commissioned system. We report the discovery of four new SX Phoenicis variables (V301–304), confirm their cluster membership, and identify fundamental-mode pulsation in one, allowing an independent period–luminosity-based distance estimate to M3. We revisited 231 previously known RR Lyrae stars, providing updated period measurements for 203 and white-light amplitudes for 198. We detected Blazhko-like modulation in 53 stars and characterized the modulation parameters for 28. Notably, we measure periods and amplitudes for the unclassified variables V286 and V287 for the first time. We also identify three foreground flaring M dwarfs, and assess the feasibility of detecting microlensing events in M3, concluding that expected rates are negligible. Alongside the scientific results, we introduce a new correction technique for flat-field images affected by scattered light and present a full characterization of the observatory’s photometric capabilities. These results demonstrate the scientific utility of TWIST for high-cadence time-domain surveys using modest-aperture instrumentation.

The European Space Agency is set to launch PLAnetary Transits and Oscillations of stars (PLATO), the third medium-class mission of its Cosmic Vision programme, in early 2027. Using the transit method, PLATO is expected to detect thousands of exoplanets orbiting bright, nearby stars of spectral types F5–K7. Although the mission is primarily designed to enable mass measurements via radial velocities, its precise photometry and long observational baselines may also permit the detection of transit timing variations (TTVs), which can provide complementary dynamical constraints in multiplanet systems. One possible PLATO observing scenario involves a 2-yr-long observation of a northern field that may partially or fully overlap with the original Kepler field, creating an opportunity to revisit known multiplanet systems with a photometric baseline exceeding 20 yr. We simulate PLATO observations of 152 Kepler host stars containing at least one planet with previously detected TTVs, yielding a sample of 361 transiting planets. Our CCD-level simulations incorporate realistic stellar variability and employ both aperture and PSF (point spread function)-fitting photometry, accounting for each target’s real photometric contaminants. While the extended temporal baseline offers the potential for improved dynamical constraints in favourable cases, our simulations show that this potential is strongest for carefully selected systems, as PLATO’s smaller collecting area and larger pixel scale limit the achievable per-transit precision relative to Kepler. We identify a subset of systems most likely to benefit from complementary dynamical constraints through PLATO observations.

Modern scientific CMOS cameras offer very fast readout speeds and low read noise. In this study, we evaluate the performance of the Andor Marana CMOS camera through on-sky testing carried out at the NGTS facility at the ESO Paranal Observatory in Chile. We mount the Marana camera to an NGTS telescope, and conduct photometric observations of bright stars. In particular, we target transit events around eight known bright exoplanet host stars. Simultaneous observations are carried out using an existing Andor iKon-L CCD camera on a neighbouring NGTS telescope. This allows for a direct comparison of the photometric precision between the CMOS and CCD cameras. We find that the Marana CMOS exhibits a similar level of photometric performance to the CCD camera, achieving 500 ppm at a 30-min time-scale for a T $=10$ mag star. Although the CCD has a slightly better quantum efficiency over the NGTS filter range (520–890 nm), we find that the faster readout speed of the CMOS compared to the CCD means that the CMOS camera detects 20 per cent more photons per unit time for a solar-type star in our standard 10 s exposure time operation mode. This results in the CMOS performing slightly better photometry in the photon-limited regime. We conclude that modern CMOS cameras, such as the Marana, are very well-suited for astronomical time-series photometry applications.

Detecting discrete space-target trajectories from optical image sequences is important for ground-based space situational awareness, but direct sequence processing can be computationally expensive and sensitive to weak target responses. This paper presents LeTD, a linearity-enhanced trajectory detection framework built on compact sequence-level projections and a YOLO11n oriented bounding box detector. The aligned image sequence is reduced to maximum, median, and temporal projection maps, and sine–cosine temporal encoding is used to inject frame-index information into the standard three-channel detector input. Additional angle and endpoint supervision terms are introduced to improve localization of sparse linear trajectories while keeping the YOLO11n-OBB backbone and detection head unchanged. On an expanded real test set containing 82 sequences and 155 trajectories, LeTD achieves a track detection rate of 0.7742, a complete track rate of 0.6903, and a false-component rate of 0.2055 per frame under a unified GT-centric trajectory protocol. The method requires 0.52 s per sequence on average on the evaluated workstation platform, including representation construction and detector inference.