Tundra orbit is a class of a highly elliptic orbit with inclination of 63.4° and orbital period of one sidereal day (almost 24 hours). A satellite placed in this orbit spends most of its time over a designated area of the earth, a phenomenon known as apogee dwell. Two bodies with similar mass orbiting around a common barycenter with elliptic orbits. ...
The orbital period is the time it takes a planet (or another object) to make one full orbit. ...
On a prograde planet like the Earth, the sidereal day is shorter than the solar day. ...
These are conceptually similar to Molniya orbits which have the same inclination but half the period (about 12 hours). Molniya orbit is a class of a highly elliptic orbit with inclination of +/63. ...
References  Sample Mission Analysis from the Danish Space Research Institute (see page 8).
