Greater Toronto Area Space Station Flyovers for the week of September 19th, 2021

As shown above, on Sunday, September 19, 2021 from 8:17 pm to 8:24 pm EDT, the International Space Station will fly over the GTA in an extremely bright pass, rising from the west-southwestern horizon, and then passing very close to the Hercules Globular Cluster M13 before entering Earth’s shadow above the northeastern horizon.

Artificial satellites are visible because they are high enough to be bathed in sunlight while the sun is below the horizon for earthbound observers. When the geometry is just right, brilliant beams of sunlight are reflected to Earth from flat, shiny surfaces on the spacecraft – which we see as a steady point of light that crosses the night sky in mere minutes.

Low Earth orbiting satellites (LEOs) like the space station can only be seen within an hour or two of dusk and dawn (even though they are passing overhead at all hours of the day and night). Satellites with higher orbits can be seen throughout the night. Geostationary satellites such as telecom and satellite television transmitters need to broadcast toward specific regions of the Earth, so they are placed in very remote orbits that hold them fixed at a specific altitude and azimuth in the sky.

Engineers do not bother attaching lights to satellites. If you see a night sky object that has flickering or flashing lights, it’s an aircraft. Decommissioned satellites and space “junk”, such as spent rocket boosters, can smoothly vary in brightness if they are tumbling.

A very good website for satellite predictions is www.heavens-above.com. Click on the Location link and enter your geographic location – manually, or by dropping a pin on the provided map. Then return to the main page and select from the provided list of object types, such as “ISS”. Apps such as Sputnik!, free ISS Detector, and Orbitrack will put satellite predictions in your pocket, alert you of imminent passes, and even show you where in the sky to look. The SkySafari 6 app also includes an extensive satellite database.

The ISS (or International Space Station) is visible gliding silently over the GTA this week. Some apps label the ISS as Zarya, since that was the first piece of it to be launched into orbit – by the Soviet Union. The best passes at (mostly) convenient times are listed below. If you can’t see the station at the start given start time, be patient. The station will become most visible once it’s a bit higher.

(Note: The more negative the Mag. number, the brighter it will look. The larger the Max Alt. number, the higher up in the sky it will be!) The higher and brighter passes are highlighted with “!!”. (Data adapted from www.Heavens-above.com. If you enter your location in their website, you will get a list of the passes for your location.) All the times below are expressed in Eastern Time.

My Insider’s Guide to the Galaxy session about satellites is on YouTube here.

Keep looking up, and enjoy the sky when you do. I love questions and requests. Send me some!