• Highly Elliptical Orbit Altitude
• Highly Elliptical Orbit Asteroids And Comets
• Highly Elliptical Orbit Comet Or Asteroid
• Highly Elliptical Orbit Uses
• Highly Elliptical Orbit Asteroid

Satellite systems using HEOs

1. Highly Elliptical Orbits (HEOs) about the Earth are often selected for astrophysics and astronomy missions, as well as for Earth missions, such as Molniya or Tundra orbits, as they offer vantage point for the observation of the Earth and the Universe (Draim et al., 2002).
2. It would be desirable to include a new definition in the Radio Regulations that would state that: “A satellite in a highly elliptical orbit has a repeating ground track, only operates in a portion of its orbit, the active arc, and is switched off elsewhere. At all times there is only one satellite in the active arc.
3. In a highly elliptical orbit, where is the Sun located? Kepler's Laws In the early 17th century, based on observations made by Tycho Brahe, Johannes Kepler postulated the first three laws of.
4. Click here👆to get an answer to your question ️ A comet orbits the sun in a highly elliptical orbit. Does the comet have a constant (a) Linear speed, (b) angular speed, (c) Angular momentum, (d) Kinetic energy, (e) potential energy, (f) total energy throughout its orbit? Neglect any mass loss of the comet when it comes very close to the Sun.

A highly elliptical orbit (HEO) is an elliptic orbit with a low-altitude (often under 1,000 kilometres (540 nmi)) perigee and a high-altitude (often over 35,786 kilometres (19,323 nmi)) apogee. The 'highly elliptical' term refers to the shape of the ellipse, and to the eccentricity of the orbit, not to the high apogee altitude. Such extremely elongated orbits have the advantage of long dwell.

Henry J. Meyerhoff
Space Spectrum Coordination Consultants Ltd

At present, the ITU regulatory provisions for registering frequency assignments on space stations depend on the category of their orbit: those in the geostationary-satellite orbit (GSO), and those in other orbits (non-GSO). This article advocates the addition of a third category: that of satellites in highly elliptical orbits (HEO), and for which registration in the Master International Frequency Register (MIFR) would follow the procedures applicable to GSO systems.

The Radio Regulations define GSO as “the orbit of a geosynchronous satellite whose circular and direct orbit lies in the plane of the Earth’s equator”. But this definition is rather ambiguous in the sense that it gives no bounds on either the degree of eccentricity of the circular orbit, or on the inclination angle of the orbit within which the satellite may be registered as being in the GSO.

In the beginning, communication satellites were placed in low-earth orbits (LEO), and 24 hour per day communication between associated earth stations required a constellation of identical satellites that moved in and out of view.

There was also the Russian Molniya system based on HEOs in which the satellite only operates around the apogee, and is switched off elsewhere. The Molniya system, having a 12-hour orbit had two very narrow longitudinal locations 180° apart in space with common latitude around 50° North, where there appeared an operating satellite 24 hours per day.

Then came the realization of Arthur C. Clarke’s dream (expressed in 1945) of a single satellite in the equatorial orbit that would revolve around the planet once in 24 hours — a period of time that corresponded to the rotation of the Earth about its axis. Major features of such a satellite were that:

• The satellite would appear stationary at a longitude above the equator, thereby not requiring the associated earth station antennas to track it.
• Directional earth station antennas and satellite spot beams would allow efficient frequency reuse for closely spaced satellites in the equatorial plane.
• With a system of only three such satellites suitably separated in longitude, it is possible to provide global coverage for all but the polar regions.

The advent of the geostationary satellite for civilian telecommunication services eclipsed the use of satellites in low-earth orbits, and also the Molniya system. This led the fixed-satellite service (FSS) for the GSO to be granted priority recording status in the Master International Frequency Register over all other orbits categorized as non-GSO. That priority status requires non-GSO not to cause unacceptable interference to the GSO in FSS bands.

On the other hand, the ITU procedures for registering space stations in the GSO FSS were more complicated than for non-GSO systems, requiring a coordination process before entry into the MIFR. This coordination process enables GSO FSS systems to share the 360° of longitude orbit spectrum among themselves on the basis of earth station antenna angular discrimination and satellite antenna spot beam coverage. Sharing of the spectrum between GSO FSS space stations and terrestrial services, based on the potential of steady state interference, is assured by:

• requiring limits on the power-flux density (pfd) of the GSO FSS satellites;
• restrictions on the pointing of terrestrial systems in the direction of the GSO, assuming directive antennas.

