KILLER ASTEROID PROJECT

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Near Earth Object Observations  

 

 

The earth is continually threatened by the collision of rogue objects in our solar system by asteroids and comets.  Our goal in the Killer Asteroid Project is to bring the opportunity of Near Earth Object Observations (NEOs) to to the academic community that wish to participate and conduct real scientific observations in the classroom.  Our goal is not discovering new NEOs but to do essential follow-up observations of the discoveries made by the large sky surveys like NEAT, Catalina, Linear and Loneos.  However in our observations we often make new discoveries of main belt asteroids as the move in their orbit between the planets Mars and Jupiter.  There are so many discoveries of Near Earth Objects that the ability to follow-up on all of these objects is a very difficult and time-consuming.

 

With the recent addition of the Astro-Research 0.81-meter (32 inch) telescope, we have been able to branch out beyond the realm of  typical amateur observations.  To date we have made measures of NEOs as faint as unfiltered magnitude 23.6 and routinely observe asteroids in the 22nd magnitude.  A particular problem relates to fainter objects, typically those dimmer than magnitude 21, where the number of amateur observers declines rapidly.  Therefore, these objects are less well observed and have shorter orbital arcs which means such observations are highly desirable.  Fainter observations are particularly important for two reasons. 

 

            1.    Many new objects are discovered at these dimmer magnitudes. 

 

            2.    If the asteroid is bright at discovery yet is quite small, it dims rapidly. 

 

It is important to get the longest observation arc possible so the data we contribute provides valuable information on the apparent orbit of the object.  This means observing the asteroid when it has moved away from the earth and becomes increasingly faint.  This is similar to the Moon where the phase angle decreases making it less visible than when the Moon is full.

 

The Astronomical Research Institute uses a 0.81m (32 inch) astrograph instrument with an effective focal length of f/4.6.  The telescope was custom built at the Astronomical Research Institute and has provided excellent data for Near Earth Object Observations for the past 2 years.  We currently use a Santa Barbara Instruments Group STL-1001E for observations providing us with a field of view that is 21.9X 21.9 arc minutes. 

 

Imaging NEOs with this setup allows us to reach the 22nd Magnitude with a 300 second exposure.  The difficulty with NEOs and asteroid observations is the combination of faintness with rapid motion.  Once the image of an asteroid begins to trail then further exposure will not increase the ability to observe it any fainter.  The optimal exposure is calculated by dividing the FWHM of a star image by the rate of motion of an object.  For star images with seeing of 2.5 arc seconds the maximum exposure for a main belt asteroids moving at 0.4 arc seconds per minute would be about 5 minutes.  A typical NEO rate of motion is often greater than 2.5 arc seconds per minute giving an optimal exposure of 1 minute.  In order to reach ever fainter objects it is necessary to use stack and track to build up the signal to noise ratio for a positive centroid on the target object.  However many objects travel faster than this and in some cases the optimal exposure is as little as 10 seconds.  Needless to say these fast objects present an extreme challenge in imaging especially when the object is fainter than the 21st magnitude.

 

Our main source of targets in our observations are found on the Minor Planet Center’s NEO Confirmation Page and Dates Of Last Observation Of NEOs.   Once a candidate is identified, an ephemeris is placed on the MPC Confirmation Page.  Some of these Confirmation Page objects will be real NEOs, some might actually be main belt asteroids and some will be false objects in the survey images.  The MPC also puts potential comets on the confirmation page and are not recognized as such to prevent biasing observers in their reports.  They leave it up to the observer to confirm whether or not an object is an actual comet or asteroid.  The MPC Confirmation Page is frequently updated through the night adding new objects or removing objects as they are confirmed.  Our rate of success with new objects has been very good with better than 60% having been confirmed as real objects.  The large field of view and the faint limiting magnitude of our instruments have made this achievement possible. 

 

A main feature of the Killer Asteroid Project is exciting opportunity to have your asteroid observations recognized and published in the Minor Planet Electronic Circulars MPECs.  To date ARI has made over 5,700 NEO observations and has over 350 published articles annually in the MPECs.  To be able to do this it is important that students and teachers get their observations submitted the same night or very early the morning the observations are made.  MPECs are issued when the MPC has sufficient observations on specific objects that are on the MPC Confirmation Page.  Typically the biggest problems most student and educators have is meeting the observation deadline and are late in submitting measures of an object.  This results in the MPECs having been issued before a student or teacher is able to provide astrometry on the new NEO.  This is one of the few areas of science where student and teachers are credited with observations and may have their observations published within 24 hours of your effort!

 

We also put in a considerable amount of time into conducting general follow-up observations of NEOs.  For efficient follow-up ovservations, students and teachers should only measure objects when you are likely to improve the orbital fit of the asteroid.  Most bright NEOs are over observed and additional observations have only a marginal impact on the asteroids orbit.  A good source for objects that  need follow-up observations is the MPCs Dates Of Last Observation Of NEOs.  Another very useful source of information is the Near Earth Objects Dynamics site ‘NEODyS’ from the University of Pisa.  This has a special risk page, that shows those objects that are “Virtual Impactors.”  These are categorized as key targets and additional observations are required to resolve their orbital impact solutions.  There is considerable information on each NEO at this site including a listing of all observations and residuals, plus summary pages for each observatory that have contributed observations.