Feelings of an amateur observer of NEAs

Dilemma: can you hit the bear with a sling?
Yes, sometimes you can.

There are several factors, such as quality of the sky or focal relation, to be taken into account when trying to observe an asteroid that requires excellent measurements to elucidate whether it has some probabilities of impacting the Earth. But, in general, the limitation in the aperture is the most decisive one. From the point of view of an amateur observer, two conflicting feelings then arise: on one hand, the will to collaborate and provide good measuraments which can be useful and necessary to know the behaviour of such an asteroid in the future; on the other hand, the discretion and humbleness to recognize that your own work, even if meticulous and methodical, due to the lack of a better equipment, can end up disturbing instead of adjusting and determine a good orbital solution. Jaime uses a 0.4m f/2.0 Schmidt telescope and a commercial CCD of medium performance.

by Jaime Nomen* - copyright Tumbling Stone 2001

Again, the uncertainty increased when I checked the measurements. Due to the poor signal in the image, they were not giving the usual and desired consistency, though... they didn't seem to be so off, either. And then I reach the critical point: the submission is ready and about to be mailed out, the conflicting feelings fight with intensity; you are sure to have made a good job, but you also doubt about its quality, the quality that such an object deserves and for some reason it is not getting... Finally, you press the "send" button and there is nothing you can do about, but wait and hope that your observations are good enough, that they are really going to help to determine a good orbit... and, of course, you eagerly wish to see your residuals and if they are all under 1 arcsec... and you are afraid of the corrective "parenthesis" used by the MPC to denote those observations that are discarded, as well as of the instructive "No" of NEODyS. It's late (or it is better say, early in the morning) and I went to bed.

This animation of 2001 PM9 has been made up with 5 frames .On the right, the asteroids have been circled (2001PM9 appears in the yellow circle). Note that the high contrast used in the images to stress the weak signal of the faint asteroid introduces many artifacts, even after the calibration process, which clearly disturb the finding.

The following day I checked the Risk Page of NEODyS: 2001 PM9 goes on being there, but the impactor table does not contain the possibility of impacting in 2003!, while those of 2005 and 2007 are still there. Next, I looked at the residuals of my observations, they are not excellent, but I feel good knowing that I succeeded to observe it with my medium equipment and that my observations have contributed to discard one impact solution.
According to the suggestion of keeping on following up the object, the next night I tried to catch 2001 PM9 again. After the previous night experience, I knew better the optimum exposure times, so that I was convinced that night I was to get better images, my astrometry would be better and thus I would not suffer with the reduction. I start the process, insert the new ephemerides generated by Genny and wait patiently. There it was 2001 PM9 again! Without doubt, I was getting a better signal than that of the previous night. I followed it for a big while and took many images. I reduced them more comfortably than the previous night and checked that the residuals looked more than acceptable. So, I mailed the observations to Tim Spahr at the MPC and this time I was not submitting the usual prudent 3 observations, but 7... I was so sure I had done a good job!
But 15 minutes after, I got a mail from Tim saying that they were off by about 50 arcsec. Impossible. I checked everything, configurations, times and redid the reduction... but I was getting the same results. I only notice one discrepancy: the PA giving the direction of motion is 17 degrees off with respect to that provided by the ephemerides. I was starting to think that 2001 PM9 had changed the trajectory and that I was facing another case of a WIND satellite... But my common sense tells me to take another look at the images at the exact point provided by the ephemerides. All of a sudden, I see the "true" and faint 2001 PM9 jumping at a few arc seconds from the object I have just measured and that, in reality, is a new "unknown" asteroid. While doing this, I received a reply from Tim who, from his office and after revising the astrometry I had sent to him, guesses what was really happening.
Once again, I reduced the faint signal of 2001 PM9 in the same images... and, once again, like the previous night, I was suffering to do it... my doubts, my contradictory feelings: "why do you try to observe such faint objects?"... I submitted 3 observations and this time I was thinking they were too many! The other 7 observations were referred to as JNT067, a supposedly new asteroid with an approximate apparent magnitude 19. Yes, I know it now, it has received the designation 2001 PO35.
That night, another three amateur observers from Sormano, San Marcello Pistoiese and Powell Obs. also took some images of 2001 PM9. I checked my residuals the following day: they were better than those of the first night! and, more importantly, all our observations together with a few more got in the next two nights by some other amateur observers (Badlands Obs., Linz, Starkenburg Sternwarte and Loomberah) have made possible to exclude any chance of 2001 PM9 impacting the Earth at any time until 2080. All the suffering, doubts, conflicting feelings have been worth... now I feel I have done my job and my mind is in peace.

Jaime Nomen (*) - Amateur observer at (946)-Ametlla de Mar and (620)-Observatorio de Mallorca

The images and the animations of this issue are courtesy of Jaime Nomen.