The Molniya HEO system provides service to northern latitudes of Russia from East to West with associated earth station limited tracking directive antennas. ITU registration of this system as a non-GSO without coordination produced no complaints of unacceptable interference, neither from the GSO nor from the terrestrial community. The type of potential interference is of a steady state nature as compared to that produced by other non-GSO, such as LEO systems.

Within the last decade, renewed interest was shown for LEO satellite systems to provide FSS on a worldwide basis. Such systems, being classified as non-GSO, could be registered in bands allocated to the FSS with the caveat that they do not cause harmful interference to GSO FSS systems, but without qualifying what that constitutes. It was recognized that networks using such satellites might cause random intermittent interference to GSO FSS and terrestrial systems compared to the steady state interference arising from GSO satellites. Study Groups of the ITU Radiocommunication Sector (ITU–R) developed statistical criteria to quantify, for coordination purposes, harmful interference levels which such systems must not exceed in order to share the FSS (and later the broadcasting-satellite service, or BSS) bands on an equal status with GSO systems. (In order to meet the statistical criteria to protect the GSO systems, mitigation techniques were suggested that would require the LEO satellites not to operate within +/–10° of the equator, with the communication link replaced intermittently with that of other satellites in the LEO system.) These statistical criteria were then incorporated in the Radio Regulations for application to all non-GSO systems.

However, just as the renewed interest was appearing for large numbers of low-earth orbiting satellites, various HEO satellite systems (like the Molniya) were being proposed for FSS and BSS. The type of interference they might cause to other HEO and GSO systems sharing the same frequency bands is of a steady state rather than the random intermittent nature coming from large numbers of LEO satellites. Furthermore, these proposed HEO systems are inherently compatible with, and complementary to, GSO systems where HEOs maintain a wide angular separation from the GSO.

Consequently, in order to use the orbit spectrum efficiently, it is considered that registration of proposed HEO systems follow procedures more akin to those that apply to GSO systems (i.e. sharing based on steady state interference).

The paragraphs below highlight a number of determining features of the category of HEO satellite systems that would follow the procedures applicable to GSO systems, with coordination based on potential steady state interference for their registration in the MIFR.

• The satellites in HEO constellation have repeating ground tracks, operate only in portions of their orbit, the active arcs, and are switched off elsewhere. At all times there is only one satellite in the active arc. For highly inclined orbits (25<i°<155), this ensures that there is a minimum angular separation of at least 20° between an operating satellite and the GSO. Most HEO constellation earth station antennas will track the satellite in its active arc, but some may have a broad beam that covers a small active arc but is of sufficient directivity to protect the FSS GSO. For BSS, GSO and HEO systems rely on satellite spot beam discrimination for frequency reuse. To better protect terrestrial networks, the service area for HEO systems is generally restricted to earth stations having high elevation angles to the operating satellite. Of practical interest for inclusion in the third category are the HEOs with periods of 24, 16, 12 and 8 hours.
• A distinction has been drawn between FSS and BSS systems, in that a common feature of BSS systems is cheap omnidirectional non-tracking receiver antennas. For sharing the same frequencies, such systems, be they GSO or HEO, rely entirely on the satellite spot beam, rather than their angular separation.
  HEO constellations may share with LEO non-GSO systems. The latter systems, in order to stay within the statistical sharing criteria developed for the protection of GSO systems, may necessitate the application of a similar mitigation technique to protect HEO systems that is used to protect the GSO. It has already been found that not more than four such LEO systems can share the orbit spectrum, and certainly to require them to provide similar protection to HEO constellations as given to GSO networks would add to their complexity.
• In order to share the FSS/BSS orbit spectrum, HEO constellations must coordinate with each other as well as with GSO and terrestrial networks. HEO constellations sharing criteria with terrestrial systems are based on pfd masks as with GSO systems. Whereas the spacing of GSO satellites for effective orbit spectrum utilization over common service areas has been reduced to a few orbital degrees, the HEO constellations will require broader angular separation among themselves since the active arcs occupy a greater portion of the sphere than the dot corresponding to a GSO orbit location. At this stage, it is impossible to predict the future number of HEO constellations. However, for the efficient use of orbit spectrum, a relatively small number (less than 10) should be taken to estimate the aggregate interference to terrestrial systems with a given pfd mask. As far as sharing with GSO systems, the minimum angular separation from the GSO should provide sufficient protection, given that GSO networks among themselves can share when separated by only a few orbital degrees. Hence the HEO constellations with high inclination angles complement the GSO systems.
• In the azimuth elevation angle diagram, terrestrial systems make use only of the circumference belt corresponding to elevation angles normally less than 3°. Although terrestrial networks will be subjected to additional interference from other azimuths than the two ranges corresponding to the position of the GSO, HEO constellations make effective use of the total sphere surrounding any terrestrial station.
• As far as sharing criteria for the HEO constellations described above are concerned, the type of interference they may cause to other HEO, GSO and terrestrial systems is of a steady state nature, and bears no relationship to the intermittent statistical interference associated with LEO non-GSO systems.
• Conclusion. It would be desirable to include a new definition in the Radio Regulations that would state that: “A satellite in a highly elliptical orbit has a repeating ground track, only operates in a portion of its orbit, the active arc, and is switched off elsewhere. At all times there is only one satellite in the active arc. The inclination angle of the orbit lies between 25° and 155°. The period of the orbit is a multiple of that of the geostationary-satellite orbit. Eccentricity of the orbit should be greater than 0.05.

