DISCOVERY of 2012 DA14 and SEE YOU NEXT YEAR

During the night of 2012 February 22, the regular La Sagra Sky Survey program was ongoing. The NEO search had been restarted after few months of Space Debris experimental surveillance. The sky was already quite well covered along that darkrun, so it was decided to search on that night at quite high declinations, far from the ecliptic plane and on eastern skies, trying to scan over some more “virgin” areas, as the morning sky was reaching at enough altitude.

As soon as the sky is getting covered each month, mostly by the extremely high efficient big USA-Surveys, some changes are performed in the observing strategy, in order to still get any possibility to find something new with our very limited hardware resources, particularly adjusting the CCD exposure times and the gaps among the images, to try to better detect the smallest and closest to the Earth objects, due to they usually are detectable quite “suddenly” when they only become very near to us and that most of them move at rather high angular speed, therefore they can be discovered in any place, no matter if that sky region was already searched few days before.

These adjustments usually involves reducing the exposure times and taking a shorter delay among the images of the same area in order to try to avoid the long trails left by these fastest objects and to prevent they could escape out of the field of view.

The CCD cameras used at LSSS have a rather slow read-out time (close to 1 minute), this is the most limiting factor to reach a good survey performance, which particularly affects on these fastest moving objects detection.

From last year, one of the 3 CCD cameras was upgraded thanks to the 2010 Planetary Society Shoemaker NEO Grant. This camera has a much faster read-out time and thanks to that, during these last months, the telescope that holds this camera has been the most performing for detecting new objects of all three and also was the one which has discovered 2012 DA14.

When adjusting the telescopes for make them handy for detect faster moving objects, some additional changes on the processing software are also introduced, setting different parameters and filtering tools developed and lately improved under the recent space debris observing experience. One of them, generates the expected trail that should be produced by the object in the images, and the software tries to match it after is binarized, therefore, only trailed detections that are fitting with the same length and PA than the expected synthetic ones are considered as candidates from other rejected false detections.

Expected trail matching tool

The shorter exposures, the smaller gaps and the new software tools allowed to us, thanks to the new CCD camera, to catch 2012 DA14, when it was moving at almost 11 arc-second per minute.

2012 DA14 was detected and measured automatically. This is the reason why the 3 first astrometric measurements over the trail were not fitting the best on the orbit. The processing software popped it up in almost real time. The new NEO candidate was identified then as 22MB316, quickly, an immediate follow-up was performed by means of another telescope, to try to confirm it and to avoid it got lost. First measurements were reported at Minor Planet Center after confirmation and immediately 22MB316 was added and shortly updated in the NEOCP page.

Cropped windows of confirming images of 22MB316

2012 DA14 of approximately 50 meters wide, was first detected when it was already leaving us, at 4.335.000 kilometers from Earth. The closest distance occurred one week before at some more than 2.600.000 kilometers. Considering its path on the morning sky, its rather fast angular motion, the quite faint and fading brightness and the high declination, very far from the ecliptic plane, it was somehow an slippery target, and easily could have escaped undetected during this encounter, with no option to predict and prepare the next really close one it comes.

The preliminary orbit shows a very Earth-Like orbit with a period of 366.24 days, just one more day than our terrestrial year, with a low eccentricity but enough to “jump” inside and outside of the path of the Earth two times per year. Similar as to some racing rings sports: When the Earth “moves” by the outer “track”  is overtaken by 2012 DA14 running by the shortest path, and when the Earth “crosses” the asteroid path and goes by the inner track overtakes 2012 DA14. Is precisely on such crossing situations when the closest encounters occurs and when perhaps in the far future an impact could happen.

To the date, and with the daily incoming observations, the uncertainty is being slowly reduced and can be confirmed that an impact is completely ruled-out, but we will enjoy an extremely close approach of around 30.000 kms from the center of the Earth in less than one year!!: 2013 February, 15th. This distance is below of many commercial satellites, and will allow not only a nice event, but an opportunity to carry out physical studies and track and calculate the gravitational effects on it and the resulting orbit after the closest approach in order to compute any future risk of impact. Therefore might be a good test previous to the 2029 Apophis encounter, a bigger asteroid of around 270 meters that is expected to have a very close encounter too, at around 36.000 kms.

On the other hand, such Earth-Like orbit, with these short periodic close encounters with the Earth seem interesting for planning future space missions to the asteroid or even test mitigating technology.

Find here below 2 orbit diagrams and 2 animated gifs of the first night when confirming it. We hope to obtain better ones next year…! (Animations and diagrams may be used freely if credit is given to the La Sagra Sky Survey (LSSS)).

 
 


These animated gifs of the discovery night of 2012 DA14 were created by co-adding several consecutive frames of an small cropped part of the field of view of the telescope centered on the asteroid. Stars are shown as dark dots and don't move!, 2012 DA14 changes its position in each frame, moving towards top-right, and is not rounded as the sourronding stars: It is already trailed as a "worm" due to its fast angular motion even during the short exposure times of the CCD camera. This faint signal was coming from the sun reflected light on part of its 50 meters size at more than 4.3 million kilometers distance.


Jaime Nomen on behalf of La Sagra team