# Areostationary orbit

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An areostationary orbit, areosynchronous equatorial orbit (AEO), or Mars geostationary orbit is a circular areo­synchronous orbit (ASO) approximately 17,032 km (10,583 mi) in altitude above the Mars equator and following the direction of Mars's rotation.

## Contents

An object in such an orbit has an orbital period equal to Mars's rotational period, and so to ground observers it appears motionless in a fixed position in the sky. It is the Martian analog of a Geostationary orbit (GEO). The prefix areo- derives from Ares, the ancient Greek god of war and counterpart to the Roman god Mars, with whom the planet was identified.

Although it would allow for uninterrupted communication and observation of the Martian surface, no artificial satellites have been placed in this orbit due to the technical complexity of achieving and maintaining one. [1] [2]

## Characteristics

The radius of an areostationary orbit can be calculated using Kepler's Third Law.

${\displaystyle T^{2}={2\pi \over {\sqrt {GM}}}*a^{3 \over 2}}$ [3]

Where:

VariableDefinitionValue
TRotational Period88,642 seconds
G Gravitational constant 6.674×10−11 N⋅m2/kg2
MMass of central object6.4171×1023 kg
a Semimajor axis 20,428 km

Substituting the mass of Mars for M and the Martian sidereal day for T and solving for the semimajor axis yields a synchronous orbit radius of 20,428 km (12,693 mi) above the surface of the Mars equator. [4] [5] [6] Subtracting Mars's radius gives an orbital altitude of 17,032 km (10,583 mi).

Two stable longitudes exist - 17.92°W and 167.83°E. Satellites placed at any other longitude will tend to drift to these stable longitudes over time. [6] [7]

## Feasibility

Several factors make placing a spacecraft into an areostationary orbit more difficult than a geostationary orbit. Since the areostationary orbit lies between Mars's two natural satellites, Phobos (semi-major axis: 9,376 km) and Deimos (semi-major axis: 23,463 km), any satellites in the orbit will suffer increased orbital station keeping costs due to unwanted orbital resonance effects. Mars's gravity is also much less spherical than earth due to uneven volcanism (i.e. Olympus Mons). This creates additional gravitational disturbances not present on earth, further destabilizing the orbit. Solar radiation pressure and sun-based perturbations are also present, as with an earth-based geostationary orbit. Actually placing a satellite into such an orbit is further complicated by the distance from earth and related challenges shared by any attempted Mars mission. [2] [7] [8]

## Uses

Satellites in an areostationary orbit would allow for greater amounts of data to be relayed back from the Martian surface easier than by using current methods. Satellites in the orbit would also be ideal advantageous for monitoring Martian weather and mapping of the Martian surface. [9]

In the early 2000s NASA explored the feasibility of placing communications satellites in an areocentric orbit as a part of the Mars Communication Network. In the concept, an areostationary relay satellite would transmit data from a network of landers and smaller satellites in lower Martian orbits back to earth. [10] [11]

## Related Research Articles

A geosynchronous orbit is an Earth-centered orbit with an orbital period that matches Earth's rotation on its axis, 23 hours, 56 minutes, and 4 seconds. The synchronization of rotation and orbital period means that, for an observer on Earth's surface, an object in geosynchronous orbit returns to exactly the same position in the sky after a period of one sidereal day. Over the course of a day, the object's position in the sky may remain still or trace out a path, typically in a figure-8 form, whose precise characteristics depend on the orbit's inclination and eccentricity. A circular geosynchronous orbit has a constant altitude of 35,786 km (22,236 mi).

A geostationary orbit, also referred to as a geosynchronous equatorial orbit (GEO), is a circular geosynchronous orbit 35,786 km (22,236 mi) in altitude above Earth's equator, 42,164 km (26,199 mi) in radius from Earth's center, and following the direction of Earth's rotation.

A communications satellite is an artificial satellite that relays and amplifies radio telecommunication signals via a transponder; it creates a communication channel between a source transmitter and a receiver at different locations on Earth. Communications satellites are used for television, telephone, radio, internet, and military applications. Many communications satellites are in geostationary orbit 22,236 miles (35,785 km) above the equator, so that the satellite appears stationary at the same point in the sky; therefore the satellite dish antennas of ground stations can be aimed permanently at that spot and do not have to move to track the satellite. Others form satellite constellations in low Earth orbit, where antennas on the ground have to follow the position of the satellites and switch between satellites frequently.

Phobos is the innermost and larger of the two natural satellites of Mars, the other being Deimos. The two moons were discovered in 1877 by American astronomer Asaph Hall. It is named after Phobos, the Greek god of fear and panic, who is the son of Ares (Mars) and twin brother of Deimos.

The Mars Observer spacecraft, also known as the Mars Geoscience/Climatology Orbiter, was a robotic space probe launched by NASA on September 25, 1992, to study the Martian surface, atmosphere, climate and magnetic field. On August 21, 1993, during the interplanetary cruise phase, communication with the spacecraft was lost, three days prior to the probe's orbital insertion. Attempts to re-establish communications with the spacecraft were unsuccessful.

Areography, also known as the geography of Mars, is a subfield of planetary science that entails the delineation and characterization of regions on Mars. Areography is mainly focused on what is called physical geography on Earth; that is the distribution of physical features across Mars and their cartographic representations. In April 2023, The New York Times reported an updated global map of Mars based on images from the Hope spacecraft. A related, but much more detailed, global Mars map was released by NASA on 16 April 2023.

