| Palermo Technical Impact Hazard Scale |
Article Index for Palermo |
Limousines in Palermo |
Website Links For Palermo |
Information AboutPalermo Technical Impact Hazard Scale |
| CATEGORIES ABOUT PALERMO TECHNICAL IMPACT HAZARD SCALE | |
| alert measurement systems | |
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The scale compares the likelihood of the detected potential impact with the average risk posed by objects of the same size or larger over the years until the date of the potential impact. This average risk from random impacts is known as the background risk. The Palermo Scale value, ''P'', is defined as the base 10 logarithm of the ratio of the impact probability ''pi'' to the background impact probability over the time in years T to the event: : The annual background impact frequency is defined for this purpose as: : where the energy threshold E is measured in Megaton s. The near-Earth object was the first near-Earth object detected by NASA 's latest NEO program to be given a positive rating on the scale of 0.06, indicating a higher than background threat. The value was subsequently lowered after more measurements were taken; 2002 NT7 is no longer considered to pose any risk within the next 100 years. As of September 2006, the record for Palermo scale values is held by asteroid (29075) 1950 DA , with a value of 0.17 for a possible collision in the year 2880 . For a brief period in late December 2004, asteroid 99942 Apophis (then known only by its Provisional Designation ) held the record for Palermo scale values, with a value of 1.10 for a possible collision in the year 2029 . The 1.10 value indicated that a collision with this object was considered to be almost 12.6 times more likely than a random background event: 1 in 37 instead of 1 in 472. With further observations, the possibility of a 2029 impact was eliminated, but as of October 2006 a cumulative Palermo rating of −2.52 applies, largely due to a possible event in 2036. SEE ALSO EXTERNAL LINKS
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