From Asteroid/Comet connection (www.hohmanntransfer.com)...
2004 BX159 was posted as an impact risk by JPL on 14 Feb. 2007, which presented a bit of a mystery since apparently no astrometry has been made public for this kilometer-size object. The Minor Planet Ephemeris Service (MPES) shows that 2004 BX159 was discovered by unidentified astronomers at the European Southern Observatory on Cerro Paranal in Chile on 20 Jan. 2004, with two positions taken each night from the 20th to 23rd. An orbit was published in the DOU MPEC of 20 Aug. 2004, but, as far as A/CC can find, the observational data isn't available to the public, not via MPEC nor via NEODyS or AstDyS.
This may be embargoed data, which the Minor Planet Center (MPC) accepts from professional astronomers who use large telescopes to observe distant minor objects and who operate differently from those engaged in the discovery and tracking of potentially hazardous objects where openness and quick response are paramount. Or it may just be the kind of astrometric data that doesn't get published in MPECs, such as observations of Main Belt asteroids, and which may take awhile to appear in the AstDyS database.
The MPC's own risk analysis has an orbit calculation for 2004 BX159 that is far from hazardous, but JPL since Feb. 14th has been showing that it cannot rule out orbit solutions that intersect with Earth in August 2009 and in later years. This risk assessment is based on very little data and will, of course, change with more observations, when more observations can be made. Based on the MPC's nominal, non-hazardous orbit calculation, MPES indicates that this object had a slim recovery opportunity in mid-January, a month before it came to the attention of NEO observers, and that there is some possibility it can still be caught if a concerted effort is made now using larger telescopes through maybe June and then returning in November. The next best opportunity is indicated beginning next January and continuing through early December, brightening to perhaps magnitude V=19.4 in mid-April, which may be good enough for accidental, if not planned, recovery. Otherwise, MPES indicates that 2004 BX159 won't be next visible even for larger telescopes until around the time of JPL's first impact solution in 2009. Again, this viewability prediction comes from the MPC's nominal orbit calculation, which has 2004 BX159's Earth MOID (minimum orbit intersection distance) at 0.49034 AU, or more than 190 lunar distances (LD). JPL's own nominal orbit calculation classifies this object as not being a near-Earth object. Ephemerides for 2004 BX159 based on JPL's Earth-intersecting orbit calculations do not appear to be readily available.
Link: Consolidated Risk Tables: Asteroid/Comet Connection
This was awhile ago, but another weird fact is that JPL lists this object as a _Mars_ crossing asteroid. There are considerable discrepancies between the SSD and NEO data. Considerable meaning a difference of about 0.5 AU for closest approach!
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