A Molniya orbit is a type of satellite orbit designed to provide communications and remote sensing coverage over high latitudes. 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. The name comes from the Molniya satellites, a series of Soviet/Russian civilian and military communications satellites which have used this type of orbit since the mid-1960s.

The areosynchronous orbits (ASO) are the synchronous orbits for artificial satellites around the planet Mars. They are the martian equivalent of the geosynchronous orbits (GSO) on the Earth. The prefix areo- derives from Ares, the ancient Greek god of war and counterpart to the Roman god Mars, with whom the planet was identified. The modern Greek word for Mars is Άρης (Áris).

The two moons of Mars are Phobos and Deimos. They are irregular in shape. Both were discovered by American astronomer Asaph Hall in August 1877 and are named after the Greek mythological twin characters Phobos and Deimos who accompanied their father Ares into battle. Ares, the god of war, was known to the Romans as Mars.

Colonization or settlement of Mars is the theoretical migration of humans to Mars and the establishment of long-term human presence on the planet. The prospect has garnered interest from public space agencies and private corporations and has been extensively explored in science fiction writing, film, and art. Organizations have proposed plans for a human mission to Mars, the first step towards any colonization effort, but thus far no person has set foot on the planet, and there have been no return missions. However, landers and rovers have successfully explored the planetary surface and delivered information about conditions on the ground.

A supersynchronous orbit is either an orbit with a period greater than that of a synchronous orbit, or just an orbit whose major axis is larger than that of a synchronous orbit. A synchronous orbit has a period equal to the rotational period of the body which contains the barycenter of the orbit.

A Tundra orbit is a highly elliptical geosynchronous orbit with a high inclination, an orbital period of one sidereal day, and a typical eccentricity between 0.2 and 0.3. A satellite placed in this orbit spends most of its time over a chosen area of the Earth, a phenomenon known as apogee dwell, which makes them particularly well suited for communications satellites serving high-latitude regions. The ground track of a satellite in a Tundra orbit is a closed figure 8 with a smaller loop over either the northern or southern hemisphere. This differentiates them from Molniya orbits designed to service high-latitude regions, which have the same inclination but half the period and do not loiter over a single region.

A geosynchronous satellite is a satellite in geosynchronous orbit, with an orbital period the same as the Earth's rotation period. Such a satellite returns to the same position in the sky after each sidereal day, and over the course of a day traces out a path in the sky that is typically some form of analemma. A special case of geosynchronous satellite is the geostationary satellite, which has a geostationary orbit – a circular geosynchronous orbit directly above the Earth's equator. Another type of geosynchronous orbit used by satellites is the Tundra elliptical orbit.

The ExoMars Trace Gas Orbiter is a collaborative project between the European Space Agency (ESA) and the Russian Roscosmos agency that sent an atmospheric research orbiter and the Schiaparelli demonstration lander to Mars in 2016 as part of the European-led ExoMars programme.

MAVEN is a NASA spacecraft orbiting Mars to study the loss of that planet's atmospheric gases to space, providing insight into the history of the planet's climate and water. The name is an acronym for "Mars Atmosphere and Volatile Evolution" while the word maven also denotes "a person who has special knowledge or experience; an expert". MAVEN was launched on an Atlas V rocket from Cape Canaveral Air Force Station, Florida, on 18 November 2013 UTC and went into orbit around Mars on 22 September 2014 UTC. The mission is the first by NASA to study the Mars atmosphere. The probe is analyzing the planet's upper atmosphere and ionosphere to examine how and at what rate the solar wind is stripping away volatile compounds.

Mars Cube One was a Mars flyby mission launched on 5 May 2018 alongside NASA's InSight Mars lander. It consisted of two nanospacecraft, MarCO-A and MarCO-B, that provided real-time communications to Earth for InSight during its entry, descent, and landing (EDL) on 26 November 2018 - when InSight was out of line of sight from the Earth. Both spacecraft were 6U CubeSats designed to test miniaturized communications and navigation technologies. These were the first CubeSats to operate beyond Earth orbit, and aside from telecommunications they also tested CubeSats' endurance in deep space. On 5 February 2019, NASA reported that both the CubeSats had gone silent by 5 January 2019, and are unlikely to be heard from again. In August 2019, the CubeSats were honored for their role in the successful landing of the InSight lander on Mars.

The International-Mars Ice Mapper (I-MIM) mission is a proposed Mars orbiter being developed by NASA in collaboration with the Japan Aerospace Exploration Agency (JAXA), the Canadian Space Agency (CSA), and the Italian Space Agency (ASI). As the mission concept evolves, there may be opportunities for other space agency and commercial partners to join the mission. The goal of the orbiter is the quantification of extent and volume of water ice in non-polar regions of Mars. The results are intended to support future Mars missions, especially with respect to the search for habitable environments and accessible In situ resource utilization (ISRU) resources. The International-Mars Ice Mapper is an "exploration precursor mission", comparing it to the Lunar Reconnaissance Orbiter (LRO) mission. The mission was envisioned to be launched as early as 2026. However, in March 2022, it was revealed in its fiscal year 2023 budget proposal that the US government would terminate NASA financial support for the Mars Ice Mapper, casting the project's future into uncertainty.

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