Highly elliptical orbit

Highly EllipticalHEOhighly elliptical Earth orbithighly eccentric earth orbitHighly Elliptical Orbit (HEO)highly elliptical orbitshighly-eccentric Earth orbitHighly-elliptical Earth Orbitlow Earth orbit
A highly elliptical orbit (HEO) is an elliptic orbit with high eccentricity, usually referring to one around Earth.wikipedia
103 Related Articles

Molniya orbit

Molniyahighly elliptical orbitMolniya orbit satellite
Examples of inclined HEO orbits include Molniya orbits, named after the Molniya Soviet communication satellites which used them, and Tundra orbits.
It is a highly elliptical orbit with an inclination of 63.4 degrees, an argument of perigee of 270 degrees, and an orbital period of approximately half a sidereal day.

Tundra orbit

TundraTundra elliptical orbit
Examples of inclined HEO orbits include Molniya orbits, named after the Molniya Soviet communication satellites which used them, and Tundra orbits.
A Tundra orbit (Russian: Орбита «Тундра») is a highly elliptical geosynchronous orbit with a high inclination (usually near 63.4°), an orbital period of one sidereal day, and a typical eccentricity between 0.2 and 0.3.

Geocentric orbit

GeocentricEarth orbitEarth-orbit
A highly elliptical orbit (HEO) is an elliptic orbit with high eccentricity, usually referring to one around Earth.
A special case of high Earth orbit is the highly elliptical orbit, where altitude at perigee is less than 2,000 km.

Sirius Satellite Radio

SiriusSirius RadioSiriusXM
Sirius Satellite Radio used inclined HEO orbits, specifically the Tundra orbits, to keep two satellites positioned above North America while another satellite quickly sweeps through the southern part of its 24-hour orbit.
The highly elliptical orbit of the Sirius satellite constellation can pose difficulties for the reliable delivery of the signal to stationary antennas in certain parts of the country.

Elliptic orbit

elliptical orbitellipticalelliptic
A highly elliptical orbit (HEO) is an elliptic orbit with high eccentricity, usually referring to one around Earth.

Orbital eccentricity

eccentricityeccentriceccentricities
A highly elliptical orbit (HEO) is an elliptic orbit with high eccentricity, usually referring to one around Earth.

Molniya (satellite)

MolniyaMolniya 1Molniya-1
Examples of inclined HEO orbits include Molniya orbits, named after the Molniya Soviet communication satellites which used them, and Tundra orbits.

Apsis

perigeeperihelionapogee
Such extremely elongated orbits have the advantage of long dwell times at a point in the sky during the approach to, and descent from, apogee.

Horizontal coordinate system

altitudezenith distancecelestial horizon
Bodies moving through the long apogee dwell appear to move slowly, and remain at high altitude over high-latitude ground sites for long periods of time.

Communications satellite

satellite communicationssatellitecommunication satellite
This makes these elliptical orbits useful for communications satellites.

Geostationary orbit

GeostationaryGEOgeostationary satellite
Geostationary orbits cannot serve high latitudes due to their altitude from ground sites being too low.

North America

NorthNorth AmericanNA
Sirius Satellite Radio used inclined HEO orbits, specifically the Tundra orbits, to keep two satellites positioned above North America while another satellite quickly sweeps through the southern part of its 24-hour orbit.

Longitude

WestlongitudinalE
The longitude above which the satellites dwell at apogee in the small loop remains relatively constant as Earth rotates.

Earth's rotation

rotation of the EarthrotationEarth rotates
The longitude above which the satellites dwell at apogee in the small loop remains relatively constant as Earth rotates.

Ground track

ground pathTrackpass over
The three separate orbits are spaced equally around the Earth, but share a common ground track.

Ekspress (satellite bus)

EkspressEkspress-1000HEkspress-2000
It is an unpressurized bus originally designed for GEO, but that has been adapted for medium Earth orbit and to highly elliptical orbit.

Amateur radio satellite

OSCARamateur satelliteAmateur-satellite service
Amateur satellites have been launched into low Earth orbits and into highly elliptical orbits.

Proton-K

ProtonProton 8K82KProton 8K82K rocket
During the so-called "Moon Race" these Proton/Soyuz/Zond flights consisted of several uncrewed test flights of Soyuz spacecraft to highly elliptical or circumlunar orbits with the unrealized aim of landing Soviet cosmonauts on the Moon.

Lunar Lander (spacecraft)

Lunar LanderLunar Lander (space mission)
Launching from Centre Spatial Guyanais, Kourou in late 2018 on a Soyuz launcher, the Lander is injected into a Highly Elliptical Orbit (HEO) by a Fregat-MT upper stage, through a series of intermediate orbits.

Geostationary transfer orbit

geosynchronous transfer orbitGTOtransfer
GTO is a highly elliptical Earth orbit with an apogee of 42164 km, or 35786 km above sea level, which corresponds to the geostationary altitude.

Low Earth orbit

Low EarthLEOlow-Earth orbit
Some highly elliptical orbits may pass through the LEO region near their lowest altitude (or perigee) but are not in an LEO Orbit because their highest altitude (or apogee) exceeds.

USP (satellite bus)

USP BusUSPUSP (Victoria)
The bus can offer up to 3000 W of power and a payload capacity up to 1000 kg for Low Earth orbit or HEO an up to 300 kg for geostationary orbit.

S-45A

The satellite was intended to operate in a highly elliptical orbit, from which it was to have provided data on the shape of the ionosphere, and on the Earth's magnetic field.

S-45 (satellite)

S-45
The satellite was intended to operate in a highly elliptical orbit, from which it was to have provided data on the shape of the ionosphere, and on the Earth's magnetic field.

Explorer 34

Explorer 34 was placed into a high-inclination, highly eccentric earth orbit.