Satellite Orbits Includes:
Satellite orbit types & definitionsLow earth orbit, LEOGeostationary orbit, GEOHighly elliptical orbit HEOTechniques for launching satellites into orbit

While circular orbits may be the obvious solution for many satellites, elliptical orbits have many advantages for certain applications.

Highly Elliptical Orbit Altitude

The elliptical orbit is often called the Highly Elliptical Orbit, HEO.

As a result of this many satellites are placed in elliptical orbits, especially where certain attributes are required. For example it does not require the orbits to be equatorial like the geostationary orbit. This means that polar and high latitude areas can be covered with highly elliptical orbits, HEO.

The satellite elliptical orbit gives a number of coverage options that are not available when circular orbits are used.

Highly elliptical orbit, HEO, basics

Highly Elliptical Orbit Asteroids And Comets

As the name implies, an elliptical orbit or as it is more commonly known the highly elliptical orbit, HEO, follows the curve of an ellipse. However one of the key features of an elliptical orbit is that the satellite in an elliptical orbit about Earth moves much faster when it is close to Earth than when it is further away.

For any ellipse, there are two focal points, and one of these is the geo-centre of the Earth. Another feature of an elliptical orbit is that there are two other major points. One is where the satellite is furthest from the Earth. This point is known as the apogee - this is where the satellite moves at its slowest as the gravitational pull from the earth is lower. The point where it is closest to the Earth is known as the perigee - this is where the satellite moves at its fastest.

Highly Elliptical Orbit Comet Or Asteroid

If the satellite orbit is very elliptical, the satellite will spend most of its time near apogee where it moves very slowly. This means that the satellite can be in view over its operational area for most of the time, and falling out of view when the satellite comes closer to the Earth and passes over the blind side of the Earth. By placing a number of satellites in the same orbit, but equally spaced apart, permanent coverage can be achieved.

The plane of a satellite orbit is also important. Some may orbit around the equator, whereas others may have different orbits. The angle of inclination of a satellite orbit is shown below. It is the angle between a line perpendicular to the plane of the orbit and a line passing through the poles. This means that an orbit directly above the equator will have an inclination of 0° (or 180°), and one passing over the poles will have an angle of 90°.

Those orbits above the equator are generally called equatorial obits, whilst those above the poles are called polar orbits.

Highly elliptical orbit, HEO, applications

Highly Elliptical Orbit Uses

The highly elliptical satellite orbit can be used to provide coverage over any point on the globe. The HEO is not limited to equatorial orbits like the geostationary orbit and the resulting lack of high latitude and polar coverage.

As a result it ability to provide high latitude and polar coverage, countries such as Russia which need coverage over polar and near polar areas make significant use of highly elliptical orbits, HEO.

Highly Elliptical Orbit Asteroid

With two satellites in any orbit, they are able to provide continuous coverage. The main disadvantage is that the satellite position from a point on the Earth does not remain the same.

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