Case Study of 2017 YZ1: Long-term Impact Monitoring and IAWN

On December 20 of last year, observer D. C. Fuls of the Catalina Sky Survey discovered a new Near-Earth Asteroid drifting southward in the constellation of Sextans. Over the next few days, the object was observed by other worldwide observing facilities such than an orbit could be calculated. The Minor Planet Center announced the object on M.P.E.C 2017-Y79 and designated the object 2017 YZ1.

As with all new NEO discoveries, JPL's CNEOS and the University of Pisa ran the object through their impact monitoring systems to check for possible Earth impacts. When this was completed, it was found that 2017 YZ1 had an impact probability of around 1 in 50,000 with the Earth in 2047. While still very low, an impact probability in this range dictates that the object merits careful observation for as long as possible on the discovery arc, not only to hopefully lower the impact probability but also allow the object to be easily observed in subsequent returns.

Fast forward to the third week of January and Sentry lists the impact probability for 2017 YZ1 as now less than 1 in a million! This is good news, obviously, and indicates how well the current system works. Surveys make discoveries, they are published by the Minor Planet Center,JPL and Pisa compute impact probabilities, inform observers of objects in need of observations, observations are made, and impact probabilities are reevaluated.

Even with quite low impact probability, 2017 YZ1 will be monitored carefully. The current observing window for extends through early autumn next year. IAWN expects many optical observations for orbital refinement in the next 9 months. In particular, observations in coming weeks when the object is too far south for northern-hemisphere observations will be critical. Further, these observations help demonstrate the global and international nature of the Network as a whole.

Discoveries such as 2017 YZ1 demonstrate the success of current discovery programs. This object was detected and recognized as something that merits careful monitoring more than 25 years before the close approach will take place.


  1. Catalina Sky Survey:
  2. the discovery MPEC:
  3. Minor Planet Center:
  4. CNEOS:
  5. CNEOS risk page:
  6. NEODys2: