The sky check: planets, stars, comets and meteors

At night a camera pointed at the sky sees things that are not in the air: Venus low in the west, Jupiter, a bright star, the Moon, a comet, a meteor. To a detector each of these is a light it cannot name, which is exactly what it is meant to flag. Before DroneTracker flags such a detection, it checks the sky.

What it checks

• The Sun and the Moon, at any time of day.
• The planets Mercury, Venus, Mars, Jupiter and Saturn, once the Sun is a few degrees below the horizon.
• Bright stars, once it is properly dark. By default the 50 or so brightest; you can include all 179 stars brighter than magnitude 3.
• Comets bright enough for a camera to see, from the Minor Planet Center’s orbit list. The rig downloads the list every three days and keeps the last copy, so it keeps working without a network.
• Meteors. A brief, fast streak at night is a meteor. If its path, traced backwards, passes near the radiant of a shower that is active that day, it is marked as that shower’s (for example, the Orionids in late October). Otherwise it is marked as a sporadic meteor. The rig knows the 37 annual showers in the International Meteor Organization’s working list, including when each is active and where its radiant is.

A detection the sky explains is marked Celestial or Meteor. The target card shows what it was and why, for example “Jupiter (planet, 0.4° away)” or “probable meteor from the Orionids”. It is treated as tracking, not as an alert. Every explanation is also logged, so a report can show why a detection was ruled out.

When it applies

The check only explains detections nothing else explained:

• no aircraft transponder matched it;
• no satellite was there;
• the detector could not name it with confidence. A confident drone, aircraft, helicopter or bird is never overruled.

It also needs to know where the camera is pointing. Until the rig has that, from a star-field match or from Lock Pos on an aircraft, the check says nothing rather than guess. No meteor is called while the telescope or a phone is turning, because then everything in the picture streaks.

Where it is seen from

The sky depends on where you stand, so each camera is checked from its own location:

• The rig’s telescope: the position entered for it under Admin → Hardware → Dwarf, or else the Operator Location.
• A forwarder’s camera: the forwarder’s location, set under Admin → Signals Intelligence → Remote Devices → Edit → Location. A forwarder with a GPS receiver, or a paired phone, reports its own position, which the rig follows unless you turn off Follow its GPS. A location you type in is kept as entered.
• The phone apps check the sky from the phone’s own location, with the same rules.

Seeing what it is checking

Admin → Hardware → Astro → Sky check shows the meteor showers active today, how far each is from its peak, where its radiant is, what is up now, and the state of the comet list.

Settings

Under System Settings (search for “celestial” or “comet”):