2000 PH5 Recovery Campaign

 

Breaking News!

LONEOS has recovered 2000 PH5!

 

Congratulations are in order for the LONEOS team for recovering 2000 PH5 on the first night of the recovery campaign!  The asteroid was recovered near the center of the 2000 PH5 [E031] search field.  Further observations are needed to reduce the ephemeris uncertainty for radar imaging.

 

Aten asteroid 2000 PH5 will be making its first return to the vicinity our planet since its discovery by LINEAR on 3 August 2000.  It will be making a relative close approach to earth, at a distance of 0.012 AU, on 2001 July 25.83.  Although its size has been recently downgraded to the point of no longer being categorized as a Potentially Hazardous Asteroid (PHA), there is still interest by professional astronomers to obtain radar images in the next few weeks.   Observation time has been scheduled for the Goldstone radar on July 27, 28, and 30.

 

Now, here is the kicker.  2000 PH5 is lost!  At least as far as radar is concerned.  Although the radar has a beamwidth of 60 arc-seconds, the pointing uncertainty has to be less than 15 arc-seconds, to ensure reliable acquisition.  Without further optical observations, the sky-plane uncertainty of 2000 PH5 will be about ±17 degrees (3-sigma), on 27 July!  However, there will be a short two day period where the asteroid can be recovered prior to the scheduled radar time.

 

The approach geometry is such that 2000 PH5 will come out of the sun in the northwestern sky, brightening and moving quite rapidly.  It is going to be a tough object, moving at 45 arc-seconds per minute.  What this means in terms of amateur recovery, is that one will need a system that is fast enough to record the asteroid in a very short exposure or guide the telescope in the direction of the asteroid to get longer exposures.

 

As time progresses, over a period of a few days, the asteroid will move toward the opposition point, get brighter and slow down.   In fact, the conditions will become so favorable, that I am confident that the probability of recovery by August 4, 2001 is 100%!   The recovery circumstances are summarized in the following table:

 

          2001 Recovery Predictions for Aten Asteroid 2000 PH5

Date (0h UTC)	Earth Distance (au)	solar elongation (Degs)	Approx. Nom. Dec. (Degs)	motion (degs/day)	Approx 3-sig Uncertainty (Degs)	nominal mag (v)
July 25	0.013	64.8	+60.1	17.0	±16	17.4
July 26	0.012	83.4	+55.5	18.3	±18	16.3
July 27	0.013	101.3	+44.3	16.0	±17	15.8
July 28	0.015	115.5	+33.0	12.2	±15	15.6
July 29	0.018	125.8	+24.2	8.8	±13	15.7
July 30	0.021	133.1	+17.7	6.4	±11	15.8
July 31	0.025	138.2	+12.9	4.8	±9	16.0
August 1	0.028	141.8	+09.3	3.6	±8	16.3
August 2	0.032	144.5	+06.5	2.9	±7	16.4
August 3	0.036	146.4	+04.2	2.3	±6	16.6
August 4	0.040	147.8	+02.4	1.9	±5	16.8

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

However, a late recovery will not help our radar colleagues, who will require an improved orbit, with the requisite sky-plane uncertainty, within the first few days of the recovery window.  Click on the hyperlinks above to see how the geometry changes with time, and how the expected motion of the asteroid will be different depending on where it may be found along the uncertainty path.  Note how quickly the line-of-variation (uncertainty path) rotates, and the direction of the asteroid’s motion (small circles), relative to the uncertainty path.  On July 25th for example, the uncertainty path will be almost directly north-south, yet the asteroid’s motion is nearly east-west.

 

Without getting into too much detail here, a paper was presented at the Minor Planet Amateur/Professional Workshop 2001, in Tucson a few months ago.  The technique is fairly simple (at least that is the intent!)  The sky-plane uncertainty is divided into a number of 10’ by 10’ fields, representing a good cross-section of the existing amateur instrumentation.  The center of each field, is represented by a set of orbital elements, in the standard MPC format.  Team members select the number of fields that they feel they can cover, and extract the orbital elements for those fields.  For those who are interested in details of the technique, here is a postscript version of the paper.

 

For this campaign, there are about 210 fields that need to be covered.  A status of field assignments (html), (text), will be kept up to date as volunteers sign up.  Hopefully, we will have enough observers to allow triple coverage of each field.  Note that a recovery in the northeastern direction of the uncertainty path can be up to 0.5 magnitude brighter than predicted.  A recovery in the southwestern direction can be as much as 0.5 magnitude fainter.  Therefore, I would ask that observers with larger telescopes and SITE cameras, select the fainter “[W???]” fields.  The posted orbital elements have an osculating epoch of 27 July 2001, which should be good for the first few days of the window.  If it is not recovered by then, then a fresh set of elements for a later epoch will be posted.

 

Also, it may be beneficial to bin your CCD images to the maximum extent possible.  Although the astrometry may suffer slightly, the detection capability should be greatly improved.   Keep in mind, even 10” arc-second astrometry early on will greatly reduce the ephemeris uncertainty!

 

Please let me know if you have any questions.  I will update this site appropriately.  If you are interested in joining this recovery campaign, please email me privately with your preference for field assignments.  I will do the best I can to provide you with your request.  You should select no more fields than you can cover in one night.