The
Palermo Technical Impact Hazard Scale is a
logarithmic scale used by
astronomers to rate the potential hazard of impact of a
near-earth object. A rating of 0 means the hazard is as likely as the
background hazard (defined as the average risk posed by objects of the same size or larger over the years until the date of the potential impact). A rating of +2 would indicate the hazard is 100 times more likely than a random background event.
The near-Earth object 2002 NT7 was the first near-Earth object detected by NASA's NEO programme to be given a positive rating on the scale of 0.06, indicating a higher than background threat.
See also: Torino scale, Near-Earth object