Among the very diverse population of asteroids cruising our solar system, some objects have an orbit very close to the Earth's one, and some of them have their entire orbit inside the Earth's orbit. They should not be confused with NEAs, Near Earth Asteroids, which often have an orbit quite different from the Earth's one, but can come close to the Earth from time to time. These IEAs (let's call them Inner Earth Asteroids) can however be NEAs, and even become Potentially Hazardous Asteroids (PHAs), which make their study quite important in the general search (largely focused to opposition direction) for PHAs undertaken over the next ten years by many agencies in many countries around the world.

A sub-family of the IEAs as defined above is made of the Earth's Trojans. Recent studies have clearly demonstrated that the Earth's Lagrange points L4 and L5 can lead to stable orbits, and there is a tremendous interest in finding asteroids around these points. If some of this search will be hopefully made using CFH12k (TACs permitting), the larger field and better sensitivity of MegaCam will allow a second deeper and larger survey of this area.

In addition to the now classical interest in the asteroid population for studying the evolution of our solar system, and the discovery of PHAs that such a survey would bring, the Earth's Trojans are particularly interesting:
- they could tell us about the transfer dynamics of asteroids in the vicinity of the Earth's orbit
- they provide a close look (better composition analyses, etc.) at what were probably at one point main belt asteroids.
- they do require typically low delta-v to reach them, making them natural targets for space missions, etc. (at least if they orbit close to the L points).

While most of the asteroids spend a large part of their orbit well outside the Earth's orbit, allowing us to observe them at opposition in a more or less easy way, the IEAs can only be observed for a short time of each night, as their elongation is never going to be large (think to when you can see Venus in the sky...). They are going to be faint when we can observe them, as the phase won't be favorable... The combination of a large telescope, a sensitive camera and a wide field is then very attractive for a search for IEAs.

As a by-product, this search would turn up many Aten asteroids, which are dangerous Earth crossers, and whose distribution and density are very poorly known, as they spend most of their time in the day light seen from Earth.

The search should cover a first set of two Earth's orbit (2 years), with systematic observations of the L4 and L5 areas at each MegaCam run for at least two nights in a row at the beginning and the end of the run for 1.5 hr. in the evening and morning (partly between twilight and astronomical twilight).  We could then try to map as continuously as possible the ecliptic in the vicinity of the L4/L5 points. A more detailed analysis of the proposed schedule will be provided in the course of the WG work, based on the results of the first tests made with CFH12k.