Yesterday, June 30th, was Asteroid Day. The following is quoted directly from the Asteroid Day website.
Asteroid Day is a global awareness campaign where people from around the world come together to learn about asteroids, the impact hazard they may pose, and what we can do to protect our planet, families, communities, and future generations from future asteroid impacts. Asteroid Day is held each year on the anniversary of the largest impact in recent history, the 1908 Tunguska event in Siberia.
The primary activity at the PTO is asteroid and comet orbit verification. The PTO’s primary telescope is too small to have any real chance of discovering a new asteroid or comet. But discovery is only part of the effort. The orbits of these objects can and have been changed by any number of physical processes. So, the PTO monitors known asteroids and comets to make sure they are where we think they are.
The way the PTO does this is to take a series of nine 300 second images of the target asteroid and then through computer analysis, determine sub arc second positions for the object. The information of at least three of the observations is then transmitted to the Minor Planet Center for comparison with predicted positions. The image below is a stack of 3 images with the asteroids circled showing their movement. The image is a negative of the stacked exposures. It is quite often easier to see darker objects against a white background than the other way around. Also visible is the track of a satellite recorded during one of the images.
The motion of all the asteroids is from the top of the image (East) toward the bottom (West). Since 2009 the PTO has submitted ≈2700 observations to the MPC.