A significant use of Winer Observatory time on the
Project ASTEROID telescope will be for follow-up astrometry
of previously-discovered NEO's. The need for this work is
explained in the Near Earth Object Threat section of this
Web site. This work is not expected to consume all the time
on the telescope available to the Winer Observatory for the
highest-priority targets. As a result, we plan to pursue
a program of NEO science that helps planetary scientists
better understand the nature of Near Earth Asteroids.
Scientifically, there are two reasons for studying Near Earth
Objects (NEO's): (1) determining whether or not they are
Potentially Hazardous Asteroids (PHA's) and (2) placing them
in the context of the Main Belt asteroids and the asteroid /
meteorite connection.
It is now estimated that there are about 1000-1100 NEO's larger than 1km and tens of thousands down to the limit of Potentially Hazardous Asteroids (about 150 m). As of early January 2005, about 750 NEO's 1km or larger and a total of more than 3200 NEO's have been discovered. Nearly 700 of these are considered to be potentially hazardous (coming within 0.05 AU of the Earth at least once in the next 100 years). However, while the total number discovered each year is increasing thanks to improved discovery techniques, the discovery rate for larger ones is decreasing. This probably reflects the fact that the surveys are getting close to having observed all of the larger ones.
The majority of discoveries are being made by telescopes that are dedicated to just that, NEO discovery, and not follow-up. Without follow-up to determine their orbits, these asteroids are likely to be lost. Unlike Main Belt asteroids with synodic periods of a few years, it may be decades between times that these asteroids are close enough to observe them again, not something one wants to wait for if there is a chance that they might hit the Earth. As an example, in the case of 99942 Apophis (previously known as 2004 MN4, that for a while was a PHA with a relatively high probability of impacting the Earth), it is observable only once every 12 years. Without accurate photometry, there is no way to estimate accurately the sizes and shapes of these asteroids. As discovery techniques improve, the mean discovery magnitude of these asteroids is getting fainter. It is increasingly difficult for the average amateur (the typical follow-up observer) to do the necessary follow-up observations and thus critical that larger telescopes be dedicated to follow-up astrometry and photometry.
The studies of both asteroids and meteorites date back to the early 19th century with the discovery of asteroid 1 Ceres in 1801 and within two years, the realization that meteorites are "rocks from space." However, it took until the 1970's for the two communities to start talking to one another and collaborating to understand how the asteroids we see in the Asteroid Belt relate to the pieces of asteroids that we study on Earth -- the meteorites, and how they get from there to here. The NEO's represent that connection. By studying the NEO's, using both photometry and spectroscopy, we can determine (approximately) their size, shape, and composition. Also, since they most likely represent pieces recently broken off larger Main Belt asteroids, they are less "weathered" than Main Belt asteroids and can be compared more easily to meteorites compositionally.
There is also a practical aspect to studying NEO composition. If the NEO surveys were to discover an NEO on a collision course with Earth, and if follow-up astrometry were to confirm this, then anyone from NASA or the DoD involved in planning a mission to intercept the body and to destroy it or to change its orbit would need to know the body's composition. What is its density? How would it respond to thermonuclear explosives? Would it fragment into a few smaller bodies on the same trajectory for Earth to do approximately the same damage, or would the body be pulverized and essentially destroyed? Is the body solid or a rubble pile? The Project proposes some science programs to assist in addressing such questions, and is beginning to study these now, instead of waiting until the Design Study Phase of the Project.
Last modified: January 3, 2008.