High Earth orbit

To-scale diagram of low, medium and high Earth orbits

Short description: Geocentric orbit with an altitude entirely above that of a geosynchronous orbit

One of the main benefits of HEO is that it provides a nearly unobstructed view of the Earth and deep space. This makes it an ideal location for astronomical observations and Earth monitoring. In addition, satellites in HEO can provide a continuous coverage of the Earth's surface, making it very useful for communication and navigation purposes.[1]

There are four main reasons that most satellite are placed in lower orbits. First, a HEO can take a month or more per orbit. This is because HEOs are very large orbits and move at only 7000 mph. Meanwhile, a LEO (low Earth orbit) can take less than 90 minutes.[2] So, for satellites that need to orbit quickly, HEO is not a good fit. Second, HEOs take far more energy to place a satellite into than LEOs. To place a satellite into HEO takes nearly as much energy as to place it into a heliocentric orbit. For example, an expended Falcon 9 can carry 50,000 pounds to LEO. However, it can only carry around 10,000 pounds to HEO. [3] This means that it costs 5 times more to place a payload in HEO versus placing it in LEO. Third, HEOs are incredibly far from Earth. This means that there is a constant communication delay when sending signals to and from the satellite. This is actually because the signals can only travel at the speed of light. This means that it can take around 0.1 to 4.5 seconds in delay time each way. This makes it useless for internet, and hard to use for other things as well. The fourth reason is radiation. HEO is outside of the magnetic field of Earth. This means that there is far more radiation in HEO. As a result, spacecraft in HEO require specialized equipment and shielding to protect them from radiation. As a result, only satellites that require the unique characteristics of HEO use this orbit.

The development of HEO technology has had a significant impact on space exploration and has paved the way for future missions to deep space. The ability to place satellites in HEO has allowed scientists to make groundbreaking discoveries in astronomy and Earth science, while also enabling global communication and navigation systems.[4]

## Examples of satellites in high Earth orbit

Name  | NSSDC id.  | Launch date  | Perigee  | Apogee  | Period  | Inclination

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Vela 1A[5][6] | 1963-039A  | 1963-10-17  | 101,925 km  | 116,528 km  | 108 h 39 min  | 37.8°
IBEX | 2008-051A  | 2008-10-19  | 61,941 km  | 290,906 km  | 216 h 3 min  | 16.9°
TESS[7][8] | 2018-038A  | 2018-04-18  | 108,000 km  | 375,000 km  | 328 h 48 min  | 37.00°
Propulsion module | 2023-098B  | 2023-07-14  | 115,000 km  | 154,000 km  | 13 days  | 27°

## See also

* Ukrainian Optical Facilities for Near-Earth Space Surveillance Network

## References

1. ↑ "Advantages of HEO Highly Elliptical Orbit | Disadvantages of HEO orbit". https://www.rfwireless-world.com/Terminology/Advantages-and-Disadvantages-of-HEO.html#:~:text=Benefits or advantages of HEO orbit,-Following are the&text=➨Coverage area is smaller,the Earth unlike Geostationary orbits..
2. ↑ "Popular Orbits 101" (in en-US). 30 November 2017. https://aerospace.csis.org/aerospace101/earth-orbit-101/.
3. ↑ "Capabilities & Services". https://www.spacex.com/media/Capabilities&Services.pdf.
4. ↑ "Catalog of Earth Satellite Orbits" (in en). 2009-09-04. https://earthobservatory.nasa.gov/features/OrbitsCatalog/page2.php.
5. ↑ "Vela". Astronautix.com. http://www.astronautix.com/v/vela.html.
6. ↑ "Trajectory Details for Vela 1A from the National Space Science Data Center". https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1963-039A.
7. ↑ "MIT TESS mission". https://tess.mit.edu/.
8. ↑ "NASA - TESS Science Support Center". 25 July 2023. https://heasarc.gsfc.nasa.gov/docs/tess/.

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Gravitational orbits

Types|

| General|

* Box
* Capture
* Circular
* Elliptical / Highly elliptical
* Escape
* Horseshoe
* Hyperbolic trajectory
* Inclined / Non-inclined
* Lagrangian point
* Osculating
* Parabolic trajectory
* Parking
* Prograde / Retrograde
* Synchronous
* semi
* sub
* Transfer orbit

|

Geocentric|

* Geosynchronous
* Geostationary
* Geostationary transfer
* Graveyard
* High Earth
* Low Earth
* Medium Earth
* Molniya
* Near-equatorial
* Orbit of the Moon
* Polar
* Sun-synchronous
* Tundra

About other points|

* Mars
* Areosynchronous
* Areostationary
* Lagrange points
* Distant retrograde
* Halo
* Lissajous
* Lunar
* Sun
* Heliocentric
* Earth's orbit
* Heliosynchronous

Parameters|

* Shape
* Size

* e Eccentricity
* a Semi-major axis
* b Semi-minor axis
* Q, q Apsides

|

Orientation|

* i Inclination
* Ω Longitude of the ascending node
* ω Argument of periapsis
* ϖ Longitude of the periapsis

Position|

* M Mean anomaly
* ν, θ, f True anomaly
* E Eccentric anomaly
* L Mean longitude
* l True longitude

Variation|

* T Orbital period
* n Mean motion
* v Orbital speed
* t0 Epoch

Maneuvers|

* Bi-elliptic transfer
* Collision avoidance (spacecraft)
* Delta-v
* Delta-v budget
* Gravity assist
* Gravity turn
* Hohmann transfer
* Inclination change
* Low energy transfer
* Oberth effect
* Phasing
* Rocket equation
* Rendezvous
* Transposition, docking, and extraction

Orbital mechanics|

* Celestial coordinate system
* Characteristic energy
* Escape velocity
* Ephemeris
* Equatorial coordinate system
* Ground track
* Hill sphere
* Interplanetary Transport Network
* Kepler's laws of planetary motion
* Lagrangian point
* n-body problem
* Orbit equation
* Orbital state vectors
* Perturbation
* Retrograde motion
* Specific orbital energy
* Specific relative angular momentum
* Two-line elements

* List of orbits

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