The observability of each NEA is analyzed by generating its geocentric ephemeris through to the year 2040.
Optical observing constraints vary widely from observatory to observatory. The constraints used for the NHATS table were purposely chosen to represent programs with access to large-aperture telescopes, in order to include even the difficult observational opportunities. The optical constraints are as follows:
The peak visual magnitude (Vp) during the tracking opportunity is shown as a guide to observers.
Many asteroids with poorly-determined orbits violate the plane-of-sky uncertainty constraint soon after discovery; these objects are considered lost. A secondary filter is then applied to simulate a serendipitous re-discovery of such an object by one of two asteroid survey programs. The survey programs are simulated by removing the plane-of-sky uncertainty constraint and imposing the following survey constraints:
The dates of possible survey recoveries are shown in the table with leading and trailing ‘?’ in order to indicate that these are far from certain.
Radar tracking opportunities for Arecibo and Goldstone are determined by calculating the daily signal-to-noise ratio (SNR) values using the best known physical parameters for the asteroid (primarily size and rotation period), as well as the actual parameters for these antennas. The radar constraints are as follows:
The entry in the table shows the date of the peak SNR, and the estimated SNR value follows in square brackets.