To illustrate the capabilities of the Heliospheric Imagers onboard the STEREO observatories, we performed a three-dimensional (3-D) magneto-hydrodynamic (MHD) simulation of three Coronal Mass Ejections (CMEs) propagating and interacting from the Sun to the Earth (N. Lugaz et al, Astrophysical Journal, 2007, doi:10.1086/512005). We used the Space Weather Modeling Framework (SWMF) developed at the University of Michigan.

We picked the events from November 24, 2000 (NOAA active region 9236) and produced synthetic images and movies of what would have been observed by STEREO if the spacecraft had been launched in November 1999.
This provides a visualization of the nominal observational capabilities of some of the STEREO instruments as the two satellites are separated by 45 degrees.

This series of events was chosen for a number of reasons. First, the active region was Sun-centered at the time of the ejections. This is the most interesting localization for an active region as the ejections are directed towards Earth. Also, in this case, the stereographic capabilities of the STEREO instruments are best tested, since the ejections propagate in-between the two satellites. Choosing to study not an isolated event but a series of successive ejections makes it also possible to study the ability of the Heliospheric Imagers to detect the interaction and merging of successive CMEs in the inner heliosphere.

There were six full-halo CMEs from this active region between November 24 and November 26, 2000. We "only" investigated the first three as they were faster than the following ones. The ejection from NOAA active region 9240 was directed about 90 degrees away from the Sun-Earth line (in the eastern limb) and it probably did not interact strongly with the other six ejections. Below is a table summarizing the properties of these ejections (from Burlaga et al, 2002, doi:10.1029/2001JA000255 except the speeds which are taken from the SOHO/LASCO CME catalog).