Monitor predicted satellite crossings in the active telescope field.
sensor crossings across the last 0 300-second exposures
LookUp.Network uses current orbital data to show predicted satellite transits across an astronomical sensor during a 300-second exposure, then compares the unprotected image with the response a StealthTransit installation could make in real time.
The forecast field is computed from the orbital catalogue identified in the field metadata and holds the selected pointing fixed for the full exposure. It is a forecast, not a live telescope feed. Selected positions are independently cross-checked with SatChecker during development.
Estimated image area lost is the fraction of the green camera frame excluded from analysis during one exposure. The displayed range runs from the bright trail core to a conservative mask including faint wings. Trail brightness and angular speed determine the mask width; overlapping areas count once. A fixed illustrative instrument model is used, not an observatory calibration.
DECam observations of five Starlink satellites measured trail FWHM of 1.82–2.43 arcsec at 0.50–0.77 deg/s in 120-second exposures. These measurements ground the scale of the bright core; the broader exclusion range remains an explicit demonstration assumption.
The live view does not control a telescope. It shows the unprotected contamination first; this panel describes how a wide-field detector could measure the approaching object's brightness and trajectory, then command an active shutter only while the crossing affects the science sensor.
The Active Shutter blocks incoming light without interrupting detector integration. Integration continues in darkness until the satellite leaves the field of view.
The wide-field monitor covers 4.5° × 6° around a central 1° × 1.33° science sensor. The observation direction is selected before each exposure to prioritize predicted satellite transits and then remains fixed for all 300 seconds.
Satellites leave trails in the simulated image as they do in real long-exposure astronomical photographs. The estimate includes satellite range, solar phase angle, and Earth's shadow.
The star field is rendered from Gaia DR3 for the simulated telescope pointing, with bright Hipparcos supplements. Available Gaia spectra set stellar colors and relative light; other colors are approximate. Core saturation and halos are illustrative. OpenNGC adds schematic galaxy, nebula and cluster shapes; Solar System positions use Astronomy Engine. Satellite trails are rendered from the orbital forecast and enlarged four times for visibility. Area and exposure-loss estimates use their original calculated scale. Star-field sources and licences.
Traditional post-processing can remove valuable scientific data together with satellite trails. TLEs carry positional uncertainty that grows between updates, do not account for manoeuvres, and contain no brightness information.
In an installed system, once a satellite appears in the wide field of view, the detector measures its trajectory and brightness directly. If the object would contaminate the exposure, the system commands the shutter installed in the telescope's optical path. The online forecast only illustrates this response; it does not claim that a real shutter moved.
The system is designed for optical observations with small to medium fields of view, including observations in spectroscopic mode. Extended technical material and publications are available in the Library.
Astronomer at the European Southern Observatory, studying the impact of satellites on astronomical observations.
“As the population of satellites in orbit continues to grow, astronomical observations face increasing interference. A real-time detection system that monitors satellites approaching a telescope's field of view and automatically closes the shutter during a crossing offers a robust layer of protection. The StealthTransit system is particularly promising for instruments with small-to-mid-sized fields of view, notably spectrographs, which are essential for analyzing the chemical composition of the universe.”
Executive Officer and Principal Consultant at Dark Sky Consulting, LLC; Lead of Community Engagement Hub of the IAU Center for the Protection of the Dark and Quiet Sky.
“The StealthTransit method could very well become part of the standard tool kit for observatories while we continue to work on issues like the brightness of satellites. The proof of concept is important, and I think the StealthTransit team have already shown promising results.”
Watch the field demonstration, follow project updates, or continue into the technical record behind StealthTransit.
Follow project updates and review the published patent.
A compact reading list for observatories evaluating satellite contamination, shutter timing and constellation-scale orbital risk.
Send a technical question, observatory request, or deployment note to the StealthTransit team.