How to find Fast Moving Objects (FMOs)

What does a real FMO look like?

Common falses

Long tracks caused by artificial objects (satellites, aircrafts, space debris)

Flashes caused by artificial objects

Masked bright star and/or its diffraction spikes

Dementors and ghosts

Cosmic rays and detector artifacts

Bad subtractions

Blank stamps

Originally by Quan-Zhi Ye

You will be given a number of "stamps" that contain plausible FMOs identified by the ZTF pipeline. The challenge is to identify what we would consider a real (asteroidal) FMO.

What does a real FMO look like?

A real FMO will look like a star smeared across the image. The edge should be soft due to atmospheric and optic effect on the light, and the width and brightness should be somewhat uniform. As ZTF has relatively short exposure time (30 seconds), a real asteroidal FMO usually does not extend beyond the size of the stamp (which is about 150 by 150 arcsec). Anything longer than that is most likely an artificial object.

2018 KM1, a real asteroidal FMO.

This is actually a high-orbit satellite or space debris, but its appearance is identical to a real FMO and you should classify it as such. We will not know whether it is an artificial object or a natural asteroid until we calculate its orbit.

Also, this one turns out to be an artificial object later, but it should be classify as a real FMO.

Not all FMOs are as bright as the examples shown above. Actually, most new ones are faint -- like this one (R~18.5).

Common falses

### Long tracks caused by artificial objects (satellites, aircrafts, space debris)

The most common falses are artificial objects. Anything that extends beyond the edge of the stamp or shows non-uniform changes in width or brightness is most likely artificial objects -- don't bother!

Note that ZTF data pipeline is designed to mask out satellite tracks, but sometimes it only mask out part of those tracks. Pay attention to the masks as sometimes partially masked tracks look like legit real FMOs.

Note that part of this track is masked out, making it looking like a real FMO

Note that part of this track is masked out, making it looking like a real FMO

This is too long to be a real FMO, note that some portions are masked out by the ZTF pipeline

## Flashes caused by artificial objects

Similar to the category above but objects in this class can be quite confusing -- remember that anything that shows non-uniform changes in width or brightness is most likely artificial objects.

![strkid5033298019150001_pid503329801915_scimref]() This candidate is short in length, however the brightness is not uniform along the streak, therefore it is most likely a satellite flash

![strkid5033038548150003_pid503303854815_scimref]() This object is apparently flashing

![strkid5082263559150009_pid508226355915_scimref]() Another object that flashes periodically

![strkid5083605902150005_pid508360590215_scimref]() Flash, note that both ends are fading away

![strkid5083687555150007_pid508368755515_scimref]() Flash, note that both ends are fading away

### Masked bright star and/or its diffraction spikes

These are found next to a bright, and usually masked, star.

![strkid5034440300150003_pid503444030015_scimref]() ![strkid5034107027150003_pid503410702715_scimref]() ![strkid5034793134150004_pid503479313415_scimref]()

### Dementors and ghosts

Various optical illusions can generate FMO-like features. Compared to real FMOs, optical illusions are more fuzzy, with variable brightness along the track, and are usually non-linear.

![strkid5033932721150001_pid503393272115_scimref]() ![strkid5033676561150005_pid503367656115_scimref]() ![strkid5033676552150005_pid503367655215_scimref]() ![strkid5033810361150002_pid503381036115_scimref]() ![strkid5033932719150005_pid503393271915_scimref]() ![strkid5032262201150001_pid503226220115_scimref]() ![strkid5082246151150001_pid508224615115_scimref]() ![strkid5082201203150001_pid508220120315_scimref]()

### Cosmic rays and detector artifacts

Some of these artifacts can look very similar to real FMOs. The key is that the edge of these artifacts are "hard" (because they lack the atmospheric/optical effect that real FMOs should have)

![strkid5083081149150001_pid508308114915_scimref]() ![strkid5081991749150001_pid508199174915_scimref]() ![strkid5083057853150001_pid508305785315_scimref]() ![strkid5082671613150001_pid508267161315_scimref]()

### Bad subtractions

ZTF pipeline will subtract stationary objects (mostly background stars). The pipeline may report residuals as possible FMOs when the subtraction is not done perfectly.

![strkid5034793157150002_pid503479315715_scimref]() ![strkid5032820961150001_pid503282096115_scimref]() ![strkid5034523110150009_pid503452311015_scimref]() ![strkid5094276721150009_pid509427672115_scimref]()

### Blank stamps

Stamps that contain nothing.

![2c25aaff-ab66-4231-81e9-d678bcae4060]() ![bf032c34-ddf7-41b6-af9b-d8b14bd71d54]() ![99b8bc6f-e76d-4dd5-ad0b-68d995c619c1]()

-- EmilyKramer - 06 Aug 2018